What is trachoma? Trachoma?eye diseases

 TRACHOMA

Trachoma is a chronic infectious disease of the conjunctiva and cornea, caused by Chlamydia trachoma ti's, but other pathogenic microorganisms often contribute to the disease Trachoma inflammation may undergo spontaneous resolution or may progress to conjunctival scarring which can cause inward deviation of eyelashes (trichiasis) or of the lid margin (entropion). The abrasion of the cornea by eyelashes frequently result in corneal ulceration, followed by scarring and visual loss. From the public health point of view, trachoma is classified as blinding and non-blinding. A community with blinding trachoma can be recognised by the presence of persons with lesions such as entropion, trichiasis and corneal ulcers. It is the blinding trachoma often becomes blinding trachoma when other ocular pathogens interact synergistically and enhance the risk of damage of eye sight.


Diagnosis:

 In epidemiology studies, more stress is now put on the upper tarsal conjunctiva as a convenient index of trachomatous inflammation in the eye as a whole. For the purpose of diagnosis in the field, cases must have at least 2 of the following diagnostic criteria:
• follicles on the upper tarsal conjunctiva
• limbal follicles or their sequelae, Herbert’s pits
• typical conjunctival scarring(trichiasis, entropion)
• vascular pannus, most marked at the superior limbus

Problem statement:

 Trachoma is a major preventable cause of blindness in developing countries. The incidence and prevalence of trachoma has shown a significant decrease in many endemic countries of SEAR during the past few decades. This decrease has been mainly due to improved sanitation, water and housing, and implementation of control measures. However, trachoma, particularly its active form, still remains a public health concern in some parts of Myanmar, in the westren region of Nepal and in a few rural areas in India.


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Agent factors:

a) Agent:
The classical endemic trachoma of developing countries is caused by C.trachoma-tis of immune types A, B or C. The sexually transmitted C. trachoma ti's(serotypes D,E, F, G, H , I, J or K) may also infect, causing an eye disease difficult to differentiate from endemic trachoma. Milder cases of this are usually called “inclusion conjunctivitis”. These strains rarely produce permanent visual loss but they cause respiratory infections( pneumonia) in infants and genital tract infections in adults.

b) Reservoir:
Children with active disease, chronically infected older children and adults.

c) Source of infection:
Ocular discharges of infected persons and fomites

d) Communicability:
Trachoma is a disease of low infectivity. It is infective as long as active lesions are present in the conjunctiva, but not after complete cicatrization.

Host factors:

a) Age:
In endemic areas, children may show signs of the disease at the age of only a few months. But typically, children from the age of two to five years are the most infected, and this contributes not only to the high rate of blindness but also to the rate of occurrence among children.

b) Sex:
Prevalence equal in younger age groups. In older age groups, females have been found to be affected more than males. The explanation for this may be that women remain more in contact with children who infect them. Further, females are more exposed to irritating factors such as smoke than males.

c) Predisposing Factors:
Direct sunlight, dust, smoke and irritants such as kajal or surma may predispose to infection.

Environmental factors:

a) Season:
Seasonal epidemics are associated with vastly increased number of eye-seeking flies. The higher temperature and rainfall favour the increase in fly population.

b) Quality of Life:
Trachoma is associated with poor quality of life. The disease thrives in conditions of poverty, ignorance, poor personal hygiene, squalor, illiteracy and poor housing. As living conditions improve the disease tends to regress.

c) Customs:
The custom of applying kajal or surma to the eyes is a positive risk factor.

Mode of transmission:
In communities where trachoma is endemic, eye-to-eye transmission can be considered as a rule. This may occur by direct or indirect contact with ocular discharges of infected persons or fomites, e.g., infected fingers, towels, kajal or surma. Eye-seeking flies (e.g., Musca spp., Hippelatus spp) play some role in spreading the infection by mechanical transmission. In countries where only sporadic cases of trachoma occur, genital localisation of C.trachoma-tis(urethral, cervical) may lead to venereal transmission.
It has been shown that trachoma is a familial disease. When one case is detected, others will almost certainly be found in the family group. There is a continuous feedback of infection, partly as a result of grandfather’s or sisters and brothers tending small children.

Incubation period:
5 to 12 days

Control of trachoma:

Trachoma control still requires long-term effort. It requires proper planning and organization, which should include the following elements:
1. Assessment of the problem:
The primary objective of a programme for the control of trachoma is the prevention of blindness. Control programmes should be focussed on communities with a substantial prevalence of “blinding trachoma” as indicated by the presence of corneal blindness, trachomatous trichiasis and entropion, and moderate and severe trachomatous inflammation.Such communities are likely to be found in countries with blindness rates that are above 0.5%. The first task therefore is to undertake an epidemiological survey to identify and delimit communities with blinding trachoma; assess the magnitude of the problem, local conditions and other cause of blindness and to obtain information on existing facilities. The basic principles of these surveys are set out in the WHO publication: “ Methods of Assessment of Avoidable Blindness “

2. Chemotherapy:

In trachoma control the main activity is chemotherapeutic intervention. The objective of chemotherapy is to reduce severity, lower the incidence and in the long run decrease the prevalence of trachoma. The antibiotic of choice is 1% ophthalmic ointment or oily suspension of tetracyclines. Erythromycin and rifampicin have also been used in the treatment of trachoma. Treatment may be given to the entire community- this is known as mass treatment (or blanket treatment). In some programmes, selective treatment is chosen in which case, the whole population at a risk is screened, and treatment is applied only to persons with active trachoma.

a) Mass treatment:
A prevalence of more than 5% severe and moderate trachoma in children under 10 years is an indication for mass or blanket treatment. The treatment consists of the application twice daily of tetracycline 1% ointment to all children for 5 consecutive days each month or once daily for 10 days each month for 6 consecutive months, or for 60 consecutive days. An alternative antibiotic is erythromycin.
 From the practical point of view, one of the main difficulties is the need for repeated applications of the antibiotic over long periods of time. Emphasis is now being placed on the active participation of the community itself in trachoma control activities and on the utilization of village health guides(primary health care workers). This makes possible a wider coverage and a greater efficacy of the programme.

b)Selective treatment:
In communities with a low to medium prevalence, treatment should be applied to individuals by case finding rather than by community-wide coverage, the principals of treatment remaining the same. For the selective treatment to be effective, the whole population at risk must be screened for case finding.

3. Surgical correction:
Antibiotic ointment is just one component of a trachoma control programme. Individuals with lid deformities should be actively sought out, so that necessary surgical procedures can be performed and followed-up. It has an immediate impact on preventing blindness.

4. Surveillance:
Once control of blindness trachoma has been achieved, provision must be made to maintain surveillance, which may be necessary for several years after active inflammatory trachoma has been controlled. Since trachoma is a familial disease, the whole family group should be under surveillance.

5. Health education:
In the long run, most of the antibiotic treatment must be carried out by the affected population itself. To do this, the population need to be educated. The mothers of young children should be the target for health education. Measures of personal and community hygiene should also be incorporated in programs of health education. Thus real primary prevention could only come through health education for the total elimination of transmission.

6. Evaluation:
Lastly evaluation. Trachoma control programme must be evaluated at frequent intervals. The effect of intervention can be judged by changes in the age-specific rates of active trachoma and in the prevention of trichiasis and entropion.
The 28th World Health Assembly in 1975, in a resolution requested the Director-General of WHO “to encourage Member countries to develop national programmes for the prevention of blindness especially aimed at the control of trachoma, xerophthalmia, onchocerciasis and other causes”.