Biological control of malaria vectors.

A comprehensive review is presented of the potentiality of biocontrol agents viz. entomophagus bacteria (Bacillus thuringiensis var. israelensis and Bacillus sphaericus), fungi, microsporidians, predators and parasites against malaria vectors in the field condition. Unlike insecticides, these control agents are host specific and safer to the environment. However, barring fishes which are being used in certain situations, other biocontrol agents have not yet reached the operational stage. Two spore forming bacteria B. thuringiensis var. israelensis and B. sphaericus have been extensively tested against malaria vectors in the field. Though they are effective in suppressing anopheline larval population, their recycling capacity and availability of toxin hearing spores on the water surface are limited. Therefore, there is a need for developing improved formulations through bio-engineering techniques for enhancing their residual activity and availability of spores for anopheline larvae which feed mostly on the water surface. The biocontrol potentiality of other agents in the field condition is yet to be explored fully. The use of biocontrol agents for malaria control also poses certain operational constraints in view of the vastness of the anopheline breeding habitats and less acceptance for their use in domestic environments. However, there is a scope for using these biocontrol agents in conjunction with other control methods in integrated control programmes.