Larvicidal effects of a neem (Azadirachta indica) oil formulation on the malaria vector Anopheles gambiae
1 University of Nairobi, School of Biological Sciences, P.O. Box 30197 00100 GPO Nairobi Kenya
2 Ifakara Health Research and Development Centre, Public Health Entomology Unit, P.O. Box 53 Kilombero Tanzania
3 Laboratory of Entomology, Wageningen University and Research Centre, P.O. Box 8031, 6700 EH, Wageningen, The Netherlands
4 Durham University, School of Biological and Biomedical Sciences, South Road, Durham, DH1 3LE, UK
Malaria Journal 2007, 6:63 doi:10.1186/1475-2875-6-63Published: 22 May 2007
Larviciding is a key strategy used in many vector control programmes around the world. Costs could be reduced if larvicides could be manufactured locally. The potential of natural products as larvicides against the main African malaria vector, Anopheles gambiae s.s was evaluated.
To assess the larvicidal efficacy of a neem (Azadirachta indica) oil formulation (azadirachtin content of 0.03% w/v) on An. gambiae s.s., larvae were exposed as third and fourth instars to a normal diet supplemented with the neem oil formulations in different concentrations. A control group of larvae was exposed to a corn oil formulation in similar concentrations.
Neem oil had an LC50 value of 11 ppm after 8 days, which was nearly five times more toxic than the corn oil formulation. Adult emergence was inhibited by 50% at a concentration of 6 ppm. Significant reductions on growth indices and pupation, besides prolonged larval periods, were observed at neem oil concentrations above 8 ppm. The corn oil formulation, in contrast, produced no growth disruption within the tested range of concentrations.
Neem oil has good larvicidal properties for An. gambiae s.s. and suppresses successful adult emergence at very low concentrations. Considering the wide distribution and availability of this tree and its products along the East African coast, this may prove a readily available and cheap alternative to conventional larvicides.