After the resurgence of eastern equine encephalitis (EEE) in Connecticut last year, state and local officials are taking preventative measures this year to identify and reduce the risks of mosquito-borne illnesses to the public.

The state’s mosquito monitoring program, coordinated by the Connecticut Agricultural Experiment Station (CAES), started trapping and testing mosquitoes for different viruses the first week in June. This includes a trapping location at Cockaponset State Forest in Chester.

CAES Lead Scientist Philip Armstrong said by email that 16 new sites have been added this year “in high-risk areas for EEE virus in eastern Connecticut. We selected sites based on the habitat, wooded swamps or nearby woodlands, and ease of access to set and retrieve the mosquito traps.”

Although testing, as of press time, has not revealed any mosquitoes with West Nile virus or EEE, several have tested positive for Jamestown Canyon virus, which can cause neurological illness in humans.

“We detect Jamestown Canyon virus every year in mosquitoes and there is no indication that it is becoming more prevalent based on the mosquito surveillance data,” said Armstrong.

Last year, 122 mosquito samples tested positive for EEE. There were four confirmed human cases of EEE, and three deaths associated with the virus. This was after a period of nine years, from 2009 to 2018, in which only one case was reported in Connecticut, according to data from the federal Centers for Disease Control and Prevention (CDC).

Consistent with prior years, the majority of EEE virus activity in 2019 was in Middlesex, New London, and New Windham counties.

In Chester last year, a total of 3,044 mosquitoes were trapped with five testing positive for EEE and five testing positive for West Nile virus, according to CAES’s cumulative data report on Nov. 7, 2019.

Mosquito Breeding

Fresh or stagnant water is an ideal breeding site for mosquitoes, including Culex pipiens, the species most often responsible for carrying viruses harmful to humans, according to the CDC.

Roger Wolfe, the mosquito management coordinator and wetland restoration biologist for the Connecticut Department of Energy & Environmental Protection, said mosquitoes that don’t have access to a wetland habitat will seek out “storm drains with a deeper basin” or “backyard artificial containers” in which to reproduce.

“These storm drains can be ideal stagnant water habitat for Culex species, which happen to be the primary amplifiers and vectors of West Nile virus,” said Wolfe by email.

Despite the recent dry weather conditions in Connecticut, “drought conditions actually favor Culex production because the catch basins still hold water and become a stagnant, organic-rich soup, which is ideal habitat for Culex to lay their egg rafts,” said Wolfe.

In a written statement issued June 19, Scott Martinson, director of health for the Connecticut River Area Health District, indicated that the storm drains in the towns that the district services, including Chester and Deep River, were treated for mosquitoes. This mosquito abatement measure will be ongoing throughout the season.

“Although these measures do not eliminate every mosquito, it does help to control the adult population, which therefore reduces risk,” said Martinson in the written statement.

“In Connecticut, the peak of the Culex population is early July, so during early May and June, those stagnant water areas are developing loads and loads of Culex, so this time of year is precisely when towns should be treating catch basins and homeowners should be emptying containers and preventing standing water,” said Wolfe.

Lisa Fasulo, director of health in Essex, said the Essex Public Works Department typically treats select catch basins that don’t empty directly into the town’s waterways with “mosquito dunks,” which uses a bacteria harmless to humans and wildlife to kill mosquito larvae.

“We want people to go outside. Just don’t forget that mosquitoes and ticks are still there, so take the standard precautions [such as using] bug spray, [wearing] long sleeves, and go out and enjoy the day,” said Fasulo.