Selective exposure of active and sociable children to schistosomiasis.

Investigations into the impact of schistosomiasis on the physical and psychological development of children have yielded contradictory findings. This may be due to a failure to take account of transmission factors. In areas where Schistosoma haematobium is endemic, children who bathe regularly in contaminated water are more likely to contract the disease. The harmful effects of the disease may be masked in these more active and gregarious children, particularly when infections are mild and other parasitic infections and nutrional deficiencies are common. The social interaction of schoolchildren in an endemic area was monitored over a period of four months, and the principal finding was that infected children were more sociable than uninfected children in terms of their membership of the main playground groups. This paper discusses the evidence for selective exposure and the implications of the hypothesis for future research.