**7. Predisposing factors**

Evans blue. Peroxidase-conjugated monoclonal antibodies are also available for the detec‐

ELISA or enzyme immunoassay (EIA) commercial assays are available to detect chlamydiae, but the sensitivity is only 70% to 85%. However, these assays can be cost effective compared with other commercially available tests such as the DNA detection assays. These tests detect the EB via polyclonal or monoclonal antibodies directed against the genus-specific chlamy‐ dial LPS. The antibodies are conjugated with an enzyme that reacts with a substrate to pro‐ duce a change in color that can be detected by a specific wavelength in a spectrophotometer. One advantage is that a 96-well format can be used to process multiple samples at one time. Less technical expertise is required than for the above-mentioned tests. Another advantage

The commercial LCR and PCR tests are the most recent assays to be developed for detecting Chlamydia. Primers that are specific for the organism anneal to the complementary strand of DNA after denaturation. This target DNA is usually the plasmid, which is only present in C. trachomatis and C. psittaci species. LCR amplifies a signal that occurs when the primers hybridize with the plasmid DNA. In PCR, the actual DNA is amplified after hybridization. Both tests can be used in a 96-well format in which 92 to 94 samples can be assayed at one time. Both products are detected by spectrophotometers that are set at specific wavelengths for the particular assay. An advantage to the commercial PCR test is that an internal control plate can be run in parallel with the chlamydial detection plate to identify which samples have inhibitors. Those samples that contain inhibitors can then be run by in-house PCR as‐

Chlamydial DNA can also be detected by commercially available hybridization probes. These also hybridize with complementary plasmid or ompA DNA. The sample is usually a swab of the conjunctiva that has been applied to a special filter paper immediately after the sample has been obtained from the patient. Occasionally, DNA is extracted from a swab that has been placed in a special collection media and then is applied to a filter. In both cases, the filter is what is probed. The advantage of this technique is that the filter paper that contains the samples can be stored at room temperature under field conditions and transported back to the lab at a convenient time, without the necessity of a cold chain. The sensitivity of the

There are two serologic tests for Chlamydia: the microimmunofluorescent (MIF) test and the complement fixation (CF) test. However, neither is specific for the organism because patient sera can cross react with different serovars and species and may represent current or previ‐ ous sexually transmitted infection as opposed to conjunctival infection. The highest antibod‐

says that employ a DNA purification protocol that removes the inhibitors.

tion of chlamydial inclusion bodies.

is that the kits contain a confirmatory test.

*6.2.3. Antigen detection*

238 Common Eye Infections

*6.2.4. DNA detection*

probes is 70% to 90%.

*6.2.5. Serology*

Children are considered the primary source of infection because they usually become easily infected from close contacts during frequent play and within small, crowded households. However, female caregivers can also serve as an important reservoir in which the infection is passed to them and then back to their children. Thus, children younger than 10 years are at greatest risk for infection and reinfection.

Young women of childbearing age and other female caregivers are reported to have infec‐ tion rates that range from 5% to 10%. These infections likely represent transmission within the household from and to children. Adult women develop more severe disease and seque‐ lae than their male counterparts; repeat infection is considered an important factor in dis‐ ease progression to trichiasis.

Other factors are low socioeconomic status, poor facial hygiene and lack of water. Flies have historically been considered vectors for transmission in Africa. However, data from recent studies do not support the theory. In one study, fluorescein was used to stain the secretions in the eyes of children. Within 15 to 30 minutes, the legs and bodies of the flies were also stained with fluorescein. Eye-seeking flies such as Musca sorbens have been shown to land on the eyes of multiple children as was reported in a study in Africa, but it is not clear how many infectious EBs can be carried on the flies, how long they are viable, and whether the inoculum is sufficient to cause infection. In The Gambia, of 395 flies captured from the eyes of C. trachomatis-infected children, only two were positive by PCR and could not be con‐ firmed. It is certainly possible that flies carry other bacteria from eye to eye, which might promote inflammatory disease and trachoma. Indeed, in many trachoma endemic countries, there are seasonal outbreaks of conjunctivitis resulting from multiple bacterial species in‐ cluding Haemophilus influenzae, Haemophilus aegyptius, Streptococcus pneumoniae, Neis‐ seria meningitidis, N. gonorrhoeae, and Moraxella spp. These infections may actually precede periods of increased trachoma prevalence rates. In a study in Tunisia, moderate to severe trachoma was found significantly more often among children with bacterial coinfec‐ tions. Furthermore, pathogenic and nonpathogenic bacteria commonly colonize children who reside in trachoma areas. Coinfection of C. trachomatis with these bacteria may be one mechanism that is important for promoting severe inflammation, which results in conjuncti‐ val scarring and corneal vascularization years later.

