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Malaria vector control by indoor residual spraying of insecticides (IRS) and insecticide-treated bednets (ITNs) have important shortcomings. ITNs are expensive (US $ 5) for people living on less than US $ 0.30 per day, coverage is incomplete, and people with ITNs do not use them properly. On the other hand, IRS does not reach remote communities and is not sustainable because it requires heavy investment, special equipment, trained staff, and good road access.

According to WHO, IRS programs fail because of community rejection. Rural villagers live in mud and wattle huts whose walls are customarily ‘decorated’ with colored and freely available local plaster materials (soil, clay, cow dung, or wood ash). Our solution involves community incorporation of WHO-approved insecticides into smearing plaster of hut walls. The treated plaster is applied on the inside and outside of walls by villagers 1-2 times a year. According to WHO estimates, if > 80 % of homesteads are covered by IRS, malaria transmission may be interrupted, thus heralding eradication.

We anticipate that similar coverage of the vast Northern Region if the innovation is effective and scaled-up.  The project overcomes the shortcomings of IRS and ITNs by (1) the community-ownership which ensures long term  sustainability and high penetration; (2) low cost because plaster materials are  locally and freely available; (3) its high penetration and coverage unlike IRS which does not reach all areas; (4) ensuring a unique partnership between communities and health authorities. Preliminary results are promising. Insectary-reared An. gambiae mosquitoes were exposed to pirimiphos-methyl/plaster (black soil, red soil, and loam soil) in suspension on test papers or smeared on a wall. 

The knockdown effect after 60 minutes of exposure was higher for IRS-treated walls by comparison with that by smeared walls (KD60 85.6 % versus 60-67 %); whether or not this difference was due to a dose effect is under investigation. However, the wall surface smeared with pirimiphos-methyl-impregnated plaster killed 100 % of mosquitoes over 24 hours. This was comparable to the 100 % 24-hour mortality of mosquitoes exposed to a wall surface sprayed with pirimiphos-methyl (IRS gold standard). The best local material appeared to be loam soil in terms of KD60 and KT50. KD60  is the proportion of mosquitoes knocked down after 60 minutes of exposure to the test papers, smeared wall, or sprayed wall. KT50 is the time required to knock down 50 % of the mosquitoes.

The next steps include sporozoite ELISA to establish the number of infective bites/person before and after the intervention using mosquito heads from the baseline and final surveys, assessing the insecticidal activity on wild mosquito populations of hut mud walls smeared with plaster by villagers versus IRS by the team (gold standard); assessing the residual insecticidal activity of smeared insecticide-impregnated plaster versus IRS on mud walls after 6 months; and clinical monitoring of villagers over 6 months for the safety/toxicity of the DIY. This approach is relevant to other vector-borne diseases currently controlled by indoor residual spraying IRS and ITN such as lymphatic filariasis, dengue, and Chagas’ Disease.

This work was funded by Grand Challenges Canada (Grant # S5-0448-01) and UBS-Optimus Foundation (Grant #6060).