Twenty years of data show Connecticut's mosquitoes are getting more diverse and abundant
West Nile virus was first detected in North American mosquitoes right here in Connecticut.
That was back in 1999, just two years after the state launched a surveillance program to trap and test for mosquito-borne diseases making their way around the world. Now, more than 20 years later, West Nile virus is the dominant mosquito-borne illness in the continental United States. And Connecticut has amassed more than two decades of data yielding new insights into these insects.
“When we’ve looked at our long-term trapping and testing data … we’re picking up new species over time, and they’re also becoming more abundant,” said Philip Armstrong, a medical entomologist with the Connecticut Agricultural Experiment Station.
This year, Armstrong is leading a state effort to trap and test mosquitoes at more than 100 locations.
Scientists are looking for West Nile virus and eastern equine encephalitis (EEE). Both diseases were detected in state traps last year. But only six human cases of West Nile Virus were reported. No cases of EEE were found in people or horses.
Most people infected with West Nile virus do not feel sick, but about 1 in 5 people infected develop a fever and other symptoms. A very small percentage can develop a serious, sometimes fatal illness, according to the Centers for Disease Control and Prevention (CDC).
Eastern equine encephalitis is significantly rarer – only a handful of cases each year – but it can be serious, causing death or possible neurological problems. During 2019, the number of confirmed human cases nationwide spiked to 38 with four cases (and three fatalities) occurring in Connecticut.
More than 50 species of mosquito have been detected in Connecticut. Worldwide, over 3,500 types of mosquitoes can be found, according to the CDC.
Armstrong said warmer weather is affecting mosquito populations in the state and bringing mosquitoes that typically live elsewhere into Connecticut.
“Some species that historically have had a more southern distribution are appearing in our state,” he said, adding that climate change may only make the state’s mosquito problem worse.
“In general, wetter, warmer weather will lead to greater mosquito abundance,” Armstrong said.
“Mosquitoes are very sensitive to weather, temperature, precipitation and, essentially, climate change,” he said. “We are seeing those changes even over a 20-year time scale.”
What purpose do mosquitoes serve?
For people, not much. Other than making us sick.
While mosquitoes do serve as food for certain animals and predatory insects, “it’s not something that benefits us,” Armstrong said. “Particularly when you’re in the tropics, they’re a major killer.”
That’s because mosquitoes that bite (that’s right – not all mosquitoes bite), can be “vectors.”
Typically a mosquito bite causes only itching and swelling, but mosquito vectors can spread germs (like viruses and parasites) to people and animals that can cause illness. West Nile, dengue, yellow fever, malaria and Zika are just a few of the diseases caused by mosquitoes.
Armstrong said that “you could probably get rid of” the species that transmit those diseases “and it wouldn’t have a huge impact on other organisms.”
But for the foreseeable future, he said, disease-carrying mosquitoes will be with us.
How can you protect yourself?
Simply put: Dress appropriately.
“When you go outside – particularly between dusk and dawn, that’s when mosquitoes are most active – you’re going to want to cover up,” Armstrong said. “We also recommend that you wear repellent on any of those exposed skin surfaces to keep mosquitoes at bay.”
Wear shoes, socks, long pants, and a long-sleeved shirt when outdoors for long periods of time, or when mosquitoes are more active. Light-colored clothing is preferable and ideally would be made of tightly woven materials that keep mosquitoes away from the skin, Armstrong said.
If you have loose screen doors and windows, or standing water on your property, Armstrong said you should also try to fix that.
“Water that collects in cups and containers and tires are perfect breeding sites for mosquitos,” Armstrong said. “Dump that water out to prevent the mosquitoes from developing to the adult stage.”
In a nutshell, he said, minimize time spent outside between dusk and dawn, cover up and use bug spray.
“Really the first line of defense,” Armstrong said, “is personal protection measures against the bites.”