Aspects of the ecology and public health importance of snails in the Weija lake

ABSTRACT

A survey was undertaken in water-contact sites of communities on the Weija lake over a 12-month period to update information on the snails in the lake. The study involved the collection of snails with scoop-net from the sediments; floating; marginal and submerged aquatic vegetation and other objects in the lake. All snails collected were identified. Bulinus truncatus; B.(Physopsis) globosus and Biomphalaria pfeifferi were examined for trematode infection. Nine species of snails were encountered. They were either autochthonous fauna of the River Densu basin or possibly introduced. Four of the snail species encountered Biomphalaria pfeifferi; Bulinus trucatus; B.(Physopsis) globosus and Lymnaea natalensis were of medical and veterinary importance. B.(Physopsis) globosus however; has been unsuccessful in colonising the lake though it was the dominant bulinid snail transmitting S. haematobium before the impoundment. The previously rather rare B. truncatus has become the dominant S. haematobium transmitting snail in the lake. Biomphalaria pfeifferi has also established itself in the lake with the possibility of the introduction and increased transmission of intestinal schistosomiasis. This species succession is likely to heighten schistosomiasis transmission in the lake