Evaluation of the residual efficacy of permethrin-impregnated screens used against mosquitoes in Marigat, Baringo district, Kenya.

Insecticide-impregnated screens and bednets are gradually finding wider use in malaria control programmes. The efficacy of these devices is dependent on the method of application, the acceptability by the people and effectiveness of the insecticide used. The present studies were carried out to determine the duration of the effectiveness of a permethrin-impregnated wall cloth (Mbu cloth) used in the Marigat area of Baringo District, Kenya in order to ensure its effective use. Cotton cloth impregnated with permethrin was hung inside an experimental house in Marigat and small pieces cut off each month for bioassay against mosquitoes over a twelve month period. The wall cloth remained effective for 6, 4 and 10 months against Anopheles gambiae s.l. the known vector of malaria, Culex quinque-fasciatus and Aedes aegypti, respectively.