[Toxicity of Bacillus thuringiensis var. israelensis for Simulium larvae, vectors of onchocerciasis].

On field trials in infested streams, the primary powder R 153-78 made of B. thuringiensis var. israelensis with a potency of 3,000 I.T.U. Aedes aegypti/milligramme is very toxic for Blackfly larvae, especially for Simulium damnosum s.l. larvae. The lethal concentration 100, in 24 h. is 0.2 X 10(-6) for a 10 min. treatment. This high toxicity, specific for Diptera larvae such as Mosquitoes and Blackflies, is related to the special characteristic of the bacterial crystal protein which has a clear serological and chemical individuality compared to the crystal proteins of the other B. thuringiensis serotypes essentially pathogenic for Lepidoptera larvae. These preliminary results are very promising and could lead, on further research, to the utilization of B. thuringiensis var. israelensis on large scale for onchoceriasis vector control in Africa.