Global Veterinary Summit

Biography

Biography: Ashraf M Ahmed

Abstract

The bacterium Bacillus thuringiensis is a safe eco-friend entomopathogenic bio-control agent widely used to complement chemical control. Hence there is an urgent need for characterizing novel isolates with potent larvicidal activity against mosquito vectors. The present study was initiated to characterize new native Bacillus thuringiensis isolates with mosquitocidal activity from various samples from 16 regions across the Saudi Arabia. Various samples were collected from mosquito breeding sites across different regions in the country and screened for Bacillus thuringiensis isolation. Bacillus thuringiensis 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 and LC95) of standardized spore/crystal mixtures of Bacillus thuringiensis isolates were tested against larvae of the Rift Valley Fever (RVF) mosquito vector in Saudi Arabia, Aedes caspius at 24 hours post-treatment and compared with that of the Bacillus thuringiensis israelensis (Bti-H14). A total of 23 (out of 68 native Bacillus thuringiensis 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 Bacillus thuringiensis strains native to Saudi Arabia with significantly enhanced larvicidal efficacy against the RVF mosquito Aedes caspius. These novel Bacillus thuringiensis strains may therefore contribute to novel potent biopesticides and help mitigate the risk of Bacillus thuringiensis resistance emergence in bio-control programs targeting RVF vector populations.