Attempts to control schistosomiasis have hitherto involved
the use of one or more of the following methods, either in isolation
or in combination: (1) control of the intermediate host using
molluscicides or biological methods; (2) basic sanitation and clean
water supply; (3) health education; (4) individual or mass treatment; (5)
protection of individuals in such a way as to prevent cercariae from
penetrating the skin; (6) vaccine-based strategies against
schistosomiasis.
None of these methods is capable, on its own, of bringing
about effective control of schistosomiasis, except in populations of a
very limited size or under very special conditions. Molluscicides,
besides expensive and toxic, have only a temporary effect. As for
biological control, there is no effective method yet. Basic sanitation
and clean water supply combined with health education potentially
constitute the most effective approach, but only in the mid-to-long term.
Mass treatment reduces morbidity, but does not control transmission.
Protection of individuals has proved to be impraticable on a large scale.
Vaccine-based strategies against schistosomiasis are still in the
experimental stage.
Experiments carried out in Brazil in the last 20 years have
shown that mass treatment with single doses of oxamniquine or
praziquantel can rapidly reduce levels of Shistosoma mansoni infection
and morbidity in endemic areas. They have also shown that subsequent
transmission and reinfection frequently occur in defined foci or
"clusters", due to human contact with water, and in inverse
proportion to the number and frequency of treatments carried
out. On the basis of these experiments, the author suggests a
multidisciplinary strategy for schistosomiasis control.
