by Sarah King
Mosquitoes are known for dispersing many different kinds of diseases that affect human health. Asian tiger mosquitoes (Aedes albopictus), originating in Southeast Asia, are among the most invasive and widespread species of mosquitoes in the world. This species has been the cause of the reemergence of several mosquito-borne diseases such as chikungunya and dengue, and in the United States it is largely responsible for the reemergence of West Nile Virus. Using census information, temperature data, precipitation data, CO2 emissions forecasts, and generated maps of Ae. albopictus population distributions, Rochlin and his collgues (2013) statistically modeled projections of Ae. albopictus expansion through the next seventy years (2020s, 2050s, and 2080s). Their modeling shows that the range of Ae. albopictus will grow over the next seventy years to cover nearly half of the northeastern United States. They found this increased reach of the Ae. albopictus population due to the projected warmer winter temperatures. As climate change causes temperatures to rise, policymakers and practitioners need to prepare for effective ways to control Ae. albopictus in order to minimize future mosquito-borne disease outbreaks.
Rochlin and his team accumulated the environmental data that they needed from WorldClim, the special Report on Emissions Scenarios by the Intergovernmental Panel on Climate Change, the International Center for Tropical Agriculture, the National Landcover Database, and population information from the US Census Bureau. The team also collected mosquito samples in the current range of the Ae. albopictus in Pennsylvania, New Jersey, and New York. The samples were used to map exactly how many and in what density the Ae. albopictus were living in each area. Then Rochin et al. analyzed their data using two statistical models. They found that winter temperature and rainfall were the two most limiting variables for Ae. albopictus distribution, but, landscape factors and urbanization also contributed to model significance. The model was run twenty-five times, each time with slightly altered regions to maximize accuracy. Once the model was determined to be useful, it was run at the baseline and future (2020s, 2050s, and 2080s) climate conditions.
Ultimately, the model found that “temperature of the coldest quarter” was the most significant variable, that urban areas are much more likely than rural or wild areas to accommodate the mosquito, and that the range would be about 5% of the northeast region of the U.S. In the moderate CO2 emission scenario, Ae. albopictus distribution was forecasted to increase from about 5% to 16% between 2010 and 2039. Furthermore, the model predicted the range to increase to nearly 27% of the area from 2040 to 2069, and then up to 43% from 2070 to 2099. Under the more extreme CO2 emissions scenario, the model demonstrated similar trends but at a greater rate. By 2040-2069, the second scenario calculated a 32% expansion of the Ae. albopictus range. The model critically predicts that all of the major urban areas in the most northeast part of the country will be densely infested with Ae. albopictus by the end of the 21st century.
Given this outcome, it is fair to say that the public needs to be aware of the future effects of climate change on the current mosquito population. Currently, there are not any practical ways to control Ae. albopictus, let alone if its range grows the way the model predicts. Therefore, it is essential for policy makers and medical practitioners to inform the people of the best preventative measures against mosquito bites and to prepare to treat possible outbreaks of mosquito-borne diseases like West Nile Virus.
Rochlin I., Ninivaggi D.V., Hutchinson M.L., Farajollahi A., 2013. Climate Change and Range Expansion of the Asian Tiger Mosquito (Aedes albopictus) in Northeastern USA: Implications for Public Health Practitioners. PLoS ONE 8: e60874. Full paper at http://bit.ly/X2xWia