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Durham University

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Publication details for Prof Steve Lindsay

Mbare, O., Lindsay, S.W. & Fillinger, U. (2013). Dose-response tests and semi-field evaluation of lethal and sub-lethal effects of slow release pyriproxyfen granules (Sumilarv®0.5G) for the control of the malaria vectors Anopheles gambiae sensu lato. Malaria Journal 12: 94.

Author(s) from Durham

Abstract

Background: Recently research has shown that larviciding can be an effective tool for integrated malaria vector
control. Nevertheless, the uptake of this intervention has been hampered by the need to re-apply larvicides
frequently. There is a need to explore persistent, environmentally friendly larvicides for malaria vector control to
reduce intervention efforts and costs by reducing the frequency of application. In this study, the efficacy of a 0.5%
pyriproxyfen granule (SurmilarvW0.5G, Sumitomo Chemicals) was assessed for the control of Anopheles gambiae
sensu stricto and Anopheles arabiensis, the major malaria vectors in sub-Saharan Africa.
Methods: Dose–response and standardized field tests were implemented following standard procedures of the
World Health Organization’s Pesticide Evaluation Scheme to determine: (i) the susceptibility of vectors to this
formulation; (ii) the residual activity and appropriate retreatment schedule for field application; and, (iii) sub-lethal
impacts on the number and viability of eggs laid by adults after exposure to SumilarvW0.5G during larval
development.
Results: Anopheles gambiae s.s. and An. arabiensis were highly susceptible to SumilarvW0.5G. Estimated emergence
inhibition (EI) values were very low and similar for both species. The minimum dosage that completely inhibited
adult emergence was between 0.01-0.03 parts per million (ppm) active ingredient (ai). Compared to the untreated
control, an application of 0.018 ppm ai prevented 85% (95% confidence interval (CI) 82%-88%) of adult emergence
over six weeks under standardized field conditions. A fivefold increase in dosage of 0.09 ppm ai prevented 97%
(95% CI 94%-98%) emergence. Significant sub-lethal effects were observed in the standardized field tests. Female
An. gambiae s.s. that were exposed to 0.018 ppm ai as larvae laid 47% less eggs, and females exposed to 0.09 ppm
ai laid 74% less eggs than females that were unexposed to the treatment. Furthermore, 77% of eggs laid by
females exposed to 0.018 ppm ai failed to hatch, whilst 98% of eggs laid by females exposed to 0.09 ppm ai did
not hatch.
Conclusion: Anopheles gambiae s.s. and An. arabiensis are highly susceptible to SumilarvW0.5G at very low dosages.
The persistence of this granule formulation in treated habitats under standardized field conditions and its sub-lethal
impact, reducing the number of viable eggs from adults emerging from treated ponds, enhances its potential as
malaria vector control tool. These unique properties warrant further field testing to determine its suitability for
inclusion in malaria vector control programmes.