Malacological and parasitological surveys along the Xe Bangfai and its tributaries in Khammouane Province, Lao PDR

Malacological and parasitological observations were conducted along the Xe Bangfai River between 2010 and 2012 after a dermatitis outbreak. Mollusc populations were surveyed at 28 stations. Mollusc family and species lists were compiled. A sub-sample of 4033 snails from 10 gastropod families was screened for the presence of trematode cercariae. The findings demonstrated that mollusc populations declined after the initial operation of the Nam Theun 2 hydropower project. The species composition of the snail populations also underlined ecological changes. No definitive cause of cercarial dermatitis was found. However, cercariae resembling echinostome and xiphidiocercariae were respectively observed in one population of Bithyniidae and one population of Neotricula aperta . Further hydrobiological studies are thought to be necessary to study the succession of the molluscan community in the Xe Bangfai River until populations become stable.