Epidemiology and control of schistosomiasis : report of a WHO expert committee. Technical Report Series N°643
Overview
Since the meeting of the WHO Expert Committee on Schistosomiasis Control in 1972 (J), many important advances have been made in the control of this disease. In recent years there has been a marked movement towards an integrated approach to control. There is now less reliance on single control techniques such as mollusciciding, much used in the past, and this has followed the development of improved chemotherapeutic drugs and the realization of the preventive value of the installation of domestic water supplies in endemic areas. Current integrated control methods employ all the available forms of chemotherapy, the latest mollusciciding techniques, methods to meet basic health needs such as the supply of potable water at village level and the provision of sanitation, as well as continuing health education and socioeconomic improvement.
The moves towards an integrated approach to control depend essentially on an accurate ecological assessment-of the human community and its parasitological characteristics, of the biology of the snail intermediate hosts, and of the physical and geographical characteristics of the environment. Man's behavioural attitudes and customs are being given increasingly greater attention because it has been realized that they may play a crucial role in the success or failure of a control programme.
Reliable and effective schistosomiasis control measures have now become available but the most suitable combinations of these measures, applicable in different habitats and under various conditions of schistosomiasis transmission, still need to be worked out. Further studies on the ways of ensuring community participation in control activities are also needed.
Control may be subdivided into disease control in the human population and transmission control of the biological cycle. Both are essential 'to the concept of total control of schistosomiasis.
The advances in chemotherapy during the past 10 years make it clear that drug treatment will play an increasingly important role in both disease control and transmission control. However, there is a need for much operational research in order to define the best ways of using the available drugs.
In these changing circumstances it is essential to know to what extent the control measures against schistosomiasis can be integrated into the general health services and particularly those at the primary · health care level. It is also necessary to ascertain which of the highly specialized biological techniques involving bionomics and control of the intermediate hosts can be taught to health auxiliaries. It appears that the present shortage of skilled personnel in communicable diseases control will continue for some years.
An increase, sometimes marked, in the prevalence of infection frequently occurs in association with different water resources development schemes. The creation of' man-made lakes, and the introduction of new irrigation schemes or the extension of existing ones in endemic areas or in areas adjacent to existing transmission foci, are significant factors in the pread of the infection. This highlights the importance of planning for prevention and control not only of schistosomiasis but also of other communicable water-related diseases in such schemes. Inadequate planning may result in the spread of the infection, and this may .,nullify some of the planned economic benefits owing to the increased costs of control.
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