by Sally Colby

Horses are social animals, and most are eager to rub noses as a way of getting to know each other.

But Dr. Roberta Dwyer, University of Kentucky, and Dr. Joe Lyman of Neogen agree that nose-to-nose contact among horses isn’t healthy. The veterinarians discussed biosecurity for horses and how horse owners can prevent disease.

Lyman’s interest in biosecurity comes from his background as a resident veterinarian at a Lexington, KY, breeding farm where he saw the consequences of disease outbreaks in large populations of horses. Dwyer’s interest in infectious disease control began shortly after she finished vet school and saw that disease outbreaks were due to either vaccine failure or a disease for which no good preventive measures were available.

“What’s on a lot of people’s minds right now is herpes virus, strangles, equine infectious anemia (EIA) and influenza,” said Dwyer, mentioning the diseases most often publicized by the media. “But biosecurity, in total, is reducing risk, and that includes diseases transmitted by ticks, mosquitoes and other insects.”

Lyman says when caring for a horse with an infectious disease, consider that animal ‘dirty’ and always take care of healthy horses first. Ideally, anyone handling the sick horse and everything associated with it should change clothes and footwear prior to returning to healthy horses. “Engage in good surveillance on healthy horses,” he said. “Take temperatures, look for signs of illness and plan early intervention if signs are noticed.”

Dwyer says when a new horse arrives at a facility and will become part of that facility’s herd, the general rule of thumb is to keep that horse in a separate area for about 14 days. “That takes into account most of the incubation times for contagious diseases,” she said. “Incubation time is from the time a horse is exposed to a virus or bacteria to the time it shows clinical signs. While the horse is in confinement, take its temperature twice a day and get them up to date on vaccines and deworming. Keep them totally isolated, as if they were ill, from the resident population.” During isolation, use separate grooming tools, manure forks, buckets and feed pans. Horses often become upset during isolation, but usually settle quickly if they’re within calling distance of one another.

For cleaning and disinfecting stalls, Dwyer says there’s risk in using power washers. “Power washers can aerosolize pathogens in the stalls and floors and move them to ledges where they’ll dry and fall back into stalls,” she said. “That’s a potential source of recontamination.”

She suggests scrubbing stalls with detergent, then rinsing to remove organic matter. Dwyer also says that bleach is not a good disinfectant because it becomes inactivated in the presence of organic matter, including dirt and the 50 pounds of manure produced daily by the average horse. Horse owners should consult with their with veterinarian for a list of appropriate disinfectants.

For those boarding at barns where biosecurity is less than optimal, develop a good relationship with the barn owner. Boarders should realize the risk of disease cannot be reduced to zero, and may have to speak up about biosecurity breaks that could be exposing horses to disease.

Lyman explains that managing horses in an environment where others are not concerned about biosecurity is practicing the basic tenants of biosecurity. “Bioexclusion is everything we do to keep disease away,” he said. “Biomitigation is what we do about disease that is present, and biocontainment is preventing disease from moving where it is to other parts of the facility.”

Lyman encourages horse owners who board to consider which areas can be controlled, such as the horse’s stall. “Do you have control over the pasture, or is it communal?” he said. “If you can control your horse’s stall, make sure you have dedicated tools that only go into your horse’s stall and are not used to clean other stalls. Dedicated tack is especially important to prevent exposure to respiratory disease. Limiting contact with personnel is another important point. Make sure the same hose isn’t dunked into every horse’s water bucket down the aisle, which can transmit disease along the way.”

What about uninvited guests such as rodents, or dogs and cats that are part of the barn scene? “Insects, rodents, dogs and cats can bring disease,” said Lyman. “Influenzas are usually species-specific, but influenza can be inhaled by both humans and animals and remain infective for around 24 hours — they inhale influenza at one end of the barn and exhale at the other end.” Lyman added that any animal can be a biosecurity risk, so insecticides and rodenticides should be part of biosecurity protocol. “Wildlife control is vitally important in a barn,” he said. “A lot of diseases are carried specifically by skunks and opossums. Don’t let a dog wander around in the barn at the same time you’re trying to practice good biosecurity.”

The list of disease-carrying insects is long, and insects can be difficult to manage. “Insects can play a biological role in the disease, such as in West Nile where they are part of the process,” said Lyman, “or landing on one animal then another, carrying bacteria. Any commercially available fly spray applied as directed should be enough to protect against most flies and mosquitoes. In areas where ticks are endemic, include tick control — ticks require different management than just fly spray.”

Dwyer discussed biosecurity in the face of emergency evacuations during hurricanes and other emergency events. She suggested that those who offer to house horses during a disaster should keep incoming horses separate and use separate tools, feed pans and water buckets. “They’re stressed horses, and they’ve been on the road,” she said. “Give them good fresh water and clean hay and try to decrease stress in a stressful environment, but separate them from your horses.”

As for keeping horses from becoming ill from other horses at events such as shows, the number one priority is keeping vaccinations up to date and avoiding nose-to-nose contact with other horses. “If you tie your horse to bathe him at a common railing, wash the railing before you let your horse nuzzle it,” said Dwyer. “That’s nose-to nose contact by way of a tie rack. Manure management at a venue is also important in preventing pathogens in manure and also preventing flies.” Dwyer added that some venues use posters throughout the grounds to spread the word about biosecurity.

When horse owners participate in casual or competitive group rides, sometimes the only watering option is a stream or a common tank used by all horses. In such cases, horse owners have to weigh risks and benefits — the risk of potentially ‘dirty’ water versus the horse not being properly hydrated.

“Everything about biosecurity is about ‘what is acceptable risk?’” said Lyman. There is no way to bring the risk to zero.”