Combining Synthetic Human Odours and Low Cost Electrocuting Grids to Attract and Kill Outdoor Biting Mosquitoes: Field and Semi Field Evaluation of an Improved Mosquito Landing Box
Background On going malaria transmission is increasingly mediated by outdoor biting vectors, especially where indoor insecticidal interventions such as long lasting insecticide treated nets (LLINs) are widespread. Often, the vectors are also physiologically resistant to insecticides, presenting major obstacles for elimination. We tested a combination of electrocuting grids with synthetic odours as an alternative killing mechanism against outdoor biting mosquitoes. Methods An odour baited device, the Mosquito Landing Box (MLB) was improved by fitting it with low cost electrocuting grids to instantly kill mosquitoes attracted to the odour lure, and automated photo switch to activate attractant dispensing and mosquito killing systems between dusk and dawn. MLBs fitted with one, two or three electrocuting grids were compared outdoors in a malaria endemic village in Tanzania, where vectors had lost susceptibility to pyrethroids. MLBs with three grids were also tested in a large semi field cage (9.6x9.6x4.5m) to assess effects on biting densities of laboratory reared Anopheles arabiensis on volunteers sitting near MLBs. Results Significantly more mosquitoes were killed when MLBs had two or three grids, than one grid in wet and dry seasons (P<0.05) The MLBs were highly efficient against Mansonia species and malaria vector, An. arabiensis. Of all mosquitoes, 99% were non blood fed, suggesting host seeking status. In the semi field, the MLBs reduced mean number of malaria mosquitoes attempting to bite humans fourfold. Conclusion The improved odour baited MLBs effectively kill outdoor biting malaria vector mosquitoes that are behaviourally and physiologically resistant to insecticidal interventions e.g. LLINs. The MLBs reduce human biting vector densities even when used close to humans, and are insecticide free, hence potentially antiresistance. The devices could either be used as surveillance tools or complementary mosquito control interventions to accelerate malaria elimination where outdoor transmission is significant.
PloS one