West Nile issue: to spray or not?
- Published: August 30, 2012
Last Thursday about 6:30 a.m, as many villagers still slept, a Greene County Combined Health District truck rolled slowly through a neighborhood in southern Yellow Springs spraying a fine mist of insecticides. The chemical fog hung in the air for about 20 minutes, engulfing and killing any adult mosquitoes and similar-sized airborne insects.
The county’s effort, part of a mosquito control agreement with the Village, is aimed at culling the neighborhood’s mosquito population since a test the previous week revealed that mosquitoes on Southgate Avenue carried West Nile virus. The county health district decided to spray the surrounding area to lessen the chance that any person will contract West Nile virus, a potentially serious disease that can lead in less than one percent of the cases to inflammation of the brain and spinal cord, paralysis and death.
Further spraying in the village may be on the horizon. Three additional mosquito traps were set last week farther south on Southgate Avenue as well as on nearby Orton Road and on Dayton Street. Results are pending, but any positive test result could lead to more local insecticide applications in both the air and in free-standing water. In the mean time, some villagers have expressed concern about the health and environmental impacts of pesticides while county and state health officials defended their use.
“I think it’s crazy to spray because of how few [mosquitoes] they’ve found, and just because a mosquito is carrying it doesn’t mean you’re going to get it,” said Vickie Hennessy of Green Environmental Coalition this week. Only one mosquito in a pool of 50 needs to carry the disease for the test to be positive, and the odds that anyone would be bitten by that mosquito is low, she said.
Dr. Richard Gary, a state public health entomologist with the Ohio Department of Health contends that spraying is important to keep mosquito populations that carry the disease at bay, that the insecticides are relatively safe and that West Nile is a disease with potentially serious consequences for those infected.
“For the people that get this disease it can be devastating,” he said. While 80 percent of people who contract the disease through a mosquito bite experience no symptoms, about 20 percent of those infected get a fever, headache, body aches, skin rash and swollen lymph glands, according to a Greene County brochure. About 1 in 150 cases can result in high fever, stiff neck, disorientation, coma, tremors, paralysis and death. These severe cases are most common among those over 50 or with compromised immune systems and resulted in death about 3 to 15 percent of the time, according to the U.S. Centers for Disease Control and Prevention.
This year Ohio — and the U.S. — is seeing much more West Nile virus activity than usual, likely because of a hot, dry summer, according to the Ohio Department of Health. Statewide there have been 15 human cases of West Nile virus reported this year, including one each in Miami, Montgomery and Clark counties, but no fatalities. By comparison, at the end of last year there were 21 total cases in Ohio and one death. And during 2002, in the state’s worst outbreak since the disease was first detected in the U.S. in 1999, there were 441 cases and 31 deaths.
Since Yellow Springs became the first location in the county to test positive for West Nile virus last week, mosquito tests in Bellbrook and Beavercreek have also come back positive, according to the county health district. Greene County is one of 13 counties in Ohio to have mosquitoes test positive for West Nile.
West Nile on the rise
The primary culprit behind the West Nile virus is the Culex mosquito, especially Culex pipiens, the common household mosquito. The disease can also be spread by other species, including Aedes albopictus, the Asian Tiger mosquito, an invasive species that only breeds in small, usually man-made, containers and is active during the day. Mosquitoes require stagnant pools of water to reproduce, and can do so in as little as a bottlecap of water. Old tires, swimming pool covers, flowerpots, bird baths, buckets, rain gutters and catch basins are common breeding spots in suburban areas, according to the U.S. Centers for Disease Control and Prevention.
This year the Culex pipiens mosquito has thrived locally because of a mild winter followed by a hot and dry summer, according to Gary with the Ohio Department of Health. Hot weather speeds up the mosquito’s lifecycle and drought conditions can lead to more standing pools of water since dry ground can’t absorb rain as well, he explained.
“The drier and warmer-than-normal summer has amplified the virus,” Gary said. “Our mosquito surveillance is showing that conditions are getting worse.”
And since the virus has an incubation period in humans from 3 to 14 days, meaning that symptoms might not show up for two weeks after a bite from an infected mosquito, more human cases are expected through early October, Gary said.
Spraying in YS
Local mosquito testing began when Greene County received a complaint from a Yellow Springs resident that mosquitoes were abundant on the resident’s property. Though Greene County randomly tests other areas for West Nile virus, the county only tests in Yellow Springs when it receives a complaint, according to Mark Isaacson, program manager for the county health district.
The county has an integrated pest management plan, meaning it attempts to kill still-developing mosquitoes in area water sources by spraying them with larvicide as well as killing adult mosquitoes by fogging insecticides through the air. And they use education to encourage residents to remove any potential breeding sources on their property. Last week Greene County passed out brochures to area households to ask for their assistance in mosquito prevention, and larvicide was applied to catch basins along Southgate Avenue and a detention pond at the south end of Southgate.
