**4.2 Efforts to control human malaria in Nigeria**

Nigeria is a large country and the most populous country in Africa (169 million; Nigeria population commission) and one of the hardest hit by malaria in the entire globe [25].

The Nigeria Federal Ministry of Health reported that Nigeria loses about 1.1 trillion naira annually to control malaria. A lot of funds have been invested on malaria drugs, insecticides, and mosquito nets for control of malaria. The Nigerian Minister of Health claimed that malaria reduces the country's gross domestic product (GDP) by 1% annually [26].

The burden of malaria in Nigeria is being managed through effective case management and vector control measures, including the use of insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS). ITNs are now distributed freely to vulnerable groups in Nigeria. IRS is also one of the major vector control interventions used in Nigeria today. However, these methods have limitations in their usage [27].

Vector control has proven record in the prevention and control of vector-borne diseases. However, it is bad news that despite all the efforts to control mosquitoes in Nigeria, they are not even threatened or on the verge of extinction [9]. Malaria still remains a deadly scourge and formidable foe of public health concern. These are the main challenges:

## **4.3 Diverse anopheles species complexes and sibling species**

Malaria transmission dynamics is a complex system that is superficially understood. For example, one has to deal with diversity of mosquito species in the tropics. The *An. gambiae* complex is the predominant vector in sub-Saharan Africa, but it is not the only vector in the field [18, 23].


**95**

techniques [32].

*Nipping the Malaria Vectors in the Bud: Focus on Nigeria*

*An. funestus ss* like *An. gambiae ss* is also very widespread, highly endophilic, and anthropophilic and hence anthropophagic. Both complexes are polymorphic, biologically and genetically. Evidences suggest that they may share the same habitat, although *An. funestus ss* is more restricted in habitat choice than *An. gambiae ss* [18, 23, 30].

The behavior of each of the sibling species in both complexes varies and so their roles in malaria transmission. Hence, targeting only one sibling species by whatever method is not going to curb the menace of malaria. The diversity of the epidemiological situations within sub-Saharan ecotypes presents different malaria situation [31]. Comprehensive knowledge of behavior and heterogeneities that exist within, and among these vectors, will always be of benefit. Any strategy aiming at control

Malaria transmission dynamics is variable throughout Africa with huge variability in transmission patterns even within villages few kilometers apart [33]. The correct analysis of the distribution of specific malaria vectors is one of the prerequisites for meaningful epidemiological studies and for planning and monitoring of

In the past, large areas of Nigeria had no reliable data in the past on presence and absence of vectors [23]. It has been established that there are diversities of malaria vectors in Nigeria and they have different bionomics and vector competences. In Nigeria today, 35 *Anopheles* species have so far been recognized, but they do not all transmit malaria under the same circumstances. Some *Anopheles* mosquito species have unknown vector status, while some are non-malaria vectors ([9, 12]. However, the malaria transmission dynamics in Nigeria is mainly vectored by members of the *An. gambiae* complex such as *An. gambiae ss*, *An. coluzzi*, and *An. arabiensis*. *An .funestus s*s is also an important main vector, while *An. nili*, *An. melas*, and *An. moucheti* are localized vectors in Nigeria [9, 23, 29]. Secondary vectors in Nigeria include *An. pharoensis*, *An. coustani*, *An. hancocki*, and *An. longipalpis* [9, 12]. Control measures can only be effective if the abundance, behavior, and proportion of the vectors are known. The existence of species complexes containing morphologically cryptic sibling or isomorphic forms presents a major challenge to malaria control program as these require vector identification using molecular

Failure to know which sibling species one is dealing with will result in wasting

The malaria problem in sub-Saharan Africa represents a peculiar case because the vectorial system is the most complex anywhere. This vectorial system diversity

Vectorial capacity and vectorial competence have been used interchangeably to describe the ability of mosquitoes to serve as a disease vector. The two terms are not synonyms because vectorial capacity is qualitative and is influenced by such variables as vector density, longevity, and vector competence itself [3]. Vectorial capacity takes into account environmental, behavioral, and cellular and biochemical factors that influence the association between a vector, the pathogen transmitted

However, vectorial competence is a component of vectorial capacity which is governed by intrinsic and generic factors that influence the ability of a vector to transmit a pathogen. For example, the susceptibility of an *Anopheles* mosquito to sporozoite stage of *Plasmodium* species is an important component of vectorial competence [37]. Vector competence, however, differs from one species to another and from place to place. There are *Anopheles* species complexes that vary in their

**4.4 Vectorial capacity and vectorial competence of the malaria vectors**

by the vector, and the host to which the pathogen is being transmitted [36].

will have to account for this heterogeneity in species diversity [32].

successful malaria control or eradication program [34].

scare resources and time to control non-malaria vectors [9].

absolutely impacts malaria epidemiology and control [35].

