Background: The fight against vector is essential in malaria prevention strategies in several endemic countries in Africa. In Burkina Faso, malaria transmission is seasonal in most parts of country, so a single round of spraying should provide effective protection against malaria, provided the insecticide remains effective over the entire malaria transmission season. The outcomes of indoor residual spraying towards curtailing malaria transmission are firstly to decrease the life span of vector

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... osquitoes and also to reduce the malaria vectors density.Methods : CDC light trap and early morning collections by pyrethrum spray catches were performed monthly to determine the change in malaria vector indices in sprayed (Diebougou) and unsprayed sites (Dano). The female's malaria vectors collected by both methods were used to determine their blood feeding, biting and sporozoites rate and malaria transmission risk estimated by entomological inoculation rate.Results: Anopheles gambiae complex composed to Anopheles gambiae, Anopheles coluzzii and Anopheles arabiensis were present throughout the transmission season, but An. gambiae was the predominant species collected (P =0.0005), comprising 88% of the total collected and the most infected species. Malaria vectors densities were significantly lower in sprayed villages (n=4,303) compared with unsprayed villages (n=12,569) during post-spraying period (P = 0.0012). In addition, mean human biting rate of An. gambiae sl and An. funestus sl were significantly lower in sprayed areas compared to unsprayed areas (P<0.05). Overall, malaria vector transmission risk was significant lower in villages which received IRS (P=0.0001) whatever the malaria vectors species (An. gambiae sl and An. An. funestus sl).Conclusions: The results showed that in the sprayed area (Diebougou), vector densities, human biting rates and malaria transmission risks were very lower than unsprayed areas (Dano). The findings also showed a change in vector behavior especially within An. funestus which became more zoophagic following IRS. The indoor residual spraying could be recommanded as control tool in areas where malaria transmission occured a given period of year.