STETSON, Maine — A horse in Stetson died last week of Eastern equine encephalitis, the third Maine horse death in August related to the mosquito-borne virus.
The deadly virus, known as EEE, also can infect humans, and appears to be moving into new geographic territory.
“This is the farthest north EEE has ever been detected in this country,” said Dr. Dora Anne Mills, director of the Maine Center for Disease Control and Prevention, announcing the latest case at a press conference Monday. Mills urged Mainers to protect themselves against mosquitoes in order to avoid contracting the virus.
The horse deaths are “a strong red flag that the risk of EEE is much greater than we thought,” she said. “In the past, we’ve seen it later in the fall. What we’re concerned about now is that it is still very warm out and there are a lot of mosquitoes still biting.”
Horses in the Waldo County towns of Troy and Thorndike died of confirmed EEE earlier this month. Test results from three other dead horses are pending — one each in York County, Cumberland County and the Waldo County town of Unity — as well as from one sick horse in Unity.
State veterinarian Dr. Don Hoenig said infected horses cannot transmit the disease to humans, and mosquitoes cannot pick up the virus by feeding on an infected horse. Mosquitoes become carriers of the virus only by first biting an infected bird — songbirds, pheasant and quail, primarily — and then biting a horse, human or other host, he said.
All horses should be vaccinated yearly against EEE, Hoenig said, especially now that the virus has been found in central and coastal Maine. The disease is almost 100 percent fatal in horses, and a horse can go from seemingly good health to seizures, coma and death within 24 hours, he said.
There is no human vaccine against EEE. Mainers, especially those who live, go to school or spend time near wetland areas, should take extra precautions to protect themselves from exposure to mosquitoes from now until cold weather sets in — including two hard frosts to kill mosquito populations, Mills said. These precautions include wearing long pants, long-sleeved shirts and socks, and applying DEET or another effective insect repellent for extended outdoor activities such as outside work and school field trips.
While cases of EEE in humans are rare, Mills said, the severity of the virus should not be underestimated. Of those humans who become infected, more than 30 percent die, and half of those who survive suffer permanent neurological damage, she said.
Although anyone can be sickened with EEE, children under 15 and adults over 50 are most likely to suffer serious illness, Mills said. Early symptoms are flulike — fever, fatigue and general aches and pains — but also are likely to include neurological elements such as headaches and seizures.
No human case of EEE has ever been confirmed in Maine, but last October, a Massachusetts man died of EEE he may have contracted while vacationing in the Naples area. His was the first Massachusetts death from EEE in a human since 2005, when four cases were reported, including two fatalities.
Because of the concentration of horse cases this summer in Waldo County, the Maine CDC will conduct a public meeting at 6 p.m. Thursday, Sept. 3, at the new Mount View High School in Thorndike.