*DOI: http://dx.doi.org/10.5772/intechopen.83554*

*Malaria*

the planet earth [4].

globe [25].

usage [27].

main challenges:

by 1% annually [26].

global malaria deaths [20]. Malaria is one of the greatest causes of outpatient visits and work and school absenteeism in Nigeria [21, 22]. It has a familiar reputation of causing fever, headache, and teeth chattering shills and shakes [22]. Malaria is the number one killer disease in Nigeria where unfortunately, it is called "common" malaria. This is an irony! Malaria death has been described by an expert as causing death more than the deaths due to the first and second world wars [9]. No wonder the World Health Organization described mosquitoes as the deadliest animals on

*P. falciparum* is the most virulent species of malaria parasite in Nigeria. It causes 95% of infections, while *P. malariae* causes 5% of infections in Nigeria [23]. *P. ovale* is rarely seen, while *P. vivax* is absent in the whole of West Africa [24]. The risk of malaria exists throughout the country where it is a disease of public health concern. Malaria imposes immense morbidity and mortality as well as socioeconomic

Nigeria is a large country and the most populous country in Africa (169 million; Nigeria population commission) and one of the hardest hit by malaria in the entire

The Nigeria Federal Ministry of Health reported that Nigeria loses about 1.1 trillion naira annually to control malaria. A lot of funds have been invested on malaria drugs, insecticides, and mosquito nets for control of malaria. The Nigerian Minister of Health claimed that malaria reduces the country's gross domestic product (GDP)

The burden of malaria in Nigeria is being managed through effective case management and vector control measures, including the use of insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS). ITNs are now distributed freely to vulnerable groups in Nigeria. IRS is also one of the major vector control interventions used in Nigeria today. However, these methods have limitations in their

Vector control has proven record in the prevention and control of vector-borne diseases. However, it is bad news that despite all the efforts to control mosquitoes in Nigeria, they are not even threatened or on the verge of extinction [9]. Malaria still remains a deadly scourge and formidable foe of public health concern. These are the

Malaria transmission dynamics is a complex system that is superficially understood. For example, one has to deal with diversity of mosquito species in the tropics. The *An. gambiae* complex is the predominant vector in sub-Saharan Africa, but it is

• The *Anopheles gambiae* species complex consists of at least eight different sibling species: *An. gambiae (ss), An. arabiensis*, *An. melas*, *An. merus*, *An. quadrimaculatus A*, *An. quadrimaculatus B*, *An.bwambae*, *and An. coluzzi* [9, 23, 28].

• *An. funestus* species complex is another group of mosquitoes that play significant role in malaria transmission in sub-Saharan Africa. This complex occurs in sympatry with the *An. gambiae* complex [23, 29]. The eight sibling species of the *An. funestus* species complex are *An. funestus* ss, *An. rivulorum*, *An. vaneedi*,

*An. leesoni*, *An. parensis*, *An. brucei*, *An. confuscus*, and *An. aruni.*

**4.3 Diverse anopheles species complexes and sibling species**

not the only vector in the field [18, 23].

burdens on both individuals and the nation at large [21, 22].

**4.2 Efforts to control human malaria in Nigeria**

**94**

*An. funestus ss* like *An. gambiae ss* is also very widespread, highly endophilic, and anthropophilic and hence anthropophagic. Both complexes are polymorphic, biologically and genetically. Evidences suggest that they may share the same habitat, although *An. funestus ss* is more restricted in habitat choice than *An. gambiae ss* [18, 23, 30].

The behavior of each of the sibling species in both complexes varies and so their roles in malaria transmission. Hence, targeting only one sibling species by whatever method is not going to curb the menace of malaria. The diversity of the epidemiological situations within sub-Saharan ecotypes presents different malaria situation [31]. Comprehensive knowledge of behavior and heterogeneities that exist within, and among these vectors, will always be of benefit. Any strategy aiming at control will have to account for this heterogeneity in species diversity [32].

Malaria transmission dynamics is variable throughout Africa with huge variability in transmission patterns even within villages few kilometers apart [33]. The correct analysis of the distribution of specific malaria vectors is one of the prerequisites for meaningful epidemiological studies and for planning and monitoring of successful malaria control or eradication program [34].

