The Ohio Department of Agriculture (ODA) confirmed on Aug. 29 that an Ashtabula County, Ohio, horse tested positive for Eastern equine encephalitis (EEE).
The unvaccinated yearling Morgan cross’s clinical signs began on Aug. 25 with abnormal stance, ataxia (incoordination), depression, fever, and reluctance to move without stimulation. Veterinarians treated her that afternoon and collected blood samples, but she was found deceased the morning of Aug. 26. Two other horses on the premises became ill on Aug. 26, one of which also died spontaneously. No horses on the premises had been vaccinated for EEE.
State veterinarian Tony Forshey, DVM, of the Ohio State Board of Animal Health, wants horse owners to contact their veterinarians to ensure their animals’ EEE vaccines and boosters are up to date.
“This is a serious disease, and the most effective way to prevent your horses from getting EEE is to have the animals vaccinated by a licensed veterinarian,” Forshey said in a statement. “It is spread through mosquitoes and can also affect people, so taking steps to manage the mosquito population, such as eliminating standing water, will also help prevent EEE and other vector-borne viruses, like West Nile virus.”
Eastern equine encephalomyelitis is caused by the Eastern equine encephalitis virus, for which wild birds are a natural reservoir. Mosquitoes that feed on EEE-infected birds can transmit the virus to humans, horses, and other birds. Horses do not develop high enough levels of these viruses in their blood to be contagious to other animals or humans. Because of the high mortality rate in horses and humans, EEE is regarded as one of the most serious mosquito-borne diseases in the United States.
Tips for preventing mosquito-borne diseases include:
- Avoid mosquito bites: Use insect repellent when outdoors, especially from dusk to dawn.
- Look for EPA-labeled products containing active ingredients such as DEET, picaridin (KBR3023), or oil of lemon eucalyptus (p-menthane 3,8-diol).
- Apply more repellent, according to label instructions, if mosquitoes start to bite.
- Mosquito-proof homes: Fix or install window and door screens, and cover or eliminate empty containers with standing water where mosquitoes can lay eggs.
- Protect your horses: Veterinarians recommend commercially available licensed vaccinesagainst EEE for all horses in the U.S. Horses should be vaccinated at least annually (recommendations vary in high-risk areas). It’s not too late this year to vaccinate your horses.
- Use approved insect repellents to protect horses.
- If possible, put horses in stables, stalls, or barns during the prime mosquito exposure hours of dusk and dawn.
- Eliminate standing water, drain water troughs, and empty buckets at least weekly.
- Stock water tanks with fish that consume mosquito larvae (contact your local mosquito control for assistance), or use mosquito “dunks” (solid “donuts” of Bacillus thuringiensis israelensis[BTi], which are nontoxic to horses) available at hardware stores.