Franklin Co., Vt., Horses Test Positive for EEE

Franklin Co., Vt., Horses Test Positive for EEE

A viral disease, EEE affects the central nervous system and is transmitted to horses by infected mosquitoes.


The Vermont Agency of Agriculture, Food, and Markets has received laboratory confirmation that a deceased horse in Franklin County tested positive for Eastern equine encephalitis (EEE) virus, the second in the county this year, the agency reported Sept. 12. The first EEE-positive horse, reported Sept. 4, was euthanized.

The two horses were located on separate properties, and these two cases represent the first time there has been evidence of EEE in Franklin County. In 2012, two people and two horses from southern Addison County and northern Rutland County died from EEE.

A viral disease, EEE affects the central nervous system and is transmitted to horses by infected mosquitoes. Clinical signs of EEE include moderate to high fever, depression, lack of appetite, cranial nerve deficits (facial paralysis, tongue weakness, difficulty swallowing), behavioral changes (aggression, self-mutilation, or drowsiness), gait abnormalities, or severe central nervous system signs, such as head-pressing, circling, blindness, and seizures.

The course of EEE can be swift, with death occurring two to three days after onset of clinical signs despite intensive care; fatality rates reach 75-80% among horses. Horses that survive might have long-lasting impairments and neurologic problems.

EEE can also cause disease in camelids (such as llamas and alpacas) and emus.

“Vermont owners of horses, camelids, and emus, regardless of where their animals are located in the state, should consult with their veterinarians to ensure that these susceptible animals are appropriately vaccinated for EEE,” reminded Kristin Haas, DVM, Vermont state veterinarian. “Susceptibility of horses … to EEE infection is not linked to travel to shows, fairs, or other commingling events. Even animals that spend the majority of their time on isolated properties are susceptible and should be vaccinated.”

Although vaccination is the most effective tool for preventing EEE in susceptible animals, owners can also protect horses from infection by using an acceptable insect repellent seasonally and mechanical barriers, such as fly sheets and masks. Changing out water troughs regularly and removing other items that hold water will also help to reduce mosquito breeding areas.

Cases of EEE confirmed in Vermont must be reported to the office of the state veterinarian. In 2012, two Vermont horses were confirmed positive for the virus.

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