Background: Recently research has shown that larviciding can be an effective tool for integrated malaria vector\r\ncontrol. Nevertheless, the uptake of this intervention has been hampered by the need to re-apply larvicides\r\nfrequently. There is a need to explore persistent, environmentally friendly larvicides for malaria vector control to\r\nreduce intervention efforts and costs by reducing the frequency of application. In this study, the efficacy of a 0.5%\r\npyriproxyfen granule (SurmilarvW0.5G, Sumitomo Chemicals) was assessed for the control of Anopheles gambiae\r\nsensu stricto and Anopheles arabiensis, the major malaria vectors in sub-Saharan Africa.\r\nMethods: Doseââ?¬â??response and standardized field tests were implemented following standard procedures of the\r\nWorld Health Organizationââ?¬â?¢s Pesticide Evaluation Scheme to determine: (i) the susceptibility of vectors to this\r\nformulation; (ii) the residual activity and appropriate retreatment schedule for field application; and, (iii) sub-lethal\r\nimpacts on the number and viability of eggs laid by adults after exposure to SumilarvW0.5G during larval\r\ndevelopment.\r\nResults: Anopheles gambiae s.s. and An. arabiensis were highly susceptible to SumilarvW0.5G. Estimated emergence\r\ninhibition (EI) values were very low and similar for both species. The minimum dosage that completely inhibited\r\nadult emergence was between 0.01-0.03 parts per million (ppm) active ingredient (ai). Compared to the untreated\r\ncontrol, an application of 0.018 ppm ai prevented 85% (95% confidence interval (CI) 82%-88%) of adult emergence\r\nover six weeks under standardized field conditions. A fivefold increase in dosage of 0.09 ppm ai prevented 97%\r\n(95% CI 94%-98%) emergence. Significant sub-lethal effects were observed in the standardized field tests. Female\r\nAn. gambiae s.s. that were exposed to 0.018 ppm ai as larvae laid 47% less eggs, and females exposed to 0.09 ppm\r\nai laid 74% less eggs than females that were unexposed to the treatment. Furthermore, 77% of eggs laid by\r\nfemales exposed to 0.018 ppm ai failed to hatch, whilst 98% of eggs laid by females exposed to 0.09 ppm ai did\r\nnot hatch.
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