Bacillus thuringiensis search as an alternative for the biological control of Aedes aegypti (Diptera: Culicidae) in Valledupar - Colombian Caribbean

Introduction: The irrational use of chemical insecticides for control of diseases’ vectors has led to an imbalance of ecosystems, pollution, toxicity to humans, animals and the development of resistance by vector insects.

Objective: To characterize Bacillus thuringiensis with toxic activity against Aedes aegypti (Diptera: Culicidae), isolated from soils of Valledupar.

Materials and Methods: Samples were selected from urban and non-urban areas of Valledupar to isolate B. thuringiensis by microscopic, biochemical and molecular tests. Bioassays were conducted with larvae of Aedes aegypti, Rockefeller strain, to determine the larvicidal capacity of B. thuringiensis. The isolates were genotyped by Polymerase Chain Reaction (PCR), seeking for cry and cyt genes. Association between genes and toxicity was estimated by multiple variance analysis.

Results and Discussion: 102 B. thuringiensis were isolated. The obtained wealth index for urban soils was 0,13 and for non-urban soils was 0,23. B. thuringiensis was present in 52,2 % of the analyzed sites.

We detected anti-larva effect in five samples of B. thuringiensis, with mortality percent ranging from 10 to 30%.

The presence of cry11 genes was demonstrated in 58,3% of the analyzed samples and one isolate (3,6%) presented cry4Ba gene. No relationship between the presence of cry11 genes and larval mortality was found.

Study significance: B. thuringiensis strains which may be used as biological control of Aedes aegypti were isolated.