WESTERLY — Not since 1996 has Rhode Island conducted aerial spraying for adult mosquitoes. Back then, the spraying was confined to Westerly, where several species known to transmit the Eastern Equine Encephalitis virus, or EEE, were detected.
This year, however, aerial spraying has been widespread. With four human cases reported so far, one resulting in death, the state began treating areas of concern with larvicide in late summer, but quickly ramped up to aerial spraying of adult mosquitoes when it became apparent that more intensive control measures were necessary.
Michael Healey, chief public affairs officer for the Rhode Island Department of Environmental Management, said the mobilization to fight the virus was comprehensive, involving many departments.
“It’s really taken a massive amount of coordination and alignment,” he said. “The Department of Health and DEM have been attached at the hip for about six weeks on just this response, and many times, having two or three planning calls and policy calls a day.”
Spraying took place overnight in four zones from Sept. 8 to Sept. 10. Areas of Hopkinton, Westerly and Charlestown, which were sprayed on Sept. 10, were treated a second time on Sept. 25.
The areas of concern were selected based on input from the Mosquito Borne Disease Advisory Group, which collects and interprets the scientific data.
Ken Ayars, DEM’s chief of agriculture, said the group begins its work in June, soon after mosquito trapping gets underway. Meeting every other week at first, and then once a week, as the season progressed "it became more frequent than that, with the idea that we’re constantly going back and forth getting scientific input as to the decision making. The response follows a matrix that we have long developed and constantly manage to make sure we’re accurate and responsive and doing what we think we need to do to ultimately protect the public.”
The state plans its control measures based on several factors: Results from tests on mosquitoes trapped by a team led by Alan Gettman, the mosquito abatement coordinator; cases of EEE reported in humans and other mammals such as deer and horses, and statistics from neighboring states.
As of Sept. 27, Massachusetts had reported 12 cases of EEE and three deaths, and Connecticut reported two deaths. There have also been several cases of infections in horses and deer.
Utpala Bandy, medical director of the Rhode Island Health Department's Division of Preparedness, Response, Infectious Disease and Emergency, said that the high degree of concern surrounding EEE virus is reasonable, considering the virus' lethal potential.
“There may be people walking around who were infected and who had a mild illness or no illness at all and fought off the virus successfully,” he said. “And then, there’s the population, the tip of the iceberg, if you will, who get what’s called neuroinvasive disease, so the virus actually reaches the central nervous system. Of that population with the most severe form of the disease, one third will die.”
Massachusetts has conducted aerial mosquito spraying, but Connecticut has not.
Theodore Andreadis, director of the Connecticut Agricultural Experiment Station, said the advent of cooler fall weather will end the mosquito breeding season. In addition, the pesticide is ineffective in temperatures lower than 58 degrees.
“It’s getting late in the season and we are beginning to see a significant decline in the number of infected mosquitoes, especially those that we know bite humans,” he said. “We don’t think that wide-scale aerial application of pesticides would be warranted at this point. If we were in July, with the type of activity that we’re seeing and knowing that the virus is going to continue to amplify, we might consider it.”
Howard Ginsberg, an entomologist and University of Rhode Island professor, said the target mosquito species in Rhode Island are Culiseta melanura, which feeds on birds, and two species, Coquillettidia perturbans and Aedes canadensis, which act as bridges from infected birds to mammals, including humans.
Ginsberg said that Coquillettidia perturbans has been one of the most important species in recent outbreaks. It is present in ponds with emergent vegetation. Aedes canadensis, he said, "is a good vector of the EEE virus in the laboratory but is not usually associated with it." That species, a forest dweller, he said, will "bite reptiles, it’ll bite all kinds of things. It’ll bite humans as well. That was fairly common as well, so we were concerned, especially for people who live in rural areas.”
The pesticide of choice in most states, including Rhode Island, is Anvil 10+10, which is applied by fixed wing aircraft at night, when adult mosquitoes are active and pollinators such as bees are in their hives.
Several areas were excluded from the spraying, including bodies of open water (Anvil is toxic to fish) organic farms and biologically sensitive areas, including the Richmond Land Trust property where endangered spade foot toads have recently been released.
The map of the areas being sprayed, Ayars explained, is programmed into the planes’ navigation computers. “They fly a pattern, depending upon wind direction and speed, so that the product ends up where it’s intended to end up, which may or may not match the flight lines, because the plane drops product to take into account wind speed and direction,” he said. “The nozzles are controlled automatically via the onboard system.”
This year's mosquito control initiative has cost Rhode Island about $500,000 so far, and the state's congressional delegation, in a Sept. 21 letter, requested additional funds from the Centers for Disease Control and Prevention to deal with the public health threat.
This year, Gettman had 41 mosquito traps deployed at the peak of the season. Bandy, with the health department, said the state could use even more.
“We need work on getting funding and staff to a little bit more robust mosquito surveillance,” he said. “It’s not that we don’t know how to do it, we just don’t have the resources do it more robustly.”
Aerial spraying has been welcomed by some Rhode Islanders and condemned by others, although opposition appeared to decrease after the first fatality was reported.
Westerly resident Joanne French, who lost her daughter to the virus in 1984, urged authorities to do whatever they have to do to stop it. Molly Jo French was just 1½-years-old when she had several mosquito bites and began having seizures. She was taken to Westerly Hospital and later transferred to Yale New Haven Hospital where she remained for two weeks.
“Her nervous system was totally shot,” French said. “She couldn’t focus, her eyes were everywhere.”
Molly Jo returned to Ashaway, where the French family was living at the time. French was preparing to learn how to care for her daughter, who was left with permanent disabilities, but one morning, she found that Molly Jo had died in her crib.
“Even if people are complaining they’re not getting notified of the spraying, please just let it go,” she said. “Whatever you do to help prevent this is better than having someone contract the disease.”
The spraying has ended for now and any remaining mosquitoes will be killed in the first hard frost. On Friday, DEM said that it had submitted 78 pools, or samples sorted by mosquito species, from 25 traps set on Sept. 22-23 to the state health lab, which confirmed that all the samples had tested negative for EEE and for the West Nile virus.
But Healey said it was still important for Rhode Islanders to take measures to protect themselves from mosquito bites, including limiting their time outdoors at sunrise and sunset, and using mosquito repellent.
“Maybe our biggest challenge between now and the first frost is just that, guiding Rhode Islanders, advising them, please, take every personal precaution that you can,” he said. “Human nature being what it is, people hear about the spraying, they see in on the news and they say ‘OK, that’s killed all the mosquitoes.’ No, it hasn’t. No spraying is 100 percent effective.”