Seasonal changes in the distribution of Biomphalaria sudanica sudanica (Martens) in Lake Zwai, Ethiopia

Abstract

Biomphalaria sudanica has a restricted temporal and spatial distribution in Lake Zwai, being found commonly in sheltered habitats behind Aeschynomene thicket during periods of high lake levels. Evidence is presented to show that the snail aestivates.

If proposals for irrigation are adopted, the amplitude of lake level variation will be reduced and controlled by a dam on the Bulbula River. If Aeschynomene adapts to lower levels, the distribution of B. sudanica will remain unchanged, but stabilization of lake levels may prolong the existence of habitats and extend the period during which snails are active.

The consequences for schistosomiasis transmission are discussed.