Auburn, April 25, 2002---Horse owners should have all their horses vaccinated immediately for West Nile virus (WNV).

"Horses are affected by WNV more often than other domestic animals," says Dr. Tony Frazier, the state veterinarian. "The simplest way to ensure their horses do not contract this potentially deadly disease is to have the animals vaccinated."

The U.S. Department of Agriculture issued a conditional license for an equine WNV vaccine late last summer. Conditional licensing means that the product has been shown to be safe, pure, and have a reasonable expectation of efficacy in preventing illness caused by WNV.

Frazier, whose office is a division of the Alabama Department of Agriculture and Industries, says horse owners should have their animals revaccinated even if they were inoculated last fall.

"Since this is a new vaccine, it's not firmly established how long the vaccination will last," says Frazier.

Dr. Cindy McCall, an animal scientist with the Alabama Cooperative Extension System, says the vaccine will only be available from veterinarians.

"The vaccine manufacturer recommends giving two intramuscular doses three to six weeks apart," says McCall.

McCall says the vaccine may be more expensive than the more routine vaccinations given to horses.

"Cost may be higher, but that's not really surprising," says McCall. "There is only one manufacturer and they probably have not brought their production up to full capacity yet."

WNV was first identified in the United States in 1999 in New York and has been spreading for the last two years. It is a mosquito-borne virus that can cause encephalitis (an inflammation of the brain) in animals and sometimes in humans. The virus is spread by mosquitoes that get the disease from infected birds.

Many horses infected with WNV do not develop any illness, but more than 35 percent of those that became sick in 1999 and 2000 died or were euthanized. Other livestock and poultry do not commonly show illness if infected with WNV.

Like humans, horses are particularly vulnerable to both WNV and eastern equine encephalitis (EEE). Last year in Alabama, more than 160 horses were screened for both diseases.

In 2001, there were four equine cases of WNV in Alabama. Three of the animals fully recovered, but one had to be euthanized because of the disease. In neighboring Florida, more than 450 horses were infected with WNV.

EEE was identified in 15 Alabama counties, primarily across the southern part of the state in 2001. Thirty-six Alabama horses tested positive for EEE in 2001.

McCall says there is little reason for a horse to contract EEE because there is a safe and inexpensive vaccine available.

"Horse owners in Alabama should vaccinate their horses twice a year for EEE or sleeping sickness," says McCall. She adds that the best time to revaccinate is mid to late summer, such as in August when some cases of EEE are seen in Alabama. Revaccinating before this time will increase protection against the disease.

"EEE is far worse than WNV in horses," says Frazier. "The mortality rate of horses infected with EEE is over 90 percent, and from what we know about WNV, the mortality of infected horses is about 30 to 40 percent."

EEE is almost always fatal in horses and is characterized by the progressive failure of the horse's central nervous system.

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Auburn, April 25, 2002---One of the most important steps horse owners can take to reduce their horses' exposure to diseases such as West Nile virus (WNV) and eastern .equine encephalitis (EEE) is to reduce their animals' exposure to mosquitoes as well as vaccinate the animals against both diseases. Mosquitoes are the primary carriers of both diseases.

First, horse owners should control mosquito populations by removing all potential sources of stagnant water in which mosquitoes might breed. Mosquitoes can breed in any puddle that lasts more than four days.

Livestock watering troughs should be thoroughly cleaned on a monthly basis. Troughs should be dumped and refilled on a weekly basis if they are small enough to handle easily.

Housing animals in structures with well-maintained insect screening can reduce exposure to adult mosquitoes. However, these mosquito-resistant structures may actually lead to mosquito exposure unless precautions are first taken to eliminate mosquitoes from inside the structure. This can be done in a variety of ways including the use of pesticides targeting all life stages of mosquitoes. In addition, using fans may reduce the potential ability of mosquitoes to feed on horses.

A recently completed study of WNV suggests that keeping horses in stalls at night may be helpful in reducing their risk of infection.

Use of insect repellents may decrease exposure of horses to adult mosquitoes. Due to practical limitations in the coverage area that may be achieved and the limited duration of effectiveness, repellents should not be solely relied upon to prevent exposure.

Repellents should be used according to their label instructions regarding appropriate species, method of application and other precautions. Topical application of a product containing a synthetic pyrethroid compound (e.g., permethrin) as the active ingredient may offer the best combination of safety and effectiveness.

SOURCE: Dr. Cindy McCall, Animal Scientist, Alabama Cooperative Extension System, (334) 844-1556