Potential use of pyriproxyfen for control of mosquito-borne diseases: (2) Impact on Aedes albopictus populations in semi-field condition

Pyriproxyfen (PPF) is classified as a juvenile hormone analog (JHA) and has been used against a range of pest insects including mosquitoes since early 1990s. Aedes albopictus is an important vector of dengue and chikungunya and expanding distribution in European and American countries. In this study, impact of PPF treated bed net on populations of Ae. albopictus in a semi-field condition was evaluated using 6 small microcosms. Three microcosms were containing a miniature bed net treated with 350 mg/m² and 35 mg/m² PPF in Experiment I and II respectively, and remained 3 microcosms were used for controls with untreated bed net. One hundred pairs of Ae. albopictus were released into each microcosm and allowed to feed on a mouse around one week intervals under the miniature bed nets which have artificial holes. The number of laid eggs from the released adults was significantly reduced in PPF treatment compared to untreated controls. The egg hatchability was also significantly suppressed in PPF treated microcosms. Consequently, a few pupae occurred in PPF treated microcosms. Laboratory bioassays showed that pupal mortalities were significantly higher in the water from breeding site in PPF treated microcosms than that from controls. The result implies a possibility for horizontal transfer of PPF by the mosquitoes. As a result, adult density in the next generation was highly suppressed in the PPF treated microcosms.