Incubation period days

Period of communicability continues as long as active lesions are still present. Once treatment commences, infectivity ceases within 2-3 days although the clinical disease persists.

Occurrence and distribution Trachoma is found mainly in the dry regions of the world (Fig. 7.1), especially Africa, South America and the extensive semi-desert

Fig. 7.1. The distribution of trachoma.

co Un regions of Asia. A disease of antiquity, it was first described by the ancient Egyptians.

In endemic areas, 80-90% of children are infected by the age of 3 years. In conditions of improved sanitation, there is a natural cycle lasting until the age of 11 years, with little residual damage. Females develop trachoma and blindness as adults more commonly than males because they are directly concerned with looking after children. The chance of acquiring infection is increased by large families with short birth intervals, as there are more children of a young age living in close proximity.

Control and prevention The use of water to wash away secretions, clean clothes and the surroundings is perhaps the single most effective method. Washing the face often has been shown to reduce the risk of developing trachoma so regular daily face washing should be encouraged. Long-term preventive measures include improved sanitation and the provision of water supplies.

Flies proliferate in rubbish and excrement, reaching their maximum numbers during the dry, sunny period of the year. The damp, moist conditions in open pit latrines may be more important in encouraging fly breeding than non-use of latrines. Any flushing mechanism or improved latrine will discourage flies.

A strategy for a control programme is as follows:

• conduct a survey to find the worst-affected areas;

• give mass treatment;

• conduct health education through schools, stressing regular face washing;

• provide back-up services.

WHO has launched a programme for the global elimination of trachoma by 2020 and given it the acronym of SAFE. This stands for:

• Surgery for trichiasis;

• Facial cleanliness;

• Environmental improvement.

Treatment Mass treatment is preferable, as the majority of the population in an infected area will have trachoma. This is given easily in schools, but is better done at home, where the main transmission takes place. A single dose of azithromycin (20 mg/kg) is better than topical tetracycline and one dose a year may be sufficient to eliminate the blinding propensity of trachoma. Mothers can be taught to regularly treat all children in the household.

Preventing blindness, once scarring and trichiasis have developed, is very easily done by a simple operation that a Medical Assistant can be trained to do. This involves cutting through the scarred conjunctiva of the upper lid and everting it so that the eyelashes no longer rub on the cornea.

Surveillance After the initial survey, follow-up surveys should be conducted at regular intervals. This is most easily done in primary schools.

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