Vaccination can help keep trail horses healthy, safe

Trail riding can be fun and relaxing, but it can also leave horses exposed to disease, especially if they are traveling to a new area or haven’t been given the proper vaccinations to help protect them from local disease threats.

“Whenever horses travel, they can be exposed to disease — either from contact with other horses or disease agents in the area,” says April Knudson, DVM, manager, Veterinary Services, Merial. “Even though they may not travel as often, trail horses can still be at risk for contracting serious equine diseases, including rabies, Potomac horse fever, West Nile virus and equine influenza.”

While on the trail, there is a possibility horses will come in contact with animals potentially infected with rabies. This is a serious encounter because an infected horse could possibly expose its owners and handlers to the disease.¹ Rabies is transmitted through the saliva of infected animals — including common wildlife seen on the trail like skunks, raccoons, foxes and bats — and the disease is 100 percent fatal for horses and almost always fatal for humans.¹

“While there are no documented cases of horse-to-human transmission, vaccination is the best way to keep horses and owners safe and healthy,”¹ Dr. Knudson recommends.

Horse owners also should consider diseases of concern in other areas, especially if they plan to ride out of state or in unfamiliar areas.

For instance, Potomac horse fever (PHF) is commonly found near freshwater streams and rivers.² However, it has also been found in uncommon places, including Wyoming³ and Minnesota.⁴ In fact, PHF has been found in 43 of the United States, parts of South America, The Netherlands and France.²

On the trail, horses could contract the disease by consuming infected insects, such as caddisflies and mayflies,² while riding or grazing near waterways, rivers or creeks.² The signs of PHF can include fever, laminitis and even death.⁵

In addition to diseases like rabies and PHF, horses could potentially be exposed to West Nile virus (WNV) in warmer climates that may have a longer mosquito season. To ensure horses are protected, horse owners should ask their veterinarian for a vaccine that has a long duration of immunity to help protect horses whether they’re on the trail or at home in the pasture.

“No matter where horse owners plan to take their horses, WNV is going to be a concern in that area,” Dr. Knudson says. “WNV is endemic to all areas of the United States.⁶ That’s why WNV is listed as a core vaccination in the American Association of Equine Practitioner’s guidelines.”⁷

Many equine diseases, like PHF and WNV, are not transmitted from horse to horse. However, equine influenza is a disease horses can contract from people who have had contact with other infected horses, contaminated inanimate objects or other horses on the trail,⁸ and then take the disease back home, infecting their barn mates.

Equine influenza is a leading cause of respiratory disease in horses⁹ and can be a concern any time horses are commingled. Almost all unvaccinated horses become infected with equine influenza when exposed to the disease.⁸ While up to 20 percent of infected horses may not show signs of influenza, they can still shed the virus and spread the infection. In fact, it’s possible that a single horse infected with influenza can infect up to 10 other horses.¹⁰

“Horses that travel only once or twice a year are not out of the woods when it comes to equine diseases,” Dr. Knudson says. “A complete vaccination program developed and monitored by a veterinarian can help keep horses healthy and safe year-round.”

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For more information, contact:
Rachel Torbert
Bader Rutter
(402) 434-5307
rtorbert@bader-rutter.com

®IMRAB and RECOMBITEK are registered trademarks and ™POTOMAVAC is a trademark of Merial Limited. ©2009 Merial Limited. Duluth, GA. All rights reserved. EQUIBIM908 (02/09).

¹Marteniuk J. Rabies in horses. Michigan State University, College of Veterinary Medicine. Available at: http://old.cvm.msu.edu/extension/equine/RabiesinHorses.pdf. Accessed January 3, 2009.

²Madigan JE and Pusterla N. Life cycle of Potomac horse fever — implications for diagnosis, treatment and control: a review. AAEP Proceedings 2005;51:158-162.

³Hamende V. Potomac horse fever cases confirmed in northern Wyoming. University of Wyoming Cooperative Extension Service. Press Release, Sept. 13, 2002. Available at: http://wyovet.uwyo.edu/Diseases/2002/PotomacConf.pdf. Accessed January 15, 2009.

⁴Wilson JH, Pusterla N, et al. Incrimination of mayflies as a vector of Potomac horse fever in an outbreak in Minnesota. AAEP Proceedings 2006;52:324-328.

⁵Merck Veterinary Manual. Ninth edition. 2005:236.

⁶West Nile virus vaccination guidelines. American Association of Equine Practitioners. Available at: http://www.aaep.org/pdfs/AAEP_WNV_Guidelines_2005.pdf. Accessed January 14, 2009.

⁷Guidelines for Vaccination of Horses. American Association of Equine Practitioners. Available at http://www.aaep.org/vaccination_guidelines.htm. Accessed January 15, 2009.

⁸Influenza updates from the AVMA. Backgrounder: Equine influenza. Available at: http://www.avma.org/public_health/influenza/equine_bgnd.asp. Accessed January 15, 2009.

⁹Paillot R, Hannant D, Kydd JH, Daly, JM. Vaccination against equine influenza: Quid novi? Vaccine 2006;24:4047-4061.

¹⁰Minke JM, Bublot M. Equine influenza: an update. Shedding is possible even when the infected horse shows no signs of sickness. Bull. Acad. Vét France 2004;157(4):43-49.

Merial
3239 Satellite Blvd.
Duluth, GA 30096
www.merial.com