With summer fast approaching, the Connecticut River Area Health District (CRAHD) is again contracting with a mosquito-control firm, to help reduce the public’s risk of exposure to life-threatening mosquito-borne illnesses.

In mid- to late June, Innovative Mosquito Management, Inc. (IMM) will apply the first of three larvicide treatments to catch basins in Chester, Deep River, and the other towns that CRAHD services. Scientific experts have identified the storm water in catch basins as an ideal breeding habitat for the types of mosquitoes that transmit illnesses, such as West Nile virus (WNV), to humans.

The catch basins “can be home to over 50 percent of vector know mosquitoes,” said Kurt Ehrhart, owner of Madison-based IMM.

The firm’s catch basin larvicide program disrupts the lifecycle of a mosquito, targeting mosquitos before they mature into adulthood and can fly.

IMM uses an organic product featuring a form of bacteria, or spore, that when mixed with a toxin, targets a specific enzyme found only in the gut wall of certain insects like mosquitoes or black flies. Because of this, the product is not harmful to the environment, people, or non-targeted animals.

“So, when the spore is eaten by this insect, it grows a protein crystal. The crystal grows in size quickly and then perforates the inside wall of the mosquito larvae,” said Ehrhart.

There are usually 30 to 40 days between treatments, he continued, adding that treating catch basins are an important part of municipal mosquito abatement measures, as “any type of sustained water habitat supports the mosquito population.”

In Essex, the town “is continuing with its standard mosquito management program this year,” said Essex Director of Health Lisa Fasulo, by email.

The Public Works Department plans to install mosquito dunks, which also prevent mosquito larvae from maturing into adulthood, at certain catch basins throughout town.

Fasulo is also encouraging residents to “go around their yards and tip out the items which collect standing water.”

State Mosquito Monitoring Program

The state’s mosquito monitoring program, which will run until the end of October, acts as an early detection system for people. It’s run by the Connecticut Agricultural Experiment Station (CAES).

“The mosquito season is here, and a lot of these viruses are around the corner,” said Philip Armstrong, medical entomologist at CAES, by phone with the Courier. “I think we’ll see them later in the summer, we just don’t know where necessarily, which is half the battle.”

There are a total of 108 mosquito-trapping stations in 87 municipalities throughout the state, including a location at Cockaponset State Forest in Chester. CAES started trapping and testing mosquitoes the first week in June; the reporting of results will begin the week of June 14 (after press time).

The number of trapping stations in Connecticut were expanded last year, after 2019 saw a spike in cases of eastern equine encephalitis (EEE) throughout the U.S., with four cases and three fatalities due to the virus in Connecticut. Prior to 2019, only about 4 to 8 cases of EEE were reported in the U.S. in a typical year.

CAES tests mosquitoes for a variety of different viruses.

“In Connecticut, we’ve detected nine different viruses from mosquitoes, so there is quite a few, but a lot of them don’t cause human disease, so we’re not necessarily concerned with those,” said Armstrong.

The detection of WNV and EEE are of primary concern for the program, he said, as both can cause neuro-invasive disease in humans including encephalitis and meningitis.

In 2020, the mosquitoes trapped and tested by CAES in Chester were negative for all viruses, according to CAES’s 2020 cumulative data report.

Throughout the state, there were no infections of EEE reported in humans or horses, although two mosquito samples from New London and Windham counties tested positive for the EEE virus. There were eight human cases of WNV, with WNV detected in 143 mosquito samples from Fairfield, Hartford and New Haven counties.

The technique used to screen mosquitoes for viruses allows the team at CAES to detect emerging infectious diseases, like the Jamestown Canyon (JC) virus.

The JC virus can cause mild symptoms in humans, such as fever, headache and fatigue, although rare cases have been associated with more severe symptoms like encephalitis or meningitis, according to the federal Centers for Disease Control and Prevention.

Last year, the JC virus was detected in 13 of the mosquito samples from Fairfield, Hartford, Litchfield, and New London Counties, according to the 2020 CAES report. No human cases were reported.

Armstrong said that although they have isolated these other viruses, “the ones that we’re really focused on are WNV and triple E, so it’s sort of a byproduct of the way that we test our mosquitoes [that we can identify other viruses].

“The advantage of testing the mosquitoes this way is it allows us to look for, if a new virus was introduced into our area, we would be in a position to pick it up,” he continued.

Several factors impact the prevalence of disease carrying mosquitoes in any given year, which makes predicting the incidence rate challenging.

“All of these viruses are highly sensitive to temperature, to weather especially, to a number of factors that affect the density of mosquitos,” said Armstrong. “For triple E and WNV, they are maintained in a bird [to] mosquito transmission cycle, so there a lot of variables that affect whether the virus activity is going to be high or low in that given year.”

There is not a vaccine for these viruses, although there are precautions that people can take to reduce risk of infection.

“We just always encourage people to take simple precautions to reduce their risk,” said Armstrong. “Things like wearing repellent when outdoors and enjoying the wooded areas, especially, and covering up and wearing long sleeve pants and shirts when outside when mosquitoes are active” between dusk and dawn.

The latest mosquito test results and human infections can be found by visiting the Connecticut Mosquito Management Program website at portal.ct.gov/mosquito.