**Community-Based Control of Schistosomiasis and Soil-Transmitted Helminthiasis in the Epidemiological Context of a Large Dam in Cote D'ivoire**

Nicaise Aya N'Guessan , Orsot Niangoran Mathieu, Abé N'Doumi Noël and N'Goran Kouakou Eliézer

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/53494

## **1. Introduction**

[29] Goher, H. A, & Gindy, H. I. (1960 a). b). The ecology of Egyptians snail vectors of Bil‐ harziasis and fascioliasis I : Physical factors Proc. Egypt Acad Sci., , 15, 70-86.

[30] Ndifon, G. T. (1979). Studies on the feeding biology, anatomical variation and ecolo‐ gy of vectors of schistosomiasis and other fresh water snails in South Western Niger‐

[31] Vercruysse, J, Southgate, V, & Rollinson, R. D. ((1994). Studies on transmission and schistosome interaction in Senegal, Mali and Zambia. Tropical and Geographical

[33] Philippe, C. (1993). Amenagements hydro-agricoles et evolution de environment

[34] Donelly, F. A, Appleton, C. C, & Schutte, C. H. (1983). The influence of salinity on the ova and miracidia of three species of schistosoma. Int. J. parasitol. , 14, 113-120. [35] Tchobanoglous, G, & Burton, F. (1991). Waste engineering: treatment, disposal, and

[36] De-MeillonB; De-Frank, G, H and Allanson, B, R. ((1958). Some aspects of snail ecolo‐ gy in South Africa, WHO technical report series. Bull World health organization; , 18,

[37] Smyth, A. J, & Montgomery, R. F. (1962). Soils and land use in central western Niger‐

[38] Ayoade, J. O. (1982). climate. In barbour K.M.J.S. Oguntoyinbo, J.O.C. Onyemelukwe & J.C. Nwafor (eds) Nigeria in maps. Hodder & Stoughton. London , 24-25.

[32] Cogels, F. X, Thiam, A, & Gac, J. Y. (1993). Premiers effect des barrages du

dans Lake Gorom-lampser (delta du fleuve Senegal. *ORSTOM.*

reuse, 3rd edition New York: Mc Graw Hill., 584-636.

ia. 320pp. Government Printer. Ibadan

ia. Ph.D thesis, University of Ibadan, Nigeria.

Medicine, , 46(40), 220-226.

771-783.

48 Parasitic Diseases - Schistosomiasis

Parasitic diseases, among which schistosomiasis and soil-transmitted helminthiasis (anky‐ lostosomiasis, ascariasis and trichuriasis), affect more than two billion people through the world (WHO, 2012). These diseases occur mainly in tropical regions, are real public health problems, and have a negative impact on socioeconomic development (WHO, 2008).

Côte d'Ivoire, located in West Africa, is not spared. Many parasitic diseases exist in this country. Schistosomiasis is widespread (Doumenge et al., 1987; N'Goran et al., 1997; N'Guessan et al., 2007; Raso et al., 2005; Utzinger et al., 2000; WHO, 2011) with prevalence generally higher in communities around the water projects built to solve the problems of electrical safety and / or food (Steinmann, 2006). As for soil-transmitted helminthiasis, there is very little data on the prevalence and intensity in Côte d'Ivoire. But according to the WHO, they are common throughout the territory [WHO, 2010.3]. The available data show that the prevalence of hookworm infection may reach 100% in endemic communities in Côte d'Ivoire, 71.6% of ascariasis and trichuriasis 24%. Concerning soil-transmitted helminth in‐ fections, hookworm is the main parasite of our study area with 50% prevalence and less than 10% for other affections (N'Guessan, 2003).

In this study, we seek lasting solutions to fight against schistosomiasis and soil-transmitted helminthiasis in the ecoepidemiological context of a large dam. Our results can be extrapo‐ lated in similar epidemiological settings elsewhere in Côte d'Ivoire, and other African coun‐ tries. To this end, our investigations were conducted in the locality of Taabo-village straddling the area of forest and savannah woodland. The set of two areas represents 2/3 of

© 2013 N'Guessan et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

the different vegetation types encountered in this country. Parasitological monitoring con‐ ducted, in such eco-epidemiological context, for two consecutive years of annual mass treat‐ ment revealed a high prevalence of urinary schistosomiasis among school children. Prevalence ranged from 94% to 74% at the beginning to the end (N'Goran et al., 2001). More‐ over, the evaluation of reinfection of *Schistosoma haematobium* in various eco-epidemiological systems has shown that it is faster in the context of large dams. The high prevalence and limited reductions after mass treatments could be explained by the almost continuous trans‐ mission of this parasite (N'Goran et al., 2001; N'Guessan et al., 2007).

tary. Parents or guardians of selected children were invited to sign a written informed con‐

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51

The selected school children participated in parasitological surveys conducted in April 2008 before treatment and on May 2009 after one year. In 2008 as in 2009, each student gave a urine sample and a stool sample. These samples were taken between 10 a.m and 2 p.m.

The search for eggs of *Schistosoma haematobium* in each urine sample was performed by the standard filtration of 10 ml of urine on a filter Nytrel ®, then the analysis of the filter under a microscope after coloration with lugol (Plouvier et al., 1975). The eggs of *Schistosoma hae‐*

The stools were examined by the Kato-Katz technique, which involved analysis of 41.7 mg of stool under a microscope after plating and clarification by malachite green (Katz

sent after explanation of the objective of the study and procedures by investigators.

**Figure 1.** Overview of the study area

*matobium* were identified and counted.

The example of Taabo-village located near the large dam Taabo where urinary schistosomia‐ sis is a real public health problem is remarkable (N'Goran et al., 1997 and 2001). Given the importance of this disease at Taabo-village, which approach control could put important pressure on large and sustained transmission of *S. haematobium* and hope to significantly re‐ duce the morbidity due to urinary schistosomiasis?

In this perspective, a preventive approach and the fight against disease caused by schis‐ tosomiasis and soil-transmitted helminthiasis as recommended by the World Health Or‐ ganization (WHO, 2003, 2004 a and 2004b) were implemented. We believe that the communication for behavior change associated with the ongoing management could al‐ low a significant decrease in the prevalence and morbidity of these diseases. To do so, parasitological surveys were conducted in schools before and after a control action to as‐ sess the epidemiological situation. Then, teachers and Community Health Workers (AUC) were trained to educate and support consistently the population. Finally, sociolog‐ ical surveys were conducted to determine the perceptions and human factors in risk as‐ sociated with the endemicity of these diseases.

## **2. Methods**

#### **2.1. Study area**

The Taabo dam is located in south-center of Côte d'Ivoire, on the river Bandama in degrad‐ ed forest area. Its construction was completed in 1979 (Sellin B. and Simonkovich, 1982). It has a maximum depth of 34 m and a dam of 7.5 km long. The water reservoir is 630 million m3 and an area of 69 km2 . It is used to generate electricity. Taabo- village is 0.5

km far from the lake (Figure 1). This study area includes 3 929 inhabitants from the database collected in 2009 by the Demographic Surveillance System of Taabo (SSD).

## **2.2. Parasitological surveys**

From the list of the two primary schools of the study site, a school was chosen according to the largest number of students. In the selected school, about 60 students at the rate of 10 per classroom from the first year of the primary (CP1) to the last year (CM2) were selected by lottery for the baseline survey and the second survey. Participation in the study was volun‐

tary. Parents or guardians of selected children were invited to sign a written informed con‐ sent after explanation of the objective of the study and procedures by investigators.

**Figure 1.** Overview of the study area

the different vegetation types encountered in this country. Parasitological monitoring con‐ ducted, in such eco-epidemiological context, for two consecutive years of annual mass treat‐ ment revealed a high prevalence of urinary schistosomiasis among school children. Prevalence ranged from 94% to 74% at the beginning to the end (N'Goran et al., 2001). More‐ over, the evaluation of reinfection of *Schistosoma haematobium* in various eco-epidemiological systems has shown that it is faster in the context of large dams. The high prevalence and limited reductions after mass treatments could be explained by the almost continuous trans‐

The example of Taabo-village located near the large dam Taabo where urinary schistosomia‐ sis is a real public health problem is remarkable (N'Goran et al., 1997 and 2001). Given the importance of this disease at Taabo-village, which approach control could put important pressure on large and sustained transmission of *S. haematobium* and hope to significantly re‐

In this perspective, a preventive approach and the fight against disease caused by schis‐ tosomiasis and soil-transmitted helminthiasis as recommended by the World Health Or‐ ganization (WHO, 2003, 2004 a and 2004b) were implemented. We believe that the communication for behavior change associated with the ongoing management could al‐ low a significant decrease in the prevalence and morbidity of these diseases. To do so, parasitological surveys were conducted in schools before and after a control action to as‐ sess the epidemiological situation. Then, teachers and Community Health Workers (AUC) were trained to educate and support consistently the population. Finally, sociolog‐ ical surveys were conducted to determine the perceptions and human factors in risk as‐

The Taabo dam is located in south-center of Côte d'Ivoire, on the river Bandama in degrad‐ ed forest area. Its construction was completed in 1979 (Sellin B. and Simonkovich, 1982). It has a maximum depth of 34 m and a dam of 7.5 km long. The water reservoir is 630 million

km far from the lake (Figure 1). This study area includes 3 929 inhabitants from the database

From the list of the two primary schools of the study site, a school was chosen according to the largest number of students. In the selected school, about 60 students at the rate of 10 per classroom from the first year of the primary (CP1) to the last year (CM2) were selected by lottery for the baseline survey and the second survey. Participation in the study was volun‐

collected in 2009 by the Demographic Surveillance System of Taabo (SSD).

. It is used to generate electricity. Taabo- village is 0.5

mission of this parasite (N'Goran et al., 2001; N'Guessan et al., 2007).

duce the morbidity due to urinary schistosomiasis?

sociated with the endemicity of these diseases.

**2. Methods**

50 Parasitic Diseases - Schistosomiasis

**2.1. Study area**

and an area of 69 km2

**2.2. Parasitological surveys**

m3

The selected school children participated in parasitological surveys conducted in April 2008 before treatment and on May 2009 after one year. In 2008 as in 2009, each student gave a urine sample and a stool sample. These samples were taken between 10 a.m and 2 p.m.

The search for eggs of *Schistosoma haematobium* in each urine sample was performed by the standard filtration of 10 ml of urine on a filter Nytrel ®, then the analysis of the filter under a microscope after coloration with lugol (Plouvier et al., 1975). The eggs of *Schistosoma hae‐ matobium* were identified and counted.

The stools were examined by the Kato-Katz technique, which involved analysis of 41.7 mg of stool under a microscope after plating and clarification by malachite green (Katz et al., 1972). The readings of the slides were made after 30 to 60 min for clarification in order to observe hookworms in addition to other helminths. The eggs of *Schistosoma mansoni* and soil-transmitted helminths (*Ancylostoma spp*, *Ascaris lumbricoides* and *Trichuris trichiura*) were detected and counted by species. The intensity of infection was expressed as number of eggs per gram of stool. After microscopic examination, a quality control was used to check the consistency of results. Prevalences and intensities of parasites were classified into three categories: mild, moderate and heavy according to WHO classi‐ fication (WHO, 2004 and 2004a).

**2.6. Data analysis**

**3. Results**

survey have been analised by the same test.

schistosomiasis is the main parasite of Taabo-village.

32.9% were treated against 8.2% in the village.

The data were analyzed using STATA software, version 9 (Stata Cooperation, College Sta‐ tion, Tx, USA). The various parasites were collected in two groups of diseases: schistosomia‐ sis and soil-transmitted helminthiasis. For each condition, the prevalences and intensities of infection were calculated for each survey. the 2008 data were compared with those of 2009 by comparison test of two proportions unrelated. The treatement results of the sociological

Community-Based Control of Schistosomiasis and Soil-Transmitted Helminthiasis in the Epidemiological Context...

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53

Both parasitological surveys were conducted in Taabo-village 1 primary school, successively in 2008 and 2009. The age group of school children who participated in the survey is be‐ tween 6 and 15 years. The urine and feces analyzes of 114 school children have identified 62 (54.4%) school children infected. Among schoolchildren examined, 42.1% are infected with schistosomes and soil-transmitted helminths by 28.9% (Table 1). At the baseline, 37.5% of school children were carriers of at least one parasite against 70.1% a year later. The school children infected in the second survey appeared to be significantly (*P* < 0.0001) more numer‐ ous than those of the baseline survey, regarding schistosomiasis (*P* <0.0001). For soil-trans‐ mitted helminths difference is not significantly (*P* = 0.131). Considering prevalence of the parasitic species, *Schistosoma haematobium* attained 41.2% as judged by urine analysis, and *Ancylostoma spp*. (27.2%) excreted in the feces. *Trichuris trichiura* (2.6%) and *Schistosoma man‐ soni* (0.9%) were rarely observed following stool analyses. Based on prevalence, urinary

The intensities of infections reported in Table 2, indicate that whatever the year, the majority of the population is infected with schistosomes i.e more than 75% have a mild infection (<50 eggs in 10 ml of urine for *S. haematobium* and <100 eggs in 1 g of stool for *S. mansoni*) (WHO, 2004). Heavy infections (≥ 50 eggs in 10 ml of urine for *S. haematobium* and ≥ 400 eggs in 1 g of stool for *S. mansoni*) appear to be solely due to *S. haematobium*. As for those who are infect‐ ed by soil-transmitted helminths, they all have a mild infection (Table 2). It is of note that the

Awareness, prevention and treatment were made by two teachers from the school age popu‐ lation and a community health worker (CHW) to other members of the community. In the general population of Taabo-village, the number of infected individuals is estimated at 70% and yet only 12% were treated between 2008 and 2009 (Table 3). This low rate indicates that there was no enthusiasm in general; however it was more encouraging in schools where

The sociological survey involved 176 people including 78 school-age children and 98 adults. The quantitative information reported in Table 4 indicate that schistosomiasis and soil are considered as diseases by over 65% of respondents. However, the majority states that these parasites do not have serious consequences on their health and more than 95% confirms that

intensities of infection of these parasites remained invariant after treatment.

## **2.3. Training of teachers and community health workers (CHW) for awareness and treatment**

During a workshop held in 2008 at Taabo city, two teachers and one community health worker (CHW), selected per locality and by their authorities, attended a course of half a day. They were trained to use the awareness tools and prevention on the one hand and on the other hand administration of praziquantel against schistosomiasis and mebendazole against soil-transmitted helminthiasis. Then they received the tablets, treatment forms and media for awareness and health education.

#### **2.4. Awareness and treatment**

The awareness, prevention and control studies were conducted in the two primary schools by two teachers among the school-age populations and by a CHW among the other community members. Everyone was aware of the opportunity to treat himself ac‐ cording to his convenience because drugs were available to them from teachers and CHW. Treatment (praziquantel and mebendazole) cost per student was 100 CFA francs in schools and 150 CFA in community during the first year. At the end of the study, all parasitized individuals were treated with praziquantel and/or mebendazole for free for ethical reasons.

#### **2.5. Sociological survey**

The sociological survey concerned on the one hand the school-age children (children attend‐ ing school or not) and on the other hand the general population, particularly the heads of households. The selection of children attending school was done by a reasoned choice of 12 students per class from the first year elementary classes (CE1) to the last year of primary school (CM2). As for children who do not attend school, they have been chosen unintention‐ ally on the ground during the investigation. Based on the estimated number of households, the quota of households to be interviewed has been determined. This survey was made after the awareness and treatment. The majority of respondents are farmers and students, the sur‐ vey took place when they were free i.e in the morning (from 6:00 to 10:00) and in the eve‐ ning (from 16:00 to 20:00). We collected qualitative information from focus group and quantitative information by questionnaire.

#### **2.6. Data analysis**

et al., 1972). The readings of the slides were made after 30 to 60 min for clarification in order to observe hookworms in addition to other helminths. The eggs of *Schistosoma mansoni* and soil-transmitted helminths (*Ancylostoma spp*, *Ascaris lumbricoides* and *Trichuris trichiura*) were detected and counted by species. The intensity of infection was expressed as number of eggs per gram of stool. After microscopic examination, a quality control was used to check the consistency of results. Prevalences and intensities of parasites were classified into three categories: mild, moderate and heavy according to WHO classi‐

**2.3. Training of teachers and community health workers (CHW) for awareness and**

During a workshop held in 2008 at Taabo city, two teachers and one community health worker (CHW), selected per locality and by their authorities, attended a course of half a day. They were trained to use the awareness tools and prevention on the one hand and on the other hand administration of praziquantel against schistosomiasis and mebendazole against soil-transmitted helminthiasis. Then they received the tablets, treatment forms and media

The awareness, prevention and control studies were conducted in the two primary schools by two teachers among the school-age populations and by a CHW among the other community members. Everyone was aware of the opportunity to treat himself ac‐ cording to his convenience because drugs were available to them from teachers and CHW. Treatment (praziquantel and mebendazole) cost per student was 100 CFA francs in schools and 150 CFA in community during the first year. At the end of the study, all parasitized individuals were treated with praziquantel and/or mebendazole for free for

The sociological survey concerned on the one hand the school-age children (children attend‐ ing school or not) and on the other hand the general population, particularly the heads of households. The selection of children attending school was done by a reasoned choice of 12 students per class from the first year elementary classes (CE1) to the last year of primary school (CM2). As for children who do not attend school, they have been chosen unintention‐ ally on the ground during the investigation. Based on the estimated number of households, the quota of households to be interviewed has been determined. This survey was made after the awareness and treatment. The majority of respondents are farmers and students, the sur‐ vey took place when they were free i.e in the morning (from 6:00 to 10:00) and in the eve‐ ning (from 16:00 to 20:00). We collected qualitative information from focus group and

fication (WHO, 2004 and 2004a).

52 Parasitic Diseases - Schistosomiasis

for awareness and health education.

**2.4. Awareness and treatment**

ethical reasons.

**2.5. Sociological survey**

quantitative information by questionnaire.

**treatment**

The data were analyzed using STATA software, version 9 (Stata Cooperation, College Sta‐ tion, Tx, USA). The various parasites were collected in two groups of diseases: schistosomia‐ sis and soil-transmitted helminthiasis. For each condition, the prevalences and intensities of infection were calculated for each survey. the 2008 data were compared with those of 2009 by comparison test of two proportions unrelated. The treatement results of the sociological survey have been analised by the same test.

## **3. Results**

Both parasitological surveys were conducted in Taabo-village 1 primary school, successively in 2008 and 2009. The age group of school children who participated in the survey is be‐ tween 6 and 15 years. The urine and feces analyzes of 114 school children have identified 62 (54.4%) school children infected. Among schoolchildren examined, 42.1% are infected with schistosomes and soil-transmitted helminths by 28.9% (Table 1). At the baseline, 37.5% of school children were carriers of at least one parasite against 70.1% a year later. The school children infected in the second survey appeared to be significantly (*P* < 0.0001) more numer‐ ous than those of the baseline survey, regarding schistosomiasis (*P* <0.0001). For soil-trans‐ mitted helminths difference is not significantly (*P* = 0.131). Considering prevalence of the parasitic species, *Schistosoma haematobium* attained 41.2% as judged by urine analysis, and *Ancylostoma spp*. (27.2%) excreted in the feces. *Trichuris trichiura* (2.6%) and *Schistosoma man‐ soni* (0.9%) were rarely observed following stool analyses. Based on prevalence, urinary schistosomiasis is the main parasite of Taabo-village.

