Bacteriological control of mosquitoes and blackflies: present aspects and perspective of research

Abstract

Biological control of mosquitoes and blackflies, which transmit severe diseases, rely mainly on Bacillus thuringiensis israelensis (Bti) and B. sphaericus. Their lack of toxicity to non-target organisms and to the environment has favored their development in vector control programs. Bti is now widely used in blackfly control as well as against most of the mosquito species. The host range of B. sphaericus is restricted to Culew sp. and to lesser extent to Anopheles sp. and some Aedes species. However, to the contrary of Bti, B. sphaericus toxicity persists in polluted water, therefore this bacterium is increasingly applied against the urban mosquitoes Culex sp. Recent advances in the knowledge of the bacterial toxins and in genetic engineering have opened the field of designing new formulations, modifying the host range of Bti or B. sphaericus and introducing toxin genes into microorganisms which serve as food for the larvae, e.g. cyanobacteria. Research undertaken in our laboratory on Clostridium bifermentans serovar malaysia, an anaerobic strain which has been recently demonstrated to be highly toxic to mosquitoes and blackflies, will be also discussed. This is the first time that an anaerobe toxic to Diptera is isolated and this allows to find new toxins, different of the known toxins of B. sphaericus or B. thuringiensis