Introduction: Malaria is one of the most prevalent public health problems worldwide. Globally, nearly half the world’s population remains at risk of malaria transmitted by Anopheles mosquito vector. Chemical insecticides, which are toxic and cause environmental deprivation, have been used to control the vector. So,safe environmentally friendly and effective alternative method are need to control malaria vectors. Objective: To isolate and characterize Bacillus thuringiensis (BT) strains and evaluate their insecticidal activity against malaria vectors. Methods: Soil samples were collected from different sites (Jawi, Debre Birhan, Tara Gedam and Enjibara) in Amhara Regional state, Ethiopia Each 1g of samples was suspended in 9ml normal saline and homogenize for 2 minutes and samples were heat shocked at 80°C for 10 minutes in water bath. Serial dilution was conducted in normal saline and then aliquots of 0.1 ml from dilution above 10-3 was plated on nutrient agar media. Finally, incubated at 28°C for 24-48 hrs and conduct Coommasie Brilliant Blue staining. BT strains were isolated and characterized based on morphological, microscopic parasporal crystal staining and biochemical characteristics. Toxicty was assessed by bioassay against Anopheles mosquito laravae. Results: Thirteen isolates of Bacillus thuringiensis were identified and characterized based on their morphological, microscopic parasporal crystal staining and biochemical characteristics. They were evaluated for their toxicity against larvae of Anopheles mosquito. It was found that BT strains JW2wRLF, JW4wRLsr, JW3wrlf, JW2wzlr and JW7wrlf) were potentially effective and JW3wrlf, JW4wRLsr and JW7wrlf showed 100% larvicidal potential similar with the reference strain Bti and better than Btk NCIM 2514 within 24 hrs. Those five potential isolates were glucose fermenter, motile, urease and catalase positive, Ampicillin resistant and sensitive for ciprofloxacin antibiotics. Conclusion: Five Bacillus thuringiensis isolates were obtained from soil samples with significantly higher larvicidal efficacy against Anopheles mosquito larvae. Among them, three isolates, JW3wrlf, JW4wRLsr and JW7wrlf were a promising candidate for future applications in mosquito biocontrol.

Keywords: Anopheles Mosquito, Bacillus thuringiensis, Bio-control, Insecticidal proteins, Malaria