The intensities of infections reported in Table 2, indicate that whatever the year, the majority of the population is infected with schistosomes i.e more than 75% have a mild infection (<50 eggs in 10 ml of urine for *S. haematobium* and <100 eggs in 1 g of stool for *S. mansoni*) (WHO, 2004). Heavy infections (≥ 50 eggs in 10 ml of urine for *S. haematobium* and ≥ 400 eggs in 1 g of stool for *S. mansoni*) appear to be solely due to *S. haematobium*. As for those who are infect‐ ed by soil-transmitted helminths, they all have a mild infection (Table 2). It is of note that the intensities of infection of these parasites remained invariant after treatment.

Awareness, prevention and treatment were made by two teachers from the school age popu‐ lation and a community health worker (CHW) to other members of the community. In the general population of Taabo-village, the number of infected individuals is estimated at 70% and yet only 12% were treated between 2008 and 2009 (Table 3). This low rate indicates that there was no enthusiasm in general; however it was more encouraging in schools where 32.9% were treated against 8.2% in the village.

The sociological survey involved 176 people including 78 school-age children and 98 adults. The quantitative information reported in Table 4 indicate that schistosomiasis and soil are considered as diseases by over 65% of respondents. However, the majority states that these parasites do not have serious consequences on their health and more than 95% confirms that they are not dreadful. The concept of illness and fear is determined by a set of characters which are: immobility, pain, costly treatment, lack of effective remedy, contagiousness, disa‐ bility, lack of knowledge of symptoms and rapid death. To fight against the parasites, the most common practice (19.4%) is the association of pharmaceutical products and plants. In the control project against the diseases in question, the community generally wants to or‐ ganize neighborhood with awareness as major roles (35.7%) and environmental health (18.4%). According to the qualitative data, people think that these ailments do not require treatment because they are supposed to heal over time. Also they do not know the mode of contamination which they think would be done by drinking dirty water from the lake, span‐ ning the urine of a schistosomiasis patient, or by bathing in the lake water.

**Schistosomiasis** Soil-transmitted helminths

in south-center of Côte d'Ivoire

coffee and cocoa.

**Knowledge of diseases**

soil-transmitted helminths

Schistosomiasis

**Light infection** 76.9 77.1 100 100 **High infection** 23.1 22.9 0 0

**Population**

**Reactions et reponses to**

**Communities attitudes** Non dreadful schistosomiasis 168 95.5

**questions**

Attending school 598 197 32.97 Not attending school 3 331 275 8.25 Total 3 929 472 12.01

**Table 3.** Percentage of treated population to Taabo-village of 2008 – 2009

**Table 2.** Percentages of intensities of schistosomiasis infection and soil-transmitted helminths in the Taabo lake dam

They use water from Lake dam for all daily activities including laundry, washing dishes, cooking, bathing, swimming and even sometimes for drinking when drinking water is inac‐ cessible. Fishing takes place in the lake, and the water is also used to irrigate nurseries of

> Know 128 72.7 Do not Know 48 27.3 Serious 39 22.2 Less serious 137 77.8

> Know 115 65.3 Do not Know 61 34.7 Serious 55 31.2 Less serious 121 68.8

Dreadful schistosomiasis 8 4.5

Infection intensities (%) in years

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55

**2008 2009 2008 2009**

Community-Based Control of Schistosomiasis and Soil-Transmitted Helminthiasis in the Epidemiological Context...

**Workforces Treated Treated Percentage**

**Workforces** Percentages


**Table 1.** Prevalence of schistosomiasis and soil-transmitted helminths before (2008) and after deworming (2009) in Taabo lake dam in south-center of Côte d'Ivoire

Community-Based Control of Schistosomiasis and Soil-Transmitted Helminthiasis in the Epidemiological Context... http://dx.doi.org/10.5772/53494 55


**Table 2.** Percentages of intensities of schistosomiasis infection and soil-transmitted helminths in the Taabo lake dam in south-center of Côte d'Ivoire


**Table 3.** Percentage of treated population to Taabo-village of 2008 – 2009

they are not dreadful. The concept of illness and fear is determined by a set of characters which are: immobility, pain, costly treatment, lack of effective remedy, contagiousness, disa‐ bility, lack of knowledge of symptoms and rapid death. To fight against the parasites, the most common practice (19.4%) is the association of pharmaceutical products and plants. In the control project against the diseases in question, the community generally wants to or‐ ganize neighborhood with awareness as major roles (35.7%) and environmental health (18.4%). According to the qualitative data, people think that these ailments do not require treatment because they are supposed to heal over time. Also they do not know the mode of contamination which they think would be done by drinking dirty water from the lake, span‐

**Taabo-village 1 TOTAL**

**2008 2009**

ning the urine of a schistosomiasis patient, or by bathing in the lake water.

Number of subjects examined 56 58 114 Number of parasitized individuals 21 41 62 Prevalence % 37.5 70.1 54.4

Number of parasitized individuals 13 35 48 Prevalence (%) 23.2 60.3 42.1

Number of parasitized individuals 12 35 47 Prevalence (%) 21.4 60.3 41.2

Number of parasitized individuals 1 0 1 Prevalence (%) 1.8 0 0.9

Number of parasitized individuals 13 20 33 Prevalence (%) 23.2 34.4 28.9

Number of parasitized individuals 13 18 31 Prevalence (%) 23.2 31.0 27.2

Number of parasitized individuals 0 3 3 Prevalence (%) 0 5.1 2.6

**Table 1.** Prevalence of schistosomiasis and soil-transmitted helminths before (2008) and after deworming (2009) in

**Schistosomiasis**

54 Parasitic Diseases - Schistosomiasis

*S. haematobium*

*S. mansoni*

Soil-transmitted helminths

Taabo lake dam in south-center of Côte d'Ivoire

*Ancylostoma spp.*

*T.trichiura*

They use water from Lake dam for all daily activities including laundry, washing dishes, cooking, bathing, swimming and even sometimes for drinking when drinking water is inac‐ cessible. Fishing takes place in the lake, and the water is also used to irrigate nurseries of coffee and cocoa.



we made another sample because we adopted a population-based approach to see how the home would evolve in real conditions when the population was aware and had medicines at their disposal. On the contrary, this result reveals that the treatment did not have a great influence on morbidity indicators such as the prevalence and intensity of infection. It is explained by the fact that only 12% of the population was treated. Thus, for the treatments have a significant impact, they must extend at least 75% of the school age population and for a long-term as recommended by the WHO (2012). Based on the categories of prevalences and intensities of infection, we offer an annual treate‐ ment of the entire community with praziquantel in the case of schistosomiasis. As for soil-transmitted helminthiasis, albendazole may also be distributed once a year. Howev‐ er, all children of preschool and school age and women of childbearing age and adults at risk should be given priority in accordance with the recommendations of the WHO (WHO, 2004.9; 2010.3). For ongoing management, it would be appropriate after the an‐ nual mass distribution campaign to,make anthelmintics available to the public through

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It should be noted that while anthelmintics were made available to the Taabo village's population, very few people were treated. There was no enthusiasm for the treatment for the simple reason that these parasites are considered by the majority of the popula‐ tion as non-serious illnesses and less dreadful. For this population it is not necessary to observe measures of prevention and fight as they think diseases are supposed to heal over time. We think that these perceptions are a major obstacle to control actions by che‐

To develop an appropriate approach of prevention, we must attract the attention of the pop‐ ulation through advocacy and health education as suggested by Monday (Useh, 2012). This awareness action and the population's education aim to significantly alter his perception of the severity of these infections, the effectiveness of existing treatments anthelmintics and the risk behaviors. Emphasis will be placed on the causes of the outbreak of schistosomiasis, the consequences associated with schistosomiasis and soil-transmitted to the modes of transmis‐ sion of these parasites and the importance of seeking treatment for infections. However, awareness sessions will be done with the involvement of opinion leaders such as religious and customary authorities and groups of associations. Awareness must be held at school in the village, in places of worship and preferably on Sunday, which is the market day or the gathering of this farming population. These control actions will take place between Decem‐

Instead of preventing people from visiting the lake shore, we suggest people to collect water for their domestic activities early in the morning i.e before 10 am or in afternoon after 2:00 p.m. The interval between 10 am and 2 p.m corresponds to the maximum period of cercariae emission in water during which people would better avoid attending it. Moreover, the au‐ thorities should ensure that drinking water is accessible and that latrines are available. To reduce transmission, we recommend people not to urinate and defecate in the lake or to def‐

the channels of teachers and community health worker.

ber and February which is the rest period for farmers.

ecate far away from the lake.

motherapy.

**Table 4.** Results of sociological surveys conducted in Taabo-village community near the dam Taabo in south-center of Côte d'Ivoire.

## **4. Discussion**

Parasitic diseases highlighted in the locality of the Taabo-village are schistosomiasis and hookworm. Schistosomiasis was the predominant parasitosis. It was followed by ankylosto‐ somiasis. This classification is different from the distribution observed in Africa south of the Sahara where ankytosmosomiasis is top of the list (Hotez et Kamath, 2009). The prevalence of these parasitoses are moderate overall. However, a high prevalence of *Schistosoma haema‐ tobium* in the order of 60% was recorded at the end of the study in 2009 where no case of *S. mansoni* infection was observed. The study area is an environment with a high prevalence of urinary schistosomiasis as already reported by N'Goran and colleagues more than 20 years ago (N'Goran et al., 1987).

The high prevalence of 60.3% recorded only a year later, does not demonstrate that rein‐ fection is fast because we have not reviewed all of the students selected in 2008. Rather we made another sample because we adopted a population-based approach to see how the home would evolve in real conditions when the population was aware and had medicines at their disposal. On the contrary, this result reveals that the treatment did not have a great influence on morbidity indicators such as the prevalence and intensity of infection. It is explained by the fact that only 12% of the population was treated. Thus, for the treatments have a significant impact, they must extend at least 75% of the school age population and for a long-term as recommended by the WHO (2012). Based on the categories of prevalences and intensities of infection, we offer an annual treate‐ ment of the entire community with praziquantel in the case of schistosomiasis. As for soil-transmitted helminthiasis, albendazole may also be distributed once a year. Howev‐ er, all children of preschool and school age and women of childbearing age and adults at risk should be given priority in accordance with the recommendations of the WHO (WHO, 2004.9; 2010.3). For ongoing management, it would be appropriate after the an‐ nual mass distribution campaign to,make anthelmintics available to the public through the channels of teachers and community health worker.

**Reactions et reponses to**

Dreadful soil-transmitted

**Practices in communities** None 2 2.1

**Control Project** By neighborhood 57 58.1

**Role in participation** Decision making 10 10.2

Côte d'Ivoire.

**4. Discussion**

ago (N'Goran et al., 1987).

Never infected 61 62.2 Pharmaceutical products 10 10.2 Medicinal Plants 6 6.1 Pharmaceutical products + Plants 19 19.4

Combination 2 2.1 Gender 9 9.2 No answer 30 30.6

Environmental health 18 18.4 Awareness 35 35.7 Supervision 5 5.1 No answer 30 30.6

**Table 4.** Results of sociological surveys conducted in Taabo-village community near the dam Taabo in south-center of

Parasitic diseases highlighted in the locality of the Taabo-village are schistosomiasis and hookworm. Schistosomiasis was the predominant parasitosis. It was followed by ankylosto‐ somiasis. This classification is different from the distribution observed in Africa south of the Sahara where ankytosmosomiasis is top of the list (Hotez et Kamath, 2009). The prevalence of these parasitoses are moderate overall. However, a high prevalence of *Schistosoma haema‐ tobium* in the order of 60% was recorded at the end of the study in 2009 where no case of *S. mansoni* infection was observed. The study area is an environment with a high prevalence of urinary schistosomiasis as already reported by N'Goran and colleagues more than 20 years

The high prevalence of 60.3% recorded only a year later, does not demonstrate that rein‐ fection is fast because we have not reviewed all of the students selected in 2008. Rather

Non dreadful soil-transmitted

**Workforces** Percentages

172 97.7

4 2.3

**questions**

56 Parasitic Diseases - Schistosomiasis

helminthes

helminthes

It should be noted that while anthelmintics were made available to the Taabo village's population, very few people were treated. There was no enthusiasm for the treatment for the simple reason that these parasites are considered by the majority of the popula‐ tion as non-serious illnesses and less dreadful. For this population it is not necessary to observe measures of prevention and fight as they think diseases are supposed to heal over time. We think that these perceptions are a major obstacle to control actions by che‐ motherapy.

To develop an appropriate approach of prevention, we must attract the attention of the pop‐ ulation through advocacy and health education as suggested by Monday (Useh, 2012). This awareness action and the population's education aim to significantly alter his perception of the severity of these infections, the effectiveness of existing treatments anthelmintics and the risk behaviors. Emphasis will be placed on the causes of the outbreak of schistosomiasis, the consequences associated with schistosomiasis and soil-transmitted to the modes of transmis‐ sion of these parasites and the importance of seeking treatment for infections. However, awareness sessions will be done with the involvement of opinion leaders such as religious and customary authorities and groups of associations. Awareness must be held at school in the village, in places of worship and preferably on Sunday, which is the market day or the gathering of this farming population. These control actions will take place between Decem‐ ber and February which is the rest period for farmers.

Instead of preventing people from visiting the lake shore, we suggest people to collect water for their domestic activities early in the morning i.e before 10 am or in afternoon after 2:00 p.m. The interval between 10 am and 2 p.m corresponds to the maximum period of cercariae emission in water during which people would better avoid attending it. Moreover, the au‐ thorities should ensure that drinking water is accessible and that latrines are available. To reduce transmission, we recommend people not to urinate and defecate in the lake or to def‐ ecate far away from the lake.

It must be noted that the relatively low percentage of 23.2% of schistosomiasis, recorded at the beginning of the study has not yet been determined in this locality to our knowledge. This level of prevalence could be explained by the previous effect of control actions. We can mention as examples the mass treatment against schistosomiasis conducted in five primary schools around the dam of Taabo and in hyperendemic primary school of Tiassalé's district that Taabo-village is part of it (N'Goran et al., 1997 and 1998). In addition, control activities are performed in Taabo-village for only about a decade (Esse, 1997; N'Goran et al., 1997, 2001 and 2003). This is also probably the reason why the intensities of infection were mostly minor. Morbidity is less severe in the population examined. Indeed, the population exam‐ ined would be concerned because it is often affected by the programs against schistosomia‐ sis and soil-transmitted helminthiasis. It could be that the category of population such as adultes that do not fall often in programs against these infections have more severe lesions. This was noted by Keita et al. Mali (Keita et al., 2009).

**Author details**

**References**

e412.

6:817-825.

de São Paulo 14:397-400.

978-953-307-852-6. DUI:10.5772/25326

Coast. Bull World Health Org 75:541-545.

Tropical Medicine and Hygiene 68 (1): 24-32.

Nicaise Aya N'Guessan 1

N'Goran Kouakou Eliézer1

, Orsot Niangoran Mathieu1

2 Faculty of Communication Environment and Society, University of Bouaké, Côte d'Ivoire

Community-Based Control of Schistosomiasis and Soil-Transmitted Helminthiasis in the Epidemiological Context...

[1] Doumenge JP, Mott KE, Cheung C, Villenave D, Chapuis O, et al. (1987). Atlas of the global distribution of schistosomiasis. World Health Organization, Geneva: 16:398. [2] Esse AMC. (1997). The impact of hydroelectric dams on the health of local popula‐ tions: the case of urinary schistosomiasis in the region Taabo. Master's thesis, Science

[3] Hotez PJ & Kamath A (2009). Neglected tropical diseases in Sub-Sahara Africa: Re‐ view of Their prevalence, distribution and disease burden. PLoS Negl Trop Dis, 3,

[4] Katz N, Chaves A, Pellegrino JA (1972). Simple device for quantitative stool thicksmear in Schistosomiasis mansoni. technical. Revista do Instituto Medicina Tropical

[5] Keita AD, Sacko M, Coulibaly SY, et al. (2009). Imaging of urological tumors in an

[6] Useh MF (2012). Control of schistosomiasis in Schistosomiasis, In-Tech, ISBN :

[7] N'Goran EK, Diabaté S, Utzinger J, Sellin B (1997). Changes in human schistosomia‐ sis Levels the after the Construction of Two hydroelectric dams in wide central Ivory

[8] N'Goran EK, Utzinger J, Gnaka HN, Yapi A, N'Guessan NA, Kigbafori SD et al. (2003). Randomized, double-blind, placebo-controlled trial of oral artemether for the prevention of patent Schistosoma haematobium infections. American Journal of

[9] N'Goran EK, Utzinger J, N'Guessan NA, Muller I, K Zamble et al. (2001). Reinfection with Schistosoma haematobium following school-based chemotherapy with prazi‐ quantel in endemic villages in oven Highly Ivory Coast. Trop Med Int Health

of Man and Society, University of Cocody, Abidjan, Ivory Coast. 30p

endemic area of schistosomiasis in Mali. J. Afr. Cancer 1:135-140.

\*Address all correspondence to: nicaisayan@yahoo.fr

1 UFR Biosciences, University of Cocody-Abidjan, Côte d'Ivoire

, Abé N'Doumi Noël2

and

http://dx.doi.org/10.5772/53494

59

The prevention and control proposed above should extend at least 75% of the school age population and make long-term as recommended by the WHO (2012). We propose to this end a period of at least five years.

## **5. Conclusion**

The results of this study allow us to identify an approach for prevention and sustainable fight against schistosomiasis and soil-transmitted helminthiasis in the context of a large dam in Côte-d'Ivoire. It is partly based on the awareness of the population in order to change significantly their perception of the seriousness of these infections and the effec‐ tiveness of existing anthelmintics treatments. On the other hand, the population will change habits in relation to periods of attendance at the lake and the discharge of excre‐ ment in the water. This fight will be the responsibility of community and must be sus‐ tained for a long term This community approach of prevention and control proposed at the end of our study is most applicable in the context of eco-epidemiological of large dams, where soil-transmitted helminthiasis and schistosomiasis are generally a serious, but neglected, public health problem.

## **Acknowledgements**

We specially acknowledge the Agence Universitaire de la Francophonie (AUF), which fund‐ ed the research. The authors wish to thank Mr TP Gonety, Taabo Hospital Director and Dr. L. Adiossan the chief doctor of the said hospital for treatments supervision. We acknowl‐ edge inspector of primary teaching, principals and teachers of Taabo-village and the Head of this locality. We also acknowledge the laboratory technicians, KL Lohourignon, M. Traore, S. Diabaté, A.S. Brou, J. Brou, S. Kouadio, M. N'Cho, N. Kouadio and MG Gry for the quality of the work they have done and Mr Zahoui André for the translation from English.

