Alabama Agriculture and Industries Commissioner John McMillan has announced that two positive tests for Eastern equine encephalitis (EEE) have been reported by the department’s diagnostic laboratory located in Auburn. One sample was collected from a horse in Dallas County and the other sample was collected from a horse located in Mississippi.

“This is the time of year that we are extremely vulnerable to the spread of mosquito-borne viruses and we need to protect our livestock and ourselves,” said McMillan. “I want to encourage horse owners to vaccinate their horses for both EEE and West Nile virus (WNV) as soon as possible.”

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.

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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.

West Nile is also transmitted to horses via bites from infected mosquitoes. Clinical signs for WNV include flulike signs, where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculations (twitching); hyperesthesia (hypersensitivity to touch and sound); changes in mentation (mentality), when horses look like they are daydreaming or "just not with it"; occasional somnolence (drowsiness); propulsive walking (driving or pushing forward, often without control); and "spinal" signs, including asymmetrical weakness. Some horses show asymmetrical or symmetrical ataxia. Equine mortality rate can be as high as 30-40%.

The clinical signs of both EEE and WNV can be consistent with other important neurologic diseases such as rabies and equine herpesvirus; therefore it is important to work with your veterinarian to get an accurate diagnosis through laboratory testing.

McMillan and State Veterinarian Tony Frazier, DVM, recommend vaccinating Alabama horses every six months against both EEE and WNV. Horse owners are encouraged to contact their veterinarian to schedule a vaccination for their horses. The public is also advised to make every effort to reduce human exposure to mosquitoes during this time of year.