Extremely high biting densities of Aedes albopictus (Skuse) (Diptera: Culicidae) at a university campus in Nagasaki, Japan

Abstract

Aedes albopictus (Skuse) transmits several arboviral diseases. This mosquito was the vector responsible for the past and the recent dengue outbreaks in Japan. Sites with high density of A. albopictus are at potential risks of outbreaks of arboviral diseases. This study describes extremely high biting densities of A. albopictus at a campus of Nagasaki University, southwestern Japan. In August of 2015 and 2016, human-bait-sweep collection for 8 min obtained on average 33.4 and 38.9 females, respectively. In both 2015 and 2016, the highest and the second highest biting densities were observed in sites densely shaded by trees and covered with a lot of understory plants. In addition, major breeding sites were identified near these sites in 2016. A predaceous larval mosquito, Lutzia vorax Edwards, appeared to strongly suppress the breeding of A. albopictus in catch basins near the site with highest adult density, although its effect was insufficient to keep A. albopictus density at a low level. After cleaning the catch basins, A. albopictus immatures become more abundant especially in shallow catch basins in shaded sites.