Finding Ways to Keep Mosquitoes at Bay

Editor’s Note: This is a guest post by Emily Reed, a Ph.D. candidate in NC State’s Department of Biological Sciences. This post is part of a series highlighting ways that NC State is helping us understand, mitigate and prepare for the impacts of climate change.

My work is focused on finding ways to limit the extent to which people come into contact with mosquitoes, a goal that most people in North Carolina probably think is worth pursuing.

I feel comfortable saying that because I have lived in North Carolina all my life. First growing up in the woods west of Chapel Hill, then in the mountains as an undergraduate, before returning to the Piedmont to pursue a Ph.D. in biology at NC State. I feel some pride in my familiarity with the state and its many communities, traditions and landscapes.

Hurricanes and mosquito research are not as distantly related as they may seem.

When I think about climate change in my state, the first thing that comes to mind is hurricanes. I vaguely remember retreating to Greensboro during Hurricane Fran with my very-pregnant mom in 1996, while my dad remained at home to watch over the animals and house. My uncle was one of the 26 people killed by the storm. I remember Hurricane Floyd more clearly, when my family took shelter in our downstairs bathroom with the lights out and radio on, listening to the all-too-familiar weather emergency alarm blare over and over.

Both anecdotally and scientifically, hurricane frequency and intensity has increased in North Carolina. This shift can be attributed to climate change, and many researchers at NC State are studying the relationship between climate and hurricanes and the consequent environmental and economic effects. I am not one of them. My scientific pursuits are on a much smaller scale: I study mosquitoes.

Hurricanes and mosquito research are not as distantly related as they may seem. The effects on each from climate change are rather similar: global warming means more of each over longer periods of time each year. Some mosquitoes, like Psorophora ciliata, known as the “gallinipper” in the Southeast, have eggs that hatch during floods, leading to a direct increase in their abundance following hurricanes. Other species, such as Aedes albopictus, the Asian tiger mosquito and the focus of my research, lay their eggs in small natural and artificial containers, such as the flowerpots, water bowls, tarps, and other refuse we keep in our backyards. When rain fills these items, the eggs hatch and we become much more aware of how pesky these critters are.

While North Carolinians currently get a reprieve from the bites when the weather turns cold, this window is shortening as warmer, wetter weather allows mosquitoes to survive and breed later into the year. I predict our mosquito season will eventually be the same as Florida’s: 365 days a year.

Climate change and more mosquitoes also bring sinister public-health risks.

Mosquito bites can be quite irritating to many – I can personally attest to this, since I counted a total of over 400 bites myself during my field season in 2018. But climate change and more mosquitoes also bring sinister public-health risks. Mosquito-borne diseases also thrive in warmer weather, and diseases that are currently restricted to the tropics, such as dengue fever and Zika virus, have the potential to spread.

Of the approximately 60 mosquito species found in North Carolina, only a handful are vectors of disease. Mosquitoes here are by-and-large a nuisance, and with proper management, they will stay that way despite climate change. History has shown that mosquito-borne illnesses can be contained and even eliminated from areas using proper preventative and adaptive measures.

For example, malaria was extirpated from the United States in the 1950s, following the increased use of window screens, improved drainage, and lots of insecticide. With improved technology, we can further mitigate the risks of disease and the ecological impacts of chemical control methods by managing smarter, not harder.

This is where my research comes in.

I look at how landscape features and climate influence the way tiger mosquitoes disperse across Wake County. I use a combination of GIS (Geographic Information Systems) and genomic tools to look at patterns of genetic relatedness between individuals – essentially, “23&Me” for mosquitoes. I can then identify corridors and barriers of dispersal and areas that are sources for mosquito spread. Corridors, barriers and mosquito “hotspots” are associated with landscape and climate variables. Once I know which variables are most important for mosquito dispersal, I can then use land-use and climate projections to predict future areas of mosquito occurrence and dispersal.

This research has several important management implications. By knowing landscapes that are sources of mosquitoes, we can target control methods in those areas. We can also use this knowledge to design our roads and development to help control mosquito dispersal and human contact. Eradication of these pests is highly unlikely, but this improved understanding of their ecology and interaction with the environment can help mitigate the public health and nuisance risks that are being exacerbated by climate change.