## **Author details**

It must be noted that the relatively low percentage of 23.2% of schistosomiasis, recorded at the beginning of the study has not yet been determined in this locality to our knowledge. This level of prevalence could be explained by the previous effect of control actions. We can mention as examples the mass treatment against schistosomiasis conducted in five primary schools around the dam of Taabo and in hyperendemic primary school of Tiassalé's district that Taabo-village is part of it (N'Goran et al., 1997 and 1998). In addition, control activities are performed in Taabo-village for only about a decade (Esse, 1997; N'Goran et al., 1997, 2001 and 2003). This is also probably the reason why the intensities of infection were mostly minor. Morbidity is less severe in the population examined. Indeed, the population exam‐ ined would be concerned because it is often affected by the programs against schistosomia‐ sis and soil-transmitted helminthiasis. It could be that the category of population such as adultes that do not fall often in programs against these infections have more severe lesions.

The prevention and control proposed above should extend at least 75% of the school age population and make long-term as recommended by the WHO (2012). We propose to this

The results of this study allow us to identify an approach for prevention and sustainable fight against schistosomiasis and soil-transmitted helminthiasis in the context of a large dam in Côte-d'Ivoire. It is partly based on the awareness of the population in order to change significantly their perception of the seriousness of these infections and the effec‐ tiveness of existing anthelmintics treatments. On the other hand, the population will change habits in relation to periods of attendance at the lake and the discharge of excre‐ ment in the water. This fight will be the responsibility of community and must be sus‐ tained for a long term This community approach of prevention and control proposed at the end of our study is most applicable in the context of eco-epidemiological of large dams, where soil-transmitted helminthiasis and schistosomiasis are generally a serious,

We specially acknowledge the Agence Universitaire de la Francophonie (AUF), which fund‐ ed the research. The authors wish to thank Mr TP Gonety, Taabo Hospital Director and Dr. L. Adiossan the chief doctor of the said hospital for treatments supervision. We acknowl‐ edge inspector of primary teaching, principals and teachers of Taabo-village and the Head of this locality. We also acknowledge the laboratory technicians, KL Lohourignon, M. Traore, S. Diabaté, A.S. Brou, J. Brou, S. Kouadio, M. N'Cho, N. Kouadio and MG Gry for the quality of the work they have done and Mr Zahoui André for the translation from English.

This was noted by Keita et al. Mali (Keita et al., 2009).

end a period of at least five years.

but neglected, public health problem.

**Acknowledgements**

**5. Conclusion**

58 Parasitic Diseases - Schistosomiasis

Nicaise Aya N'Guessan 1 , Orsot Niangoran Mathieu1 , Abé N'Doumi Noël2 and N'Goran Kouakou Eliézer1


## **References**


[10] N'Goran KE, Utzinger J, Traore M, Lengeler C & Tanner M (1998). Rapid identifica‐ tion by questionnaire of the main foci of urinary bilharziasis in central Ivory Coast. Med Trop 58, 253-260. 25.

[24] Plouvier S, Leroy JC, Colette J (1975). About a simple filtration of urine in the diagno‐

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[25] Raso G, Matthys B, N'Goran EK, Tanner M, Vounatsou P and Utzinger J (2005). Spa‐ tial risk Prediction and mapping of Schistosoma mansoni infections among school

[26] Sellin B and Simonkovich E (1982). Schistosomiasis and dams in Côte d'Ivoire. In : From epidemiology to human geography. Works Tropical and Geographical Papers

[27] Steinmann P, Keiser J, Bos R, Tanner M, Utzinger J (2006). Schistosomiasis and water resources development: systematic review, meta-analysis, and estimates of people at

[28] Utzinger J, N'Goran EK, Ossey YA, Booth M, Traore M et al. (2000). Rapid screening for Schistosoma mansoni in western Côte d'Ivoire using a simple school question‐

sis of urinary schistosomiasis in mass survey. Med Trop 35:229-230.

children living in western Côte d'Ivoire. Parasitology 131:97-108.

48:209-214.

risk. Infection.thelancet.com 6:411-425.

naire. Bull World Health Org 78 (3):389-397.


[24] Plouvier S, Leroy JC, Colette J (1975). About a simple filtration of urine in the diagno‐ sis of urinary schistosomiasis in mass survey. Med Trop 35:229-230.

[10] N'Goran KE, Utzinger J, Traore M, Lengeler C & Tanner M (1998). Rapid identifica‐ tion by questionnaire of the main foci of urinary bilharziasis in central Ivory Coast.

[11] N'Guessan AN (2003). The fight against schistosomiasis in Côte d'Ivoire : epidemio‐ logical factors of complexity and control operational constraints. Thesis, University

[12] N'Guessan NA, Acka CA, Utzinger J, N'goran EK (2007). Identification of high risk regions of schistosomiasis in Ivory Coast. Bull Soc Pathol Exot 100(2):119-123.

[13] World Health Organization (2000). Ultrasound in schistosomiasis. A practical guide to the use of ultrasonography standardized for the assessment of schistosomiasis-re‐

[14] World Health Organization (2001). Schistosoiasis and geohelminthiasis. 19th session of the 54th World health assembly. http://www.who.int/mediacenter/factscheets/

[15] World Health Organization (2003). Act against worms, Bull PPC, World Health Or‐

[16] World Health Organization (2004). Act against worms, Bull PPC, World Health Or‐

[17] World Health Organization (2004a). Fight against helminth infections among school age children. Guide for managers of control programs. World Health Organization,

[18] World Health Organization (2004b). Prevention and control of schistosomiasis and soil-transmitted helminthiasis. Report of a WHO expert committee. WHO Technical

[19] World Health Organization, UNICEF (2004.9). Schistosomiasis and soil-transmitted helminthiasis: Action of prevention and control of 16/09/2012 (whqlibdoc.who.int/hq/

[20] World Health Organization (2008a). Act against worms. Bull PPC, World Health Or‐

[21] World Health Organization, UNICEF (2010.3). Communicable disease epidemiologi‐ cal profile Côte d'Ivoire. (2010.3 whqlibdoc.who.int/hq/2010/WHO\_HSE\_GAR\_DCE\_

[22] World Health Organization (2011). Schistosomiasis. Number of people treated, 2009.

[23] World Health Organization (2012). Geohelminthiasis. Reminder N°366 of 19/8/2012

Med Trop 58, 253-260. 25.

fs366/fr/

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Geneva.

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eng.pdf)

of Cocody in Abidjan, Ivory Coast.

lated morbidity. WHO, document TDR/STR/SCH/00.1

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2004/WHO\_CDS\_CPE\_PVC\_2004.9\_fre.pdf)

Weekly Epidemiological Record 9, 86:73-80.

http://www.who.int/mediacenter/factscheets/fs366/fr/


**Chapter 4**

**Schistosomiasis**

Monday Francis Useh

http://dx.doi.org/10.5772/53553

**1. Introduction**

stages of schistosomes [3]:

some parts of Africa and

in Africa. These include:

Additional information is available at the end of the chapter

all parts of Nigeria although the former predominates [2].

schistosomiasis in Nigeria among other places in Africa.

disease in eastern, central and west Africa

Schistosomiasis is a chronic water-borne infection caused by digenetic trematodes that be‐ long to the genus *Schistosoma*. There are two main forms of the disease namely; urinary and intestinal schistosomiasis. The major aetiologic agents of the intestinal form are *Schistosoma mansoni* and *Schistosoma japonicum*. The less common species that have also been associated with intestinal disease are *Schistosoma mekongi*, *Schistosoma guineensis* and the related species *Schistosoma intercalatum. Schistosoma haematobium* is the only known agent of urogenital schistosomiasis [1]. *S. haematobium* and *S. mansoni* infections have been widely reported in

Schistosomiasis is transmitted by snails. Each of the species is transmitted by a snail of a different species. The intermediate host of *S. haematobium* is a fresh water snail be‐ longing to the genus *Bulinus*. It is a turreted snail with a left-handed opening when looked at with the spire upwards. Three main species are known to harbour the larval

**•** The Africanus group (sub-genus *Physopsis*) which are involved in the transmission of the

**•** The truncatus group (sub-genus *Bulinus)* which transmits infection in the near East and in

**•** The forskalli group. This group has been associated with the transmission of urinary

*S. mansoni* is transmitted by flattened planorbid snails belonging to the genus *Biomphalaria.* Four main groups have been associated with the transmission of intestinal schistosomiasis

and reproduction in any medium, provided the original work is properly cited.

© 2013 Useh; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

© 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution,

distribution, and reproduction in any medium, provided the original work is properly cited.

**Chapter 4**

## **Schistosomiasis**

Monday Francis Useh

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/53553

## **1. Introduction**

Schistosomiasis is a chronic water-borne infection caused by digenetic trematodes that be‐ long to the genus *Schistosoma*. There are two main forms of the disease namely; urinary and intestinal schistosomiasis. The major aetiologic agents of the intestinal form are *Schistosoma mansoni* and *Schistosoma japonicum*. The less common species that have also been associated with intestinal disease are *Schistosoma mekongi*, *Schistosoma guineensis* and the related species *Schistosoma intercalatum. Schistosoma haematobium* is the only known agent of urogenital schistosomiasis [1]. *S. haematobium* and *S. mansoni* infections have been widely reported in all parts of Nigeria although the former predominates [2].

Schistosomiasis is transmitted by snails. Each of the species is transmitted by a snail of a different species. The intermediate host of *S. haematobium* is a fresh water snail be‐ longing to the genus *Bulinus*. It is a turreted snail with a left-handed opening when looked at with the spire upwards. Three main species are known to harbour the larval stages of schistosomes [3]:


*S. mansoni* is transmitted by flattened planorbid snails belonging to the genus *Biomphalaria.* Four main groups have been associated with the transmission of intestinal schistosomiasis in Africa. These include:


a potential for resurgence exists [8]. About 120 million people infected with schistoso‐ miasis are estimated to be symptomatic while about 20 million develop severe disease. The disability adjusted life years due to schistosomiasis is about 1.7-4.5 million while between 150,000 to 280,000 people are known to die as a consequence of schistosomia‐ sis per year. Africa accounts for 85% of the disease burden [9,10]. Urinay schistosomia‐ sis has been reported in 38 countries in Africa. Annual mortality due to *S. haematobium* infection in east Africa has been estimated at 1 per 1000 infected adults [11]. In Malawi, Save the children's 1998 survey of schoolchildren in Mangochi found that the overall prevalence of schistosomiasis in coastal and upland schools was 36%. In some of the schools, the prevalence was as high as 87% [12]. In a related study in Cameroon, Mba and Useh [13] reported urinary schistosomiasis among 39.2% of the subjects studied. Mixed infection of *S. haematobium* and *S. mansoni* occurred in 4.5% of the subjects. The number of infected subjects treated for the disease using praziquantel rose for 12.4 mil‐ lion in 2006 to 33.5 million in 2010. It is estimated that 90% of those that require treat‐ ment live in Africa. This implies that over 60% of people suffering from schistosomiasis particularly in Africa are not able to procure treatment or have access to treatment due

Schistosomiasis

65

http://dx.doi.org/10.5772/53553

It is estimated that 30 million Nigerians are infected with schistosomiasis. When examined against a projected population of 162 million Nigerians, it becomes clear that over 18.5% of the populace have schistosomiasis. The problem becomes more glaring when the projected population of infected people is examined in terms of those who carry the greatest burden of the disease; in this case, school age children. About 23 years ago, Ejezie *et al* [2] published a major review entitled "the schistosomiasis problem in Nigeria" where they highlighted the embarrassing and increasing endemicity of schistosomiasis without any concrete plan for control. Not much has changed almost two and half decades after. In another landmark re‐ view on the "Nigerian environment and parasitic infections", Ejezie [14] noted that "a large proportion of the people consist of men and women who are ignorant of the rules of basic hygiene. These people are entrapped by the worst manifestations of poverty, worsened by infectious tropical diseases, malnutrition, high birth and death rate". They are, as it were, caught in the so-called vicious circle-"they are sick because they are poor, they become poor‐ er because they are sick and sicker because they are poorer" [15]. The problem seems to have grown worst. In the above publication, infection with *S. haematobium* was reported in all the regions in Nigeria with a prevalence as high as 60-75% among schoolchildren in some communities. The endemicity of *S mansoni* was also reported though not as wide spread as the former. Perhaps this report and others encouraged the government of Nigeria to consti‐ tute the 'National Schistosomiasis Control Committee". Regrettably, this Committee only existed on paper as funds were not made available to organize operational research to delin‐

The morbidity of schistosomiasis in Nigeria reflects what has been published for endemic countries in Africa and Asia. Infection predominates in schoolchildren aged between 5-19

to the relatively high cost of praziquantel.

**2.1. Schistosomiasis situation in Nigeria**

eate endemic communities for treatment.

**•** The Alexandrina group which occur sporadically in north, east and south Africa [3]

The intermediate host of *S. japonicum* are operculated snails that belongs to the genus *Oncomelania*. Important species such as *O. hupensis*, *O. nosophora*, *O. formosana* and *O. quadrasi* are involved in the transmission of infection in different areas of Asia where the infection predominates [3].

The role of water bodies in the transmission of infection cannot be over emphasized [4]. Such water bodies include fresh water streams, water accumulated as a consequence of con‐ struction of dams and irrigation projects and slow flowing or stagnant water. Although, the main courses of large rivers may not be associated with the transmission of schistosomiasis, but water sustained by them through seasonal flooding and impoundment may provide avenues for the sustenance of the snail intermediate host. Water also provides an opportuni‐ ty for the cercariae to survive and penetrate the definitive host. Humans are also pivotal in the transmission of schistosomiasis. Through insanitary disposal of urine or faeces, water bodies are contaminated with the eggs of schistosomes. Worldwide, 900 million people do not have access to an improved water source, while an estimated 2.5 billion, half of all peo‐ ple in developing countries lack access to adequate sanitation [5,6]. In rural and poor agri‐ cultural communities without pipe-borne water, the locals depend on cercariae infested streams for their economic and recreational needs thereby exposing themselves to infection.

The control of schistosomiasis involves an integrated process directed at the infected sub‐ jects, snail intermediate hosts, environmental modification, health education and the provi‐ sion of pipe-borne water [7]. In this review, the epidemiology, diagnosis and control of schistosomiasis is examined in details with notes on the factors impeding the control of the disease in Africa with inferences drawn from the Nigerian experience.

## **2. Epidemiology of schistosomiasis**

Schistosomiasis is estimated to infect about 240 million people worldwide while an esti‐ mated 779 million people (more than 10% of the world population) are at risk of ac‐ quiring infection. Although, the transmission of schistosomiasis has been documented in 77 countries worldwide, only 52 of these countries are endemic for the disease, majority of which are in the Africa continent. Forty six [46] of these countries are in Africa. Un‐ like the situation in Africa, some countries in Latin America and Asia and most coun‐ tries of the Caribbean and the Middle East have brought down the prevalence of schistosomiasis and prevented severe morbidity from the infection through a concerted public health effort. But in many of these countries, there are still endemic regions and a potential for resurgence exists [8]. About 120 million people infected with schistoso‐ miasis are estimated to be symptomatic while about 20 million develop severe disease. The disability adjusted life years due to schistosomiasis is about 1.7-4.5 million while between 150,000 to 280,000 people are known to die as a consequence of schistosomia‐ sis per year. Africa accounts for 85% of the disease burden [9,10]. Urinay schistosomia‐ sis has been reported in 38 countries in Africa. Annual mortality due to *S. haematobium* infection in east Africa has been estimated at 1 per 1000 infected adults [11]. In Malawi, Save the children's 1998 survey of schoolchildren in Mangochi found that the overall prevalence of schistosomiasis in coastal and upland schools was 36%. In some of the schools, the prevalence was as high as 87% [12]. In a related study in Cameroon, Mba and Useh [13] reported urinary schistosomiasis among 39.2% of the subjects studied. Mixed infection of *S. haematobium* and *S. mansoni* occurred in 4.5% of the subjects. The number of infected subjects treated for the disease using praziquantel rose for 12.4 mil‐ lion in 2006 to 33.5 million in 2010. It is estimated that 90% of those that require treat‐ ment live in Africa. This implies that over 60% of people suffering from schistosomiasis particularly in Africa are not able to procure treatment or have access to treatment due to the relatively high cost of praziquantel.

#### **2.1. Schistosomiasis situation in Nigeria**

**•** The Pfeifferi group which are the main vectors in Africa

and

64 Parasitic Diseases - Schistosomiasis

the infection predominates [3].

**•** The sudanica group which occur in both east and west Africa

**•** The choanomphala which are found in the great lakes and act as agent in Lake Victoria

The intermediate host of *S. japonicum* are operculated snails that belongs to the genus *Oncomelania*. Important species such as *O. hupensis*, *O. nosophora*, *O. formosana* and *O. quadrasi* are involved in the transmission of infection in different areas of Asia where

The role of water bodies in the transmission of infection cannot be over emphasized [4]. Such water bodies include fresh water streams, water accumulated as a consequence of con‐ struction of dams and irrigation projects and slow flowing or stagnant water. Although, the main courses of large rivers may not be associated with the transmission of schistosomiasis, but water sustained by them through seasonal flooding and impoundment may provide avenues for the sustenance of the snail intermediate host. Water also provides an opportuni‐ ty for the cercariae to survive and penetrate the definitive host. Humans are also pivotal in the transmission of schistosomiasis. Through insanitary disposal of urine or faeces, water bodies are contaminated with the eggs of schistosomes. Worldwide, 900 million people do not have access to an improved water source, while an estimated 2.5 billion, half of all peo‐ ple in developing countries lack access to adequate sanitation [5,6]. In rural and poor agri‐ cultural communities without pipe-borne water, the locals depend on cercariae infested streams for their economic and recreational needs thereby exposing themselves to infection.

The control of schistosomiasis involves an integrated process directed at the infected sub‐ jects, snail intermediate hosts, environmental modification, health education and the provi‐ sion of pipe-borne water [7]. In this review, the epidemiology, diagnosis and control of schistosomiasis is examined in details with notes on the factors impeding the control of the

Schistosomiasis is estimated to infect about 240 million people worldwide while an esti‐ mated 779 million people (more than 10% of the world population) are at risk of ac‐ quiring infection. Although, the transmission of schistosomiasis has been documented in 77 countries worldwide, only 52 of these countries are endemic for the disease, majority of which are in the Africa continent. Forty six [46] of these countries are in Africa. Un‐ like the situation in Africa, some countries in Latin America and Asia and most coun‐ tries of the Caribbean and the Middle East have brought down the prevalence of schistosomiasis and prevented severe morbidity from the infection through a concerted public health effort. But in many of these countries, there are still endemic regions and

disease in Africa with inferences drawn from the Nigerian experience.

