CONTROL OF DELTAMETHRIN RESISTANT Anopheles gambiae FROM WESTERN KENYA HIGHLANDS USING Datura stramonium AND Tamarindus indica

Abstract

Malaria, the most important mosquito-borne disease affecting millions of people globally. The disease is spread from one person to another by the bite of Anopheles mosquitoes infected with Plasmodium parasite. Malaria vectors thrive in habitats with bio-chemical properties attractive to gravid mosquitoes and which favour their development. Chemical insecticides used in long lasting insecticide treated nets and internal residual spraying, are currently challenged due to increasing resistance of the vectors to the insecticides. Vector resistance to insecticides necessitates the need for research on novel eco-friendly control tools. This study sought to evaluate the potential of ethyl acetate extracts of Datura stramonium leaf, seed and Tamarindus indica fruit pulp individually and in synergy on adult deltamethrin resistant Anopheles gambiae mosquitoes and their mid gut and cuticular microbiota. The study investigated Anopheles gambiae larvae productive sites in Chwele, Bungoma county, Western Kenya Highlands for larval sampling to determine their deltamethrin resistance status. Deltamethrin resistant adult An. gambiae and its mid-gut and cuticular microbiota were exposed to crude extracts of D. stramonium seed, its isolate F7, leaf and T. indica fruit pulp at concentration between 0.01g to 1g per 100ml of water to test for knockdown effect on deltamethrin resistant Anopheles gambiae. Data was analysed with R version 4.3.2. Stable and unstable habitats did not have significant differences in productivity p<0.05. Based on seasons larval instar one and two had significant seasonal differences in stable habitats p<0.05 while larval instar four in unstable habitats p<0.05. Plant secondary metabolites in the extracts were saponin, phenols, terpenoids, steroids, alkaloids and flavonoids. The quantities of major bio-active compounds in the eluents were: D. stramonium seed areas ranged between 28.24% -9.18%, its leaf extracts had one major compound taking area of 53.34% of entire eluent whereas D. stramonium seed isolate F7’ had compounds ranging between 16.8% and 7.54% and Tamarindus indica crude fruit pulp extracts had area ranges of 13.04% to 7.76%. While all extracts showed significant knockdown on deltamethrin resistant An. gambiae over time p<0.05, growth inhibition effectiveness on its mid mid-gut and cuticle microbiota, F7 was the most potent in small concentrations. F7 at 60 minutes post treatment, had LC₅₀ of 0.164g/100ml and LC₉₀ of 0.6558g/100ml. D. stramonium crude seed extracts had LC₅₀ of 1g/100ml and LC₉₀ of 1.5g/100ml at 60 minutes. Datura stramonium leaf extracts and T. indica, remained ineffective until at 120 minutes. Seed extracts isolate F7’ had superior growth inhibition efficacy p<0.05 comparable only to lincomycin on Elizabethkingia, Aeromonas, Pseudomonas, Klebsiella, Proteus, Serratia, Shigella, Acinetobacter, salmonella Enterobacter, and Citrobacter, bacteria isolated from the mosquito. There is need to consider habitats positive of larvae around Chwele for larval source management. The novel botanical, F7 should therefore be considered for processing as an ecofriendly insecticide for control of knock-down and bacteria mediated resistant malaria vector and this is hoped to significantly reduce the spread of malaria, its morbidity and mortality.