Browsing by Author "Mutagahywa, Joshua"

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    The effect of different sprayable surfaces on theEffectiveness of indoor residual spraying using lambda-cyhalothrin against anopheles gambiae sensu stricto
    (University of Dar es Salaam, 2014) Mutagahywa, Joshua
    The type of spray able surface impacts on the residual efficacy of insecticide used in indoor residual spraying (IRS). However, there is limited data on common types of wall surfaces sprayed in Zanzibar and Mainland Tanzania. The study investigated residual efficacy of lambda-cyhalothrin sprayed on common surfaces in Zanzibar and Mwanza where IRS is one of the malaria vector control interventions. An experimental hut was constructed with materials simulating common sprayable surfaces in the study areas. Surfaces included cement plastered, mud daub, white-wash, wood, palm thatch, iron sheet, burnt bricks, limestone and oil painted. Using WHO standard operating procedures for IRS, the study surfaces were sprayed with lambda-cyhalothrin at the dose of 20–25mg/m2. Residual efficacy of the insecticide was monitored through cone bioassay using laboratory reared mosquitoes Kisumu strain (R – 70) of Anopheles gambiae ss. Cone bioassay was done every fortnight throughout 152 days using a total of 20—25 mosquitoes per cone. The World Health Organization Pesticide Evaluation Scheme (WHOPES) threshold (70% mortality) was as cut point for acceptable residual efficacy. A total of 5,000 mosquitos were subjected to contact bioassay to test residual efficacy of lambda-cyhalothrin. There was a statistically significant variation in residual efficacy between the different types of wall surfaces (R2 = 0.24; p-value < 0.001). Residual efficacy decreased with increasing pH of the substrate (R2 = 0.2; p < -0.027). Based on WHOPES standards, shorter residual efficacy (56-77 days) was found in wall substrates made of cement, limestone, mud daub, oil paint and white wash. Walls made of burnt bricks; iron sheet, palm thatch and wood retained the recommended residual efficacy beyond 152 days. The study found a wide variation in residual efficacy of micro encapsulated formulation of lambda-cyhalothrin across the types of wall surfaces studied. In areas where malaria transmission is bimodal and wall surfaces of short residual efficacy (2 – 3months) compose > 20% of sprayable structure, two rounds of IRS using lambda- cyhalothrin should be considered. Further studies are required to investigate the impact of sprayable surfaces on residual efficacy of other insecticides commonly used for IRS in Zanzibar and Mainland Tanzania