Equine encephalitis causes horse’s death

Posted Aug. 11, 2009, at 9:39 p.m.

The death last week of a riding horse in Waldo County has prompted Maine health officials to raise an alarm about the mosquito-borne virus that causes eastern equine encephalitis in both horses and humans.

“A horse with EEE does not pose a health threat to humans,” Dr. Dora Anne Mills, director of the Maine Center for Disease Control and Prevention, said in a prepared statement on Tuesday. “However, a horse with EEE indicates that local mosquitoes are infected, contracting it from birds. Since mosquito bites are how EEE is transmitted to humans and horses, it is important people and horse owners take precautions.”

For humans, protection consists of avoiding mosquito bites by wearing long-sleeved shirts and long pants while outside, using DEET-containing repellent and eliminating pools of standing water where mosquitoes breed.

Taking these steps also reduces the likelihood of contracting tick-borne Lyme disease, Mills said, which is prevalent in Maine with about 900 cases reported each year.

Although an annual vaccine can prevent EEE in horses, there is no effective treatment once infection occurs. Seizures in horses resulting in death typically occur within 48 to 72 hours of the onset of symptoms. The 4-year-old quarter horse was put down after it became ill with symptoms associated with EEE, which include lethargy, unsteadiness, loss of coordination and erratic behavior. A laboratory test confirmed the presence of the virus on Monday.

Four horses in Maine have died of EEE since 2005, according to state veterinarian Don Hoenig. None was vaccinated against the EEE virus.

“We’re really urging people to protect their horses from this disease,” Hoenig said Tuesday. “The owners [of the Waldo County horse] are hoping other people will learn from their experience.”

For humans, there is no vaccine against EEE. Symptoms in humans range from mild flulike illness to seizures and coma, and may result in death. Although EEE is rare in humans, the mortality rate is about 30 percent, making EEE one of the most deadly mosquito-borne diseases in the United States.

There has never been a confirmed cased of human EEE in Maine, but in 2008 an elderly Massachusetts man died from EEE that he may have contracted while vacationing in the Naples area.

EEE was first detected in Maine in 2005 in horses, mosquitoes and birds in York County. In 2008, a horse in the southern Maine town of Lebanon died with EEE. State scientists have tested mosquito pools and dead birds for EEE since 2005, but Mills said funding for that surveillance has decreased dramatically.

Historically, states with the most cases of EEE in humans include Florida, Georgia, New Jersey and Massachusetts, according to the U.S. Centers for Disease Control and Prevention.

Between 2004 and 2006, 13 cases of human EEE have been reported in Massachusetts, with six associated deaths.

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