About 60 people crowded into Whiting's Town Hall last night for a public meeting on the mosquito-transmitted disease Eastern Equine Encephalitis. Information was provided by a panel of state officials, including Vermont Health Commissioner Dr. Harry Chen, entomologist Alan Graham of the state agriculture agency, and epidemiologists Erica Berl and Patsy Kelso.
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Alan Graham, entomologist with the
Vermont agriculture agency, speaks to
Whiting residents last night. |
The panel had a request of Whiting residents: a bit of their blood. "We're looking to test about 200 to 300 people from each impacted town," explained Berl (perhaps unaware that the entire population of Whiting is around 400). Vermont has acquired approval from the national Centers for Disease Control and Prevention (CDC) to test the blood of human residents in area towns for the presence of EEE antibodies. Those antibodies would show that individuals had been exposed to the EEE disease without exhibiting its life-threatening symptoms. The Vermont Department of Health is working with the Town of Whiting to set up a voluntary and anonymous blood testing program, with blood draws possibly scheduled to coincide with annual Town Meeting in March.
Ms. Berl noted that residents would not be informed of the results of the tests on their blood and nothing other than EEE antibodies would be tested. "It would be a truly selfless act," she said.
Only a handful of EEE cases are known to exist in humans each year. (
Click here for CDC information on EEE.) Severe EEE infections can be fatal. Two residents of this region - an 87-year-old man in Brandon and a 49-year-old man in Sudbury - died from the disease in the past year. (The Brandon victim, former educator
Dick Breen, experienced an EEE outbreak the previous year among his flock of emus, which left many of the large birds dead.) However, health authorities believe the severe infections occur only in a small percentage of those humans bitten by EEE-carrying mosquitoes. Many others may be bitten and have no symptoms or very mild symptoms. The blood testing program is expected to provide better numbers for gauging the extent of EEE exposure in humans and the rate of severe infections in that population.
The state officials discussed mosquito-monitoring efforts, lab testing done on trapped mosquitoes and blood drawn from deer and moose felled by hunters around the state, as well as the aerial spraying of Anvil (Sumithrin) insecticide that was performed in the Whiting-Brandon-Leicester area in early September after the state discovered its first-ever human cases of EEE.
According to Mr. Graham, the aerial spraying resulted in a dramatic reduction of overall mosquito populations in the area, but Mr. Graham was unable to provide specific data on the targeted culiseta melanura mosquitoes known to spread the EEE virus through interaction with infected birds.
Some Whiting residents expressed appreciation for the aerial spraying efforts as well as interest in aligning Whiting with regional "mosquito districts," such as the Brandon, Leicester, Salisbury and Goshen Insect Control District, which supervise mosquito control efforts. Other residents were concerned about the costs and side effects of pesticide application. Town Selectboard Chair Ellen Kurrelmeyer asked state officials if it was necessary to join or create a district in order to engage in townwide mosquito control and said she would check into the town's authority and insurance for performing its own control measures.
A few Whiting residents complained that the state was not more active after learning of the EEE outbreak at an emu farm in Brandon in 2011. The implication was that additional steps could have been taken to avoid the infections that cost two people their lives. Dr. Chen said he also questions whether more could have been done. But he explained that ground-based spraying of mosquitoes was performed after that outbreak and a program of monitoring for EEE in regional mosquito populations was put in place. One resident feared that the rare emus were somehow involved in transmitting the disease. The panel was unanimous in its opposition, noting that emus originated in areas where EEE is entirely unknown. As birds, they are preferred as targets by the disease-carrying mosquitoes, but they do not retain the virus for very long. EEE, Ms. Berl explained, exists in birds for a very short time, either vanishing after that time or resulting in the death of the bird.
Resident Paul Quesnel noted the some government agencies seemed to be at cross-purposes over the mosquito issue and local taxpayers looked to be caught picking up the cost of their conflicting programs. He referred to a USDA program under which easements are purchased "at one thousand or two thousand dollars an acre" to take active farmland out of service and turn it into restored wetlands. The increased wetlands result in an increase in mosquito populations. Mr. Quesnel noted that the government-sponsored growth of the wetlands also was causing an increase in water levels in adjacent active farmland and reducing crop yields from those areas.
Mr. Graham noted that, while the new restored wetlands certainly were a source of mosquitoes, they were probably not a source for the mosquitoes most related to the spread of the EEE virus. The culiseta melanura typically resides in underground "crypts" within acidic hardwood swamps that feature, for example, mature maple trees. The adult mosquitoes of this breed travel into small channels in the root mat of the trees to lay their eggs in the protected watery environments within. The mosquitoes, he said, overwinter as larvae.
These unusual tendencies of the culiseta melanura mosquito create control problems. Mr. Graham noted that mosquito larvicide, such as the naturally occurring bacteria bacillus thuringiensis (BT), would be highly effective against the moquito larvae if it could be delivered to where the larvae reside and grow. The mosquitoes' use of underground crypts makes that virtually impossible. As a result, he said, control measures must be directed against the adult mosquito population.
Ms. Berl explained that ground spraying against mosquitoes, such as performed by the BLSG District, may not be effective in more rural communities, like Whiting. That spraying is done from trucks driving along the roads. There are many areas in Whiting that could not be reached by truck spraying, making aerial spraying for mosquitoes the only workable option. Mr. Graham added that the mosquito populations that tested positive for the EEE virus last summer were far from any roads.
Panelists were asked about whether a human vaccine for EEE existed or could be created. While a vaccine for farm livestock has been in use for many years, Dr. Chen said no vaccine has ever been created for humans. He said he did not anticipate any vaccine would be created, as there are very few human cases of EEE and vaccine side effects would be more widespread than its benefits.
The panel acknowledged that much about the EEE virus remains a mystery. There is no explanation as to why the virus seems to fluctuate from year to year. "Just because we had it here this year doesn't mean it will be back next year," Mr. Graham said. The virus previously has exhibited a pattern of taking a decade off between outbreaks. Also a puzzle is what becomes of the virus during the winter and how so much of the deer and moose population across the state - even in areas where EEE mosquitoes are completely unknown - came to possess antibodies for EEE, indicating exposure to the virus at some time in the past. (Officials explained that there is no EEE risk to humans involved with the consumption of deer meat.) No one could say for certain whether the presence of EEE antibodies in a person's blood provided any meaningful protection against becoming ill with EEE at some time in the future. Ms. Kelso said some lasting protection is associated with antibodies related to West Nile Virus, another mosquito-borne illness, and EEE could be similar, but there is no useful data on that issue.
The panel is scheduled to hold similar meetings in Brandon and Sudbury at the end of this month. The Brandon meeting is set for Otter Valley Union High School, 7-9 p.m., on Wednesday, Nov. 28. The Sudbury meeting will be held at the Town Hall, 7-9 p.m., on Thursday, Nov. 29.
