What to Expect When Vaccinating Horses: Common Response or Cause for Concern?

Horse owners understand that vaccinations protect the health of their horse and may even be life saving. What some owners may not realize is that adverse reactions can occur after vaccination. While most side effects from vaccines are minor, it’s important to know when not to worry – and when to call the veterinarian.

“It’s important to remember that annual vaccinations are the best way to help prevent potentially deadly equine diseases and help keep horses healthy,” says April Knudson, DVM, Equine Specialist for Merial’s Large Animal Veterinary Services. “Equally important is the understanding that some horses may experience an adverse reaction following vaccination. That reaction, however, will likely be far less devastating than if the horse actually acquired the disease for which it was being vaccinated against.”1

Vaccines are designed to stimulate an immune response, notes Dr. Knudson. Each horse is unique – and one horse’s specific immune response may be different from another horse’s.2 In particular, Dr. Knudson says that it’s fairly common for horses to experience mild, temporary side effects a few hours after intramuscular vaccination, such as:3

* Local muscle soreness or swelling * Fatigue * Fever * Loss of appetite * Lack of energy or alertness

“Even humans experience signs like this following vaccination,” says Dr. Knudson. “These types of clinical signs help demonstrate that an immune response has been stimulated, which is exactly what we want the vaccine to do.”

However, Dr. Knudson recommends contacting a veterinarian immediately if any of these signs persist for more than 24 hours or if more serious side effects, such as hives, difficulty breathing, collapse, colic or swelling at the injection site several days post vaccination, occur. While these more serious side effects are rare, they do require veterinary consultation and, in some cases, medical intervention.3,4

Working with your veterinarian is the best way to ensure your horses are being vaccinated for the area’s disease risks and also to make certain the vaccines are handled and administered properly. Vaccines that are handled improperly can become ineffective or may actually increase the risk of side effects.2,5

With many vaccines available online or through farm supply stores, some horse owners are choosing to purchase and administer their own vaccines to try to save money. But Dr. Knudson maintains one of the easiest ways to keep horses healthy and protected year round is to make sure your veterinarian is involved in developing a vaccine protocol.

“Veterinarians are the best source for quality vaccines and vaccine information, and checking in a couple of times a year helps make sure your horse is healthy year-round,” says Dr. Knudson. “A good rule of thumb is to communicate with your veterinarian at least twice a year – usually in the spring and fall – to identify the area’s disease threats, assess your horse’s level of risk and discuss potential travel plans – all of which will help enable you and your veterinarian develop a vaccination programthat specifically addresses the needs of your horse.

“And if your horse has a prior history of vaccine reactions, no matter how mild, it is critically important you consult with your veterinarian before vaccines are administered.”

Horse owners should demand effective vaccines for their horses. Today’s advanced vaccine technology provides choices for vaccination and helps protect horses. For instance, the RECOMBITEK® line of equine vaccines includes advanced recombinant canarypox-vectored vaccine technology to aid in the prevention of WNV and equine influenza, in addition to a combination vaccine featuring recombinant West Nile virus with Eastern Equine Encephalomyelitis, Western Equine Encephalomyelitis and tetanus. Merial also provides leading equine vaccines such as IMRAB® rabies vaccine and POTOMAVAC™ vaccine for Potomac Horse Fever.

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 2010 sales were more than $2.6 billion. Merial is the Animal Health subsidiary of sanofi-aventis. For more information, please see  www.merial.com .

®RECOMBITEK and IMRAB are registered trademarks, and TM POTOMAVAC is a trademark, of Merial Limited. ©2011 Merial Limited, Duluth, GA. All rights reserved. EQUIBGN1114 (02/11)

1MacAllister C, Gilliam L. Equine vaccination programs. Oklahoma Cooperative Extension Service Publication VTMD-9119. Available at: http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-2072/VTMD-9119web.pdf. Accessed December 5 http://cts.vresp.com/c/?SullivanHigdonSink/2d32234c89/9b77e29a82/00ef5eb95e , 2008. 2Merck Veterinary Manual. Ninth edition. 2005:2181. 3Adverse reactions. American Association of Equine Practitioners. Available at: http://www.aaep.org/adverse_reactions.htm. Accessed December 5 http://cts.vresp.com/c/?SullivanHigdonSink/2d32234c89/9b77e29a82/5736f2eeaa , 2008. 4Povey RC, Carman PS. Technical basics of vaccination. In: Pastoret PP, Blancou J, Vannier P, Verschueren C, eds. Veterinary Vaccinology. New York: Elsevier; 1997;15:574-578. 5Merck/Merial Manual for Pet Health. Home edition. 2007:561.