### **8. Management**

Management of trachoma involve curative as well as control measures. The World Health Assembly has resolved to eliminate blinding trachoma by the year 2020. To this, the Global Alliance for the Elimination of Blinding Trachoma (GET2020) was formed in 1998. Control activities focus on the implementation of the SAFE strategy, surgery for trichiasis, antibiotics for infection, facial cleanliness (hygiene promotion) and environmental improvements, to re‐ duce transmission of the organism. Each of these components tackles the pathway to blind‐ ness at different stages.

#### **8.1. Active trachoma**

Antibiotics for treatment of active trachoma may be given locally or systematically, but topi‐ cal treatment is preferred because:It is cheaper, there is no risk of systemic side-effects, and Local antibiotics are also effective against bacterial conjunctivitis which may be associated with trachoma.

The following topical and systemic therapy regimes have been recommended:

**1.** Topical therapy regimes. It is best for individual cases. It consist of 1percent tetracycline or 1 percent erythromycin eye ointment 4times a day for 6 weeks or 20 percent sulface‐ tamide eye drops three times a day along with 1 percent tetracycline eye ointment at bed time for 6 weeks.


It is increasingly appreciated that there can be a major mismatch between the signs of active trachoma and the detection of chlamydial infection (Relationship between clinical signs and infection). This is a particular problem for control programmes in determining who should be offered antibiotic treatment; if only those with signs of trachoma are given antibiotic, many infected individuals with significant loads of infection would be left untreated. The WHO currently recommends that mass community-wide treatment should be used.


In communities in which the prevalence of TF in 1–9-year-old children is less than 5%, anti‐ biotic distribution is not recommended

#### **8.2. The sequelae**

Other factors are low socioeconomic status, poor facial hygiene and lack of water. Flies have historically been considered vectors for transmission in Africa. However, data from recent studies do not support the theory. In one study, fluorescein was used to stain the secretions in the eyes of children. Within 15 to 30 minutes, the legs and bodies of the flies were also stained with fluorescein. Eye-seeking flies such as Musca sorbens have been shown to land on the eyes of multiple children as was reported in a study in Africa, but it is not clear how many infectious EBs can be carried on the flies, how long they are viable, and whether the inoculum is sufficient to cause infection. In The Gambia, of 395 flies captured from the eyes of C. trachomatis-infected children, only two were positive by PCR and could not be con‐ firmed. It is certainly possible that flies carry other bacteria from eye to eye, which might promote inflammatory disease and trachoma. Indeed, in many trachoma endemic countries, there are seasonal outbreaks of conjunctivitis resulting from multiple bacterial species in‐ cluding Haemophilus influenzae, Haemophilus aegyptius, Streptococcus pneumoniae, Neis‐ seria meningitidis, N. gonorrhoeae, and Moraxella spp. These infections may actually precede periods of increased trachoma prevalence rates. In a study in Tunisia, moderate to severe trachoma was found significantly more often among children with bacterial coinfec‐ tions. Furthermore, pathogenic and nonpathogenic bacteria commonly colonize children who reside in trachoma areas. Coinfection of C. trachomatis with these bacteria may be one mechanism that is important for promoting severe inflammation, which results in conjuncti‐

Management of trachoma involve curative as well as control measures. The World Health Assembly has resolved to eliminate blinding trachoma by the year 2020. To this, the Global Alliance for the Elimination of Blinding Trachoma (GET2020) was formed in 1998. Control activities focus on the implementation of the SAFE strategy, surgery for trichiasis, antibiotics for infection, facial cleanliness (hygiene promotion) and environmental improvements, to re‐ duce transmission of the organism. Each of these components tackles the pathway to blind‐

