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.