Snail control in relation to a strategy for reduction of morbidity due to schistosomiasis

The control of schistosomal disease is now distinctly feasible in endemic situations where a capable health care delivery system exists. Effective integrated control of schistosomiasis morbidity, within available resources at national level, is now being carried out in many countries. The control of snail hosts by chemical, environmental and/or biological means can still play a significant supporting role in many endemic situations. Today, however, as compared to earlier decades when disease control procedures were far less advanced, there is need for reappraisal of snail host control strategies to ensure that objectives are now correctly set, that the potential operational mechanisms are carefully chosen under the headings of desirability, feasibility and cost-effectiveness and that implementation and evaluation of the operations have, as far as possible, both theoretical and practical validity. Nowadays snail host control procedures must be intimately linked to knowledge of transmission sites and seasonal patterns, focal and periodic transmission being the rule rather than exception; in particular, they must be associated with local schemes for the delivery and evaluation of population based chemotherapy campaigns.