Publication: Soil Bacteria that Kill Mosquito Larvae
Date
2024
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Kathmandu University
Abstract
ABSTRACT
Background
To control the deadliest mosquitoes, Bacillus thuringiensis var israelensis and
Bacillus sphaericus are the tools to prevent the development of adult mosquitoes
by killing the larvae in different water sources. Various countries formulated Bacillus
thuringiensis and Bacillus sphaericus larvicide in different forms isolated from various
sources to control mosquitoes. These bacteria are nontoxic for humans and other
living organisms. In Nepal, unawareness and unavailability of these isolates made
us inaccessible to these tools to control mosquito vectors. To address the increasing
trend of mosquito-borne diseases in Nepal these bacteria should be included as a
vector control tool.
Objective
To isolate and test the novel bacteria Bacillus thuringiensis and Bacillus sphaericus
from the soil sample of Nepal as a biological mosquito control tool.
Method
Soil samples collected from seven provinces of Nepal were processed by two different
techniques to isolate these two bacteria. The isolates were characterized by different
staining techniques, and by larvicidal bioassay against Aedes aegypti larvae.
Result
From 282 soil samples analyzed by the acetate selection method 846 Bacillus
thuringiensis isolates were obtained producing different types of crystal protein.
Among 846 isolates only one isolate showed 100% mortality against Aedes aegypti
larvae. On analysis of 32 soil samples by heat shock selection method, 11 Bacillus
sphaericus and 11 Bacillus thuringiensis were obtained. Only one Bacillus sphaericus
showed 25% mortality against Aedes aegypti larvae.
Conclusion
Two different Bacillus strains obtained from the soil sample of Nepal showed 100%
and mild toxicity against Aedes aegypti larvae.
KEY WORDS
Bacillus sphaericus, Bacillus thuringiensis, Control, Nepal, Vector
Description
GC G,1,2 Banjara MR,1 Gautam I,1,3 Ghimire P,1 Rijal KR1
1Central Department of Microbiology
Tribhuvan University, Kirtipur, Kathmandu, Nepal
2Trichandra Multiple Campus
Ghanta Ghar Kathmandu, Nepal
3Natural History Museum
Tribhuvan University,Swayambhu, Kathmandu, Nepal
Keywords
Bacillus sphaericus, Bacillus thuringiensis, Control, Nepal, Vector