Ashraf M Ahmed
King Saud University, KSA
Title: The battle against the filaria vector, Culex pipiens mosquito with special reference to bacterial biocontrol measure
Biography
Biography: Ashraf M Ahmed
Abstract
Mosquitoes are intermediate hosts of several human pathogens and thus serve as vectors of several human threatening diseases worldwide. Recent studies have focused interest on entomopathogenic microorganisms as useful alternatives to conventional insecticides, suggesting these pathogens as bio-control candidates in the battle against human mosquito-borne diseases. Yet, the mosquitocidal bacterium, Bacillus thuringiensis (Bt) is a safe eco-friend entomopathogenic biocontrol agent that faced no resistance from mosquito host due to the interactions among its multiple toxins. This interaction is the major reason for the absence of passive resistance to Bt in mosquitoes. The present study was initiated to characterize new native Bt isolates with mosquitocidal activity from various samples from 16 regions across Saudi Arabia. Various samples were collected from mosquito breeding sites and screened for Bt isolation. Native Bt isolates were characterized on the basis of colony morphology, shape of spores and parasporal crystals and through comparisons of biochemical profiles. The larvicidal activity (LC50 & LC95) of standardized spore/crystal mixtures of Bt isolates were tested against larvae of the filaria vector Culex pipiens and compared with that of the Bt. israelensis (Bti-H14). A total of 23 (out of 68 native Bt isolates) were mosquitocidal. Larvicidal strains were similar in terms of colony morphology, hemolytic and motile. Out of the 23 isolates, 9 showed significantly higher activity (LC50 range from 3.90 to 9.5 µg/ml) than the Bti-H14 (LC50 of 13.33 µg/ml), with one strain having as much as 3.4-fold higher activity than the Bti-H14. This is the first report of Bt strains native to Saudi Arabia with significantly enhanced larvicidal efficacy against Cx. pipiense. These novel Bt strains may therefore contribute to novel potent biopesticides and help mitigate the risk of Bt resistance emergence in bio-control programs targeting filaria vector populations.