Non-specific factors in the epidemiology of yaws

ABSTRACT

Yaws is found in hot countries where the mean isotherm is in the region of 80§. It is found in humid areas which implies a heavy rainfall, a non-previous soil and luxurious vegetation. It is found in rural districts where the economic circumstances are poor, where socially the order is low and the standards of hygiene and sanitation are not high. The highest incidence of yaws infection and of active lesions, and of non-immunity, appears to be in the first two decades, after which there is a decrease within the community of the above three factors. It is probable that the main mode of infection is by contact, but flies may also have a considerable part to play in the transmission of the disease. There is a low incidence of infection in adult life, the cause of which appears to be quite distinct from a low incidence due to an acquired immunity from a previous child infection. The reason for this is not understood. However, if this assumption is correct, it would be logical to introduce some method of immunization into the mass treatment programmes. After many mass treatment the attack rates within the community are considerably reduced but there remains a small residue of relapsed, reinfected, and new cases. It has been suggested that the type of case which is responsible for the continued propagation of the disease is the latent case with relapsing ulcerative plantar framboesides. In view of the fact that yaws is infrequent or even abscent in those areas of the tropics where the economic and social status of the populace is relatively high, it is possible, that with further socio-economic progress in the so-called under developed areas, that yaws may eventually be eliminated. So may it be with many other disease (AU)