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Releasing more mosquitoes might actually curb the number of mosquitoes

By Globe Staff 

It turns out more mosquitoes might be a good thing.

The Environmental Protection Agency announced this month it has approved a method for reducing populations of disease-carrying mosquitoes in 20 states — including all of New England. And it involves releasing millions more of the irritating insects into our skies.

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As alarming as that sounds, here’s how it’s supposed to work.

The released mosquitoes, all male and therefore not biters, will be lab-raised and infected with a strain of a bacteria called Wolbachia, according to EPA officials as well as scientists at MosquitoMate Inc., a Kentucky-based company that developed the method.

After the male mosquitoes seek out females to mate with, the bacteria renders the females essentially sterile. Unable to reproduce, the mosquito population shrinks as adults die off within weeks.

But what about the bacteria? Officials said it’s naturally occurring, common in most insects, and harmless to humans. Plus it doesn’t spread beyond the mosquitoes, they said.

MosquitoMate has field-tested the method with EPA oversight, agency officials said, and the results have been good, showing a 60 to 90 percent decline in mosquito populations with no discernible downside.

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Independent experts said the method requires further data collection to ensure it can work on a large scale, but they said they were encouraged by how the new, low-risk technique has produced favorable results so far.

“I believe these strategies hold promise, yet they require more evaluation to understand their efficacy and risks,” said Laura C. Harrington, an entomology professor at Cornell University.

The EPA’s approval comes with a five-year limit and applies to using this method on only one particular species of mosquito, the Asian tiger mosquito, or Aedes albopictus. This type of mosquito is invasive to the United States — it didn’t exist here until the mid-1980s. It is known to be aggressive, bite during the daytime, and spread a host of diseases, including Zika, dengue, and Chikungunya, along with heartworm in dogs and cats.

The Aedes albopictus is not one of the more prevalent species in Massachusetts, but it is particularly bothersome in the southeastern part of the state, experts said. And there’s a hope that the same method could be extended to later reduce other mosquito species, including those more common.

But before any bacterium-infected male mosquitoes are released in Massachusetts or elsewhere, at least one potential hurdle remains: State officials will have to sign off on the strategy.

In Massachusetts, that approval must go through the Department of Agricultural Resources. A spokeswoman for the department said officials there had not reviewed the plan and did not give a timeframe for when that might happen.

But Richard Pollack, chairman of the Massachusetts Mosquito Advisory Group (which might be asked to weigh in on the process, but will not play a formal role), expressed doubt that approval would be timely.

“There would be many hurdles to clear, not the least being a certain amount of fear and anxiety by persons who don’t understand the technology at hand,” said Pollack, who is also a public health entomologist at Harvard and commissioner for the Norfolk County Mosquito Control District.

Stephen Dobson, chief executive of MosquitoMate and an entomology professor at the University of Kentucky, said he’s hopeful that the positive results from his company’s testing will help persuade officials at the state level to give the plan a green light.

“We’ve been working with the EPA for several years now. We’re very pleased with the results, and we’re excited to move forward,” Dobson said.

The plan is to use the method, in combination with other longstanding population control measures, as another way to help to reduce the insects’ numbers in certain areas.

“This is not a silver bullet,” said Harrington, the Cornell professor. “We will still need conventional mosquito control and integrated methods.”

The approach, experts pointed out, might have benefits over other methods.

For one, “We’re not killing anything and we’re proud of that,” Dobson said.

In addition, the method only affects mosquitoes, which makes it different from pesticides, which can be indiscriminate, killing butterflies and bees that help pollinate plants.

The concept of sterilizing mosquitoes and other insects to reduce their populations is not new. But previous methods of sterilization relied on zapping mosquitoes with radiation, which was inefficient.

Officials acknowledged they’re keeping a close eye on the process to ensure mosquitoes don’t become resistant to the bacterium involved.


Matt Rocheleau can be reached at matthew.rocheleau@globe.com
Follow him on Twitter @mrochele.