September 17, 2013

Mosquito tests show EEE virus increase in Maine

With 13 more mosquito pools in York County testing positive for EEE, precautions are advised.

By North Cairn ncairn@pressherald.com
Staff Writer

Eastern Equine Encephalitis is hitting Maine harder than in any year since 2009, when the infection activity reached unprecedented proportions, say officials at the Maine Center for Disease Control and Prevention and the state Department of Agriculture, Conservation and Forestry.

click image to enlarge

A Culex quinquefasciatus mosquito is shown on a human finger in this undated handout photograph from the Centers for Disease Control and Prevention (CDC). Eastern Equine Encephalitis is hitting Maine harder than in any year since 2009, when the infection activity reached unprecedented proportions. (REUTERS/James Gathany/Center For Disease Control/Handout)

Tests last week also documented the first case this year of West Nile virus, collected from a mosquito pool in Alfred, health officials said. Maine experienced its first confirmed human case of West Nile last year.

No human cases of EEE have ever been reported in Maine, but 13 more mosquito pools in southern Maine tested positive for the virus last week. The test results on new cases, announced by the Maine CDC on Monday, bring the total number of positive test pools for the disease to 21 this year.

"This is clearly increased activity for EEE this year," said Dr. Stephen Sears, the state epidemiologist. "The numbers reflect that this year we're seeing a lot more EEE. I find it concerning. What we're all looking for is a little bit cooler weather."

Forecasts for this week predict significantly cooler nights, in the mid-30s to low-30s for much of the state and the possibility of frost farther north.

The infected mosquito pools are located in York and Alfred in York County, which already had documented positive tests earlier this season, and in Kittery.

"Kittery was the new one," Sears said. "Most were found in York."

Maine CDC officials also said that a horse in Oxford County, another horse in York County and a pheasant in York County had died of EEE last week. No horses perished last year from the disease, but a flock of 30 pheasants was euthanized in Lebanon when the virus was detected in the birds.

This year's level of EEE activity in mosquitoes, birds and horses has not been seen since 2009, when 10 horses succumbed to the infection, Sears said.

Assistant State Veterinarian Beth McEvoy underscored the need for proper and timely vaccinations for horses at risk of contracting EEE. Because vaccinations take time to provide protection, they must be given annually. Repellants, protective sheets and blankets also are recommended for horses.

EEE is a viral disease transmitted through the bite of an infected mosquito. The virus occurs in the eastern half of the United States and causes serious disease in five to 10 humans each year in the U.S., along with horses, some bird species and occasionally other mammals, including dogs. Because of the high mortality rate from EEE, the infection is regarded as one of the most serious mosquito-borne diseases in the country, health officials say. 

Many persons infected with EEE manifest no obvious symptoms, but those who do develop illness are likely to experience a fever, chills and a headache, Sears said. Symptoms range from this type of mild, flu-like illness to more serious inflammation of the brain, coma and death. The progression of the disease is considered quite rapid, moving from fever to brain infection in some cases within a week. Patients who become seriously ill must be hospitalized to prevent debilitating permanent brain damage or death.

There is no specific treatment for EEE.  The disease is best prevented by avoiding exposure to mosquitoes. 

EEE has not yet been reported in a Maine resident. However, in 2008 a fatal case of EEE was diagnosed in a Massachusetts resident who may have acquired the infection while vacationing in Cumberland County, the Maine CDC reported. 

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