Effect of Bacillus thuringiensis H-14 toxin on the gut peristalsis in Aedes aegypti mosquito

Effect of Bacillus thuringiensis H-14 toxin was studied on the adults and larvae of Aedes aegypti mosquitoes. Incorporation of 1% commercial formulation of toxin in the adult blood meal caused hyper-peristaltic movement in the gut. As a result mosquitoes defecated ingested blood within 15–30 min. Similar effect of toxin was seen when it was fed to mosquitoes along with 10% glucose. The toxin in the defecated blood was active and could kill fresh larvae. It seems that this is a kind of defence response against the toxin. Atropine sulphate, which is known to reduce involuntary muscle movements, was incorporated in the blood meal. Higher amount of atropine sulphate in the blood meal of adult mosquitoes caused low mortality, but its combination with toxin caused significantly higher mortality. It is suggested that due to arrest of peristaltic movement by atropine sulphate, adults could not excrete the toxin from the gut. Experiments were also conducted to determine if the toxin causes a similar effect in the larvae. Larval bioassays were conducted with and without atropine sulphate. Addition of atropine sulphate did not show any noticeable increase in mortality in the larvae.