Novel cost-effective method of screening soils for the presence of mosquito-pathogenic bacilli

AIMS: The aim was to simplify the cumbersome conventional process of isolating virulent bacilli, which involves isolating all bacilli strains from a source followed by screening for strains that are effective for bio-control of mosquito vectors. METHODS: A new simplified technique involving eight steps was devised for screening soil samples for the presence of mosquito-pathogenic bacilli before isolating individual strains. RESULTS: Using the new technique, we obtained eight bacilli strains (KSD1-8) showing pathogenic activity against mosquito larvae from three out of 10 soil samples screened. These strains were characterized, identified and the main bioassay tests were performed with three most promising strains (KSD-4, KSD-7 and KSD-8), and their pathogenic activity against Anopheles stephensi Liston, Culex quinquefasciatus, Say and Aedes aegypti Linnaeus compared well with commercial reference strains of B. thuringiensis israelensis and B. sphaericus. SIGNIFICANCE AND IMPACT OF THE STUDY: The new technique of screening soil samples for the presence of virulent pathogenic strains of bacilli against mosquito larvae proved quick, efficient and cost effective.