Anniversary of EHV-1 Outbreak Approaching… What Horse Owners Need to Know

FOR IMMEDIATE RELEASE -- MARCH 28, 2012 -- Think your horse is immune to the threat of infectious equine diseases because of a protected lifestyle? You might want to think again.

“Won’t happen to my horse.”

“I haven’t taken my horse anywhere; he’ll be fine.”

“That disease hasn’t been in our area.”

Think your horse is immune to the threat of infectious equine diseases because of a protected lifestyle? You might want to think again.

In late April 2011, horses attending an equine event in Ogden, Utah, were exposed to Equine herpsevirus type 1(EHV-1). Just three months later, when the Animal Plant and Health Inspection Service (APHIS)declared the outbreak contained, more than 2,000 horses had been exposed.1 Of those, 90 tested positive for the virus or its neurologic form, Equine Herpesvirus Myeloencephalopathy (EHM).1 Ultimately, 13 horses died or were euthanized. 

Just over half of the 90 horses were actually participating at the Ogden event, demonstrating the highly contagious nature of EHV-1 and its ability to spread quickly. The remaining 36 horses contracted the virus due to secondary or tertiary exposure. Cases were confirmed in 10 states, stretching from Oklahoma to California. 

In January 2012, 17 cases of EHV-1 were confirmed in California. “EHV-1 is so easily spread that it can affect a number of horses before owners even realize there is a problem and are able to take containment measures,” says April Knudson, DVM, equine specialist, Merial Veterinary Services. “The disease can spread from horse-to-horse contact, but also by horses touching objects contaminated with the virus, including clothing, human hands, equipment, rags, feed/water buckets and tack,” she adds.

Clinical signs of EHV-1 include fever, lethargy, anorexia, nasal discharge and cough. If the virus has advanced to the neurologic stage, lack of coordination, hindquarter weakness, recumbency and urine dribbling may occur. 

Equine influenza is another highly contagious disease. It can compromise a horse’s respiratory tract and spread quickly through a herd. Clinical signs can include high fever, nasal discharge, dry cough, depression, anorexia and weakness. 

“To guard against both communicable diseases such as these and others that spread by insects or even other animals, the most important things horse owners can do are vaccinate and be aware of disease threats,” says Dr. Knudson. “With competition season getting underway, many people will be traveling, possibly into areas where the risk of equine disease has been identified. Merial’s free Outbreak Alert program is a great way to help horse owners and veterinary practices stay informed.”

Launched in 2011, Outbreak Alert tracks and reports confirmed cases of EHV, Equine influenza, West Nile virus, Eastern Equine Encephalomyelitis, Western Equine Encephalomyelitis and Potomac Horse Fever and rabies. Since its inception, thousands of horse owners and veterinarians have received timely information by text or e-mail about disease threats. The site also incudes maps that show confirmed reports of disease throughout the country, educational resources for veterinarians to use in their practices and information about common equine diseases. To sign up for the program, go to

Infectious Disease Containment — Tips for Horse Owners

Timely and effective containment is critical when a horse has been diagnosed with or exposed to a contagious and potentially life-threatening disease such as Equine Herpesvirus (EHV-1). Take these precautions to minimize further exposure and help prevent the spread of disease.

  • Contact your veterinarian to develop a comprehensive care program and discuss safety measures to help prevent exposure to other horses.
  • Immediately isolate any horse(s) that you suspect have been exposed. This includes housing them away from other horses. 
  • Sanitize all equipment that has been used with the potentially infected group of horses, including tack, feeding buckets and human clothing used when working with the horses. Clean the items first with soap and water, rinsing thoroughly. Follow up with conventional disinfectants or detergents. 
  • People handling the horses should clean their hands with soap and water, drying thoroughly. An alcohol-based hand sanitizer can also be used. 
  • Use different equipment when handling the horses that have been exposed.
  • Take the horses’ temperatures twice a day. If elevated temperatures occur, have these horses’ nasal cavities swabbed by your veterinarian to determine if they are shedding EHV-1. 
  • Develop a separate route to the exposed horses for on-site help, farriers and veterinarians.


The RECOMBITEK rWNV vaccine offers fast-acting protection against WNV.

In a study, full protection against WNV was shown 14 days after the primary two-dose series.


RECOMBITEK rFLU helps protect horses from the viral cause of equine influenza.8,9 This product is also proven to significantly reduce viral shedding, the method by which the disease is spread.4 RECOMBITEK rFLU is fast-acting, with study results showing a quick onset of immunity and a six-month duration of efficacy.

About Merial

Merial is a world-leading, innovation-driven animal health company, providing a comprehensive range of products to enhance the health, well-being and performance of a wide range of animals. Merial employs approximately 5,600 people and operates in more than 150 countries worldwide. Its 2011 sales were more than $2.8 billion. Merial is a Sanofi company.






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