Control of schistosomiasis in large irrigation schemes by use of niclosamide. A ten-year study in Zimbabwe.

The development of chemical control strategies, and regular assessments of snail populations over a 10-year period, has resulted in reduced incidence of disease and the efficient use of niclosamide by competent administrators. Full knowledge of all water-bodies, strict surveillance programs, and timing of dam treatments have minimized the chances of snails becoming infected within a 380-km2 area. The scheme is now entirely estate-run and administered. In spite of soaring prices, particularly those of chemicals, control costs have changed minimally and are less than, or comparable with, those of schemes Puerto Rico, Brazil, St. Lucia, Iran, and Tanzania. Total cost for a 9-year period was US $696,000 and was $249/km2 in 1979-1980. Estimated cost for 10 years was US $800,000. The population of between 75,000 and 100,000 was largely unstable, and cost per capita was $0.95 to $1.21.