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Duane E. Chappell, D.V.M., Merck Animal Health

Though the days may be getting shorter and cooler, your time in the saddle this fall can be rewarding. However, this season also brings a host of disease considerations. Complicating matters, horses that have been traveling, training or competing all summer may have reduced immune function. So, while the last thing on your mind may be a visit with your veterinarian, now is the time to get it on the schedule.

Of course, there’s no magic trick that can keep horses from becoming sick, but we can do several things to make sure their immune system is functioning as efficiently as possible as winter approaches.

Consistent Veterinary Care

If you own a performance horse, you’re accustomed to having your veterinarian do regular performance and soundness checks, but don’t overlook basic healthcare needs. The same applies to recreational riders. All horses should be seen by a veterinarian at least annually for a physical and dental exam, vaccinations and deworming evaluation. During this exam, your veterinarian can give you guidance on the following items that can really make a difference in your horse’s natural ability to ward off illness.


In 2017, 307 horses were diagnosed with West Nile virus (WNV) in the United States.[1] That means more than 300 owners had to watch their horses struggle with this unforgiving disease and potentially lose their battle. As a veterinarian, nothing is more heartbreaking than watching an animal suffer from a disease; one that can be prevented through a simple vaccination.

Mosquito populations tend to peak in the late summer and fall, which is why fall is often the time when we see more cases of mosquito borne diseases, including Eastern and Western Equine Encephalomyelitis (EEE/WEE) and WNV. A fall EEE/WEE and WNV vaccine booster may be warranted for horses residing in or traveling to areas where EEE/WEE and WNV are prevalent.

In addition, for horses traveling and coming in contact with many different horses and environments, booster vaccinations may be warranted to help prevent highly contagious diseases such as equine influenza virus (EIV) and equine herpesvirus (EHV).

Although vaccines should be our first line of defense against the diseases mentioned, they can’t be the end-all-be-all.

Biosecurity is a year-round consideration

While vaccination is still the best means of protection against infectious disease, a practical biosecurity program can broaden the level of protection. Basic steps you can take to help prevent the spread of disease include:

· When you’re away from home:

o Minimize nose-to-nose contact with other horses.

o Don’t share items, including lead lines, halters, water buckets or tubes of oral medications.

o Monitor your horse’s temperature daily so you’ll know what’s “normal” for him. Deviations from normal might signify an infectious illness. Contact your veterinarian if you note a rise in temperature.

o Regularly clean your tack, equipment and stalls.

o Practice good hand hygiene. (Hand sanitizers work well in the absence of soap and water.)

· When you’re at home:

o Separate and monitor horses after returning home (two weeks is a good rule of thumb).

o Isolate new horses, and monitor them daily for fever and signs of infectious disease.

o Include all horses in your vaccination program. A single unprotected horse in a herd can serve as a reservoir of infection to others.

o Practice good hygiene and cleanliness.


Fall is a prime time of parasite transmission in much of the country. Parasite transmission is not as high during the very hot and/or cold times of the year and, thus, these are not the ideal time to deworm.

Work with your veterinarian to determine the optimal deworming program for your horse. With parasite resistance on the rise and no new deworming drug classes on the horizon, we must make sure we are deworming the right horse at the right time with the right product. A fecal egg count test may be recommended to determine the optimal timing and choice of dewormer.


Keep your horses on a balanced diet that consists of high-quality forage to give them the best chance to stay healthy. Also pay attention to minerals and vitamins they receive through forage and feed analysis and add supplements if needed.

In addition, maintaining the horse at an ideal body condition score and allowing for adequate exercise can go a long way in avoiding common problems in horses that are over- or underweight.

Your veterinarian may also perform a dental exam to make sure your horse is able to properly chew and process his feed.

Reducing Stress

Horses who travel, train and compete are under a lot of stress, whether they show outward signs or not. While stress is a part of life for all living creatures, there are things we can do to help minimize stress and thus, reduce its potential negative effects on the horse’s immune system. Sue McDonnell, M.S., Ph.D., founder and head of the equine behavior program at the University of Pennsylvania’s New Bolton Center, offers these practical tips for reducing stress for the traveling horse.

· Take care to ensure the horse trickle feeds – eating small amounts frequently. Wet the hay, and offer water at least every couple of hours. Empty bellies for most horses are stressful both psychologically and physically.

· Take a stable travel companion, even a mini or pony mascot.

· If your horse uses a toy or treat at home, take the same one he’s currently using with you, both for use in the transport vehicle and in the temporary stable.

· Take water from home in a container that doesn’t impart a chemical odor or flavor, and the home water bucket, feed tub and hay net. Anything you use at home that is easily portable will reduce the effects of a new environment and may serve as what is known as a safety signal. Be sure to disinfect these items when returning home to help prevent introduction of disease.

Take-Home Message

Fall can be the best time of year to spend quality time with your horses. Remember, an ounce of prevention is worth a pound of fall fun and happy trails with your horse. By scheduling your fall wellness exam with your veterinarian, you can make sure this opportunity isn’t interrupted due to illness. For more information, visit

Copyright © 2018 Intervet Inc., d/b/a Merck Animal Health, a subsidiary of Merck & Co., Inc.

[1] USDA APHIS 2017 Summary of West Nile Virus Equine Cases in the United States. March 2018.  

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