Fresh off the trailer, home from her first show, your filly bounds across the pasture calling for her mother. Though they've been apart only a few hours, the two greet each other like long-lost soulmates and spend the evening nuzzling under the trees. Within days both are sick with runny noses and coughs. After a two-week hiatus in her training schedule, the filly recovers, but it's several more weeks before the old mare really seems like her old self again.
Visiting a local produce farm, you come around the corner of a shed and stop short at a miserable sight: A thin and muddy pony stands before you in a mucky pen, making only feeble swipes of his tail at the flies crawling all over him. You insist that the owner sell you his "retiree" on the spot, and soon the old fellow is safely bedded in a clean stall with fresh hay and water. Days later, while grooming him you notice an ominous sign: a large, hot lump forming just behind his jaw. Turning toward your family's four Arabians in the other end of the barn, you backtrack through time, trying to remember how much contact the horses might have had, by way of grooming tools, buckets and human hands.
Picking up and moving across the country is no easy task, and amid all the details of the move one of your highest priorities is finding a reputable boarding barn for your gelding. You pick one based on the recommendation of your new boss. As you unload your horse at his new home, the barn manager hooks his thumb toward a nearby gate and says, "Go ahead and turn him out." The pasture already holds two elderly geldings, and they share a fence with a paddock holding three obviously pregnant mares. You hesitate. After his long trailer ride your horse would relish the freedom, but is it really a good idea?
No, it's not. Just as colds and flu seem to race through every kid in kindergarten, just one horse carrying contagious organisms can cause disease to sweep through an equine herd. That's why outbreaks of illnesses like rhinopneumonitis or equine influenza are so common that some consider them normal "rites of passage" for young horses.
But they don't have to be. Viruses and bacteria that are passed from horse to horse are highly contagious, but they can be stopped. Consider, for example, how successful veterinary hospitals and large breeding farms are in limiting disease transmission with quarantine barns, strict horse-handling protocols and disinfecting procedures.
But contagion-control measures need not be elaborate or expensive to be effective. Many, in fact, simply follow the precepts of good management. A paper published by George Allen, PhD, of the University of Kentucky's Maxwell H. Gluck Equine Research Center, outlined recommendations for the prevention and control of outbreaks of equine herpesvirus-1 infection, which causes rhinopneumonitis. But, he says, "These concepts would also apply to equine influenza and strangles or any other infectious disease spread by direct contact between horses."
For example, one of the best defenses against any infectious disease, says Allen, is a management program that provides regular vaccinations, good nutrition, adequate exercise and a pleasant environment--factors that contribute to good general health. "Unvaccinated, stressed, overcrowded or poorly conditioned horses are most at risk for developing infectious diseases," Allen says. Conversely, horses who are healthy and content will most likely have the immunological tools they need to ward off most infectious organisms, or at least to recover rapidly if they should become ill.
Herd size is another factor in the spread of infectious disease. The smaller the number of horses who come in contact with a carrier, the fewer who will get sick. So, on a farm with many horses, keeping smaller herds that do not commingle can help ensure that any pathogens will be contained within the small groups and probably won't spread throughout the farm. "This practice is obviously more feasible for large operations that have the facilities for such subdivision of their horses into more-or-less isolated subgroups," Allen says. But any farm with more than one pasture can implement "subherds," and it may be worthwhile, for example, to separate permanent residents from horses who travel frequently to shows and trail rides, at least for the duration of their active seasons. Allen also suggests dividing horses into like groups, keeping youngsters, older horses and pregnant mares in separate herds to avoid exposing potentially vulnerable populations to pathogens carried by other apparently healthy horses.
Going it Alone--At Least for a While
By far, the best way to protect horses from pathogens is to separate them temporarily from newcomers and herd members returning from shows, breeding farms or other situations involving contact with numerous other horses. But effective isolation involves more than keeping a horse in his stall for a few days, says Allen.
Because diseases such as rhino can incubate for weeks without obvious signs, a horse arriving on the farm would ideally be kept separate from the resident horses for a minimum of three weeks. Where the horse is kept is also critical: Some viruses can travel in airborne droplets from a horse's breath, and, says Allen, "a minimum distance for effective prevention of the spread of infection would be 50 yards." Finally, during the isolation period caregivers, including farriers, exercise riders and grooms, need to take precautions to ensure that they do not pass the pathogens to other horses.
This may seem like a lot of trouble, concedes Allen, but "the most effective basic strategy for controlling infectious diseases is strict adherence to the policy of isolating new or returning horses prior to introducing them to the resident group."