**2. Epidemiology of schistosomiasis**

**•** The Alexandrina group which occur sporadically in north, east and south Africa [3]

It is estimated that 30 million Nigerians are infected with schistosomiasis. When examined against a projected population of 162 million Nigerians, it becomes clear that over 18.5% of the populace have schistosomiasis. The problem becomes more glaring when the projected population of infected people is examined in terms of those who carry the greatest burden of the disease; in this case, school age children. About 23 years ago, Ejezie *et al* [2] published a major review entitled "the schistosomiasis problem in Nigeria" where they highlighted the embarrassing and increasing endemicity of schistosomiasis without any concrete plan for control. Not much has changed almost two and half decades after. In another landmark re‐ view on the "Nigerian environment and parasitic infections", Ejezie [14] noted that "a large proportion of the people consist of men and women who are ignorant of the rules of basic hygiene. These people are entrapped by the worst manifestations of poverty, worsened by infectious tropical diseases, malnutrition, high birth and death rate". They are, as it were, caught in the so-called vicious circle-"they are sick because they are poor, they become poor‐ er because they are sick and sicker because they are poorer" [15]. The problem seems to have grown worst. In the above publication, infection with *S. haematobium* was reported in all the regions in Nigeria with a prevalence as high as 60-75% among schoolchildren in some communities. The endemicity of *S mansoni* was also reported though not as wide spread as the former. Perhaps this report and others encouraged the government of Nigeria to consti‐ tute the 'National Schistosomiasis Control Committee". Regrettably, this Committee only existed on paper as funds were not made available to organize operational research to delin‐ eate endemic communities for treatment.

The morbidity of schistosomiasis in Nigeria reflects what has been published for endemic countries in Africa and Asia. Infection predominates in schoolchildren aged between 5-19 years and thereby decline following the typical "age verus prevalence/intensity convex curve". An earlier study conducted on urinary schistosomiasis reported a prevalence of 45.4% in Ilorin, Central Nigeria with 25.9% of infected subjects excreting 1,000eggs/10ml urine [16]. In a related study in Adim community located in south south Nigeria, this author and his colleagues reported an overall prevalence of 53.8% with males and females account‐ ing for 53.8% and 53.9% of infection respectively. In this study, the mean haematuria, protei‐ nuria and egg-output were 23.19 ery/ul, 49.9mg/100ml and 37.3 eggs/10ml urine [17]. Three years after, in the absence of a control programme, the prevalence of urinary schistosomiasis in this same community rose astronomically to 90.7% among children out of the school sys‐ tem while those who attended school had a prevalence of 86.8% [18].

ic cases, the major lesion in the liver is 'pipe stem fibrosis', an enlarged liver and fibrosed

Schistosomal infection has been associated with other negative effects among Nigerian children. These include poor attendance at school, low cognitive ability, educational achievement and malnutrition. This is exemplified in one study in which we treated schoolchildren with urinary schistosomiasis with PZQ and monitor its effect on educa‐ tional attainment in Adim community of Nigeria. The pass rate among the cohort im‐ proved following the first treatment session from 81.4% to 90.7%, latter declined to 84.2% following the second treatment session but the net improvement in performance was statistically significant [29]. On the contrary, Ejezie and Ade-Serrano [30] showed that anthropometric measurements in relation to age, to average marks scored and school attendance were not found to bear any relationship to the intensity of *S. haema‐ tobium* infection in Lagos Nigeria. Similarly, Ekanem *et al* [31] did not find any signifi‐ cant impact of infection on anthropometric parameters, school attendance and academic performance among infected children compared to controls in Nigeria. In Kenya, Corbet *et al* [32] showed that intensity of *S mansoni* infection correlated with hepatomegaly, which was more clearly related to nutritional status. Furthermore they noted that chil‐ dren with hepatomegaly were significantly more stunted and/or wasted than those without, and had less variety in their diet. Similarly, Stephenson *et al* [33,34] demon‐ strated that children infected with *S. haematobium* had evidence of poor nutritional sta‐ tus, with improved growth rates in children and weight gain in undernourished adults following treatment with metrifonate or PZQ. The consequences of infection may be a function of the morbidity of infection in the area, age, nutritional and economic status

portal tract with a varying degree of portal vein destruction.

of the infected subjects.

**Pre-Treatment N=210**

Days school open 257 270 245

No passed 171 166 171

Adopted from Meremikwu et al (2000)

**Post-treatment 1**

Pass rate 81.4 90.7 84.2 7.2 0.027

**Table 1.** Effect of treatment on attendance and pass rate in a cohort of school children over three years

**Post-treatment 11**

**X2 P**

Schistosomiasis

67

http://dx.doi.org/10.5772/53553

**N=203**

86.7 81.5 81.1 2.99 0.22

**N=183**

46,902 40,269 40,402

**Educational Performance**

Total attendance Pupils days

Attendance rate

(%)

The current picture of schistosomiasis endemicity in Nigeria is very worrisome. For instance in their investigation on urinary schistosomiasis around Oyan Reservoir, south west Niger‐ ia, Akinwale *et al* [19] reported a prevalence that ranged from 20.39%-83.9% in some com‐ munities around the reservoir. In Bida, north central Nigeria, Banji *et al* [20] reported a prevalence of 28% among school children. Recently, Goselle *et al* [21] reported the endemici‐ ty of *S. mansoni* in Jos, north central Nigeria. Yet another study reported on the epidemiolo‐ gy of schistosomiasis in six local government areas in Plateau State, Nigeria [22]. The overall prevalence of infection was 47.8%. Many water bodies in the study communities were colon‐ ized by infected *Bulinus* snails. Snail infection rates varied significantly (P<0.001) between the dry and wet seasons. Most studies on schistosomiasis are based on the school system. Not much has been done on children out of the school system and on preschool children. In one of such studies among preschool children in a rural community near Abeokuta, south west Nigeria, Ekpo *et al* [23] reported a prevalence of 58.1% with the overall geometric egg count of 1.17 eggs/10ml urine. There is gross lack of work on genital schistosomiasis in Ni‐ geria. With a high prevalence of HIV/AIDS infection in Nigeria, it is important that this be addressed. Genital schistosomiasis particularly in women may have helped to spread the transmission of HIV infection.

#### *2.1.1. Consequences of schistosomiasis infection in Nigeria*

The pathology associated with schistosomiasis in Nigeria is consistent with what have been reported in other endemic countries. The pathology of schistosomiasis is essentially a series of chronic inflammatory lesions produced in and around blood vessels by eggs which may be found lodged in practically any viscera or their products and sometimes by dead worms. There are comprehensive studies in the literature on the pathology due to urinary schistoso‐ miasis [24,25,26,27]. In summary disorders such as cercarial dermatitis, haematuria, protei‐ nuria, calcification of bladder, uteric stricture and dilatation, hydronephrosis and squamous cell carcinoma have been reported. Others include multi granulomatas in the bladder and vesicle calculus. Attah [28] noted that the pathology of intestinal schistosomiasis is charac‐ terized by the presence of a small superficial ulceration of colonic mucosa, with eggs and granulomas found much more frequently in the serosa than in the mucosa; and by lesions which are secondary to disintegration of eggs and aggravated by oviposition. Hepatic le‐ sions is marked by eosinophilic infiltration of the portal tract with or without eggs. In chron‐ ic cases, the major lesion in the liver is 'pipe stem fibrosis', an enlarged liver and fibrosed portal tract with a varying degree of portal vein destruction.

years and thereby decline following the typical "age verus prevalence/intensity convex curve". An earlier study conducted on urinary schistosomiasis reported a prevalence of 45.4% in Ilorin, Central Nigeria with 25.9% of infected subjects excreting 1,000eggs/10ml urine [16]. In a related study in Adim community located in south south Nigeria, this author and his colleagues reported an overall prevalence of 53.8% with males and females account‐ ing for 53.8% and 53.9% of infection respectively. In this study, the mean haematuria, protei‐ nuria and egg-output were 23.19 ery/ul, 49.9mg/100ml and 37.3 eggs/10ml urine [17]. Three years after, in the absence of a control programme, the prevalence of urinary schistosomiasis in this same community rose astronomically to 90.7% among children out of the school sys‐

The current picture of schistosomiasis endemicity in Nigeria is very worrisome. For instance in their investigation on urinary schistosomiasis around Oyan Reservoir, south west Niger‐ ia, Akinwale *et al* [19] reported a prevalence that ranged from 20.39%-83.9% in some com‐ munities around the reservoir. In Bida, north central Nigeria, Banji *et al* [20] reported a prevalence of 28% among school children. Recently, Goselle *et al* [21] reported the endemici‐ ty of *S. mansoni* in Jos, north central Nigeria. Yet another study reported on the epidemiolo‐ gy of schistosomiasis in six local government areas in Plateau State, Nigeria [22]. The overall prevalence of infection was 47.8%. Many water bodies in the study communities were colon‐ ized by infected *Bulinus* snails. Snail infection rates varied significantly (P<0.001) between the dry and wet seasons. Most studies on schistosomiasis are based on the school system. Not much has been done on children out of the school system and on preschool children. In one of such studies among preschool children in a rural community near Abeokuta, south west Nigeria, Ekpo *et al* [23] reported a prevalence of 58.1% with the overall geometric egg count of 1.17 eggs/10ml urine. There is gross lack of work on genital schistosomiasis in Ni‐ geria. With a high prevalence of HIV/AIDS infection in Nigeria, it is important that this be addressed. Genital schistosomiasis particularly in women may have helped to spread the

The pathology associated with schistosomiasis in Nigeria is consistent with what have been reported in other endemic countries. The pathology of schistosomiasis is essentially a series of chronic inflammatory lesions produced in and around blood vessels by eggs which may be found lodged in practically any viscera or their products and sometimes by dead worms. There are comprehensive studies in the literature on the pathology due to urinary schistoso‐ miasis [24,25,26,27]. In summary disorders such as cercarial dermatitis, haematuria, protei‐ nuria, calcification of bladder, uteric stricture and dilatation, hydronephrosis and squamous cell carcinoma have been reported. Others include multi granulomatas in the bladder and vesicle calculus. Attah [28] noted that the pathology of intestinal schistosomiasis is charac‐ terized by the presence of a small superficial ulceration of colonic mucosa, with eggs and granulomas found much more frequently in the serosa than in the mucosa; and by lesions which are secondary to disintegration of eggs and aggravated by oviposition. Hepatic le‐ sions is marked by eosinophilic infiltration of the portal tract with or without eggs. In chron‐

tem while those who attended school had a prevalence of 86.8% [18].

transmission of HIV infection.

66 Parasitic Diseases - Schistosomiasis

*2.1.1. Consequences of schistosomiasis infection in Nigeria*

Schistosomal infection has been associated with other negative effects among Nigerian children. These include poor attendance at school, low cognitive ability, educational achievement and malnutrition. This is exemplified in one study in which we treated schoolchildren with urinary schistosomiasis with PZQ and monitor its effect on educa‐ tional attainment in Adim community of Nigeria. The pass rate among the cohort im‐ proved following the first treatment session from 81.4% to 90.7%, latter declined to 84.2% following the second treatment session but the net improvement in performance was statistically significant [29]. On the contrary, Ejezie and Ade-Serrano [30] showed that anthropometric measurements in relation to age, to average marks scored and school attendance were not found to bear any relationship to the intensity of *S. haema‐ tobium* infection in Lagos Nigeria. Similarly, Ekanem *et al* [31] did not find any signifi‐ cant impact of infection on anthropometric parameters, school attendance and academic performance among infected children compared to controls in Nigeria. In Kenya, Corbet *et al* [32] showed that intensity of *S mansoni* infection correlated with hepatomegaly, which was more clearly related to nutritional status. Furthermore they noted that chil‐ dren with hepatomegaly were significantly more stunted and/or wasted than those without, and had less variety in their diet. Similarly, Stephenson *et al* [33,34] demon‐ strated that children infected with *S. haematobium* had evidence of poor nutritional sta‐ tus, with improved growth rates in children and weight gain in undernourished adults following treatment with metrifonate or PZQ. The consequences of infection may be a function of the morbidity of infection in the area, age, nutritional and economic status of the infected subjects.


**Table 1.** Effect of treatment on attendance and pass rate in a cohort of school children over three years

## **3. Diagnosis of schistosomiasis**

Diagnosis is pivotal in all aspects of the control of schistosomiasis. Feldmeier *et al* [35] noted that decisions on individual and community treatment, estimations on prognosis and as‐ sessment of morbidity, determination of transmission potential, evaluation of treatment and of control measures all build on the results from diagnostic testing. The diagnosis of human schistosomiasis is based on a combination of clinical symptoms, history of residence in an endemic or non-endemic area, parasitological examinations, serological findings and ultra‐ sonography [36]. However all presently available techniques are characterized by diagnostic imperfections or inaccuracies. Consequently, Feldmeier *et al* [35] recommended that selec‐ tion and application of methods should be related to information being sought while inter‐ pretation of test results should take cognizance of the drawbacks and constraints associated with the method being used.

and intensity of infection as measured by egg excretion in urine [42]. The best correlation between the reagent strip findings and the intensity of infection was obtained when the three parameters were combined. After treatment with metrifonate, the reduction of egg ex‐ cretion was paralleled by the normalization of the reagent strip findings. Analysis of day-today variation demonstrated a similar low variation of the filtration technique and the reagent strip findings. The authors concluded that polyvalent reagent strips may be a useful tool for diagnosis of heavily infected patients under field conditions, as they permit rapid

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Unlike the eggs of *S. haematobium*, the eggs of *S. mansoni*, *S. japonicum* and *S. intercataltum* are passed in faeces. The formol ether concentration technique may be used to demonstrate the spined eggs of any of these parasites. The problem associated with the technique is that it is not field application. Apart from the requirements of a centrifuge and a microscope, the use of ether which is highly flammable poses a hazard. The Kato thick smear technique is more widely used in field work in Africa. The samples can be prepared in the field while exami‐

For community-based studies, enormous human and financial resources are expended to es‐ tablish those infected before the administration of chemotherapy. A reasonable number of skilled manpower would be required to avoid undue waste of time. In practical terms it is usually not possible to identify infected people the same day and offer them treatment in the field. In some instances during a re-visit for treatment, infected children may miss treatment either because of sickness or lending a helping hand to their parents in the farm. Thus a lot of money that ought to be used to procure treatment is expended on diagnosis. Parasitologi‐ cal confirmation of eggs in urine or stool have been associated with some degree of poor ac‐ curacy and sensitivity [43]. The day-to-day variations in excreted egg counts in individual patients [44] and the uneven distribution of eggs in excreta [45] and the occurrence of imma‐ ture infections [46] are some of the limiting factors. Others include the immune dependence of schistosome egg excretion and the survival of worms after an immunological induced in‐ hibition of fecundity [47]. Nonetheless, the establishment of prevalence and morbidity by the presence of ova is necessary for understanding the epidemiological profile of different

The introduction of cytoscopy in 1879 [48] facilitated the visualization of bladder patholo‐ gy as a consequence of *S. haematobium* infection *in vivo*. Pyelographic and histopathologi‐ cal studies have been used to assess urinary tract pathology due to *S. haematobium* infection in Nigeria [24,27,49]. Modern radiological techniques have finally provided a va‐ riety of methods for the detection and follow-up of schistosome related morbidity. Such procedures include various radiographic techiques, isotype investigations of the kidney and liver, computed tomography and more recently, ultrasonography [50]. Table 2 is a summary comparing *S. haematobium*-related morbidity with currently available methods of

and easy identification of subjects with high egg counts.

**3.3. Detection of pathology and ultrasonography**

nation may be done later.

endemic foci.

detecting morbidity.

#### **3.1. Clinical diagnosis**

The expected clinical conditions include cutaneous lesions, urticaria, eosinophilia and pul‐ monary disorders. Others include haematuria, cystitis, urinary calculi and vesicular disor‐ ders which should be differentiated from other disease conditions giving rise to renal calculi, nephritis, tuberculosis, haemoglobinuria, benign and malignant papillomata. This method of diagnosis is not very sensitive and specific. In endemic areas children may not be able to relay their problem to the physician. On the other hand, primary health care workers who are the first set of health workers to come in contact with infected subjects may not be knowledgeable enough to relate this clinical presentation with schistosomiasis.

#### **3.2. Direct parasitological techniques**

Urine egg count is one of the three methods for estimating the intensity of infection; the oth‐ er two, tissue egg burden and number of worm pairs, can only be determined at autopsy [37]. The WHO [38] noted that quantitative egg count provides reliable baseline data for studies on chemotherapy, malacology, sociology and contamination patterns in defined communities. In the same vein, it also provides information on the transmission potential of different population subgroups. Parasite counts are usually estimated by filtration with ny‐ trel, standard filter paper (Whatman) or by centrifugation of urine. The filtration technique which gives excellent results is applicable in the field [39]. In Africa, filtration with What‐ man filter paper is predominantly used in the field and has been associated with reliable and consistent results [17,40]. Smith *et al* [41] reported that in the active stage urinary excre‐ tion can be used as an indirect estimate of tissue egg burden and severity of the disease and is particularly relevant for epidemiological studies. In the inactive stage of infection, few or no eggs may be present. Urine egg counts are of limited essence in estimating the prevalence of severe disease in inactive stage of schistosomal disease or in older population. In a related study, a significant correlation was found between haematuria, proteinuria, leucocyturia and intensity of infection as measured by egg excretion in urine [42]. The best correlation between the reagent strip findings and the intensity of infection was obtained when the three parameters were combined. After treatment with metrifonate, the reduction of egg ex‐ cretion was paralleled by the normalization of the reagent strip findings. Analysis of day-today variation demonstrated a similar low variation of the filtration technique and the reagent strip findings. The authors concluded that polyvalent reagent strips may be a useful tool for diagnosis of heavily infected patients under field conditions, as they permit rapid and easy identification of subjects with high egg counts.

Unlike the eggs of *S. haematobium*, the eggs of *S. mansoni*, *S. japonicum* and *S. intercataltum* are passed in faeces. The formol ether concentration technique may be used to demonstrate the spined eggs of any of these parasites. The problem associated with the technique is that it is not field application. Apart from the requirements of a centrifuge and a microscope, the use of ether which is highly flammable poses a hazard. The Kato thick smear technique is more widely used in field work in Africa. The samples can be prepared in the field while exami‐ nation may be done later.

For community-based studies, enormous human and financial resources are expended to es‐ tablish those infected before the administration of chemotherapy. A reasonable number of skilled manpower would be required to avoid undue waste of time. In practical terms it is usually not possible to identify infected people the same day and offer them treatment in the field. In some instances during a re-visit for treatment, infected children may miss treatment either because of sickness or lending a helping hand to their parents in the farm. Thus a lot of money that ought to be used to procure treatment is expended on diagnosis. Parasitologi‐ cal confirmation of eggs in urine or stool have been associated with some degree of poor ac‐ curacy and sensitivity [43]. The day-to-day variations in excreted egg counts in individual patients [44] and the uneven distribution of eggs in excreta [45] and the occurrence of imma‐ ture infections [46] are some of the limiting factors. Others include the immune dependence of schistosome egg excretion and the survival of worms after an immunological induced in‐ hibition of fecundity [47]. Nonetheless, the establishment of prevalence and morbidity by the presence of ova is necessary for understanding the epidemiological profile of different endemic foci.

