Insecticidal Activity of Crude Extracts of Hyptis suaveolens (Bush Mint) on Anopheles Mosquitoes Collected from Lafia, Nasarawa State, Nigeria

Abstract

Anopheles gambiae is a vector that is responsible for the transmission of malaria parasites which causes high morbidity and mortality in Nigeria and the world at large. Human-vector contact can be reduced by the use of conventional repellents being sold in the market, though some of these repellent are not environmentally friendly and An. gambiae have developed resistance to some of these repellents. To this end, the phytochemical constituents and insecticidal activity of crude extracts of Hyptis suaveolens (bush mint) was determined on adult An. gambiae mosquitoes collected from Lafia, Nasarawa State, Nigeria to evaluate its effect in controlling them. Here, 70% ethanolic and diethyl ether fat crude extracts were made from H. suaveolens dried leaves and used to carry out the experiment. The phytochemical screening of the ethanol extract revealed the presence of alkaloids, flavonoid, saponins, tannins, steroids and reducing sugar. Glycoside was not detected in the ethanol extract. Only steroids was detected in diethyl ether extract the rest of the phytochemical tested were absent. An. gambiae larvae were collected from the field and were raised to F1 progeny adults that were used for the study. WHO protocol for carrying out human bait repellency cage test was used. Human hand treated with the extracts was exposed to a cage containing 30 female mosquitoes for each of the extracts respectively. The ethanolic crude extract treatment proved to be more effective in repelling mosquitoes with 0% (0/30) mosquito landing than diethyl ether extract which had 40% (12/30) mosquitoes landing and the control hand (untreated left hand) had the highest landing rate 63.3% (19/30) which showed very high significant difference (χ2 = 27.2619, df = 2, P <0.00001) in relation to the treatments. After 24 hours holding period, the mortality rate of exposed mosquitoes was observed to be highest in the ethanolic treatment 73.3% (22/30). In conclusion, H. suaveolens extracts have repellency potential in controlling adult An. gambiae.