Intermediate host snails in Africa

Although praziquantel is an excellent anti-schistosomaiasis medicine, the selection of time for treatment is very important. Treatment of patients should be avoided when infection occurs. Surveys were carried out in two adjacent villages, Mwachinga and Mtsangatamu Villages. In these areas, two rainy seasons, a long rainy season from April to June and a short rainy season in November, occur each year. Mwachinga Village is located on a dry hill and snails infected with Schistosona haematobium are mainly collected between October and February. On the other hand, Mtsangatamu Village is located on the slopes of wooded hills, and infected snails are mainly collected between March and May. The removal of intermediate snails from the riverbed during the dry season was used as a measure for disease control in Mwachinga Village. The river in Mtsangatamu Village is a swamp because of slow water flow, so a trench was dug in the center of the river to increase the flow rate. Significant decreases in the number of intermediate snails were observed in both areas.