Spatial Distribution and Long-Term Persistence of Wolbachia-Infected Aedes aegypti in the Mentari Court, Malaysia

Simple Summary The mosquito Aedes aegypti is the primary vector of the dengue virus in humans. Wolbachia bacteria can prevent dengue virus transmission following transfer into this species. Ae. aegypti of both sexes carrying Wolbachia strain wAlbB were released in Mentari Court, Malaysia, in October 2017 for 20 weeks. This study aims to investigate the spatial distribution of Wolbachia-carrying mosquitoes in a high-rise residential site and examine the nature of the composition of the mosquito population across the site. There are numerous findings; firstly, Wolbachia-infected mosquitoes showed a high infection frequency four years after release. Secondly, there were some minor effects of floors and blocks on the frequency of Wolbachia. Thirdly, there was no evidence that the Aedes albopictus increased across the area. While the invasion of Wolbachia will vary from location to location, this study filled a knowledge gap on the invasion of such a strain in a high-rise residential area. This study can assist in planning field release strategies and the development of models that can forecast local success. Dengue is endemic in Malaysia, and vector control strategies are vital to reduce dengue transmission. The Wolbachia strain wAlbB carried by both sexes of Ae. aegypti was released in Mentari Court, a high-rise residential site, in October 2017 and stopped after 20 weeks. Wolbachia frequencies are still being monitored at multiple traps across this site, providing an opportunity to examine the spatiotemporal distribution of Wolbachia and mosquito density with respect to year, residential block, and floor, using spatial interpolation in ArcGIS, GLMs, and contingency analyses. In just 12 weeks, Wolbachia-infected mosquitoes were established right across the Mentari Court site with an overall infection frequency of >90%. To date, the Wolbachia frequency of Ae. aegypti has remained high in all areas across the site despite releases finishing four years ago. Nevertheless, the Wolbachia invaded more rapidly in some residential blocks than others, and also showed a relatively higher frequency on the eighth floor. The Ae. aegypti index tended to differ somewhat between residential blocks, whilst the Ae. albopictus index was relatively higher at the top and bottom floors of buildings. In Mentari Court, only a short release period was required to infiltrate Wolbachia completely and stably into the natural population. The results inform future releases in comparable sites in a dengue control programme.

Automated summary

This study investigates the spatial distribution of Wolbachia-carrying mosquitoes in a high-rise residential area and examines the composition of the mosquito population. The study finds that Wolbachia-infected mosquitoes maintain a high infection frequency four years after release and shows minor effects of floors and blocks on Wolbachia frequency. There is no evidence of increased Aedes albopictus population. This study fills a knowledge gap and provides insights for field release strategies and local success forecast.