Long-term effects of single-dose metrifonate on the control of urinary schistosomiasis in an endemic area.

During 1989 a survey for urinary schistosomiasis was carried out in children attending Kanhukamwe primary school where, 5 years previously, infected children had been treated with a single dose of metrifonate. The treatment programme had been supplemented by improvements in water supply and sanitation, but no mollusciciding or other vector control measures had been used. The majority of children examined had not taken part in the treatment programme but had grown up in the community where transmission was reduced. While the prevalence of infection in the children in the current study was similar to that seen 5 years previously, the intensity of infection was markedly lower. In a nearby village where improved water and sanitation had been provided but no treatments had been given, the intensity of infection in school-children of similar age remained high. About 20% of the children originally with negative urines and so untreated had now started excreting S. haematobium ova, compared with 45% of children who had been cured following treatment. Children who had been treated in 1983 but who had continued to excrete ova were retreated in this study. It was noted that children who responded well to the previous treatment (greater than 90% reduction in egg excretion) generally responded well when retreated, while poor responders (less than 90% reduction in egg excretion on original treatment) showed only a small reduction in egg excretion on retreatment.