Evaluation of attractive insecticidal treated bed nets (ITN) against resistant anopheles mosquitoes and malaria transmission: a modelling study

There is recent evidences from the field and the lab that Long Lasting Insecticidal nets (LLIN) may be attractive to An. gambiae populations and may increase bite exposure of LLIN users. However it was not clear how these attractive LLINs may impact malaria transmission at a community level. We developed a model to answer this question under various scenario of LLIN coverage and vector’s physiological (mortality), quantitative (indoor escaping) and qualitative (spatial-temporal avoidance of LLINs) behavioral resistances. We compared the effect of attractive, inert and deterrent LLINs on the spread of the common Kdr mutation in a malaria vector population using a genetic model. According to our model, attractive LLINs are expected to reduce malaria transmission in comparison to inert or deterrent LLINs whatever the coverage percentage. Maximum reduction was reached at 63-65% coverage for which a highly attractive LLIN is expected to reduce malaria transmission by 69% and 85 % compared to an inert and a deterrent LLIN, respectively. Our simulations show that whatever the level of physiological or behavioral resistance in the vector population, attractive LLINs are always most efficient than inert or deterrent LLINs but the reduction in transmission lowered as resistance increased. According to our genetic model, attractive LLIN allowed a slightly faster spreading of the Kdr mutation in the vector population than inert and deterrent LLINs. Our model clearly showed that attractive LLIN are expected to reduce malaria transmission in all scenarios even in the presence of resistant phenotypes of vectors, when compared to inert or deterrent LLINs. The possibility to increase attraction of LLINs might be considered as a new opportunity. Combining new knowledge in chemical ecology and techniques to bi-impregnate LLINs may lead to provide to the current malaria control toolbox a most efficient version of a still well-accepted and utilized tool.Pan African Mosquito Control Association (PAMCA) Annual meeting, january 2020, Yaoudé, Cameroo