In the wake of Hurricane Irene and an active tropical storm season, several states along the East Coast and in the Southeast reported record rainfall for the month of August. Saturated grounds and regional flooding has led to standing water, a breeding ground for mosquitoes. Animal health experts warn that fatal cases of Eastern equine encephalitis and West Nile virus are being reported in numerous states.

To help prevent the spread of additional cases, Pfizer Animal Health is encouraging horse owners and veterinarians to follow the American Association of Equine Practitioners (AAEP) guidelines for vaccinations against mosquito-borne diseases and vaccine label directions.

"Historically Eastern equine encephalitis has primarily been reported in the south and southeastern parts of the country," said Kevin Hankins, DVM, MBA, of equine veterinary services at Pfizer Animal Health. "However, in 2010 we saw a rise in cases of mosquito-borne diseases across the northern states including New York, Michigan, and Maine. Eastern equine encephalitis (EEE) and West Nile virus (WNV) cases once again are being reported to health officials; therefore, we encourage horse owners to take preventative measures and get their horses vaccinated."

According to the United States Geological Survey, 22 cases of EEE have been confirmed. Eleven of those were reported in New York, where areas are still recovering from devastating flooding after Hurricane Irene hit the region on Aug. 27-28. Similarly, as of Sept. 6, 21 cases of WNV have been reported in 13 states, from California to Texas, North Dakota, and New York.

The AAEP considers EEE, Western equine encephalitis (WEE), and WNV core vaccinations for horses, along with tetanus and rabies. Though annual vaccinations should be administered in early spring, the AAEP also recommends boosters after five or six months in areas with high mosquito exposure.

The Pfizer Animal Health Equine Immunization Support Guarantee program provides up to $5,000 for reasonable diagnostic and treatment costs if a horse properly vaccinated by a veterinarian contracts the corresponding equine disease. Disease protection backed by the support guarantee includes infection from WNV, equine influenza virus, tetanus, EEE, WEE, and Venezuelan equine encephalitis virus. Vaccinations must be performed by a licensed veterinarian with an established client-patient relationship to be eligible.

In addition to vaccinations, authorities advise owners to reduce or eliminate standing water around the farm. A few effective steps to remove standing water includes disposing of any old tires, buckets, cans, or anything that can collect water. Turn wheel barrows over when not in use. Clean debris from rain gutters and stock ponds or wading pools with mosquito-eating fish. Fill or drain ditches and swampy areas and other soil depressions. Eliminate standing water and seepage around watering troughs. Also, clean buckets and watering troughs frequently and refill with fresh water.

"When there is this much rain and flooding, eliminating standing water can be challenging," said Hankins. "It's important as horse owners to manage what we can, while working with a veterinarian to ensure the horses are current on their vaccinations."

A viral disease, EEE affects the central nervous system and is transmitted to horses by infected mosquitoes. The fatality rate for EEE-affected horses is 75-95%. The course of EEE can be swift, with death occurring two to three days after onset of clinical signs despite intensive care. Horses that survive might have long-lasting impairments and neurologic problems.

Clinical signs for 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.

Clinical signs for WNV include flulike conditions where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculations (twitching); hyperesthesia, or 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 (incoordination on one or both sides, respectively). Equine mortality rate can be as high as 30-40%.

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