Sterilized Anopheles funestus can autodisseminate sufficient pyriproxyfen to the breeding habitat under semi-field settings

Abstract

Abstract Background Anopheles funestus, the main malaria vector, prefer to oviposit in permanent and/or semi-permanent breeding habitats located far from human dwellings. Difficulties in identifying and accessing these habitats jeopardize the feasibility of conventional larviciding. In this way, we conducted a semi-field study to assess the potential of autodissemination of pyriproxyfen (PPF) by An. funestus for its control. Methods The study was conducted inside a semi-field system (SFS). Therein, two identical separate chambers, the treatment chamber with a PPF-treated clay pot (0.25g AI), and the control chamber with an untreated clay pot. In both chambers, one artificial breeding habitat made of a plastic basin with one liter of water was provided. Three hundred blood-fed female An. funestus aged 5–9 days were held inside untreated and treated clay pots for 30 minutes and 48 hours before being released for oviposition. The impact of PPF on adult emergence, fecundity, and fertility through autodissemination and sterilization effects were assessed by comparing the treatment with its appropriate control group. Results Mean (95% CI) percentage of adult emergence was 15.5% (14.9–16.1%) and 70.3% (69–71%) in the PPF and control chamber for females exposed for 30 minutes (p < 0.001); and 19% (12–28%) and 95% (88–98%) in the PPF and control chamber for females exposed for 48 hours (p < 0.001) respectively. Eggs laid by exposed mosquitoes and their hatch rate were significantly reduced compared to unexposed mosquitoes (p < 0.001). Approximately, 90% of females exposed for 48 hours retained abnormal ovarian follicles and only 42% in females exposed for 30 minutes. Conclusion The study demonstrated sterilization and adult emergence inhibition via autodissemination of pyriproxyfen by Anopheles funestus. Also, it offers proof that sterilized An. funestus can transfer pyriproxyfen to prevent adult emergence at breeding habitats. These findings warrant further assessment of the autodissemination of pyriproxyfen in controlling wild population of Anopheles funestus, and highlights its potential for complementing LLINs.