Taipei: The effective dispersal distance of the dengue-carrying mosquito Aedes aegypti, the primary vector in southern Taiwan, was found to be about 150 meters, supporting the 200-meter spraying radius around confirmed cases set by authorities, according to a National Health Research Institutes (NHRI) study.
According to Focus Taiwan, when an outbreak occurs, it is crucial to eliminate virus-carrying mosquitoes. Huang Chin-gi, an assistant investigator at NHRI's National Mosquito-Borne Diseases Control Research Center, emphasized the importance of understanding the mosquitoes' flight range to determine the scope of control measures. NHRI data shows that more than 98 percent of local dengue cases occur in southern Taiwan, with the Centers for Disease Control (CDC) reporting 12 local cases in Kaohsiung as of September 8.
Huang explained that outbreaks can persist despite the established spraying radius due to factors such as insecticide selection and operator technique. Inappropriate insecticide selection and subpar field operations can allow transmission to continue even when the control radius is sufficient. The control radius is only one part of a successful response, with other factors like the timeliness of interventions also playing a crucial role.
By analyzing genomes from 192 Aedes aegypti mosquitoes reared from eggs collected in Tainan, Kaohsiung, and Pingtung County, researchers inferred the dispersal distances of mosquitoes. The study found the median dispersal distance to be 154 meters, with most values ranging between 126 and 180 meters. This supports the 200-meter minimum spraying radius used by most counties and cities in Taiwan.
One notable finding from the study is that roads do not act as barriers for mosquitoes, while administrative district boundaries contribute to genetic differentiation among mosquito populations. This separation is largely human-driven, as control measures like source reduction and spraying create pressure on mosquito populations, pushing them apart.
Huang highlighted the challenges of synchronizing control measures across large administrative districts. Genetic differentiation can lead to different patterns of insecticide resistance among Aedes aegypti in neighboring districts. If a dengue-carrying mosquito can be genomically traced to its home district, responders can reference that district's effective chemicals and deploy those agents immediately.
Starting in 2020, Huang's team conducted a study spanning at least three years, resulting in an academic article titled "The Impact of Administrative Districts and Urban Landscape on the Dispersal of Aedes aegypti via Genetic Differentiation," published in the international journal Molecular Ecology in February this year.