Field studies on the bionomics of Bithynia siamensis siamensis and the transmission of Opisthorchis viverrini in Bangna, Bangkok, Thailand.

A field study on the bionomics of Bithynia siamensis siamensis and the transmission patterns of Opisthorchis viverrini was carried out in Bangna, Bangkok, Thailand, from May 1975 to April 1976. Snail populations were found to fluctuate according to rainfall. During the high rainfall period where snail habitats were deep, snail populations recovered at the water surface were higher than those recovered on the mud bottom; during the low rainfall perod where snail habitats were shallow, snails were both found copiously at the water surface and on the mud bottom. Snails infected with O. viverrini occurred almost all year round, with an overall infection rate of 1.6% (46/2800).