Introduction
Horse owners occasionally complain about bringing home “the cough” from the racetrack or a horse show. You can prevent this disease from spreading throughout your barn. It pays (in dollars saved) to be conscientious about preventing and controlling infectious diseases. Pay particular attention to the brood mares. Bringing home an infected horse to a farm with brood mares can result in a costly abortion storm and the loss of a year’s production.
Vaccination is the essential first step in controlling infectious diseases. But it only works when vaccines are administered properly. Even when used properly, vaccines have limitations. You need to do more than vaccinate. You must protect your horses from contact with infectious diseases. This concept is known as biosecurity.
Biosecurity refers to management practices that reduce:
Animal + Infectious Agent + Environment = Disease
All infectious diseases of horses result from the interplay between the animal and its ability to resist disease (its immunity), an infectious agent (bacteria, viruses, and parasites), and the environment. This relationship points out the opportunities for preventing infectious diseases. For example, you can prevent some diseases by vaccinating to increase immunity. You can also prevent disease by keeping infectious agents from coming onto your farm.
Table 1. Major Infectious Diseases of Horses in Ontario and their Means of Spread
Strategic Vaccination
Vaccination is an essential component of every disease prevention plan. Vaccination is most effective when it is planned to meet the particular needs of a farm. Setting up a strategic vaccination program means:
• determining what diseases to vaccinate against,
• identifying who will most benefit from vaccination, and • finding out when they will most need the protection that vaccines provide. Depending on your geographical area there will be core vaccines and optional vaccines which your veterinarian can advise you on. For more information on planning your vaccination program contact your local veterinarian.
It is important to vaccinate horses in Ontario for rabies and tetanus. For pregnant animals, consider giving the equine herpes virus 1 (EHV-1) (e.g., Pneumobort) vaccine to prevent abortions. Protect performance horses, which are continually being exposed to different stable mates at race barns and shows, with influenza and rhinopneumonitis (EHV-4) vaccines.
Your veterinarian may recommend protection against other diseases. These recommendations are based on the special needs of your horse farm and knowledge of what diseases occur locally.
Preventing the Introduction and Spread of Infectious Diseases
Keeping a closed herd is one way to protect horses from infectious disease. In a closed herd, no horses enter the farm either by purchase or re-entry (including horses that have left the farm for breeding, show, or racing purposes). A herd is not closed if:
• horses are purchased or boarded,
• horses return to the herd after going to shows, races, or breeding facilities, • horses use a pasture that shares a fence line with horses in pastures on a different farm, • mares are taken to a stallion for breeding, or • horses are transported by someone else or in someone else's vehicle. It is good practice to keep the herd as closed as possible. Unfortunately, horse farms are often a hive of activity. Therefore, it may be necessary to create zones that are closed. For example, separate the brood mare band from the show horse group that are continually coming and going. Impose a minimum 30-day quarantine on animals entering or re-entering the brood mare band. Ensure that these horses do not come in contact with, or share the same air space, as resident horses for at least 30 days.
Keeping a closed herd should not be your only protection against introducing infectious disease. You also need a plan to reduce the chances that a serious infectious disease will come onto the farm.
![]() Purchasing New Horses - Eventually, most owners bring horses into their herds. It is important to plan the introduction to minimize the risk that an infectious disease will be brought in at the same time. Three factors are important to reducing the risk from infectious disease when you purchase new horses:
1. the protection you have given the resident horses by proper vaccination;
2. the source of purchased horses, including how they are transported to the farm; and 3. the method you will use to actually introduce the new horses to the rest of the herd. Resident Horses - Make certain your own horses are vaccinated before bringing new horses into the herd. Even if you have vaccinated, review vaccination records to ensure horses were vaccinated at least as often as stated on the vaccine label. Vaccinate any foals over 6 months old that haven't been vaccinated. Consider vaccinating foals less than 6 months old too, even though you will have to vaccinate again when they reach 6 months.
Source of Purchased Horses
Introducing New Arrivals
It helps to know the previous health history of the horse(s) and the herd you plan to purchase from. Horses coming from outside North America go through an inspection and quarantine period dependent on the country of origin. For horses from the USA, pay special attention to diseases such as vesicular stomatitis, potomac horse fever, and equine encephalitis. The equine viral encephalitis diseases include Eastern, Western and Venezuelan equine encephalomyelitis. West Nile encephalitis is new to North America and has infected people and horses in 1999 and 2000. (These occurred in some regions of the USA more than others.) People and equipment can carry infectious diseases too. Some diseases are spread on clothing and boots. Some can even be carried on a person's body. If you borrow equipment from other farms, make sure it is cleaned before using on your farm. Animals other than horses can even carry a few horse diseases. Be mindful about controlling the movement of people and animals on the farm as well.
Summary Some steps to reduce the risk of introducing infectious diseases:
It is difficult to control all traffic on the farm but you can identify the traffic that represents the most risk. These include people who do not pay attention to control of infectious diseases, people who frequently visit other farms and people who have already visited farms on the day they visit your farm.
Updated July 2011
(This information sheet was originally created by the author and published as a factsheet with the Ontario Ministry of Agriculture, Food and Rural Affairs ) Dr. Bob Wright, Consultant - Equine Disease Prevention and Equine Industry
6958 Wellington Rd. #16
RR#1 Belwood, Ontario Canada
N0B 1J0
519-843-1783, Fax: 519-843-3628
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