Susceptibility Status of Anopheles Stephensi Liston the Main Malaria Vector, to Deltamethrin and Bacillus Thuringiensis in the Endemic Malarious Area of Hormozgan Province, Southern Iran

Background & Aims: Anopheles stephensi is one of the most important malaria vectors in Hormozgan province, southern Iran. This species with high density has an effective role in malaria transmission, especially in plain and coastal areas. At present, the country malaria vector control program in areas with local transmission is using deltamethrin 5% and Bacillus thuringiensis as insecticide and larvicide, respectively. The aim of this study was to determine the current susceptibility status of Anopheles stephensi to the mentioned pesticides. Methods: Susceptibility tests to deltamethrin in diagnostic dose (0.05%) and Bacillus thuringiensis granules were conducted against the field strain of Anopheles stephensi collected from Siahoo area in the Bandar Abbas county, and Bashagard district, Iran, as well, using standard methods of World Health Organization. Results: The mortality of Anopheles stephensi mosquitoes against deltamethrin was recorded as 97 and 98 percents, for Siahoo and Bashagard strains, respectively. Therefore, both strains were susceptible, although Siahoo strain needs more study. Larviciding test by recommended dose of Bacillus thuringiensis granules after 24 hours showed 63.5 and 39 percent mortality for Siahoo and Bashagard strains, respectively. These values increased to 77 and 56 percent after 48 hours. Conclusion: Targeted insecticide application is recommended to prevent the resistance in malaria vectors, while regular susceptibility tests are advised for monitoring of resistance status.