REPELLENT AND LARVICIDAL POTENTIAL OF ESSENTIAL OIL FROM TODDALIA ASIATICA FRUITS AGAINST ANOPHELES GAMBIAE
It is estimated that approximately 1.3 billion people are at risk of malaria. Mosquitoes are vectors of malaria and insecticides, the primary method of vector reduction, are non-selective and often harmful to other beneficial organisms. The desired qualities of a repellent include being of low toxicity to humans and being non irritating. Anopheles gambiae is the primary mosquito vector responsible for the transmission of malaria in most of sub-Saharan Africa. Investigations were carried out to evaluate the larvicidal activity and mosquito repellent potential of essential oil extracted from the fruits of Toddalia asiatica (L.). Larvicidal activity of the essential oil was evaluated against early third instar larvae of Anopheles gambiae, according to WHO larval susceptibility test method. Mortality was observed after 24 hours exposure. The essential oil was screened for repellency against 100 blood-starved female Anopheles gambiae by using human-bait method according to WHO protocol. 20% ethanolic Deet was used as positive control. Essential oils extracted from the fruits of Toddalia asiatica exhibited good larvicidal activity against 3 rd instar larvae of Anopheles gambiae with LD50 and LD 90 values of 0.6253 and 1.250 ppm respectively. Evaluation of the essential oil effective dose against adult female Anopheles gambiae, exhibited remarkable repellence potential with an ED50 of 0.001832 ppm and ED 90 of 0.6136 ppm. However present investigations revealed that protection time could not be assessed as the essential oil evaporated after elapse of 3 minutes, probably due to its high volatility. Studies are ongoing to encapsulate the essential oil in gelatin polymers to protect evaporation, before further evaluation and anti -mosquito product development. In the present study, we present preliminary data on repellent potential and larvicidal activity of essential oil extracted from Toddalia asiatica fruits prior to preparation of a cream/ointment mosquito repellent and a liquid mosquito larvicidal product for the control of mosquito population.