Evaluation of different means of control of snail intermediate host of Schistosoma mansoni.

Four water courses having the same conditions and snail density were chosen for this study. All methods were applied simultaneously in April. Snails were collected monthly to evaluate the malacological effect. A single application of 100 ppm dried A. maritima decreased the snail density significantly within one month. Snail density was maintained very low until the end of the year. Fresh Azolla pinnata applied in a dose of 280 ppm lowered snail density to a level intermediate between Ambrosia maritima and Bayluscide. Snail population began to build 5 months later. Bayluscide applied once at a dose of 1 ppm lowered significantly the snail density. This lowering was maintained for 4 months after which snails began to build up and remained high until the end of the study period. Clearing of vegetations was followed by abrupt lowering of snail density which was maintained for a period longer than that following Bayluscide and Azolla.