#### **3.3. Detection of pathology and ultrasonography**

**3. Diagnosis of schistosomiasis**

68 Parasitic Diseases - Schistosomiasis

with the method being used.

**3.2. Direct parasitological techniques**

**3.1. Clinical diagnosis**

Diagnosis is pivotal in all aspects of the control of schistosomiasis. Feldmeier *et al* [35] noted that decisions on individual and community treatment, estimations on prognosis and as‐ sessment of morbidity, determination of transmission potential, evaluation of treatment and of control measures all build on the results from diagnostic testing. The diagnosis of human schistosomiasis is based on a combination of clinical symptoms, history of residence in an endemic or non-endemic area, parasitological examinations, serological findings and ultra‐ sonography [36]. However all presently available techniques are characterized by diagnostic imperfections or inaccuracies. Consequently, Feldmeier *et al* [35] recommended that selec‐ tion and application of methods should be related to information being sought while inter‐ pretation of test results should take cognizance of the drawbacks and constraints associated

The expected clinical conditions include cutaneous lesions, urticaria, eosinophilia and pul‐ monary disorders. Others include haematuria, cystitis, urinary calculi and vesicular disor‐ ders which should be differentiated from other disease conditions giving rise to renal calculi, nephritis, tuberculosis, haemoglobinuria, benign and malignant papillomata. This method of diagnosis is not very sensitive and specific. In endemic areas children may not be able to relay their problem to the physician. On the other hand, primary health care workers who are the first set of health workers to come in contact with infected subjects may not be

Urine egg count is one of the three methods for estimating the intensity of infection; the oth‐ er two, tissue egg burden and number of worm pairs, can only be determined at autopsy [37]. The WHO [38] noted that quantitative egg count provides reliable baseline data for studies on chemotherapy, malacology, sociology and contamination patterns in defined communities. In the same vein, it also provides information on the transmission potential of different population subgroups. Parasite counts are usually estimated by filtration with ny‐ trel, standard filter paper (Whatman) or by centrifugation of urine. The filtration technique which gives excellent results is applicable in the field [39]. In Africa, filtration with What‐ man filter paper is predominantly used in the field and has been associated with reliable and consistent results [17,40]. Smith *et al* [41] reported that in the active stage urinary excre‐ tion can be used as an indirect estimate of tissue egg burden and severity of the disease and is particularly relevant for epidemiological studies. In the inactive stage of infection, few or no eggs may be present. Urine egg counts are of limited essence in estimating the prevalence of severe disease in inactive stage of schistosomal disease or in older population. In a related study, a significant correlation was found between haematuria, proteinuria, leucocyturia

knowledgeable enough to relate this clinical presentation with schistosomiasis.

The introduction of cytoscopy in 1879 [48] facilitated the visualization of bladder patholo‐ gy as a consequence of *S. haematobium* infection *in vivo*. Pyelographic and histopathologi‐ cal studies have been used to assess urinary tract pathology due to *S. haematobium* infection in Nigeria [24,27,49]. Modern radiological techniques have finally provided a va‐ riety of methods for the detection and follow-up of schistosome related morbidity. Such procedures include various radiographic techiques, isotype investigations of the kidney and liver, computed tomography and more recently, ultrasonography [50]. Table 2 is a summary comparing *S. haematobium*-related morbidity with currently available methods of detecting morbidity.


greatest intensity in patients with the highest egg output. Relatedly, Mottt *et al* [59] and Tanner *et al* [60] noted that all children between 5-14 years with more than 50 eggs per 10ml of urine had blood in the urine detected by chemical reagent strips. This author and his colleagues test‐ ed the usage of the presence/absence of haematuria and proteinuria in monitoring the out‐ come of treatment of urinary schistosomiasis with artesunate. The mean ova count, haematuria and proteinuria of 87 infected subjects who were treated significantly reduced from 55.5± 1.3ova/10ml urine, 168.6±1.23 ery/μL and 458.6± 1.4 mg/dl to 1.8±0 ova/10ml urine, 9.1±0.4 ery/μL and 65.4 mg/dl respectively (P<0.05 in all cases). We therefore concluded that re‐

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Reagent strips are cheap, fast, simple and can be readily integrated into the primary health care programme. But there may be gender bias in females that may lead to under-reporting or over-reporting (false positives). The contamination of urine with menstrual blood would yield false positive results for haematuria. A similar finding may be noted for leucocyturia and proteinuria [62]. The usefulness of a semi-quantitative grading of haematuria as a corre‐ late to intensity of infection has to be questioned in women with schistosomiasis, since the ectopic localization of eggs in the vagina, cervix or the endometrium may lead to contact bleeding, intermenstrual bleeding or to bloody discharge [63]. Evidence for false positive re‐ agent strip readings in women has been shown in a population based study on Pemba Is‐ land, Tanzania. A higher prevalence of haematuria readings were observed in women of child-bearing age than in males of similar age, although intensity of infection and morbidity as measured by the number of eggs per unit of urine, and as indicated by pathological ultr‐ sonography was significantly less in women than in men [64]. Vester *et al* [65] reported cul‐ ture-related biases for mass screening with urine analysis strips. About 15% of schistosomiasis-free Sudanese girls and women circumcised either by the "pharaonic" or the "sunna" method constantly or intermittently show mild haematuria and/or leucocyturia. Since female circumcision is practiced not only in Muslim and Coptic societies in the Sudan, but also in more than 40 ethnic groups in Africa and Arabia [66], false positive reagent strip

agent strips are reliable in monitoring the efficacy of treatment with artesunate [61].

readings are expected to occur where this tradition and schistosomiasis overlap.

A greater proportion of money slated for the control of schistosomiasis is usually spent on diagnosis particularly when eggs are to be counted. The fact that schistosomiasis is focal in distribution with millions of infected subjects in endemic communities showing different prevalence and morbidity rates compound the problem. The problem is more felt in Africa with her lean financial resources but with the largest burden of the disease. The rapid as‐ sessment procedure was conceived to maximize resources in diagnosis which could be di‐

The RAP involves the use of a rapid and inexpensive method to identify communities with a high prevalence of and morbidity due to urinary schistosomiasis. It is based on using simple questionnaires to find out how frequent schistosomiasis is in a community [67]. Kroeger [68] and Ross and Vaughan [69] showed that health interview surveys can be used in both developed and developing countries to assess morbidity as it is perceived by community members, and to in‐

*3.4.2. Rapid Assessment Procedure (RAP) using questionnaires*

rected to possible chemotherapeutic control of infection

**Table 2.** Comparison reflects possibility of detecting without rating efficiency and applicability.

#### **3.4. Indirect parasitological techniques**

#### *3.4.1. Haematuria and proteinuria*

The detection of haematuria and proteinuria is widely used in Nigeria and the rest of endemic communities in Africa to diagnose urinary schistosomiasis. Haematuria arises when migrating eggs puncture small capillaries of the viscal plexus to get into the bladder [51]. Haematuria was the first sign to be associated with schistosomiasis [52] while proteinuria was described later. Haematuria is usually seen at the end of urination (terminal haematuria), although haematuria throughout micturition may be seen in some severely infected cases. High levels of urinary pro‐ tein in *S. haematobium* infection has been linked with nephritis [53], nephritic syndrome [54] and bladder pathology [55]. Some authors have cited the reversibility of proteinuria after treatment to support the renal origin of proteinuria [56,57]. It is now generally accepted that bilharzial pro‐ teinuria is of post –renal origin and not a sign of impaired renal function [58].

Several studies have confirmed that the detection of proteinuria and haematuria when used to‐ gether is a better means to measure morbidity than when used separately [25,40,59]. In Lagos, Nigeria, Ejezie and Ade-Seranno, [40] reported haematuria in 655 of infected children with the greatest intensity in patients with the highest egg output. Relatedly, Mottt *et al* [59] and Tanner *et al* [60] noted that all children between 5-14 years with more than 50 eggs per 10ml of urine had blood in the urine detected by chemical reagent strips. This author and his colleagues test‐ ed the usage of the presence/absence of haematuria and proteinuria in monitoring the out‐ come of treatment of urinary schistosomiasis with artesunate. The mean ova count, haematuria and proteinuria of 87 infected subjects who were treated significantly reduced from 55.5± 1.3ova/10ml urine, 168.6±1.23 ery/μL and 458.6± 1.4 mg/dl to 1.8±0 ova/10ml urine, 9.1±0.4 ery/μL and 65.4 mg/dl respectively (P<0.05 in all cases). We therefore concluded that re‐ agent strips are reliable in monitoring the efficacy of treatment with artesunate [61].

Reagent strips are cheap, fast, simple and can be readily integrated into the primary health care programme. But there may be gender bias in females that may lead to under-reporting or over-reporting (false positives). The contamination of urine with menstrual blood would yield false positive results for haematuria. A similar finding may be noted for leucocyturia and proteinuria [62]. The usefulness of a semi-quantitative grading of haematuria as a corre‐ late to intensity of infection has to be questioned in women with schistosomiasis, since the ectopic localization of eggs in the vagina, cervix or the endometrium may lead to contact bleeding, intermenstrual bleeding or to bloody discharge [63]. Evidence for false positive re‐ agent strip readings in women has been shown in a population based study on Pemba Is‐ land, Tanzania. A higher prevalence of haematuria readings were observed in women of child-bearing age than in males of similar age, although intensity of infection and morbidity as measured by the number of eggs per unit of urine, and as indicated by pathological ultr‐ sonography was significantly less in women than in men [64]. Vester *et al* [65] reported cul‐ ture-related biases for mass screening with urine analysis strips. About 15% of schistosomiasis-free Sudanese girls and women circumcised either by the "pharaonic" or the "sunna" method constantly or intermittently show mild haematuria and/or leucocyturia. Since female circumcision is practiced not only in Muslim and Coptic societies in the Sudan, but also in more than 40 ethnic groups in Africa and Arabia [66], false positive reagent strip readings are expected to occur where this tradition and schistosomiasis overlap.

#### *3.4.2. Rapid Assessment Procedure (RAP) using questionnaires*

**CYSTOSCOPY RENAL FUNCTION TEST**

Granuloma + - + + + Sandy Patches + - -/+ + + Ulcers + - -/+ + -/+ Cystitis + - - -/+ - Stones + - + + + Calcification -/+ - + + -/+ Polyps + - + + + Carcinoma + - + + +

Hydroureter -/+ -/+ + + -/+ Stricture -/+ -/+ + + -

Calcification -/+ - + + -/+ Polyps -/+ - + + -/+

Congestion - -/+ + + + Hydronephrosis - -/+ + + + Performance - + + + -

**Table 2.** Comparison reflects possibility of detecting without rating efficiency and applicability.

teinuria is of post –renal origin and not a sign of impaired renal function [58].


The detection of haematuria and proteinuria is widely used in Nigeria and the rest of endemic communities in Africa to diagnose urinary schistosomiasis. Haematuria arises when migrating eggs puncture small capillaries of the viscal plexus to get into the bladder [51]. Haematuria was the first sign to be associated with schistosomiasis [52] while proteinuria was described later. Haematuria is usually seen at the end of urination (terminal haematuria), although haematuria throughout micturition may be seen in some severely infected cases. High levels of urinary pro‐ tein in *S. haematobium* infection has been linked with nephritis [53], nephritic syndrome [54] and bladder pathology [55]. Some authors have cited the reversibility of proteinuria after treatment to support the renal origin of proteinuria [56,57]. It is now generally accepted that bilharzial pro‐

Several studies have confirmed that the detection of proteinuria and haematuria when used to‐ gether is a better means to measure morbidity than when used separately [25,40,59]. In Lagos, Nigeria, Ejezie and Ade-Seranno, [40] reported haematuria in 655 of infected children with the

A. BLADDER

70 Parasitic Diseases - Schistosomiasis

B. URETER

Dilatation/ Distortion

C. KIDNEY

Adopted from Hatz *et al* [50].

**3.4. Indirect parasitological techniques**

*3.4.1. Haematuria and proteinuria*

**X-RAY COMPUTED**

**TOMOGRAPHY**

**SONOGRAPHY**

A greater proportion of money slated for the control of schistosomiasis is usually spent on diagnosis particularly when eggs are to be counted. The fact that schistosomiasis is focal in distribution with millions of infected subjects in endemic communities showing different prevalence and morbidity rates compound the problem. The problem is more felt in Africa with her lean financial resources but with the largest burden of the disease. The rapid as‐ sessment procedure was conceived to maximize resources in diagnosis which could be di‐ rected to possible chemotherapeutic control of infection

The RAP involves the use of a rapid and inexpensive method to identify communities with a high prevalence of and morbidity due to urinary schistosomiasis. It is based on using simple questionnaires to find out how frequent schistosomiasis is in a community [67]. Kroeger [68] and Ross and Vaughan [69] showed that health interview surveys can be used in both developed and developing countries to assess morbidity as it is perceived by community members, and to in‐ vestigate the utilization patterns of health services. Tanner [70] demonstrated that asking the beneficiaries of the health system about their perceptions of disease and health problems, and es‐ pecially about their priorities with regard to health related actions, can add an important ele‐ ment in the health planning cycle. Lengeler *et al* [71] observed that indirect health interview represents a methodical evolution of the traditional interview approach by the fact that ques‐ tionnaires are not administered directly by the investigators or their field staff to the key inform‐ ants. Rather, they are distributed through an existing administrative channel and selfadministered by the recipients. The school system is therefore the appropriate structure to base a study on the prevalence of schistosomiasis. This is anchored on the fact that those who bear the greatest burden of the disease can be easily reached through this channel. Additionally, schools are widely cited and are very likely to be located in remote endemic areas. Thirdly, teachers are competent enough with minimal training to carry out an exercise of this nature.

Elsewhere, self-administered questionnaires, distributed by existing administrative channels to village party chairmen, head teachers and school children, showed good diagnostic per‐ formance for the qualitative assessment of urinary schistosomisasis endemicity. At a cost 34 times below that of the WHO-recommended parasitological screening strategy, the school children's questionnaire allowed the screening of 75 out of 77 schools of a rural Tanzanian district in 6 weeks, and the exclusion of schools not at high risk for urinary schistosomiasis with over 90% confidence. The head teacher and party chairmen questionnaires made it pos‐ sible to assess the perceived importance of a spectrum of diseases and symptoms, among which was schistosomiasis. The priority rank of schistosomiasis control was strongly corre‐ lated with the prevalence rate of the disease in the community. The questionnaires also looked at the prioritization of health among other community issues and thus contributed

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73

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Using questionnaires facilitate immense savings in cost as well as reaching a vast land mass. However, in areas of low school attendance, reliable information may not be collected. In‐ fected but unidentified school-age children that are out of school would invalidate control efforts, as they would continuously contaminate water bodies. Other limitations as outlined

**•** results obtained with school children may not always be typical for the whole community especially if a lot of the children of this age are not in school or where one sex is badly

**•** the methodology does not identify which child is infected. To obtain this information, a

**•** true prevalence is usually underestimated since the method relies on re-call as those who

**•** in some countries, girls and boys may perceive the disease differently or give different an‐

Immunodiagnositic methods are so far the only alternative to parasitological test. They al‐ low the demonstration of specific anti-schistosomal antibodies and to a certain extent, the tracing of circulating antigens and/or immune complexes in sera of parasite carriers [36]. Wilkins *et al* [55] noted that they offer the most practical assays for epidemiological studies and patient management. They are particularly valuable if the density of the parasites (or their developmental stages) in a specimen is very low or if the biology of the parasite does

Serological procedures such as immunodiffusion, complement fixation test, indirect hae‐ magglutination assay, immunoflourescent antibody assay have been used for the diagnosis of schistosomiasis. Others include enzyme linked immunosorbent (ELISA), radioimmunoas‐ sy and radio-allegrosorbent assay among others. The relevance of antibody detection in the diagnosis of schistosomiasis has been reviewed in great details by Hamilton *et al* [74]. They

not allow its direct demonstration e.g localization of certain stages in internal organs.

second step using conventional diagnostic method would be necessary

are mildly infected may not recall having had haematuria

important information for planning at the district level [73].

by Chitsulo *et al* [67] are-

under-represented

**3.5. Immunodiagnosis**

swers to questions asked about it.

Several epidemiological studies are available in the literature that tested the usefulness of this mode of diagnosis. Useh and Ejezie [72] worked on the "evaluation and validation of the questionnaire approach for the diagnosis of urinary schistosomiasis in Biase Local Gov‐ ernment Area of Nigeria among school pupils". The questionnaire which enquired whether pupils had urinary schistosomiasis or blood in urine in the preceding month, was adminis‐ tered by class teachers to the pupils. Urines samples collected for the validation of the ques‐ tionnaire diagnosis was also examined using dipsticks (by teachers and the research team). There was a strong positive correlation between the pupils's knowledge of schistosomiasis as a disease and the reported presence of blood in urine (r=0.96) although the later was a better indicator of the disease. The questionnaire technique (blood in urine) gave a compara‐ ble sensitivity (85.8%), specificity (81.4%), positive and negative predictive values (96.6% and 47.9%) to the dipstick test with values of 96.6%, 88.4%, 98% and 69.1% respectively. Teachers were able to detect haematuria with a high degree of accuracy. We found this ap‐ proach to be simple, cost-effective and reliable and recommended its usage in other endemic settings with large land mass and dense population like Nigeria (See Table 3).


True Positives, TP were defined as those with ova in urine (n=267). Altogether 310 pupils were examined.

TN- True Negative, FP- False Positive, FN- False Negative

SENS- Sensitivity, SPEC – Specificity, PPV- Positive Predictive Value, NPV- Negative Predictive Value, TDST- Teachers Dip‐ stick Testing, RDST- Researchers Dipstick Testing.

Adopted from Useh and Ejezie, [72].

**Table 3.** Comparison of the performance of different survey methods in relation to parasitologically confirmed diagnosis

Elsewhere, self-administered questionnaires, distributed by existing administrative channels to village party chairmen, head teachers and school children, showed good diagnostic per‐ formance for the qualitative assessment of urinary schistosomisasis endemicity. At a cost 34 times below that of the WHO-recommended parasitological screening strategy, the school children's questionnaire allowed the screening of 75 out of 77 schools of a rural Tanzanian district in 6 weeks, and the exclusion of schools not at high risk for urinary schistosomiasis with over 90% confidence. The head teacher and party chairmen questionnaires made it pos‐ sible to assess the perceived importance of a spectrum of diseases and symptoms, among which was schistosomiasis. The priority rank of schistosomiasis control was strongly corre‐ lated with the prevalence rate of the disease in the community. The questionnaires also looked at the prioritization of health among other community issues and thus contributed important information for planning at the district level [73].

