Characterization and Mosquitocidal Potency of Bacillus thuringiensis Isolate SB1 from the Sundarbans Mangrove, West Bengal, India

Abstract

Anopheles, Culex and Aedes mosquitoes are serious disease vectors in India including the malaria endemic saline mangrove delta of the Sundarbans, West Bengal. Their impact on the health and well being of the local population warrants more effective control measures. In the present study, spore forming soil bacteria were isolated from different areas of the Sundarbans, and their effectiveness was bioassayed against the larvae of mosquitoes including Anopheles sundaicus, Aedes aegypti and Culex quinquefasciatus which are vectors of malaria, dengue and filariasis diseases, respectively. The purpose of the present study was to identify and select the potent biocides for development of an effective biocontrol strategy. From virulence assay, the most effective mosquitocidal bacterial strain SB1 was selected, characterized phenotypically and 16S rDNA phylogeny, and identified as Bacillus thuringiensis. In the laboratory, B. thuringiensis (SB1) was more virulent against An. sundaicus than Ae. aegypti and Cx. quinquefasciatus. A dose of Bt SB1 as 3.1 × 108 cfu/ml infected 67.36, 86.21 and 98.75 % of A. sundaicus larvae (late 3rd instar) within 24, 48, and 72 h, respectively. LC50 and LC90 of the Bt SB1 against A. sundaicus larvae were 5.73 × 108 cfu/ml and 4.78 × 109 cfu/ml, respectively. The results proved that B. thuringiensis (BtSB1) is an effective mosquitocide which can be used in vector control programmes of A. sundaicus, as well as, Ae. aegypti and C. quinquefasciatus.