Epidemiology and control of schistosomiasis: present situation and priorities for further research. Scientific Working Group on Schistosomiasis.

The article highlights specific aspects of the epidemiology of schistosomiasis where insufficient data are available on which to base appropriate control strategies. Emphasis is placed on the part that immunological techniques might play in improving the baseline epidemiological data. A study of acquired resistance to the disease is also important in relation to epidemiology and control. The clinical manifestations of the disease vary in different areas and further study of the relation between the clinical and pathological manifestations are therefore required. In relation to the intermediate host, the main priority for research concerns the definition of the location and time-patterns of transmission foci within any particular area: variations in transmission are of particular importance in relation to man-made water resources. Although chemotherapy will play an increasing role in control, its importance will depend on local conditions: coordinated and standardized trials are required of chemotherapeutic agents in different regions and in various defined groups of subjects. The effects of chemotherapy on immunity to reinfection and on immunopathology also require study. With all types of snail control-chemical, ecological, and biological-cost-effectiveness aspects are important. With chemicals, it is important to bear in mind other possible effects on the environment. In the field of water supplies and sanitation, several aspects are important in relation to schistosomiasis transmission and community involvement should be encouraged.