Using questionnaires facilitate immense savings in cost as well as reaching a vast land mass. However, in areas of low school attendance, reliable information may not be collected. In‐ fected but unidentified school-age children that are out of school would invalidate control efforts, as they would continuously contaminate water bodies. Other limitations as outlined by Chitsulo *et al* [67] are-


## **3.5. Immunodiagnosis**

vestigate the utilization patterns of health services. Tanner [70] demonstrated that asking the beneficiaries of the health system about their perceptions of disease and health problems, and es‐ pecially about their priorities with regard to health related actions, can add an important ele‐ ment in the health planning cycle. Lengeler *et al* [71] observed that indirect health interview represents a methodical evolution of the traditional interview approach by the fact that ques‐ tionnaires are not administered directly by the investigators or their field staff to the key inform‐ ants. Rather, they are distributed through an existing administrative channel and selfadministered by the recipients. The school system is therefore the appropriate structure to base a study on the prevalence of schistosomiasis. This is anchored on the fact that those who bear the greatest burden of the disease can be easily reached through this channel. Additionally, schools are widely cited and are very likely to be located in remote endemic areas. Thirdly, teachers are

Several epidemiological studies are available in the literature that tested the usefulness of this mode of diagnosis. Useh and Ejezie [72] worked on the "evaluation and validation of the questionnaire approach for the diagnosis of urinary schistosomiasis in Biase Local Gov‐ ernment Area of Nigeria among school pupils". The questionnaire which enquired whether pupils had urinary schistosomiasis or blood in urine in the preceding month, was adminis‐ tered by class teachers to the pupils. Urines samples collected for the validation of the ques‐ tionnaire diagnosis was also examined using dipsticks (by teachers and the research team). There was a strong positive correlation between the pupils's knowledge of schistosomiasis as a disease and the reported presence of blood in urine (r=0.96) although the later was a better indicator of the disease. The questionnaire technique (blood in urine) gave a compara‐ ble sensitivity (85.8%), specificity (81.4%), positive and negative predictive values (96.6% and 47.9%) to the dipstick test with values of 96.6%, 88.4%, 98% and 69.1% respectively. Teachers were able to detect haematuria with a high degree of accuracy. We found this ap‐ proach to be simple, cost-effective and reliable and recommended its usage in other endemic

competent enough with minimal training to carry out an exercise of this nature.

settings with large land mass and dense population like Nigeria (See Table 3).

**SENS (%)**

True Positives, TP were defined as those with ova in urine (n=267). Altogether 310 pupils were examined.

Blood in Urine 229 9 38 35 85.8 81.4 96.6 47.9 83.3 88.8 P<0.001 Schistosomiasis 207 15 60 28 77.5 65.1 93.2 31.8 73.4 83.1 P<0.001 TDST 231 7 36 36 86.5 83.7 97.1 50.0 84.3 89.1 P<0.001 RDST 250 5 17 38 93.6 88.4 98.0 69.1 91.9 95.5 P<0.001

SENS- Sensitivity, SPEC – Specificity, PPV- Positive Predictive Value, NPV- Negative Predictive Value, TDST- Teachers Dip‐

**Table 3.** Comparison of the performance of different survey methods in relation to parasitologically confirmed

**SPEC (%)**

**PPV (%)**

**NPV (%)**

**VAL (%)**

**BIAS (%)**

**P Value**

**TN d**

**Survey Method**

diagnosis

**TP a**

72 Parasitic Diseases - Schistosomiasis

**FP B**

TN- True Negative, FP- False Positive, FN- False Negative

stick Testing, RDST- Researchers Dipstick Testing.

Adopted from Useh and Ejezie, [72].

**FN C**

> Immunodiagnositic methods are so far the only alternative to parasitological test. They al‐ low the demonstration of specific anti-schistosomal antibodies and to a certain extent, the tracing of circulating antigens and/or immune complexes in sera of parasite carriers [36]. Wilkins *et al* [55] noted that they offer the most practical assays for epidemiological studies and patient management. They are particularly valuable if the density of the parasites (or their developmental stages) in a specimen is very low or if the biology of the parasite does not allow its direct demonstration e.g localization of certain stages in internal organs.

> Serological procedures such as immunodiffusion, complement fixation test, indirect hae‐ magglutination assay, immunoflourescent antibody assay have been used for the diagnosis of schistosomiasis. Others include enzyme linked immunosorbent (ELISA), radioimmunoas‐ sy and radio-allegrosorbent assay among others. The relevance of antibody detection in the diagnosis of schistosomiasis has been reviewed in great details by Hamilton *et al* [74]. They

concluded that due to the relative insensitivity of both parasitology and antigen detection, antibody detection methods could find increasing use in situations of low infection intensi‐ ty. The performance of antibody detection for the diagnosis of schistosomiasis has been test‐ ed in Kenya. Approximately 1500 blood samples from 3 areas with endemic schistosomiasis and from a non-endemic control area, were tested for their antibody reactivity in ELISA. The results were compared with infection status determined by parasitological examination. Two test antigens were used ;unfractionated *S. mansoni* egg homogenate (SEA) and CEF6, a partially purified fraction of SEA containing 2 cationic antigens. Blood from patients with *S. haematobium* infection cross-reacted significantly with the two *S. mansoni* antigen prepara‐ tions, but reactivity against CEF6 appeared more specifically indicative of *S. mansoni* infec‐ tion. There was a significant positive correlation between blood ELISA results and the number of eggs excreted by infected subjects in the area endemic for *S. mansoni* only. High‐ est correlation coefficients were obtained in children aged 10 years and CEF6 gave marginal‐ ly higher correlation coefficient than SEA. The graphs of prevalence and intensity of schistosome infection drawn from the serological results were similar in shape to the graph of these 2 quantities based on parasitological results, and the results indicate that serology merits wider use as an epidemiological tool for determining infection status in schistosomia‐ sis [75]. In a different but related study, the relative concentration of IgM and IgG antibodies to *S. mansoni* soluble egg antigen were evaluated in paired samples of venous blood, sera and buffer elutes of capillary blood drops dried on filter papers [76]. The samples were ob‐ tained from school children at early and chronic stages of schistosomiasis diagnosed on the basis of history, clinical symptomatology and parasitological criteria. ELISA simultaneously performed, revealed paired samples to display comparable antibody levels in all cases. Sam‐ ples from children with early schistosomiasis had specific IgM : IgG ratios greater than 1 in sera and blood elutes. This ratio, however was less than 1 in samples from chronically infect‐ ed children. The specific advantages of this simplified technique are the use of anti-SEA an‐ tibodies in finger-stick blood elutes, rather than sera or venous blood to serologically diagnose schistosomiasis and to differentiate early from chronic infections particularly when used for mass screening such as epidemiological surveys. Elsewhere, Mclaren *et al* [77] showed that *S. mansoni* SEA gave a sensitivity of 92.3% in diagnosing *S. haematobium* infec‐ tion and 96.2% for *S. mansoni* and a specificity of 97.4% in ELISA. Recently, Chand *et al* [78] reported on the development of a new assay for the diagnosis of schistosomiasis, using cer‐ carial antigens. They showed that the cercarial antigen assay was equivalent to the SEA as‐ say for serodiagnosis of schistosomiasis in a non-endemic setting. Since the cercarial antigens is more easily obtained and prepared than SEA, the authors inferred this assay may be preferred for routine clinical use and may be amenable for scaling up.

**•** cross-reaction with antibodies to other helminthes including animal schistosomes

to handle them.

**3.6. Rapid diagnostic test**

**4. Control of schistosomiasis**

titudes and customs [82].

fied the applicable approaches as:

**•** unresolved seropositivity remain for years after treatment or after an infection has died out.

The greatest impediment hindering the utilization of immunodiagnosis in third world coun‐ tries particularly in Africa is lack of financial resources to procure the sophisticated equip‐ ment required to carry out some of these procedures and the training of skilled manpower

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The advent of rapid diagnostic tests has facilitated the immediate treatment of subjects with infectious diseases in the field after diagnosis. Results are usually available within 30 mi‐ nutes compared to the conventional tests. Apart from its simplicity and ease of carrying out devoid of technicality, the availability of electricity is not required. Rapid diagnostic tests are being deployed in endemic countries for the identification of subjects with malaria, HIV and hepatitis for prompt treatment. Encouraging reports are available in the literature on the development of rapid diagnostic test for schistosomiasis. De jonge *et al* [79] developed a reagent strip test for detection of circulating cathodic antigen in urine. In a related study, Bosompem *et al* [80] showed that *S. haematobium* antigen complexed with complement C3 can be isolated from the urine of infected persons by using a mouse monoclonal antibody. These investigators demonstrated that goat anti-human C3 would also detect schistosome antigen/complement complex in urine of infected persons used as case-controls and subse‐ quently developed a monoclonal antibody dipstick test on the basis of these findings. How‐ ever, a lot of standardization would be required before these strips are approved by the

WHO and other regulatory organizations for deployment in endemic countries.

The cardinal objective in the control of schistosomiasis is the reduction of morbidity and mortality to levels below public health significance. Over the years, emphasis has shifted from the non-realizable goal of eradication to the more realistic goal of morbidity control. In this context, Gemmel *et al* [81], defined "a control programme" as the "implementation of specific measures by a disease control authority to limit the incidence of the disease". Such implementation may involve specific technical interventions and perhaps legislation to en‐ force compliance. The success of this type of approach is predicated on an accurate ecologi‐ cal diagnosis, that is, a diagnosis of the human community, its parasitological characteristics, its physico-geographical environmental attributes and man's behavioural at‐

The enormous morbidity associated with schistosomiasis which ranks it next to malaria in terms of public health significance re-emphasizes the need for a coordinated and sus‐ tainable means for the control of the disease. There is a consensus of opinion that the control of the disease should be integrated. In this model of control, King [83] identi‐

Although the application of serological tests has, without doubt, contributed to epidemio‐ logical surveys, such studies are of limited use because some of the tests lack reasonable lev‐ els of acceptable sensitivity and specificity or are technically difficult to be carried out in field surveys. Other drawbacks as outlined by Weiland [36] are;


The greatest impediment hindering the utilization of immunodiagnosis in third world coun‐ tries particularly in Africa is lack of financial resources to procure the sophisticated equip‐ ment required to carry out some of these procedures and the training of skilled manpower to handle them.

## **3.6. Rapid diagnostic test**

concluded that due to the relative insensitivity of both parasitology and antigen detection, antibody detection methods could find increasing use in situations of low infection intensi‐ ty. The performance of antibody detection for the diagnosis of schistosomiasis has been test‐ ed in Kenya. Approximately 1500 blood samples from 3 areas with endemic schistosomiasis and from a non-endemic control area, were tested for their antibody reactivity in ELISA. The results were compared with infection status determined by parasitological examination. Two test antigens were used ;unfractionated *S. mansoni* egg homogenate (SEA) and CEF6, a partially purified fraction of SEA containing 2 cationic antigens. Blood from patients with *S. haematobium* infection cross-reacted significantly with the two *S. mansoni* antigen prepara‐ tions, but reactivity against CEF6 appeared more specifically indicative of *S. mansoni* infec‐ tion. There was a significant positive correlation between blood ELISA results and the number of eggs excreted by infected subjects in the area endemic for *S. mansoni* only. High‐ est correlation coefficients were obtained in children aged 10 years and CEF6 gave marginal‐ ly higher correlation coefficient than SEA. The graphs of prevalence and intensity of schistosome infection drawn from the serological results were similar in shape to the graph of these 2 quantities based on parasitological results, and the results indicate that serology merits wider use as an epidemiological tool for determining infection status in schistosomia‐ sis [75]. In a different but related study, the relative concentration of IgM and IgG antibodies to *S. mansoni* soluble egg antigen were evaluated in paired samples of venous blood, sera and buffer elutes of capillary blood drops dried on filter papers [76]. The samples were ob‐ tained from school children at early and chronic stages of schistosomiasis diagnosed on the basis of history, clinical symptomatology and parasitological criteria. ELISA simultaneously performed, revealed paired samples to display comparable antibody levels in all cases. Sam‐ ples from children with early schistosomiasis had specific IgM : IgG ratios greater than 1 in sera and blood elutes. This ratio, however was less than 1 in samples from chronically infect‐ ed children. The specific advantages of this simplified technique are the use of anti-SEA an‐ tibodies in finger-stick blood elutes, rather than sera or venous blood to serologically diagnose schistosomiasis and to differentiate early from chronic infections particularly when used for mass screening such as epidemiological surveys. Elsewhere, Mclaren *et al* [77] showed that *S. mansoni* SEA gave a sensitivity of 92.3% in diagnosing *S. haematobium* infec‐ tion and 96.2% for *S. mansoni* and a specificity of 97.4% in ELISA. Recently, Chand *et al* [78] reported on the development of a new assay for the diagnosis of schistosomiasis, using cer‐ carial antigens. They showed that the cercarial antigen assay was equivalent to the SEA as‐ say for serodiagnosis of schistosomiasis in a non-endemic setting. Since the cercarial antigens is more easily obtained and prepared than SEA, the authors inferred this assay may

74 Parasitic Diseases - Schistosomiasis

be preferred for routine clinical use and may be amenable for scaling up.

field surveys. Other drawbacks as outlined by Weiland [36] are;

**•** no correlation between morbidity and sero-reactivity

Although the application of serological tests has, without doubt, contributed to epidemio‐ logical surveys, such studies are of limited use because some of the tests lack reasonable lev‐ els of acceptable sensitivity and specificity or are technically difficult to be carried out in

**•** inability to indicate the intensity of infection or differentiate active from chronic infection

The advent of rapid diagnostic tests has facilitated the immediate treatment of subjects with infectious diseases in the field after diagnosis. Results are usually available within 30 mi‐ nutes compared to the conventional tests. Apart from its simplicity and ease of carrying out devoid of technicality, the availability of electricity is not required. Rapid diagnostic tests are being deployed in endemic countries for the identification of subjects with malaria, HIV and hepatitis for prompt treatment. Encouraging reports are available in the literature on the development of rapid diagnostic test for schistosomiasis. De jonge *et al* [79] developed a reagent strip test for detection of circulating cathodic antigen in urine. In a related study, Bosompem *et al* [80] showed that *S. haematobium* antigen complexed with complement C3 can be isolated from the urine of infected persons by using a mouse monoclonal antibody. These investigators demonstrated that goat anti-human C3 would also detect schistosome antigen/complement complex in urine of infected persons used as case-controls and subse‐ quently developed a monoclonal antibody dipstick test on the basis of these findings. How‐ ever, a lot of standardization would be required before these strips are approved by the WHO and other regulatory organizations for deployment in endemic countries.

## **4. Control of schistosomiasis**

The cardinal objective in the control of schistosomiasis is the reduction of morbidity and mortality to levels below public health significance. Over the years, emphasis has shifted from the non-realizable goal of eradication to the more realistic goal of morbidity control. In this context, Gemmel *et al* [81], defined "a control programme" as the "implementation of specific measures by a disease control authority to limit the incidence of the disease". Such implementation may involve specific technical interventions and perhaps legislation to en‐ force compliance. The success of this type of approach is predicated on an accurate ecologi‐ cal diagnosis, that is, a diagnosis of the human community, its parasitological characteristics, its physico-geographical environmental attributes and man's behavioural at‐ titudes and customs [82].

The enormous morbidity associated with schistosomiasis which ranks it next to malaria in terms of public health significance re-emphasizes the need for a coordinated and sus‐ tainable means for the control of the disease. There is a consensus of opinion that the control of the disease should be integrated. In this model of control, King [83] identi‐ fied the applicable approaches as:


Only the chemotherapeutic form of control of schistosomiasis is covered in the present re‐ view. This does not in any way reduce the importance of the other methods. It has already been emphasized above that the sustainable control of schistosomiasis involves the integra‐ tion of several methods listed above. A comprehensive review on the control of schistoso‐ miasis by this author can be found elsewhere [85]. In the next few paragraphs, the modes of

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Praziquantel (PZO) is the drug of choice for the treatment of schistosomiasis. It is a broad spectrum anti-schistosomal which is principally active against the adult stage of all the schistosome species infective to man. It is a 2-cyclohexycarbonyl 1,2,3,6,7,11b-hexahy‐ dro-4H-pyrazino(2,1-a Isoquinolin-4one) compound with a melting point at 136-140C. It was developed in the laboratories for Parasitological Research of Bayer AG and Merck KGaA in Germany (Elbert and Darmstadt) in the mid 1970s. It has a molecular mass of 312.411 with a serum half life of 0.8 to 1.5 hours in adults with normal liver and kidney function and is mainly excreted in urine. PZQ is a white crystalline powder with bitter taste. It is stable un‐ der normal storage conditions. Although, it is insoluble in water, it is soluble in chloroform, dimethylsulfoxide and ethanol. It is sold as a racemate mixture consisting of equal parts of 'laevo' and 'dextro' isomers, of which only the laevo component displays anti-schistosomal

The recommended dose of PZO is 40 mg/kg body weight. The drug is available as a 600mg tablet. The quality of PZQ (proprietary and generic) currently available in the market is quite high and acceptable. Thirty four [34] PZQ samples from different manufacturers were collected at the user level in various countries and subjected to quantitative analysis of ac‐ tive ingredient, purity, disintegration and dissolution in accordance with established phar‐ macopoeial standards. The results showed that most of the samples were of high quality except two samples from the same manufacturer that had no PZQ [86]. About 90% of the damage done to organ function is known to reverse six months following the administration of PZQ. Although it is exceptionally well tolerated, reported side –effects include abdominal discomfort, nausea, headache, dizziness, drowsiness and pyrexia especially in subjects with

The mode of action of PZQ has been extensively reviewed elsewhere [88,89]. The exact mechanisms of action of PZQ is still poorly understood. PZQ is known to induce rapid calci‐ um influx that distort the morhoplogy and physiology of schistosome. Jeziorski and Green‐ berg [90] showed that the B subunits of voltage-gated Ca2+ channels is the prime molecular target of PZQ. It has recently been reported that cytochalasin D abolished the schistosomici‐ cidal activity of PZQ but calcium influx into PZQ exposed schistosomes was not halted. This therefore raises doubts whether calcium influx is essential in the antischistosomal activity of

action of several drugs use for the treatment of schistosomiasis are examined.

*4.1.1. Praziquantel (PZQ)*

properties.

high egg counts [87].

*4.1.1.2. Mode of action of PZO*

*4.1.1.1. Biochemical properties and pharmacokinetics*


The WHO Expert Committee on Epidemiology and Control of Schistosomiasis took a holistic approach at the control of the disease and noted that "comprehensive understanding of the envi‐ ronment, demographic, social, human behavioural and economic factors" in schistosomiasis is essential for the design of control programmes that are successful in the long run [84]. With the advent of praziquantel (PZQ) as a safe and efficacious drug for the treatment of schistosomiasis, the WHO in 1991 reinforced its 1984 recommendation to shift from transmission control (focus‐ ing on the prevalence of infection) to morbidity control (laying emphasis on intensity of infec‐ tion) [8]. Morbidity control will not only reduce the number of people infected but it will also drastically reduce environmental contamination with the eggs even when cure is not attained. A drastic reduction of the pollution of the environment with the eggs would also reduce the chan‐ ces of transmission. Should this occur at a level below public health importance, the probability of eventual elimination of disease is certain with a sustained integrated approach

## **4.1. Chemotherapeutic control of schistosomiasis**

Of all the methods of control listed above, chemotherapy is the only one that is widely used presently in endemic areas for the control of morbidity due to schistosomiasis. Among the first group of drugs used for the treatment of schistosomiasis included; antimonials, nirida‐ zole, hycanthone, lucanthone, oxamniquine and albendazole. PZQ is currently used for the treatment of all the species while metrifonate is active against *S. haematobium* only. Recently, artemisinins earlier synthesized for the treatment of malaria infection is being used in some endemic communities to treat schistosomiasis. The WHO [11] identified four approaches in the administration of chemotherapy programme namely;


Only the chemotherapeutic form of control of schistosomiasis is covered in the present re‐ view. This does not in any way reduce the importance of the other methods. It has already been emphasized above that the sustainable control of schistosomiasis involves the integra‐ tion of several methods listed above. A comprehensive review on the control of schistoso‐ miasis by this author can be found elsewhere [85]. In the next few paragraphs, the modes of action of several drugs use for the treatment of schistosomiasis are examined.

