The Central Massachusetts Mosquito Control Project, through a mutual-aid arrangement with its Cape Cod counterpart, performed targeted truck spraying in Falmouth late Wednesday, August 14, to kill adult mosquitoes that might be carrying the Eastern Equine Encephalitis virus.
That action came after two additional positive EEE samples were collected from a trap on Oyster Pond this week.
“The samples were taken Tuesday, August 13, and were found in the bird-biting mosquito, Culiseta melanura, and the mammal-biting mosquito, Coquillettidia perturbens,” Falmouth Health Agent Scott McGann wrote in a public health advisory yesterday, Thursday, August 15.
This area was included in the truck spraying Wednesday, and the Cape Cod Mosquito Control Project will take additional samples following the spraying, updating the Falmouth Health Department as soon as results are available, Mr. McGann wrote.
In addition, the Massachusetts Department of Public Health announced yesterday that EEE virus was detected in mosquitoes collected in Bourne.
The truck spraying in Falmouth took place between 9 and 11:30 PM, dusk hours when mosquitoes are most active, along Woods Hole Road and on side streets in the area of Devil’s Lane, Treetops Condominiums and Falmouth village, where samples tested positive for EEE last week.
“The spraying was conducted as planned, with all areas on the map being sprayed except for the properties that requested to be excluded,” Mr. McGann wrote.
“There were no issues with the spraying. We saw that people had put out signs on their properties for exclusions, but we followed a strict map,” said Gabrielle E. Sakolsky, an entomologist and the control project’s assistant superintendent. “Our crews will return to treat what we can and set out more traps. We’ll reevaluate in the next few days. The sprayers don’t need to come back at this time.”
The Falmouth boards of selectmen and health voted earlier this month to support selective truck spraying of the immediate areas surrounding the EEE-positive sites.
There have been no human cases found on Cape Cod this year, but state health officials confirmed a single case Saturday, August 10, in southern Plymouth County, which has high levels of EEE and where birds carrying the disease to Falmouth likely originated, Ms. Sakolsky said.
In the targeted spraying, a truck spread a mist of the chemical Zenivex E4 to reduce the number of adult mosquitoes that might be carrying the virus, the entomologist said.
Zenivex, which is used throughout Massachusetts, New Jersey and Delaware, is considered an environmentally safe and low-toxicity insecticide. It targets small insects such as mosquitoes, midges and black flies but disappears within 48 hours and has no negative effects on vertebrate animals, Ms. Sakolsky said.
In addition to truck spraying, the control project has increased the number of traps and crews working in Falmouth swamps, spreading a chemical that kills mosquitoes still at the larval stage.
As of Tuesday, five Falmouth residents had submitted a form to the control project to opt out of having their property sprayed Wednesday, Ms. Sakolsky said, adding that, despite the spraying, the virus will remain in mosquitoes and birds in Falmouth until the first hard frost.
“The risk will never be zero; our goal is to minimize the risk as much as possible,” she said.
To avoid mosquito bites, people should remain indoors during peak mosquito hours, from dusk to dawn; wear long sleeves, long pants and socks when outdoors; apply EPA-approved insect repellent when outdoors, and mosquito-proof their homes by draining standing water and installing or repairing screens, Mr. McGann said.
The first symptoms of EEE are fever (often 103 to 106 degrees Fahrenheit), stiff neck, headache and lack of energy. These symptoms show up three to 10 days after a bite from an infected mosquito. Inflammation and swelling of the brain, called encephalitis, is the most dangerous and frequent serious complication.
Some Falmouth residents questioned the environmental and health effects of Zenivex E4, which, according to the control project, is the safest effective “adulticide” available on the market. These voices included Spohr Gardens board president Hila Lyman of Falmouth.
“Based on inaccurate information that we were given, Spohr Gardens initially was going to opt out of the spraying for EEE. Our concern was and is the impact on our Butterfly Project host and nectar plant gardens with the eggs, larvae and butterflies that are present,” Ms. Lyman wrote in an email. “We spent a lot of time talking with the staff at the Cape Cod Mosquito Control Project, and they could not have been more helpful.”
After receiving “correct information as to where the spray truck would go and weighing the impact on the Butterfly Project gardens versus the possible public health impact of someone contracting EEE,” the board of trustees voted to have Spohr Gardens included in the spray project and notified the control project of its decision, Ms. Lyman wrote.