Principles of Disease Prevention

Editor's Note: This is Chapter 1 of Understanding Equine Preventive Medicine by author and veterinarian Bradford G. Bentz, VMD. The book is available from

Programs to control infectious disease in individual horses and groups of horses are necessary to maximize health and performance. Prevention programs extend beyond vaccination and deworming and include plans for sudden outbreaks of disease and management of horses with health problems. Having a good preventive care program ultimately can save an owner time and money.

Infectious disease occurs when infectious agents overcome inherent protection in an individual or group. A successful prevention program must, therefore, reduce the rates of exposure of the horse(s) to infectious agents and maximize resistance against such agents. The incidence of infectious disease in a given horse population rises with increased numbers of individuals, concentration of susceptible horses at the facility, movement of new horses into and out of the facility, and environmental and management factors that favor an infectious disease’s development and transmission.

On breeding farms, continually adding and mixing horses of various ages and from various locations, plus a resident high proportion of susceptible young horses and pregnant mares, heightens the risk for the introduction and transmission of infectious diseases. Separating horses by age and function can minimize the inherent risks in such situations. Mares and foals should be separated from weanlings, yearlings, horses in training, and transient mares.

Show barns and racetracks are conducive to the introduction and perpetuation of infectious diseases among the resident horses. Any new horse entering one of these facilities (including breeding farms) should have a negative Coggins test and documentation of timely vaccination and deworming. Newly arriving animals should be quarantined for two to four weeks. The farm veterinarian should oversee the quarantined horses and continually and concurrently evaluate these horses for signs or symptoms of infectious disease.  Any horse(s) with an infectious disease should be isolated, preferably in a separate facility. Because isolation is frequently impossible, the horse(s) should be placed in a location that minimizes exposure to other animals, common water sources, and shared ventilation. Buckets and feeders, grooming implements, tools, and any other items exposed to the infectious animal or to its stall should be used only for that animal. Strict isolation protocol mandates that all other horses be cared for first or by separate farm personnel before the diseased animal receives care.  This minimizes potential contact with non-diseased animals by farm personnel who have handled the infectious horses and/or items used to tend to them.  Wearing boots, coveralls, and gloves, and then strict disinfection of these garments and hands are necessary after workers have entered the stall of any horse with an infectious disease.

Most progressive farms use vaccinations to help manage disease. Deciding to use a specific vaccine for a recognized disease should be based on the risk the disease poses to those particular horses, the consequences of not vaccinating from both the economic and individual and herd health standpoint, and the possible adverse effects associated with the vaccination. In deciding which vaccines to use in the overall program, consider the age of the horses, their function, the number of animals and their density at the facility, the cost of the program versus the benefits, the facility’s management practices, and its location. Because many of these issues vary for individual animals and nearly all vary from farm to farm, there is no “standard” vaccination program for all horses or all facilities. Each situation must be evaluated independently.  Owners or managers, with input from their veterinarian, should establish a vaccination program and prerequisites aimed at controlling the entry and spread of infectious disease.

Client expectations and the overall goals of a disease control program can vary significantly. Performance-horse management is centered on minimizing the time lost from training and competition. An animal that contracts an infectious disease usually requires time off. A horse’s inability to compete and train can result in economic loss. However, the same disease in a backyard horse or a broodmare is unlikely to cause significant losses in money and time unless the horse is permanently impaired or the mare aborts.

About the Author

Bradford G. Bentz, VMD, MS, Dipl. ACVIM, ABVP (equine)

Brad Bentz, VMD, Dipl. ACVIM, ABVP, ACVECC, owns Bluegrass Equine Performance and Internal Medicine in Lexington, Ky., where he specializes in advanced internal medicine and critical care focused on helping equine patients recuperate at home. He’s authored numerous books, articles, and papers about horse health and currently serves as commission veterinarian for the Kentucky State Racing Commission.

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