#### *4.1.1. Praziquantel (PZQ)*

**•** Population based chemotherapy

**•** Proper treatment of sewage,

**•** Provision of clean and safe piped water and

**4.1. Chemotherapeutic control of schistosomiasis**

the administration of chemotherapy programme namely;

nostic survey of the whole population

bility of finance.

selectivity.

or occupational group

luscicides,

76 Parasitic Diseases - Schistosomiasis

the programme

**•** Snail control which involves habitat modification and use of plant and chemical mol‐

**•** Good environmental engineering designs for the development of irrigation and hydro‐ electric schemes to limit the availability of breeding grounds for the snail vectors

**•** Massive health education and mobilization of the population to claim ownership of

The WHO Expert Committee on Epidemiology and Control of Schistosomiasis took a holistic approach at the control of the disease and noted that "comprehensive understanding of the envi‐ ronment, demographic, social, human behavioural and economic factors" in schistosomiasis is essential for the design of control programmes that are successful in the long run [84]. With the advent of praziquantel (PZQ) as a safe and efficacious drug for the treatment of schistosomiasis, the WHO in 1991 reinforced its 1984 recommendation to shift from transmission control (focus‐ ing on the prevalence of infection) to morbidity control (laying emphasis on intensity of infec‐ tion) [8]. Morbidity control will not only reduce the number of people infected but it will also drastically reduce environmental contamination with the eggs even when cure is not attained. A drastic reduction of the pollution of the environment with the eggs would also reduce the chan‐ ces of transmission. Should this occur at a level below public health importance, the probability

Of all the methods of control listed above, chemotherapy is the only one that is widely used presently in endemic areas for the control of morbidity due to schistosomiasis. Among the first group of drugs used for the treatment of schistosomiasis included; antimonials, nirida‐ zole, hycanthone, lucanthone, oxamniquine and albendazole. PZQ is currently used for the treatment of all the species while metrifonate is active against *S. haematobium* only. Recently, artemisinins earlier synthesized for the treatment of malaria infection is being used in some endemic communities to treat schistosomiasis. The WHO [11] identified four approaches in

**i.** Mass treatment: treatment of the entire population. This is often limited by availa‐

**ii.** Selective population treatment: treatment of infected persons identified by a diag‐

**iii.** Selective group treatment: treatment of all or infected members of a high risk age

**iv.** Phased treatment: use of the above strategies in a sequence of progressively greater

of eventual elimination of disease is certain with a sustained integrated approach

#### *4.1.1.1. Biochemical properties and pharmacokinetics*

Praziquantel (PZO) is the drug of choice for the treatment of schistosomiasis. It is a broad spectrum anti-schistosomal which is principally active against the adult stage of all the schistosome species infective to man. It is a 2-cyclohexycarbonyl 1,2,3,6,7,11b-hexahy‐ dro-4H-pyrazino(2,1-a Isoquinolin-4one) compound with a melting point at 136-140C. It was developed in the laboratories for Parasitological Research of Bayer AG and Merck KGaA in Germany (Elbert and Darmstadt) in the mid 1970s. It has a molecular mass of 312.411 with a serum half life of 0.8 to 1.5 hours in adults with normal liver and kidney function and is mainly excreted in urine. PZQ is a white crystalline powder with bitter taste. It is stable un‐ der normal storage conditions. Although, it is insoluble in water, it is soluble in chloroform, dimethylsulfoxide and ethanol. It is sold as a racemate mixture consisting of equal parts of 'laevo' and 'dextro' isomers, of which only the laevo component displays anti-schistosomal properties.

The recommended dose of PZO is 40 mg/kg body weight. The drug is available as a 600mg tablet. The quality of PZQ (proprietary and generic) currently available in the market is quite high and acceptable. Thirty four [34] PZQ samples from different manufacturers were collected at the user level in various countries and subjected to quantitative analysis of ac‐ tive ingredient, purity, disintegration and dissolution in accordance with established phar‐ macopoeial standards. The results showed that most of the samples were of high quality except two samples from the same manufacturer that had no PZQ [86]. About 90% of the damage done to organ function is known to reverse six months following the administration of PZQ. Although it is exceptionally well tolerated, reported side –effects include abdominal discomfort, nausea, headache, dizziness, drowsiness and pyrexia especially in subjects with high egg counts [87].

#### *4.1.1.2. Mode of action of PZO*

The mode of action of PZQ has been extensively reviewed elsewhere [88,89]. The exact mechanisms of action of PZQ is still poorly understood. PZQ is known to induce rapid calci‐ um influx that distort the morhoplogy and physiology of schistosome. Jeziorski and Green‐ berg [90] showed that the B subunits of voltage-gated Ca2+ channels is the prime molecular target of PZQ. It has recently been reported that cytochalasin D abolished the schistosomici‐ cidal activity of PZQ but calcium influx into PZQ exposed schistosomes was not halted. This therefore raises doubts whether calcium influx is essential in the antischistosomal activity of PZQ [91]. PZQ induces contraction of schistosomes which manifest in paralysis in the con‐ tracted state. Additionally, vacuolation and blebbing near and on the surface of the worm have equally been reported [92].

phosphorus ester which is only active against *S.haematobium*. It is rapidly absorbed, me‐ tabolized and excreted. The metabolic pathway yields DDVP (2,2-dichlorovinyl dimethylphosphate), a cholin esterase inhibitor which is the active compound. The mech‐ anism of action is not known. It is relatively cheap and is not toxic. Metrifonate is ad‐ ministered as 7.5-10 mg/kg body weight, given in three divided doses in two weeks interval. Among the side effects reported following the administration of the drug in‐ clude abdominal pains, diarrhoea, fatigue and muscular weakness which dissipates with‐ in 12 -24 hours [97]. The reasoning behind the widely spread dosage has to do with its

Schistosomiasis

79

http://dx.doi.org/10.5772/53553

Metrifonate is not currently used for the treatment of urinary schistosomiasis. Several rea‐ sons account for this. One of which is poor compliance by patients as a result of the spacing and multiple dosing. The second reason is reduced level of efficacy. For instance, Mgeni *et a*l [98] reported a cure rate of 40% and egg reduction rate of 90% in Zanzibar. Lastly, the ad‐ vent of PZQ with its superior efficacy rate and broad spectrum activity meant that it was no

The artemisinins though syntheised for the treatment of malaria is the newest drug used for the treatment of schistosomiasis. Unlike PZQ, which is active against the adult stages of the parasite, artemisinin is active against the immature stage of parasite. It is a sequitterpene lactone with a peroxide group, obtained from the leaves of the plant, *Artemisia annua* which are grown in Central Europe, China, USA and Argentina among others. The major deriva‐ tives of artemisinin are artesunate, artemether, arteether with dihydroartemisinin as the principal active metabolite. Primarily they are antimalarials, but the anti-schistosomal prop‐ erties were discovered by Chinese scientists in the 1980s especially for the treatment of *S ja‐*

The precise mode of action of this drug is not known. Artemether is the most potent. It ex‐ hibits the highest level of activity on one to three weeks old liver stages of the parasite. When a dosage of 6mg/kg weight is administered, it kills the schistosomulas during the first 21 days. The invasive and adult stages are less affected and the adult females are more sus‐ ceptible than the males [100]. Following treatment, artemether induces severe and extensive tegumental damage and significant reduction in glycogen contents through the inhibition of glycolsis, but the onset of this alteration is slow. It also hinders the development of egg lay‐

PZQ is currently the drug of choice for the treatment of all forms of the disease. It is safe and well tolerated. Readers are referred to a very detailed review on "praziquantel: its use in control of control of schistosomiasis in sub-Saharan Africa and current research needs [89] and "praziquantel: mechanisms of action, resistance and new derivatives for schistosomia‐ sis" [88]. Elsewhere, we reported on the high efficacy and tolerability of PZQ [102] and arte‐

*4.1.1.6. Artemisinin and its derivatives – Biochemical characteristics and pharmacokinetics*

*ponicum* infection [99]. They are well tolerated with only minor side effects.

inhibitory effects on red cells and plasma cholinesterase.

longer cost effective and sustainable to rely on metrifonate.

*4.1.1.7. Mode of action of artemisinin*

ing adult worm pairs [101].

PZQ is known to increase exposure of antigens on the worm surface. It is believed that this in turn renders the worm more susceptible to antibody attack. Doenhoff *et al* [93] inferred that this drug induced antigen exposure is assumed to account for the synergistic effect be‐ tween PZQ and the host antibodies in killing worms invivo. Recently, it has been shown that PZQ seems to interfere with adenosine uptake in cultured worms. This may have thera‐ peutical relevance given that the schistosome is unable to synthesize purines such as adeno‐ sine *de novo.* It may be assumed that the drug interferes with schistosome's obligate need to acquire adenosine from its host. This is confounding as a relationship between Ca2+ channels and adenosine receptors has been demonstrated in cells of some other animals and adeno‐ sine can antagonize Ca2+ release. This informs the inference drawn by Angelucci *et al* [94] that PZQ-induced Ca2+ influx and adenosine receptor blockade may be connected.

## *4.1.1.3. Oxamniquine – Molecular structure and pharmacokinetics*

Oxamniquine was first described in the late 1960s. The compound is 6-hydromethyl-2 isopropyl-aminomethyl-7-nitro 1,2,4-tetrahydroquinoline. It is produced by biological processes. The drug is administered as 15mg/kg body weight for adults while children are treated with 20mg/kg given in two doses of 10mg/kg each in an interval of 3-8 hours. It is extensively metabolised through oxidation process. The metabolites are active and excreted in urine. The side effects are mild, transient and well tolerated especially when given after a meal [95].

## *4.1.1.4. Mode of action*

Unlike PZQ, the mechanism of action of oxamniquine is fairly well understood. Oxamni‐ quine is only active against *S. mansoni* but not effective against *S. haematobium* and *S. japoni‐ cum*. The active ingredient is tetrahydroquinoline which acts on the adult *S. mansoni* and immature invasive stages, with males more susceptible than the females. Its anticholinergic effect, which increases parasite motility and inhibits nucleic acid synthesis, has no notable effect on the other *Schistosome* species [96]. The mechanism of action of oxamniquine is relat‐ ed to irreversible inhibition of nucleic acid metabolism of the parasite. The drug is activated in a single step, in which the *Schistosoma* enzyme converts the oxamniquine to an ester, and spontaneously dissociates resulting in an electrophilic reactant and alkylation of the Schisto‐ soma DNA. Worm death is associated with the formation of sub-tegumental vesicules in adult parasites. Different responses are observed after therapy, with less specific morpho‐ logical alteration and hepatic shifts, occurring over a period of six days post treatment [95].

#### *4.1.1.5. Metrifonate*

Metrifonate was initially introduced as an insecticide in 1952, but later in 1960, it was used to treat helminth infection. The drug also refer to as trichlorophone is a organo‐ phosphorus ester which is only active against *S.haematobium*. It is rapidly absorbed, me‐ tabolized and excreted. The metabolic pathway yields DDVP (2,2-dichlorovinyl dimethylphosphate), a cholin esterase inhibitor which is the active compound. The mech‐ anism of action is not known. It is relatively cheap and is not toxic. Metrifonate is ad‐ ministered as 7.5-10 mg/kg body weight, given in three divided doses in two weeks interval. Among the side effects reported following the administration of the drug in‐ clude abdominal pains, diarrhoea, fatigue and muscular weakness which dissipates with‐ in 12 -24 hours [97]. The reasoning behind the widely spread dosage has to do with its inhibitory effects on red cells and plasma cholinesterase.

Metrifonate is not currently used for the treatment of urinary schistosomiasis. Several rea‐ sons account for this. One of which is poor compliance by patients as a result of the spacing and multiple dosing. The second reason is reduced level of efficacy. For instance, Mgeni *et a*l [98] reported a cure rate of 40% and egg reduction rate of 90% in Zanzibar. Lastly, the ad‐ vent of PZQ with its superior efficacy rate and broad spectrum activity meant that it was no longer cost effective and sustainable to rely on metrifonate.

## *4.1.1.6. Artemisinin and its derivatives – Biochemical characteristics and pharmacokinetics*

The artemisinins though syntheised for the treatment of malaria is the newest drug used for the treatment of schistosomiasis. Unlike PZQ, which is active against the adult stages of the parasite, artemisinin is active against the immature stage of parasite. It is a sequitterpene lactone with a peroxide group, obtained from the leaves of the plant, *Artemisia annua* which are grown in Central Europe, China, USA and Argentina among others. The major deriva‐ tives of artemisinin are artesunate, artemether, arteether with dihydroartemisinin as the principal active metabolite. Primarily they are antimalarials, but the anti-schistosomal prop‐ erties were discovered by Chinese scientists in the 1980s especially for the treatment of *S ja‐ ponicum* infection [99]. They are well tolerated with only minor side effects.

#### *4.1.1.7. Mode of action of artemisinin*

PZQ [91]. PZQ induces contraction of schistosomes which manifest in paralysis in the con‐ tracted state. Additionally, vacuolation and blebbing near and on the surface of the worm

PZQ is known to increase exposure of antigens on the worm surface. It is believed that this in turn renders the worm more susceptible to antibody attack. Doenhoff *et al* [93] inferred that this drug induced antigen exposure is assumed to account for the synergistic effect be‐ tween PZQ and the host antibodies in killing worms invivo. Recently, it has been shown that PZQ seems to interfere with adenosine uptake in cultured worms. This may have thera‐ peutical relevance given that the schistosome is unable to synthesize purines such as adeno‐ sine *de novo.* It may be assumed that the drug interferes with schistosome's obligate need to acquire adenosine from its host. This is confounding as a relationship between Ca2+ channels and adenosine receptors has been demonstrated in cells of some other animals and adeno‐ sine can antagonize Ca2+ release. This informs the inference drawn by Angelucci *et al* [94]

that PZQ-induced Ca2+ influx and adenosine receptor blockade may be connected.

Oxamniquine was first described in the late 1960s. The compound is 6-hydromethyl-2 isopropyl-aminomethyl-7-nitro 1,2,4-tetrahydroquinoline. It is produced by biological processes. The drug is administered as 15mg/kg body weight for adults while children are treated with 20mg/kg given in two doses of 10mg/kg each in an interval of 3-8 hours. It is extensively metabolised through oxidation process. The metabolites are active and excreted in urine. The side effects are mild, transient and well tolerated especially

Unlike PZQ, the mechanism of action of oxamniquine is fairly well understood. Oxamni‐ quine is only active against *S. mansoni* but not effective against *S. haematobium* and *S. japoni‐ cum*. The active ingredient is tetrahydroquinoline which acts on the adult *S. mansoni* and immature invasive stages, with males more susceptible than the females. Its anticholinergic effect, which increases parasite motility and inhibits nucleic acid synthesis, has no notable effect on the other *Schistosome* species [96]. The mechanism of action of oxamniquine is relat‐ ed to irreversible inhibition of nucleic acid metabolism of the parasite. The drug is activated in a single step, in which the *Schistosoma* enzyme converts the oxamniquine to an ester, and spontaneously dissociates resulting in an electrophilic reactant and alkylation of the Schisto‐ soma DNA. Worm death is associated with the formation of sub-tegumental vesicules in adult parasites. Different responses are observed after therapy, with less specific morpho‐ logical alteration and hepatic shifts, occurring over a period of six days post treatment [95].

Metrifonate was initially introduced as an insecticide in 1952, but later in 1960, it was used to treat helminth infection. The drug also refer to as trichlorophone is a organo‐

*4.1.1.3. Oxamniquine – Molecular structure and pharmacokinetics*

have equally been reported [92].

78 Parasitic Diseases - Schistosomiasis

when given after a meal [95].

*4.1.1.4. Mode of action*

*4.1.1.5. Metrifonate*

The precise mode of action of this drug is not known. Artemether is the most potent. It ex‐ hibits the highest level of activity on one to three weeks old liver stages of the parasite. When a dosage of 6mg/kg weight is administered, it kills the schistosomulas during the first 21 days. The invasive and adult stages are less affected and the adult females are more sus‐ ceptible than the males [100]. Following treatment, artemether induces severe and extensive tegumental damage and significant reduction in glycogen contents through the inhibition of glycolsis, but the onset of this alteration is slow. It also hinders the development of egg lay‐ ing adult worm pairs [101].

