Horse with Lighter Coat Colors Are More at Risk for West Nile Virus

"Have you heard?"

An announcement received today from the Merial corporation is putting horse owners on notice that West Nile virus (WNV) is a risk for all horses in infected areas, but that owners of light-colored horses should be particularly concerned.

The reason? A recently published study shows that light-colored horses have a greater chance of dying from West Nile virus (WNV). (Reference: Epp T, Waldner C, West K, Townsend H. Factors associated with West Nile virus disease fatalities in horses. Canadian Veterinary Journal 2007;48:1137-1145.)

Researchers at the University of Saskatchewan evaluated 133 clinical cases of WNV in the southern portion of the province. Of the total cases, 43.8 percent died. Light horses such as palominos, buckskins, grays, whites or duns were four times more likely to die than dark or multicolored horses.

“The study did not explore specific reasons for increased fatality risk for light-colored horses,” says Frank Hurtig, DVM, MBA, Director, Veterinary Services for Merial Ltd. “However, vaccinating for WNV can help protect all horses.”

WNV is transmitted from mosquitoes to horses. If infected, a horse may exhibit signs such as fever, depression, muscle tremors, weakness, lack of coordination and paralysis. (See Canadian study.) About one out of every three equine WNV cases dies.

The American Association of Equine Practitioners (AAEP) recently revised its core vaccination guidelines to include WNV. Every horse in the United States could be exposed at some point during the year, but spring and summer is an especially important time to protect against WNV. The disease shows no geographic borders and has been identified in all areas of the country. (See: Guidelines for Vaccination of Horses: West Nile Virus. American Association of Equine Practitioners. Available at: http://www.aaep.org/wnv.htm.) Plus, more temperate climates may experience longer mosquito seasons, potentially exposing horses to WNV for a longer period.

Blogger's note: this information was provided by Merial; the company is the manufacturer of Recombitek vaccine for West Nile virus. ®RECOMBITEK is a registered trademark of Merial Limited. Duluth, Georgia.

Fun photo courtesy of our friends at Equitana 2009, coming up in March 14-19 in Essen, Germany: see you there!

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Florida Horse Health Alert: 2008 EEE Deaths Up to Nine

Part of the problem with mosquito-borne illnesses becoming more prevalent is the mosquito itself. The Asian Tiger Mosquito (ATM) has invaded the southeastern USA; it was carried from Asia in container loads of used tires that were not inspected for mosquitoes and falls under the heading of "invasive species". This new breed of skeeter is particularly well-suited for spreading diseases. The University of Florida is trying to educate people that the mosquitoes around them have changed their stripes.

As convoys of horse vans and trailers prepare to head north from Florida after the winter polo, horse show and racing seasons end next month, the warm climate that lured horsemen to the Sunshine State may play a cruel and deadly trick on them.

Already, nine cases of Eastern Equine Encephalitis (EEE) have been confirmed in Florida since the beginning of 2008, even though the peak season does not begin until May. There were a total of 18 cases of EEE in 2007 for the entire year.

Sadly, according to the Florida Department of Agriculture, six of the dead horses had not been vaccinated and two had not received booster shots. Only one horse was current with vaccinations.

EEE is a viral disease that affects the central nervous system and is transmitted to horses by infected mosquitoes. Signs of the virus include fever, listlessness, stumbling, circling, coma and usually death. The disease is fatal in horses in 90% of the cases.

So far this year EEE has been confirmed in horses in Putnam, Lake, Polk, Columbia, Clay and Volusia counties, all of which were fatal. Volusia has been hit the hardest, with four of the nine cases having been found there.

If you live in Florida and if you have been in the state with your horses recently (or plan to go), please consult your health records and be certain that the horse's vaccination status for EEE is up to date.

For more information, and continuing updates on occurences of the disease in Florida, please read the state's Department of Agriculture web site's recent update.

AAEP RELEASES UPDATED EQUINE VACCINATION GUIDELINES

The Infectious Disease Committee of the American Association of Equine Practitioners has issued revised guidelines for the vaccination of horses. The Committee, chaired by Mary Scollay, DVM, has made recommendations for the use of vaccines based on the age of the horse and its previous vaccination history. The guidelines are intended to serve as a reference for veterinarians as they employ vaccines in their respective practices.

Highlights of “Guidelines for the Vaccination of Horses” include:

· The identification of tetanus, Eastern/Western Equine Encephalomyelitis, West Nile virus and rabies as “core” vaccines. Core vaccines have clearly demonstrated efficacy and safety, and exhibit a high enough level of patient benefit and low enough level of risk to justify their use in the majority of patients.

· The addition of a vaccination protocol for anthrax.· Recommendations for the storage and handling of vaccines, as well as information on vaccine labeling and adverse reactions.

· Inclusion of the AAEP’s Infectious Disease Control Guidelines, which provide an action plan for the containment of infectious disease during an outbreak.

The Committee stresses that veterinarians, through an appropriate veterinarian-client-patient relationship, should use the vaccination guidelines coupled with available products to determine the best professional care for their patients. Horse owners should consult with a licensed veterinarian before initiating a vaccination program.

The Committee, comprised of researchers, vaccine manufacturers and private practitioners, updated guidelines that were established by the AAEP in 2001. The complete document, along with easy reference charts, is available on the AAEP Web site at http://www.aaep.org/vaccination_guidelines.htm.