Antibiotics for treatment of active trachoma may be given locally or systematically, but topi‐ cal treatment is preferred because:It is cheaper, there is no risk of systemic side-effects, and Local antibiotics are also effective against bacterial conjunctivitis which may be associated

**1.** Topical therapy regimes. It is best for individual cases. It consist of 1percent tetracycline or 1 percent erythromycin eye ointment 4times a day for 6 weeks or 20 percent sulface‐ tamide eye drops three times a day along with 1 percent tetracycline eye ointment at

The following topical and systemic therapy regimes have been recommended:

val scarring and corneal vascularization years later.

**8. Management**

240 Common Eye Infections

ness at different stages.

**8.1. Active trachoma**

with trachoma.

bed time for 6 weeks.


#### **8.3. Prophylaxis**

Since immunity is very poor and short lived, reinfections and recurrences are likely.

Thus following prophylactic measures may be helpful against reinfection of trachoma.

**1.** Hygienic measures:

Transmission of trachoma is closely associated with personal hygiene and environmental sanitation. Facial cleanliness and environmental improvements the F&E components of the SAFE strategy are primarily targeting the transmission of C. trachomatis between individu‐ als. Numerous epidemiological studies have found an association between dirty faces and active trachoma in children

Eye-seeking flies are a common feature of many trachoma endemic communities and have long been considered a potential vector. Chlamydia trachomatis was found (by PCR) on 15% of flies caught leaving faces of children in a study from Ethiopia.

Many trachoma control programmes actively advocate for general improvements in water supply (for face washing) and sanitation (to suppress fly populations). This drive has fortu‐ nately coincided with the setting of the United Nations' Millennium Development Goals (MDG). The target for the seventh MDG is to halve the number of people without safe water and basic sanitation by 2015

**2.** Early treatment of conjunctivitis:

Every case of conjunctivitis should be treated as early as possible to reduce transmission of disease.

**3.** Blanket antibiotic therapy (intermittent treatment).

WHO has recommended this regime to be carried out in endemic areas to minimize the in‐ tensity and severity of trachoma. The regime is to apply 1 percent tetracycline eye ointment twice daily for 5 days in a month for 6 months.

The future of trachoma control

In previously endemic countries in Europe and elsewhere, trachoma declined in the face of general improvements in living conditions and health. Such changes are beginning to hap‐ pen in some parts of currently endemic countries. However, for many communities it may take many decades for general improvements in living standards to happen and to have an impact on trachoma. Therefore, it is necessary to pro-actively implement the SAFE strategy as the best validated approach to control this blinding disease. The limited published data on the impact of implementing the SAFE strategy indicate that even in some of the most highly endemic regions, such as South Sudan, significant reductions in the prevalence of ac‐ tive disease can be achieved.

**4.** The development of an efficacious vaccine:

Vaccine for C. trachomatis that would prevent and resolve infection has been slow largely because of the intracellular nature of Chlamydia and lack of ability to genetically transform the organism. However, recent advances in the field have identified some requirements for vaccine design. It is now generally accepted that MOMP, possibly with other antigens, would be important for a vaccine. However, because of the diversity of MOMP sequences that define different C. trachomatis strains, more than one MOMP would be required. The immune response that must be induced comprises mucosal sIgA antibody and systemic an‐ tigen-specific CD 4 TH1 lymphocyte responses. Protection of mice against challenge with MoPn has been partially successful using vaccine strategies that include conformationally intact MOMP, naked DNA constructs of ompA and intact, nonviable organisms carried by dendritic cells.175 Other attempts at vaccination were less successful and included recombi‐ nant poliovirus or Salmonella expressing MOMP, denatured MOMP, or MOMP peptides (summarized in Brunham176). It is likely that a composite vaccine that includes intact MOMP, as well as naked DNA representing ompA from various strains, may be required to stimulate appropriate B- and T-cell responses, respectively. It may also be that only a few MOMP and ompA DNA strain sequences or only specific conserved sequences from MOMP and ompA are required to elicit a protective immune response. The development of the ide‐ al vaccine remains a significant challenge.
