Malaria is a significant sub-Saharan African health challenge and control strategies mainly target the adult mosquitoes that transmit the malaria causing parasite. Unlike adults, mosquito larvae are not known to evade control strategies aimed at them. This study determined the larvicidal potential of Bacillus thuringiensis toxin (Bt) against mosquito larvae. Soil samples were collected in triplicates using a hand-held soil auger from six different locations and pooled into six composite samples. Standard cultural method was used to isolate Bacillus thuringiensis from the composite soil sample in addition to molecular identification. Following identification, sporulation and Bt toxin were carried out using standard methodologies. Mosquito larvae in their 3rd and 4th instars stages were collected, exposed to different concentrations (0.1, 0.01, 0.001, 0.0001 and 0 mg/mL) of Bt and monitored for 9 hours. The results of the first hour of exposure to Bt, showed a concentration dependent mortality of 30, 20, 10, 10 and 0 %, respectively across all concentrations (0.1, 0.01, 0.001, 0.0001 and 0 mg/mL) and 30% mortality for the positive control. However, 100% mortalities rates were recorded from the 5th hour for both the 0.1 mg/mL Bt concentration and the positive control. The results are of particular interest because Bt has shown similar larvicidal effect as the commercial based insecticide that is of a chemical origin. The excellent toxic effective activity shown by Bacillus thuringiensis shows a promising potential and should be exploited further towards our drive for malaria eradication.

Keywords : Bacillus thuringiensis, Malaria, Mosquito Larvae, Bt Toxin.