In the past, large areas of Nigeria had no reliable data in the past on presence and absence of vectors [23]. It has been established that there are diversities of malaria vectors in Nigeria and they have different bionomics and vector competences. In Nigeria today, 35 *Anopheles* species have so far been recognized, but they do not all transmit malaria under the same circumstances. Some *Anopheles* mosquito species have unknown vector status, while some are non-malaria vectors ([9, 12]. However, the malaria transmission dynamics in Nigeria is mainly vectored by members of the *An. gambiae* complex such as *An. gambiae ss*, *An. coluzzi*, and *An. arabiensis*. *An .funestus s*s is also an important main vector, while *An. nili*, *An. melas*, and *An. moucheti* are localized vectors in Nigeria [9, 23, 29]. Secondary vectors in Nigeria include *An. pharoensis*, *An. coustani*, *An. hancocki*, and *An. longipalpis* [9, 12].

Control measures can only be effective if the abundance, behavior, and proportion of the vectors are known. The existence of species complexes containing morphologically cryptic sibling or isomorphic forms presents a major challenge to malaria control program as these require vector identification using molecular techniques [32].

Failure to know which sibling species one is dealing with will result in wasting scare resources and time to control non-malaria vectors [9].

#### **4.4 Vectorial capacity and vectorial competence of the malaria vectors**

The malaria problem in sub-Saharan Africa represents a peculiar case because the vectorial system is the most complex anywhere. This vectorial system diversity absolutely impacts malaria epidemiology and control [35].

Vectorial capacity and vectorial competence have been used interchangeably to describe the ability of mosquitoes to serve as a disease vector. The two terms are not synonyms because vectorial capacity is qualitative and is influenced by such variables as vector density, longevity, and vector competence itself [3]. Vectorial capacity takes into account environmental, behavioral, and cellular and biochemical factors that influence the association between a vector, the pathogen transmitted by the vector, and the host to which the pathogen is being transmitted [36].

However, vectorial competence is a component of vectorial capacity which is governed by intrinsic and generic factors that influence the ability of a vector to transmit a pathogen. For example, the susceptibility of an *Anopheles* mosquito to sporozoite stage of *Plasmodium* species is an important component of vectorial competence [37]. Vector competence, however, differs from one species to another and from place to place. There are *Anopheles* species complexes that vary in their

behaviors, vectorial competences, and capacities, and these present a real problem to malaria control in the tropics [35].

The main factor governing the ability of *Anopheles* species to act as malaria vector is the frequency with which it feeds on humans [37]. These malaria vectors associated with stable malaria are those which are strongly antropophagic, often feeding on humans to the exclusion of other hosts. Anopheline vectors of malaria consist of various behaviors associated with their biting activities and hence transmission dynamics [38].

#### **4.5 Malariogenic activities and lifestyles of humans**

Malariogenic activities and lifestyles are human activities that promote the transmission of malaria. The ability of mosquitoes to thrive even outside their natural habitat makes them a nuisance to mankind. Man and environment are created to interact with each other on a balance basis, but man has failed in his duty to the environment. The responsibility of man is to respect, protect, and care for the environment [9, 12].

By sheer negligence, mosquito breeds just under our nose, right inside our homes, so house spraying and screening are obviously inadequate. People store water in containers in their homes because of poor water supply, being ignorant of the consequences.

In residential areas, human activities create mosquito breeding sites such as discarded trash cans, open buckets, clogged gutters, abandoned vehicles, tires, drainages, ditches, natural depressions, or just anywhere that can retain water. Inside homes, endophilic female mosquitoes rest in dark places, corners of rooms, and behind curtains, but the exophilic biters rest on vegetation after feeding. When the eggs are about to be laid, they go into any suitable water within and outside the houses to oviposit.

#### **4.6 Diverse breeding sites of the anopheles mosquito**

It will be cost-effective to deal with mosquitoes by "nipping them in the bud" through eliminating their very source. The remote source of the malaria problem in the tropics is the mosquito's adaptability to environmental conditions and diversity and indiscriminate types of breeding sites which are of great importance [16]. The crux of the matter is that the intricacy of mosquitoes extends even into their breeding sites [9].

There is a considerable paucity of adequate information regarding vector oviposition habits, where *Anopheles* rest during the day and in their preferred breeding sites [39].

This information is critical for control efforts as we will not need to bother too much on the species or sibling species type or their vectorial capacities.

However, most researchers do not take into account the menace of mosquito breeding sites and the attendant environmental factors. The source of mosquito problem can be just near you or about anywhere where stagnant or still water collects or is stored in homes. This should be appropriately incorporated into vector control program.

## **5. Recommendations for action**

• Integrated management approach has been said to be the best for malaria control program, but they must take into account the breeding sites of mosquitoes.