When deciding whether an arriving horse ought to be isolated, consider how well you know the animal, how high his stress level is and the number of horses he has been exposed to. Although you'll want to isolate any new horse before adding him to the resident herd, be especially diligent in handling "rescues" and horses who come off the track or from crowded auctions, where they may have been exposed to a wide variety of pathogens under stressful conditions.
And don't overlook the disease potential of even routine gatherings of horses. "Any horse returning from a show is also a candidate for isolation," says Lyda Denney, DVM, a field veterinarian with the New York State Department of Agriculture and Markets. "These animals have been through the stresses of showing, change in environment and traveling and can also be more prone to illness when exposed to an infectious agent."
Horses returning home from less crowded or stressful venues, such as trail rides or camping trips, are less likely to be bringing in new viruses, says Denney. "However, these horses may still have been in nose-to-nose contact with strange horses or shared a common waterer." Even if you don't isolate the horse, she adds, "it is still important to observe him closely for several days in case he was exposed to an infectious agent and is incubating an illness." If any resident horse does begin to show signs of illness, moving him into isolation may help safeguard his herdmates.
Three Simple Steps
The task of protecting your horses from "invisible" enemies will seem less daunting when you consider one fact: to keep average, healthy horses from becoming ill, you don't have to eliminate all exposures to pathogens, you only need to reduce the exposure enough so that their immune systems can fend off the threat. The following measures for isolating horses are not difficult to implement, but they can go a long way toward diminishing the chances that a pathogen will sweep through your entire barn:
1. House isolated horses as far from the other horses as possible. Ideally, says Allen, a separate barn will become the quarantine area because "it's quite common for infections like equine influenza and rhinopneumonitis to spread rapidly, via the airborne route, among horses housed within a single barn."
Even if you have only one barn, however, there are several ways to reduce the amount of exposure. Denney suggests designating an end stall as the "quarantine stall" and making sure that the airflow within the barn won't carry pathogens in the direction of other horses. Placing a fan to draw air from that stall toward the outside door will help. Since some viruses can be passed via human hands, Denney also suggests placing a sign on the stall warning visitors not to touch the isolated horse or stall.
Alternating turnout times--bringing the new horse in during the day while the other residents are out, and turning the newcomer out at night while the residents are in--will also give the horses some measure of protection. If possible, allow an hour to pass before moving the horses from one situation to another to allow any secretions to dry out.
2. Establish separate turnout areas. "If a horse is in isolation, don't let him graze in any area that might be used by other horses," Denney says. With horses on turnout as with those kept in stalls, says Allen, "the risk of transmission increases as the distance between horses decreases." Put as much distance between paddocks or fields used for isolation from resident horses as the premises will allow, Allen advises, preferably keeping the isolated horses downwind from the other pastures.
If only one pasture is available, another option would be to cordon off a section behind a temporary double fence, spaced about 10 feet apart to prevent nose-to-nose greetings. "Isolation facilities don't have to look good to be effective," Allen says.
3. Be aware of the human factor. "It's important to be aware that people and equipment can carry infectious diseases, too," Denney says. If assigning the new horse his own groom isn't possible, then the person who does care for him needs to handle him last--after finishing with any others. It's also crucial to allot an isolated horse his own grooming tools, tack, feed buckets, waterer, etc. Plus, Denney says, "The person responsible for the horse in quarantine could wear coveralls that are left at the stall, or could change clothes after working with the horse, and use equipment that stays at the isolation stall." Protective footwear that can be removed and left at the stall or shoes that can be thoroughly disinfected are also a good idea.
Once the horse has been removed from isolation, scrub and disinfect all of the equipment used with him. "The stall, too, needs to be stripped of all bedding and organic material and thoroughly cleaned," Denney says. "After all surfaces are cleaned and rinsed, remove as much excess water as possible and, using protective clothing, apply a disinfectant."
During the three-week isolation period, check the horse's vital signs daily, paying particular attention to his temperature. Also be on the lookout for cough, diarrhea, runny nose or other signs of illness. Should the horse become ill, you may need to intensify your isolation measures--for example, move the horse even further away from the others--and after he recovers Allen suggests keeping him apart from the other horses for at least another three weeks.
The measures you take to protect your horses from contagious diseases will obviously depend on several factors, including the size of your property, the number of horses who live there and the resources you can bring to bear on the effort. And while it's impossible to establish 100 percent protection from disease-causing agents, even the smallest farms can implement basic steps that will pay off in improved herd health.
This article originally appeared in the April 2003 issue of EQUUS magazine.