“The larvicide is meant to reduce the number of adults down the road,” Isaacson said. “But when we already have adults that are determined to have West Nile virus, we spray.”
In accordance with the Village’s mosquito control agreement with the health district, which includes a 2003 provision that all fogging must receive prior permission by the Village of Yellow Springs, the county sought and received the go-ahead from Village Manager Laura Curliss. The contract also states that the Village will incur the cost of spraying. In recent years, the Village’s costs to participate in the program have been low, between $200 and $300, since no spraying was done in the Village, according to Isaacson. The costs can be expected to increase this year. Last year, the most expensive bill for a county jurisdiction was about $3,000.
Once the county decided to fog in a Yellow Springs neighborhood, residents were given an opportunity to opt-out. If they did so, no fogging would take place directly in front of their property. Only three villagers did so and none lived in the area being sprayed last week, Isaacson said. Ultimately the county decided the optimal time to spray and though residents knew the fogging would take place sometime last week, they didn’t know the exact day and time.
“We can give you a general day but we then play it by ear,” Isaacson said. Spraying must take place when wind is minimal and rain is not forecasted, he said. No recommendations were given to villagers for taking precautions from the aerial insecticides, though Isaacson said that those with asthma or chemical sensitivity could close their windows to lessen exposure.
The active insecticides used for last week’s spray were sumithrin and piperonyl butoxocide, used together in a product called Anvil 2+2, which Isaacson said is safe for humans and wildlife because of the way that it is applied. The sprayer takes the liquid insecticide and turns it into tiny droplets. Only one droplet is needed to contact a mosquito to kill it. Larger insects and animals aren’t affected because the droplet size is too small to impact them, Isaacson said.
To spray or not to spray
But Jay Feldman, executive director of national non-profit Beyond Pesticides, questioned the safety of the insecticides on both humans and the environment and the effectiveness of fogging in halting the mosquito threat. Most of the chemical cloud spray is obstructed by buildings and foliage so mosquitoes are protected, he said. According to a study by David Pimentel of Cornell University, less than 0.0001 percent of the insecticide applied typically reaches the target mosquitoes. The rest spreads to the environment.
According to Feldman, sumithrin is a nerve toxin and endochrine disruptor in humans. At even small doses they can affect organ development, leading to cancer and reproductive malfunction later in life, he said. In addition, piperonyl butoxide reduces liver function, making people more susceptible to chemical exposure. Particularly vulnerable are infants, children, pregnant women, the elderly and those with chronic illness.
“We are trading off short-term immediate problems with long-term cancer and endochrine disruption,” Feldman said. “They’re really in a Catch-22,” Feldman said of government decision-makers. “When you grab for a solution without studying the implications, you’re not doing the work that will lead to the more efficacious response.”
To reduce chemical exposure, Beyond Pesticides recommends that people in a neighborhood being sprayed leave the area, close their windows, turn off air conditioners, bring toys and lawn furniture inside, remove their shoes before entering homes to avoid tracking in residues, cover swimming pools and wipe pet paws off with a wet cloth before they re-enter the house.
Gary said the Ohio Department of Health is not concerned about the human impact of insecticide applications, since the doses are so low. Compared to agricultural pesticides that people ingest through their food and commonly used household chemicals, the amount the insecticide exposure is relatively low, he said. Studies of metabolites in people whose neighborhoods have been sprayed indicate a higher amount of these other chemicals rather than those used in mosquito spraying, he added.
Feldman also said that insecticides can be counterproductive because they kill off the natural predators of mosquitoes, such as spiders and aquatic organisms.
Joyce Morrissey, a beekeeper who lives on Bryan Park Road outside of the village, is especially concerned about the potential impact of insecticides to village bee populations. In fact, some municipalities require that any registered beekeeper within a half-mile radius be notified of spraying in advance, she said. The Anvil 2+2 product label comes with a warning that the product is “highly toxic to bees exposed to direct treatment on blooming crops or weeds,” and advises the user to avoid allowing the drift to fall on blooming crops or weeds.
Isaacson said that bees are likely not affected, since the county sprays in the morning or at night, times when bees are in their hives, to reduce their exposure.
Because of the problems with insecticides spraying, Feldman recommends that agencies consider alternatives. He pointed to the mosquito control plans in Washington D.C., which bans spraying because of high asthma rates, and the Cleveland suburb of Lyndhust, which opts for larvicide and education instead of spraying.
Gary agreed that prevention is the best course of action and said that the Ohio Department of Health’s main charge is to encourage people to take precautions to avoid a mosquito bite and cut down on insect populations on their properties. People should wear long pants and long-sleeved shirts, applying insect repellant and avoid being outside when mosquitoes are most active — during dawn and dusk, according to a Greene County brochure.
“The first step is prevention and reducing breeding sites around your home,” Gary said. “We want people to take precautions — it only takes one infected bite.”
To opt out of any spraying that may take place in front of your property, call the Greene County Combined Health District at 937-374-5607 and leave a message with your name, address and phone number.