**97**

*Nipping the Malaria Vectors in the Bud: Focus on Nigeria*

under a roof or seal with a tight cover.

and garden flower pots around homes.

unused and untreated.

stages.

**6. Conclusion**

populations.

also at the domestic level.

community and is also essential for control program.

• Knowledge, attitude, and practices (KAP) is the educational diagnosis of a

• Health and environmental education of the populace on preventing domestic

• Objects, excavations, plants, and anything that can hold water must be elimi-

• People should dispose unused containers and place useful ones upside down

• People must change frequently the water troughs of domestic and pet animals

• People should keep trash cans tightly sealed and drill a hole at the bottom in

• People should fill up eroded soils, natural depressions, and excavations and empty rain-filled receptacles. Swimming pools in homes should not be left

• Outdoor spraying of domestic animal shelters, garages, outdoor latrines, and

• People should spray oil on stagnant pools around them to kill mosquito aquatic

• Drainage system, ditches, and gutters must not be dumped with waste to avoid

• People should take action to prevent sewage effluents, soakaway, domestic runoffs and empty soft drink bottles from becoming breeding sites of mosquitoes.

• People should adhere to basic architectural designs; house designs with excavations or rain-filled receptacles should be discouraged such as the eave tube

• Environmental sanitation should be everybody's business. Enforcement of environmental sanitation by clearing bushes, cleaning drainages and open gutters, destruction and removal of containers, plants, tires, sachets, and anything that can hold water around homes will go a long way. Therefore education of

No doubt, human malaria affects the health, wealth, and welfare of human

The disease causes serious morbidity, human suffering, and mortality. These adverse consequences have led to increased need to wage a continuous war against malaria vectors by prevention not only at the local, national, and global levels but

the populace on mosquito breeding sites in homes is advocated.

clogging, thereby making them stagnant for mosquitoes to breed.

order not to retain water that may serve as breeding sites.

tree hole fillings must be carried out regularly.

technology in Benue State, Nigeria [40]

mosquito breeding is essential. The following steps should be noted.

nated. Water storage containers in homes should always be covered.

*DOI: http://dx.doi.org/10.5772/intechopen.83554*

*Malaria*

to malaria control in the tropics [35].

**4.5 Malariogenic activities and lifestyles of humans**

**4.6 Diverse breeding sites of the anopheles mosquito**

mission dynamics [38].

environment [9, 12].

the consequences.

houses to oviposit.

sites [39].

control program.

mosquitoes.

**5. Recommendations for action**

behaviors, vectorial competences, and capacities, and these present a real problem

The main factor governing the ability of *Anopheles* species to act as malaria vector is the frequency with which it feeds on humans [37]. These malaria vectors associated with stable malaria are those which are strongly antropophagic, often feeding on humans to the exclusion of other hosts. Anopheline vectors of malaria consist of various behaviors associated with their biting activities and hence trans-

Malariogenic activities and lifestyles are human activities that promote the transmission of malaria. The ability of mosquitoes to thrive even outside their natural habitat makes them a nuisance to mankind. Man and environment are created to interact with each other on a balance basis, but man has failed in his duty to the environment. The responsibility of man is to respect, protect, and care for the

By sheer negligence, mosquito breeds just under our nose, right inside our homes, so house spraying and screening are obviously inadequate. People store water in containers in their homes because of poor water supply, being ignorant of

In residential areas, human activities create mosquito breeding sites such as discarded trash cans, open buckets, clogged gutters, abandoned vehicles, tires, drainages, ditches, natural depressions, or just anywhere that can retain water. Inside homes, endophilic female mosquitoes rest in dark places, corners of rooms, and behind curtains, but the exophilic biters rest on vegetation after feeding. When the eggs are about to be laid, they go into any suitable water within and outside the

It will be cost-effective to deal with mosquitoes by "nipping them in the bud" through eliminating their very source. The remote source of the malaria problem in the tropics is the mosquito's adaptability to environmental conditions and diversity and indiscriminate types of breeding sites which are of great importance [16]. The crux of the matter is that the intricacy of mosquitoes extends even into their breeding sites [9]. There is a considerable paucity of adequate information regarding vector oviposition habits, where *Anopheles* rest during the day and in their preferred breeding

This information is critical for control efforts as we will not need to bother too

However, most researchers do not take into account the menace of mosquito breeding sites and the attendant environmental factors. The source of mosquito problem can be just near you or about anywhere where stagnant or still water collects or is stored in homes. This should be appropriately incorporated into vector

• Integrated management approach has been said to be the best for malaria control program, but they must take into account the breeding sites of

much on the species or sibling species type or their vectorial capacities.

**96**

