Potential of Bacillus thuringiensis var israelensis for mosquito malaria vector control in Kenya.

Abstract

The main vectors of malaria in Kenya are Anopheles arabiensis, An. gambiae and An. funestus. In the Mwea Rice Irrigation Scheme of Central Kenya, Art arabiensis is the principal vector, accounting for over 83% of the total anopheline population. Larval breeding takes place from late March to mid-December. The population peaks correspond to the rainy seasons in April-May and October- November. The flooding phase of the rice cycle in August, an otherwise dry season, is the link that enables continuous breeding for nine months. The use of biological larvicides that are not only innocuous to other aquatic organisms but also environmentally safe is a desirable component of any futureintegTated control stralegy Bacillus thuringiensis var (B.t.i.) has already been shown to be a promising agent of riceland mosquito control in Kenya. Laboratory tests have indicated that the LC 50's for An. arabiensis and An. gambiae are 1.86 x 10-6 and 2.05x10-6B.t.i./ml respectively. Limited field testing with commercial preparations was commendably effective, but the larvicidal activity of the suspensions had limited persistence. It is suggested that further field testing with B.t.i. and more screening for local strains of B.t. should be encouraged in the future.