NORTHAMPTON — On a cloudy and humid Thursday morning, John Briggs was doing the same thing he has done since 2014: placing mosquito traps and collecting them for testing in the lab.

But this time, recent prolonged heavy rains and heat meant that he was facing more flying “vampires,” as he calls the mosquitoes, than usual.

“The two most important contributors to mosquito development are precipitation and temperature,” said Merridith O’Leary, commissioner of Northampton’s Department of Health and Human Services.

Those two factors are increasingly prevalent as climate change fosters warmer temperatures and more intense precipitation events, like the heavy rains and heat wave seen across western Massachusetts in recent weeks.

With more rain, pools of stagnant water where mosquitoes lay their eggs become more plentiful, providing mosquitos with the perfect conditions to breed. On top of that, warmer temperatures shorten the time it takes for a mosquito to develop from an egg to an adult, which only accelerates their overpopulation.

And with more mosquitoes comes a greater health risk to people. In Massachusetts, the two most concerning mosquito-borne diseases are eastern equine encephalitis (EEE) and West Nile virus, which was recently detected in West Springfield.

West Nile is more common, but is typically less severe than EEE. In most cases, people infected with West Nile do not develop any symptoms, though some experience flu-like conditions such as fever, headache, body aches, joint pain, vomiting, diarrhea or rash, and some develop severe illness.

Mosquito surveillance

Cities and towns across Hampshire, Franklin and Hampden counties work with the Pioneer Valley Mosquito Control District, a group under the state Department of Agriculture, to make decisions around mosquito surveillance and control.

Briggs, director of the mosquito control district, spends four to five days a week setting two types of mosquito traps to collect data ultimately used to detect mosquito-borne diseases.

The first type of trap is called a CDC trap, and it uses carbon dioxide and a battery-operated fan to lure mammal-biting species into what Briggs and other scientists refer to as a “catchy thing,” or a net trapping the insects. On any given day, the trap may collect 10-15 different species of mosquitoes that are “vectors,” or transmitters, of mosquito-borne diseases.

“Right now in areas where it’s densely populated with mosquitoes, like at the last place I was, you’re talking anywhere between one to five thousand trapped mosquitoes,” said Briggs.

The other trap targets gravid mosquitoes, or female mosquitoes that are ready to lay their developed eggs. The first step in creating a gravid trap is to concoct a “mosquito soup,” which involves fermenting hay-infused water for a week to produce bacteria-rich water. Such water is appealing to female mosquitoes seeking to lay their eggs.

According to Briggs, gravid traps tend to collect culex species, which are primary vectors of West Nile.

After letting the traps collect mosquitoes for 24 hours, Briggs returns to the collection site.

“The next phase is to bring them to the lab and that’s where I freeze them and then look at them under a microscope,” said Briggs.

At the lab, he sorts through the mosquitoes for the most “medically important” ones, meaning species that are vectors of diseases, and then he submits those mosquitoes for testing at a state lab.

If a positive result comes up, Briggs uses GIS software to create a 1-mile radius around the trap where the positive mosquitoes were discovered.

“That is based on the literature which indicates that this particular species can fly up to a mile or so… they’re not very strong fliers,” said Briggs. “I try to set up additional traps on the edges of that radius to see how expansive the viruses are.”

From there, data is communicated to participating municipalities, where officials can move forward with other control methods and/or relay the information to the public.

“Right now, knowledge is power,” said Briggs.

In Northampton, the city contracts a mosquito control company to use larvicide to prevent mosquito breeding in standing water.

“What we really want to do is to achieve a level of pest control by using really an environmentally-friendly approach,” said O’Leary, who helps oversee operations of the Pioneer Valley Mosquito Control District. “We want to control the mosquito population where they’re at, where they breed, and get them before they’re adults.”

Larvicide — which is species-specific and does not harm humans, animals, birds, other insects, fish or plan — works by killing mosquito larvae before they grow into adults.

Another control method, according to O’Leary, is simply removing water from areas that pool and don’t drain within 24 hours.

“Something as little as a toy truck full of water can breed hundreds of mosquitoes in four days,” said O’Leary, adding that the city recommends that individuals implement protective measures to stay safe.

Those measures include dumping out stagnant water from places like gutters, wheelbarrows and wading pools; using mosquito repellent while outdoors; being extra careful from dusk to dawn during peak biting hours; wearing long sleeves and pants, when weather appropriate; and protecting pets using veterinary-approved products containing permethrin.

A bill filed in the Senate by Sen. Jo Comerford, D-Northampton would establish “an ecologically based mosquito management program in the Commonwealth to protect public health,” and would prioritize education, monitoring, and habitat modification over pesticide use, similar to what the PVMCD and City of Northampton already do.

At a hearing in May, Comerford said there is a need to modernize and update existing mosquito-control rules which date back to the early 1900s. 

Doing so, per her bill, would involve banning aerial pesticide spraying along, with the use of chemicals containing PFAS. The bill would also allow residents to opt out of spraying and automatically opt out beekeepers and organic farmers.

Maddie Fabian can be reached at mfabian@gazettenet.com or on Twitter @MaddieFabian.]]>