Infection Protection: It's Not Just About Vaccinations Anymore

At the AAEP's Healthy Horse Workshop in Ft. Collins, Colo., on July 28, Josie Traub-Dargatz, DVM, Dipl. ACVIM, of Colorado State University's College of Veterinary Medicine and Biomedical Sciences, shared her thoughts on control of infectious disease. She stressed that horse people are very positive and more likely to think they've got the next winner than consider negative things that can happen. But because disease is prevalent in the equine world, a proactive approach is smart management.

The principles of disease control are not new (Traub-Dargatz even quoted from a USDA 1896 special report on diseases of the horse), but recent infectious disease outbreaks remind us of the necessity of implementing controls. Traub-Dargatz noted that treatment for illness has multiple impacts: It is expensive; poses some level of distress to the horse; sets up a risk for adverse drug reactions; and when antibiotics are used, there's always the possibility that the bacteria might become antibiotic-resistant.

In addition, movement of horses is often impacted, and in the case of persistent infection, the value of the horse might be affected.

Traub-Dargatz suggested that the best plans are to optimize a horse's resistance while also minimizing the horse's risk of exposure to disease organisms. Horses living in varying lifestyles experience different levels of exposure risk; for example, a horse that is isolated on a 5,000-acre ranch is less likely to contract infectious disease than a horse living in congregated areas or showing. In today's world, Traub-Dargatz noted that horses live more like people, traveling long distances by van or plane.

There are predisposing factors to disease. Horses at higher risk include foals and aged individuals, or any horse suffering from some alteration in intestinal function or being treated with medications.

Any horse that experiences stress is more prone to contracting disease. Stresses include showing, training, competition, hauling, poor stabling ventilation, social dynamics, and nutritional deficiencies--pretty much whatever we do or don't do with our horses can impose a certain level of stress. To add to this, Traub-Dargatz mentioned increased opportunities for exposure through commingling, insect vectors, or contaminated feed, water, or the environment. She puzzled over why people would feed next to the gate where every person and every horse would tread through the hay, contaminating it with dirt and manure.

She emphasized that the previous expectation has been to expect disease to be controlled by vaccination, but this is problematic since not all diseases have a related vaccine and not all vaccines can protect 100% against disease. Core vaccines recommended for all horses irrespective of their breed or use include tetanus, Eastern and Western equine encephalitis, West Nile virus, and in some areas of the country, rabies. For other immunizations, Traub-Dargatz recommended discussing with your vet the best program to tailor to your horse's use and threats in your region.

With regard to optimizing resistance, her objective is to minimize stress and to optimize ventilation to ensure nonirritated airways, both in the barn and in the trailer. Heated barns with high ammonia fume levels create a significant irritant to the respiratory tract, as do dust and debris aerosolized by barn and arena cleaning while horses are in adjacent stalls.

She said social stress can be a large factor in affecting the immune response. When at horse events, it is good sense to keep your horse tied to the trailer to decrease exposure or commingling with others.

Other methods to minimize stress include optimization of nutrition and provision of clean water. Feed should be analyzed to determine the need for supplementation, which can impact a horse's immune response. Containers of feed should be covered to prevent contamination by rodents, birds, or opossums. She said horses shielded with fly face masks seem calmer and more relieved of stress and anxiety related to fly irritation, and this is a simple technique to decrease susceptibility to disease.

The most common routes of exposure to equine infectious disease include direct contact with other horses at events or when bringing a new horse to a facility either as a resident or transient horse. Another primary route of exposure is that of environmental elements, such as feed, water, stabling, trailers, and insects.

Traub-Dargatz reminded us to consider irrigation ditches and creeks and where they originated before they pass through your property.

The third very common route of transfer of disease is that of people and things that move around with people, such as hands, clothing, equipment, and vehicles. Everyone from caretakers to vets, and farriers to stable cleaners have the potential to carry infectious disease with them from horse to horse or farm to farm.

Traub-Dargatz said managing a horse's risk of exposure is not as easy as vaccination. She said that as risk aversion increases, there is a necessity to do more things at an added cost. At horse events, use your own water buckets and don't share equipment. She stressed that one should not put the hose into the water buckets when filling them. Keep the horse at the trailer and monitor human and horse traffic. If using stalls on site, then not only clean them well, but disinfect them. Determine the level of health requirements at events or barns you might be entering with your horse: Do they require a health certificate, a Coggins test, and/or immunizations? Do they monitor for illness and have an action plan if illness occurs at an event?

To manage risk on your own operation, you should consider implementing health requirements and take precautions for mobile horses that return from events, the vet hospital, or other farms. Segregate by grouping horses by risk level, and monitor horses for illness with an action plan in mind if illness is detected.

Traub-Dargatz noted that rectal temperature is often elevated in many instances before other clinical signs of disease are appreciated. The earlier you detect sickness, the quicker you can implement action to minimize the impact. Each horse should be monitored for loose feces, abnormal eye or nasal discharge, swellings in the limbs, abnormal gait, abnormal attitude, decreased appetite, and abortion or fetal loss in pregnant mares.

In addition, she urged every farm manager to inquire about a horse's past medical history and where the horse has been before unloading him from the trailer, and whether testing has been done for EIA (Coggins test) or screening for strangles.

All incoming horses should be examined on arrival and put in an isolation area far from direct contact with resident horses. If your facility is not equipped to provide complete separation, at the very least group by contagious disease risk categories, keeping the number of horses in each group to a minimum: for example, have eight to 10 horses per group. Communicate with facility personnel and provide color-coded clothing to signify which horses the caretakers are responsible for. Regular removal and disposal of manure minimizes the insect burden, decreases the parasite and bacterial load in individual horses, and limits the risk of feed and water contamination.

Visitors to a farm pose a risk as well, as they can introduce disease agents. Traub-Dargatz recommends asking people to use good hygiene methods, such as hand washing, and to limit petting of resident horses. Tack and equipment should not be shared whenever possible.

Traub-Dargatz suggests the following specific infection control strategies:

  • Group animals based on health and exposure;
  • Use hygiene protocols for workers and implement training on protocols;
  • Plan for vehicle traffic with the least impact of carrying disease around a farm;
  • Monitor for disease occurrence;
  • Design your facility to accommodate animal grouping, hygiene protocols, and ability to clean;
  • Retrofit your facility when necessary;
  • Optimize overall health as explained above;
  • Have an action plan to minimize impact of a disease outbreak.

For detailed information, see www.aphis.usda.gov/lpa/pubs/HorseBioSecurity_final.pdf  

Traub-Dargatz said there are resources to apprise horse owners about outbreaks of infectious disease, and many of these will provide up-to-date e-mail alerts. One excellent resource is your veterinarian; another is to sign up for e-mail updates at www.TheHorse.com or at the National Surveillance Unit Web site www.aphis.usda.gov/vs/ceah/ncahs/nsu/.

About the Author

Nancy S. Loving, DVM

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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