EEE Found in Londonderry Mosquito Test Batch, Fields Sprayed

Londonderry Health Inspector Richard Canuel announced that Eastern Equine Encephalitis (EEE) was discovered in mosquitoes found in Londonderry by town mosquito control contractor Dragon Mosquito Control. The test batch was sent to Concord for analysis.

Whitney Howe, vector-borne surveillance coordinator for the state Department of Health and Human Services (DHHS), said the batch was tested Sept. 5 and the town notified residents the following day.
As a result, Dragon Mosquito sprayed the following areas on the evening of Saturday, Sept. 14: Matthew Thornton School, Londonderry Middle School, Londonderry High School, Moose Hill School, North School, South School, Nelson Road fields and West Road fields.
The notice of spraying was posted on the town website home page and stated that the insecticides Duet (prallethrin & sumithrin) and CrossCheck (bifenthrin) were used to control adult mosquitoes.
“Our contractor places traps in several locations in town and sends the mosquitoes that are caught to a lab in Concord, where they are tested,” Canuel said. “We were informed that one of the batches had a positive result for EEE and as a precaution, we are notifying the public of what precautions that they can take, and we are going to do a second spray of areas that people tend to congregate such as the athletic fields.”
Sarah McGregor of Dragon Mosquito Control said her company looks for and tests specific species of mosquitoes.
“The state gives us a list of the mosquito species that we should be looking for and I look at each mosquito trapped and send the identified species to Concord and they test them,” she said. “These are species that have tested positive in the past.”
McGregor said there are two types of mosquitoes.
“There are primary vector mosquitoes that bite birds and get infected, and then there is the bridge vector mosquitoes that bite birds and humans, creating a bridge from bird to human, and those are the ones that infect humans,” she explained. “Humans are called dead-end vectors because mosquitoes that bite humans that have EEE don’t get infected from the human.”
The best way to avoid being bitten, according to McGregor, is to wear insect repellent that has DEET as an ingredient.
“People should stay alert to the fact that mosquitoes are active in the early morning and at dusk and that they should wear insect repellent,” she said, cautioning that children should use a lower dose of repellent. “Another way to protect yourself is to stay covered up with long pants and long-sleeve shirts.”
McGregor said EEE is more dangerous than West Nile Virus.
“Eastern Equine Encephalitis has the highest mortality rate of any mosquito-borne illness, between 30 percent and 70 percent, and even if the person survives the virus, it can leave the person with disabilities for the rest of their lives,” she said. “Survivors have had to learn how to talk, walk and do other things all over again.”
A press release from the New Hampshire Department of Health and Human Services (DHHS), distributed last week by Garrett Simonsen, coordinator of the Greater Derry Public Health Network, which includes Londonderry, stated, “DHHS announced the finding of a positive test result for eastern equine encephalitis (EEE) in a horse from Derry as well as a mosquito batch in Sandown and a mosquito batch positive for West Nile virus in Hampstead. These findings necessitate the elevation of the risk level in Derry to ‘High.’ Towns surrounding Derry will be raised to a ‘Moderate’ risk level.”
“These results highlight the fact that these illnesses affect not just mosquitoes, but animals and of course people too,” said Dr. José Montero, Public Health Director at DHHS. “It is also an indication that mosquitoes do not respect borders, and as a result can infect animals and people in any corner of our state. This follows closely our identification of a person with West Nile Virus in Chesterfield, so I want to reiterate the importance of protecting against mosquito bites no matter where you live until there is a killing frost statewide.”
So far this season New Hampshire’s Public Health Lab has tested 4,263 batches of mosquitoes. Of those, 10 have tested positive for WNV and 13 for EEE. One person was also diagnosed with WNV. The latest test results include the first animal found positive for EEE this season; there have been no positive tests for animals with WNV as of press time.
Questions about EEE and WNV can be answered by calling the toll free EEE/ West Nile Virus information line at 1-866-273-6453 or visiting

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