PZQ is currently the drug of choice for the treatment of all forms of the disease. It is safe and well tolerated. Readers are referred to a very detailed review on "praziquantel: its use in control of control of schistosomiasis in sub-Saharan Africa and current research needs [89] and "praziquantel: mechanisms of action, resistance and new derivatives for schistosomia‐ sis" [88]. Elsewhere, we reported on the high efficacy and tolerability of PZQ [102] and arte‐ sunate [103] for the treatment of urinary schistosomiasis in Nigeria.These authors noted that despite the fact that PZQ is being widely used, there is no clinically relevant evidence for resistance to date, but worrying low-cure rates have been recorded in some studies. They also observed that there is also no assurance that PZQ and/or Schistosomes are in any way unique and that resistant organisms will not be selected as a result of widespread usage. Ar‐ tesiminis and the related 1,2,4-trioxolanes are now promising antischistosomal compounds, as are inhibitors of a schistosome-specific bifunctional enzyme, thioredoxin-glutathione re‐ ductase. In some endemic communities, artesunate is also used for the treatment of malaria singly or in combination. Therefore, where artesunate is used for the treatment of urinary schistosomiasis, resistance may likely develop to malaria. It is pertinent to do an analysis on why schistosomiasis is still highly endemic in some parts of Africa including Nigeria when a potent drug is available for the management of the disorder.

miasis Control Initiative [SCI] supported by a US\$ 30 million grant from the Bill and Me‐ lina Gates Foundation. The SCI is a partnership between Imperial College, London, UK; the Seattle-based Gates Foundation, WHO, Geneva; Harvard School of Public Health, Boston and high-burden country representatives. This renewed interest has encouraged the Carter Centre to be involved in the control of schistosomiasis in Nigeria. The Centre is assisting in the control of schistosomiasis in three states namely; Plateau, Nasarawa and Delta. The Centre is doing this by using the grassroots distribution system of health workers and village volunteers for onchocerciasis to also deliver health education and conduct mass drug administration with PZQ annually in areas affected by both para‐ sites. Since 1999, this programme has delivered a cumulative total of 1,079,335 treatments with PZQ. Studies in a sample of villages in two areas showed a reduction in prevalence of bloody urine assessed by dipsticks from 47% in 1999 to 8% in 2002, after just two years of annual treatments [109]. This success means that LF, onchoceriasis and schisto‐ somiasis can be treated by community health workers at the same time thereby saving enormous cost as a recent clinical trial in Thailand found no clinically relevant pharma‐ cokinetic changes or adverse reactions when ivermectin, PZQ and albendazole were giv‐

Schistosomiasis

81

http://dx.doi.org/10.5772/53553

The health system of many countries in the developing world are not synchronized and in‐ tegrated. This renders the delivery of health packages difficult and cumbersome. However, there is a conseneus that strong, well integrated and effective health systems are essentials to reduce disease burden and to achieving the health related MDGs. A Strong health sys‐ tems typically consist of seven building blocks [111,112]. These include: service delivery, governance structures, financial mechanisms, human resources, medicines and technology supply system, health information system and participatory community mechanisms (peo‐ ple). In an ideal situation, these seven components must exist and work together to generate

Failures associated with the planning and delivery of healthcare are critical issues that should be targeted to ensure success in the control of infectious diseases including schisto‐ soimasis. In this context, Mahoney and Morel [113] argued that innovation disparity has cre‐ ated 3 kinds of "health failures" namely "science failure, market failure and public health failure". Science failure refers "to a lack of knowledge and tools to address health problems e.g there are still no effective vaccines or drugs for schistosomiasis". Market failures happen "when stock-outs occur due to high demand or when the purchase costs of drugs, vaccines and health interventions prevent the poor from accessing them". Often the new drugs and diagnostics are very expensive to develop and /or require sophisticated technical and health infrastructure for optimal use. Public health failure arises "due to lack of good governance, transparency and effective delivery systems and a clear articulation of priorities and val‐ ues". Political and economic instability, cultural and religious barriers and shift in govern‐

en concurrently [110]

*4.1.1.8.4. Health failures*

*4.1.1.8.3. Lack of strong health system*

quality (accessible, equitable, responsive health care)

#### *4.1.1.8. Impediments of control of schistosomiais*

Several factors are responsible for the continuing endemicity of schistosomiasis in Africa. Some of the factors are examined below;

#### *4.1.1.8.1. High cost of PZQ*

Richards [104] identified community-based annual mass drug administration with safe and effective oral drugs as the principal strategy for the control of onchocerciasis, lymphatic fi‐ lariasis and schistosomiasis. It has been demonstrated that annual treatments with the mi‐ crofilaricide ivermectin (Mectizan, donated by Merck &Co., Inc.) prevents severe eye disease and skin manifestations of onchocerciasis while the transmission of LF by mosquitoes can be interrupted in Africa by annual single-dose combination therapy with ivermectin and alben‐ dazole (donated by GlaxoSmithKline) [105]. Mass distribution of PZQ can significantly re‐ duce schistosomiasis morbidity [106]. However, unlike ivermectin and albendazole, PZQ is not donated and costs approximately US \$0.20. Schistosomiasis is a disease that affects poor rural agricultural workers who in most cases cannot afford the cost of PZQ. This is one of the greatest impediments in the control of the disease.

## *4.1.1.8.2. Lack of political commitment and provision of finance*

Until recently, there was no sustained political and financial commitment by the WHO and her health-related agencies and governments of schistosomiasis endemic countries towards the control of schistosomiasis. The success story reported in the control of schis‐ tosomiasis in Brazil, China, Egypt, Laos and the Philippines [10,107,108] is an encourage‐ ment that the disease can be controlled when the right programmes and processes are in place. Over the years, emphasis on funding of infectious disease control was placed on HIV/AIDS, malaria and tuberculosis/leprosy. That informed the categorization of schisto‐ somiasis as one of the neglected tropical diseases. However, the situation changed dur‐ ing the 54th World Health Assembly held in May, 2001 where resolution WHA 54.19 namely that at least 75% of school-age children in the high-burden regions should be treated regularly with PZQ. This was further enhanced by the launch of the Schistoso‐ miasis Control Initiative [SCI] supported by a US\$ 30 million grant from the Bill and Me‐ lina Gates Foundation. The SCI is a partnership between Imperial College, London, UK; the Seattle-based Gates Foundation, WHO, Geneva; Harvard School of Public Health, Boston and high-burden country representatives. This renewed interest has encouraged the Carter Centre to be involved in the control of schistosomiasis in Nigeria. The Centre is assisting in the control of schistosomiasis in three states namely; Plateau, Nasarawa and Delta. The Centre is doing this by using the grassroots distribution system of health workers and village volunteers for onchocerciasis to also deliver health education and conduct mass drug administration with PZQ annually in areas affected by both para‐ sites. Since 1999, this programme has delivered a cumulative total of 1,079,335 treatments with PZQ. Studies in a sample of villages in two areas showed a reduction in prevalence of bloody urine assessed by dipsticks from 47% in 1999 to 8% in 2002, after just two years of annual treatments [109]. This success means that LF, onchoceriasis and schisto‐ somiasis can be treated by community health workers at the same time thereby saving enormous cost as a recent clinical trial in Thailand found no clinically relevant pharma‐ cokinetic changes or adverse reactions when ivermectin, PZQ and albendazole were giv‐ en concurrently [110]

#### *4.1.1.8.3. Lack of strong health system*

sunate [103] for the treatment of urinary schistosomiasis in Nigeria.These authors noted that despite the fact that PZQ is being widely used, there is no clinically relevant evidence for resistance to date, but worrying low-cure rates have been recorded in some studies. They also observed that there is also no assurance that PZQ and/or Schistosomes are in any way unique and that resistant organisms will not be selected as a result of widespread usage. Ar‐ tesiminis and the related 1,2,4-trioxolanes are now promising antischistosomal compounds, as are inhibitors of a schistosome-specific bifunctional enzyme, thioredoxin-glutathione re‐ ductase. In some endemic communities, artesunate is also used for the treatment of malaria singly or in combination. Therefore, where artesunate is used for the treatment of urinary schistosomiasis, resistance may likely develop to malaria. It is pertinent to do an analysis on why schistosomiasis is still highly endemic in some parts of Africa including Nigeria when a

Several factors are responsible for the continuing endemicity of schistosomiasis in Africa.

Richards [104] identified community-based annual mass drug administration with safe and effective oral drugs as the principal strategy for the control of onchocerciasis, lymphatic fi‐ lariasis and schistosomiasis. It has been demonstrated that annual treatments with the mi‐ crofilaricide ivermectin (Mectizan, donated by Merck &Co., Inc.) prevents severe eye disease and skin manifestations of onchocerciasis while the transmission of LF by mosquitoes can be interrupted in Africa by annual single-dose combination therapy with ivermectin and alben‐ dazole (donated by GlaxoSmithKline) [105]. Mass distribution of PZQ can significantly re‐ duce schistosomiasis morbidity [106]. However, unlike ivermectin and albendazole, PZQ is not donated and costs approximately US \$0.20. Schistosomiasis is a disease that affects poor rural agricultural workers who in most cases cannot afford the cost of PZQ. This is one of

Until recently, there was no sustained political and financial commitment by the WHO and her health-related agencies and governments of schistosomiasis endemic countries towards the control of schistosomiasis. The success story reported in the control of schis‐ tosomiasis in Brazil, China, Egypt, Laos and the Philippines [10,107,108] is an encourage‐ ment that the disease can be controlled when the right programmes and processes are in place. Over the years, emphasis on funding of infectious disease control was placed on HIV/AIDS, malaria and tuberculosis/leprosy. That informed the categorization of schisto‐ somiasis as one of the neglected tropical diseases. However, the situation changed dur‐ ing the 54th World Health Assembly held in May, 2001 where resolution WHA 54.19 namely that at least 75% of school-age children in the high-burden regions should be treated regularly with PZQ. This was further enhanced by the launch of the Schistoso‐

potent drug is available for the management of the disorder.

the greatest impediments in the control of the disease.

*4.1.1.8.2. Lack of political commitment and provision of finance*

*4.1.1.8. Impediments of control of schistosomiais*

Some of the factors are examined below;

*4.1.1.8.1. High cost of PZQ*

80 Parasitic Diseases - Schistosomiasis

The health system of many countries in the developing world are not synchronized and in‐ tegrated. This renders the delivery of health packages difficult and cumbersome. However, there is a conseneus that strong, well integrated and effective health systems are essentials to reduce disease burden and to achieving the health related MDGs. A Strong health sys‐ tems typically consist of seven building blocks [111,112]. These include: service delivery, governance structures, financial mechanisms, human resources, medicines and technology supply system, health information system and participatory community mechanisms (peo‐ ple). In an ideal situation, these seven components must exist and work together to generate quality (accessible, equitable, responsive health care)

#### *4.1.1.8.4. Health failures*

Failures associated with the planning and delivery of healthcare are critical issues that should be targeted to ensure success in the control of infectious diseases including schisto‐ soimasis. In this context, Mahoney and Morel [113] argued that innovation disparity has cre‐ ated 3 kinds of "health failures" namely "science failure, market failure and public health failure". Science failure refers "to a lack of knowledge and tools to address health problems e.g there are still no effective vaccines or drugs for schistosomiasis". Market failures happen "when stock-outs occur due to high demand or when the purchase costs of drugs, vaccines and health interventions prevent the poor from accessing them". Often the new drugs and diagnostics are very expensive to develop and /or require sophisticated technical and health infrastructure for optimal use. Public health failure arises "due to lack of good governance, transparency and effective delivery systems and a clear articulation of priorities and val‐ ues". Political and economic instability, cultural and religious barriers and shift in govern‐ ment priorities can block the uptake and implementation of health innovations. This is particularly true in Africa where frequent changes of government and dislocation of com‐ munities as a result of natural disasters and inter and intra-tribal wars have contributed to hinder outcome of disease control programmes.

and Dillion *et al* [127], current advances in post-genomic techniques are providing new ave‐ nues and hope to identify the secreted and surface-exposed antigens that mediate protec‐ tion. The search must be sustained as vaccination is the most cost-effective and sustainable

Schistosomiasis

83

http://dx.doi.org/10.5772/53553

Schistosomiasis is still endemic in many parts of Africa particularly Nigeria. Activities related to electric power development/generation and agriculture have extended areas of endemicity just as new foci of infection are being described. The control of schistoso‐ miasis requires an integrated process. However, chemotherapy with PZQ is the main‐ stay for the control of the disease in the short-term. Poverty on the part of infected subjects, lack of deployment of political and financial resources by disease endemic countries are the major factors limiting the control of the disease. The global economic recession has contributed in reducing financial resources available through bilateral and multilateral avenues for the control of the infectious diseases just as increase in interna‐ tional travels and tourism have led to the reporting of "imported schistosomiasis" in

The following recommendations are suggested for the control of schistosomiasis;

albendazole and ivermectin or in the alternative reduce the cost of the drug.

reduce the chances of coming in contact with cercariae infested water bodies

funded in line with the recommendation of the WHO.

ing the three drugs concurrently is safe and effective

for the diagnosis of schistomiasis and instant treatment.

This is the only means of long term control of this disease.

**•** Governments of disease endemic countries should show serious political and financial commitment towards the control of schistosomiasis. Overall, the health sector should be

**•** Pharmaceutical companies should be encourage to donate PZQ free as is obtainable with

**•** The delivery of PZQ should be integrated into ongoing programme of distribution of ivermectin and albendazole by community health workers as it has been shown that tak‐

**•** There should be a deliberate policy of providing piped water in endemic communities to

**•** Researchers should be encouraged to develop rapid diagnostic and cost-effective test based on antibody detection which can provide results within 15-20 minutes in the field

**•** More researches are required to hasten the development of a vaccine for schistosomiasis.

means of controlling endemic infectious diseases.

**6. Conclusion**

non-endemic countries.

**Recommendation**

## **5. Development of a schistosome vaccine**

Despite the existence of effective chemotherapeutic agents, progress towards controlling schistosomiasis has been slow. Additionally, the possible development of resistance to PZQ and other compounds, rapid re-infection and the overall economic cost, demand that other approaches be pursued [114]. Butterworth *et al* [115] argued that the aim of vaccination is to reduce morbidity. As in the various animal models, immunity in hu‐ mans appears to be frequently incomplete. "Immune" adults often do become infected, but at lower intensities than "susceptible" children. Several investigations have con‐ firmed that the severity of clinical disease is dependent on intensity of infection rather than simply the presence or absence of infection [116,117] implying that even an incom‐ plete immunity may be of considerable value.

An excellent review on the search for a schistosome vaccine was published not too long ago [118]. These authors rightly chronicled the search for the discovery of candidate vaccine molecules to have transited through mining crude extracts, monoclonal antibody targets, an‐ ti-idiotypes, expression library screening and immunogenicity. The early disappointment that was recorded with the vaccination of mice with crude worm extracts or purified compo‐ nents, followed by cercarial challenge [119,120] and utilizing the idea of concomitant im‐ munity [121] were equally reviewed. Wilson and Coulson [118] concluded that the sequencing of *S. mansoni* transriptome and genome and the development of proteomic and microarray technologies has drastically improved the possibilities for identiflying novel vac‐ cine candidates, particularly proteins secreted from or exposed at the surface of schistoso‐ mula and adult worms. The parameters of an attenuated schistosome vaccine has been evaluated in the Olive Baboon [122]. Five exposures of baboons to the attenuated schisto‐ some vaccine gave greater protection than three exposures, but this attenuation was not sus‐ tained when challenge was delayed. Within the scope of the data collected, faecal and circulating antigen levels did not accurately predict the observed worm burdens. Levels of immunoglobulin G at challenge correlated best with protection, but there was little evidence of a recall response. In a related study in baboons, Coulson and Kariuki [123] showed that neither a preceding infection, terminated by chemotherapy, nor an ongoing chronic infec‐ tion affected the level of protection. Whilst IgM responses to vaccination or infection were short-lived, IgG responses rose with each successive exposure to vaccine.

The greatest hope for the discovery of a schistosome vaccine lies in Sh28GST which has al‐ ready undergone Phases 1 and 2 human trials [124]. No adverse side effects were recorded in human recipients and high titres of antibodies were elicited in Phase 1 and phase 2 trials [125]. The results of phase 3 human trials is being awaited. As noted by Curwen *et al* [126] and Dillion *et al* [127], current advances in post-genomic techniques are providing new ave‐ nues and hope to identify the secreted and surface-exposed antigens that mediate protec‐ tion. The search must be sustained as vaccination is the most cost-effective and sustainable means of controlling endemic infectious diseases.

## **6. Conclusion**

ment priorities can block the uptake and implementation of health innovations. This is particularly true in Africa where frequent changes of government and dislocation of com‐ munities as a result of natural disasters and inter and intra-tribal wars have contributed to

Despite the existence of effective chemotherapeutic agents, progress towards controlling schistosomiasis has been slow. Additionally, the possible development of resistance to PZQ and other compounds, rapid re-infection and the overall economic cost, demand that other approaches be pursued [114]. Butterworth *et al* [115] argued that the aim of vaccination is to reduce morbidity. As in the various animal models, immunity in hu‐ mans appears to be frequently incomplete. "Immune" adults often do become infected, but at lower intensities than "susceptible" children. Several investigations have con‐ firmed that the severity of clinical disease is dependent on intensity of infection rather than simply the presence or absence of infection [116,117] implying that even an incom‐

An excellent review on the search for a schistosome vaccine was published not too long ago [118]. These authors rightly chronicled the search for the discovery of candidate vaccine molecules to have transited through mining crude extracts, monoclonal antibody targets, an‐ ti-idiotypes, expression library screening and immunogenicity. The early disappointment that was recorded with the vaccination of mice with crude worm extracts or purified compo‐ nents, followed by cercarial challenge [119,120] and utilizing the idea of concomitant im‐ munity [121] were equally reviewed. Wilson and Coulson [118] concluded that the sequencing of *S. mansoni* transriptome and genome and the development of proteomic and microarray technologies has drastically improved the possibilities for identiflying novel vac‐ cine candidates, particularly proteins secreted from or exposed at the surface of schistoso‐ mula and adult worms. The parameters of an attenuated schistosome vaccine has been evaluated in the Olive Baboon [122]. Five exposures of baboons to the attenuated schisto‐ some vaccine gave greater protection than three exposures, but this attenuation was not sus‐ tained when challenge was delayed. Within the scope of the data collected, faecal and circulating antigen levels did not accurately predict the observed worm burdens. Levels of immunoglobulin G at challenge correlated best with protection, but there was little evidence of a recall response. In a related study in baboons, Coulson and Kariuki [123] showed that neither a preceding infection, terminated by chemotherapy, nor an ongoing chronic infec‐ tion affected the level of protection. Whilst IgM responses to vaccination or infection were

short-lived, IgG responses rose with each successive exposure to vaccine.

The greatest hope for the discovery of a schistosome vaccine lies in Sh28GST which has al‐ ready undergone Phases 1 and 2 human trials [124]. No adverse side effects were recorded in human recipients and high titres of antibodies were elicited in Phase 1 and phase 2 trials [125]. The results of phase 3 human trials is being awaited. As noted by Curwen *et al* [126]

hinder outcome of disease control programmes.

82 Parasitic Diseases - Schistosomiasis

**5. Development of a schistosome vaccine**

plete immunity may be of considerable value.

Schistosomiasis is still endemic in many parts of Africa particularly Nigeria. Activities related to electric power development/generation and agriculture have extended areas of endemicity just as new foci of infection are being described. The control of schistoso‐ miasis requires an integrated process. However, chemotherapy with PZQ is the main‐ stay for the control of the disease in the short-term. Poverty on the part of infected subjects, lack of deployment of political and financial resources by disease endemic countries are the major factors limiting the control of the disease. The global economic recession has contributed in reducing financial resources available through bilateral and multilateral avenues for the control of the infectious diseases just as increase in interna‐ tional travels and tourism have led to the reporting of "imported schistosomiasis" in non-endemic countries.

## **Recommendation**

The following recommendations are suggested for the control of schistosomiasis;


## **Acknowledgments**

I wish to appreciate the assistance rendered by my wife; Mary and my daughter; Etini dur‐ ing the preparation of this manuscript. I am indebted to all the colleagues whose references are listed below which have greatly enhance the quality of the manuscript.

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TDR/WP 76.6

92-95.

## **Author details**

Monday Francis Useh

University of Calabar, Calabar, Nigeria

## **References**


[10] World Health Organisation (2002). Prevention and control of schistosomiasis and soil-transmitted helmithiasis. Report of a WHO Expert Committee. Geneva, World Health Organisation (WHO Technical Report Series, No 912).

**Acknowledgments**

84 Parasitic Diseases - Schistosomiasis

**Author details**

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University of Calabar, Calabar, Nigeria

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**Section 2**

**Clinical Schistosomiasis**
