Hot Dry Weather Fostered West Nile, Reduced EEE Populations in Southeast Connecticut


TwitterFacebookCopy LinkPrintEmail

A hot dry summer across Connecticut has increased the prevalence of mosquitoes carrying West Nile Virus, but far fewer mosquitos have been identified as carrying the Eastern Equine Encephalitis virus than last year.

Through Oct. 5, the Connecticut Agricultural Experiment Station has trapped 143 mosquitos that have tested positive for the West Nile Virus, compared to 82 it found through the end of its testing on Nov. 7 last year

Last year, 122 mosquitos the station trapped tested positive for Eastern Equine Encephalitis (EEE). So far this year, they’ve found two – one trapped at Stonington High School on Aug. 5, and one at the Hampton Reservoir a week later.

Roger Wolfe, mosquito management coordinator for the Connecticut Department of Energy and Environmental Protection, said the difference can mainly be attributed to a hot, dry summer.

Wolfe explained that mosquitoes better suited to carrying West Nile Virus do very well in stagnant, polluted water, like in catch basins in residential areas. Mosquitoes carrying West Nile were primarily found in the lower Fairfield and New Haven County, and in the urban and suburban corridors around Hartford, he said.

“We have those types of primarily bird-biting mosquitoes in those backyard habitats and catch basins in town, and birds up in the trees, and everything just mixes together right there,” Wolfe said.

There have been seven human cases of West Nile in Connecticut this year, but no human cases of EEE so far. The population of the particular mosquito species that spreads EEE, Culisita melanura, has not able to survive as well in dried-out red maple swamps, he said.

“Had it been a wetter season, we think because of last year, things would have been much more problematic,” Wolfe said. “But because everything’s dried up this year, we haven’t had the water, so we just haven’t had the mosquitoes.”

The culisita species hatch in two stages, first when temperatures start to rise in the spring, and the second usually in August, Wolfe said. If there’s a large spring hatch and the conditions keep that population alive, EEE can be carried into the bird population by the time the second hatch happens, which is when the spread really takes off, he said.

“From there it spills over into those other mosquito species that will bite either birds or mammals, they don’t care what they bite,” Wolfe said. “They can bite an infected bird and turn around and bite a human.”

While temperatures are dropping and mosquito season is coming to a close, Wolfe said that people out hunting, hiking or leaf peeping need to be cautious, especially during the day. Mosquitos largely stop biting when the temperature drops below 50 degrees, but they’ll still be out in the day until there are a few good, hard frosts, he said.