Equine Herpesvirus in Winter

The right vaccine at the right time can help your horses stay healthy.

From AQHA Corporate Partner Pfizer Animal Health

In the midst of winter, equine respiratory disease, specifically caused by equine herpesvirus, should be top of mind for horse owners. It’s three times more likely for equine respiratory disease to be rhinopneumonitis due to EHV than to be flu caused by equine influenza virus.1 Respiratory disease caused by EHV occurs most often in autumn and winter in weaned foals and yearlings.

EHV is a common virus that occurs in horse populations worldwide. Older horses are more likely to transmit the virus without showing signs of infection. The two most common types are equine herpesvirus Type 1, which causes abortion, respiratory disease and neurologic disease; and equine herpesvirus Type 4, which usually causes only respiratory disease but can occasionally cause abortion. Both EHV-1 and EHV-4 infect the respiratory tract, and they can spread via aerosolized secretions from infected coughing horses or direct or indirect contact with nasal secretions, causing disease characterized by fever, lethargy, anorexia, nasal discharge and cough.2 Although EHV-1 causes outbreaks of abortion, EHV-4 has been associated with only single occurrences and is not a risk for contagious abortions.3

EHV-1 and EHV-4 can pose serious health risks for domesticated horses and can cause significant economic harm to the U.S. equine industry.2 A recent outbreak of EHV-1

at the Hawthorne Race Course in Chicago in October 2012 resulted in four confirmed cases, two horse deaths and numerous quarantines, leading to the decision to drop a day of racing. Another EHV-1 outbreak, traced to the National Cutting Horse Association Western National Championships in Ogden, Utah, in May 2011, lead to 90 confirmed cases and 13 deaths.

Outbreaks like these can force the cancellation or rescheduling of horse shows and competitions, bringing economic loss not only to event organizers but to the communities where the events take place.4 The EHV-1 outbreak following the NCHA Western National Championships caused the cancellation of nearly 380 equine events.5

Month after month, The American Quarter Horse Journal dives into the horse health topics, such as equine herpesvirus. Subscribe today for monthly in-depth equine health stories.

The best way to help protect your horses against an EHV outbreak and against economic loss is to vaccinate them before exposure. The FLUVAC INNOVATOR® line of vaccines can help protect them against EHV. In addition to helping deliver protection against equine influenza due to Type A2 viruses, FLUVAC INNOVATOR 6 aids in the prevention of equine rhinopneumonitis due to EHV-1 and EHV-4; equine encephalomyelitis due to eastern, western and Venezuelan encephalomyelitis viruses; and tetanus. Your veterinarian can help you decide what vaccines are essential for your horse, when they should be administered

and at what frequency in order to help provide optimal immunity.

Although equine respiratory disease due to EHV is a cause for concern for many horse owners, the guidance of your veterinarian and the right vaccination program at the right time can help you prevent it — helping ensure that your horses have a healthy winter season.

Are you looking to learn more about equine health? Subscribe to the Journal! Each issue not only covers horse health, but also training, industry news and competition.

For more information on FLUVAC INNOVATOR line of vaccines, contact your Pfizer Animal Health representative, call 855-4AH-PFIZER (855-424-7349), or visit

1 Ostlund EN. The Equine Herpesviruses. Vet Clin North Am Equine Pract 1993;9(2):283-294.

2 United States Department of Agriculture, Animal and Plant Health Inspection Service. Equine Herpesvirus (EHV) Myeloencephalopathy. 2009. Avalaible at: Accessed November 7, 2012.

3 American Association of Equine Practitioners. Equine Herpesvirus. 2006. Available at: Accessed November 7, 2012.

4Larson, Erica. The Horse | EHV-1 Outbreak: USDA Releases Final Situation Report. The Horse: Your Guide to Equine Health Care. June 24, 2011. Available at: Accessed: November 7, 2012

5 Walker, Jennifer. "The Economic Effect of Canceling Horse Shows Due to EHV-1." Yahoo! Voices - 26 May 2011. Available at: Accessed: November 7, 2012.

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