EEE Strikes Indiana Horse

The Indiana Board of Animal Health (BOAH) has warned residents of Indiana counties Elkhart, LaGrange, LaPorte, and St. Joseph that Eastern equine encephalitis (EEE) is a concern in their area after a horse in Elkhart County was been diagnosed with the disease. Health officials said each of these counties has recently had enough rain to encourage breeding of large numbers of the mosquitoes that carry EEE.

"Eastern equine encephalitis is potentially a very serious disease that can cause lifetime neurological disabilities," said State Health Commissioner Judy Monroe, MD. "The only encephalitis of greater severity to humans than EEE is rabies. The combined threat of Eastern equine encephalitis and West Nile virus in northern counties of the state makes it vital for residents in those areas to take steps to prevent mosquito bites."

Eastern equine encephalitis is caused by a virus that is usually transmitted between birds and mosquitoes, like West Nile virus. The virus is found in mosquitoes and birds that live in freshwater, hardwood swamps. Humans and horses only get EEE when bitten by infected mosquitoes and cannot spread the virus. Mosquitoes must feed on infected birds to spread the virus.

"The horse population tends to be the sentinel to this disease," explained Indiana State Veterinarian Bret D. Marsh, DVM. "Unvaccinated horses are highly susceptible to this virus and will often be the first indicators of a positive mosquito population in an area."

State health officials said that although EEE is rare, 30% of people who develop the disease might die, making it one of the deadliest mosquito-borne diseases in the United States. According to the State Department of Health, approximately half of those who survive EEE illness will have permanent neurological problems.

Most people infected with the virus will not have symptoms. Health officials say if symptoms occur, they will normally show up three to 10 days after people are bitten by an infected mosquito. Symptoms of EEE in humans include: fever, malaise, headache, nausea, vomiting, abdominal pain, and eye pain when exposed to light, weakness, paralysis, confusion, incordination, seizures, and loss of consciousness. There is not a vaccine available to prevent the disease in humans, nor is there a specific treatment. There is a vaccine to prevent the infection for horses.

"The EEE vaccines for horses are excellent," Marsh said, "However, at this late date, newly vaccinated animals may not get full protection before mosquito season is over, due to cooler temperatures. That's why keeping animals sheltered during peak mosquito flight times and taking immediate steps for onsite mosquito control are the best means of defense right now."

State officials are urging Indiana residents to take steps to prevent the spread of Eastern equine encephalitis, including eliminating all sources of standing water that serve as breeding sites for mosquitoes, like gutters, birdbaths, old tires, water troughs, and puddles. Even small, shallow pools can produce a crop of mosquitoes in as few as five days. People, as well as animals, should avoid being outdoors around dusk, when mosquitoes are most active. When necessary, topical insect repellents can be used on horses, as long as they are labeled appropriately.

EEE causes central nervous system problems in horses that cannot be cured. According to the Board of Animal Health, horse owners should vaccinate their animals annually against the disease. Combination products provide excellent protection, if they are boostered regularly. The initial vaccine must be followed by a booster within three weeks to six weeks to achieve full immunity.

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