Managing Respiratory Allergies and Airway Disease in Sport Horses

Managing respiratory allergies and airway disease in most horses is fairly straightforward: You adapt their environment to be easier on their lungs, and you treat them with corticosteroids and bronchodilators. When tackling these conditions in elite sport horses, however, veterinarians and owners face a few more challenges.

Fe ter Woort, DVM, DVSc, Dipl. ACVIM, of Equine Sports Medicine Practice, in Waterloo, Belgium, reviewed how to best manage respiratory allergies in this horse population during the 2019 British Equine Veterinary Association Congress, held Sept. 11-14, in Birmingham, U.K.

The Challenges They Face

“Modern sport horses are nothing like your average pleasure horses,” ter Woort said, describing several reasons why they’re uniquely at risk of airway inflammation:

  • They travel a lot. Whether shipping by truck or plane from competition to competition, equine athletes are frequently exposed to particulates that can cause airway inflammation, as well as stressful situations that can lower immune function. Ter Woort said studies have shown that simply being transported in a confined space increases the percentage of neutrophils (infection-fighting white blood cells) and number of bacteria in their lower airways.
  • They experience different climates. As they follow competition circuits around the country and world, sport horses often experience sudden changes in climate from cold to warm and vice versa. In winter, for instance, a show jumper might fly from its chilly base in Belgium to sunny Florida to compete on that circuit.

Just being in all these different environments can induce airway inflammation,” said ter Woort. “We know the really cold air in Norway can increase the neutrophil percentage in a tracheal wash. And in really hot environments, clinical signs of equine asthma can be exacerbated. So just the climate and temperature changes can be challenging for these horses.”

  • Owners have little control over stabling conditions. While owners might be able to maintain a well-ventilated and airway-friendly environment at their home farms, they don’t have as much control over their horses’ environments while stabled at shows.
  • They compete frequently. Most sport horses compete in multiple events a month, particularly during peak seasons, to qualify for championships and prestigious events. This gives them little time to rest their airways or complete a full course of corticosteroid treatment, if needed, before shipping to their next show.

So How Do We Keep Them Healthy?

First, said ter Woort, she insists owners make modifications to their horses’ routines and environments. This might include steaming hay, avoiding dust-distributing barn chores such as sweeping and mucking while horses are inside, and storing hay and shavings away from horses’ stalls. Then she visits the farms in person to make individualized recommendations.

“Just taking the time to see the horses in their own environment is really important,” she said. “Eighty percent of the work in these cases is the environment.”

If horses develop mild lower airway inflammation, ter Woort said owners and their veterinarians should base treatment decisions on their competition goals for that horse.

“These horses have huge competition schedules,” she said. “You have to decide which shows are important and which aren’t. Certainly not every horse with a few neutrophils in their bronchoalveolar lavage (BAL) needs three weeks off for treatment.

“But sometimes it’s our responsibility to say, ‘No, sorry, you can’t take him to this show next week, he needs time off,’” she continued. “So how do you then decide?”

Ter Woort said she evaluates each horse as a whole, taking into consideration signs such as coughing, breathing hard, and longer respiratory recovery after working, in addition to neutrophil numbers and cytology (looking at cells under a microscope). She also performs an exercise test to assess the horse’s heart rate and blood lactate levels during exercise, which gives an indication of the horse’s fitness and the impact of the respiratory condition on his metabolic capacity.

“If all those things are good, I feel a lot more comfortable letting the horse compete than if lactate or heart rate are still high at exercise,” she said. “It’s important to remember that their job is to compete, and ours is to be able to get them to do that as much and as healthy as possible.”

Ter Woort did note that any horse with significant mucus in his airways, with excessive neutrophils in his BAL, or recovering from exercise-induced pulmonary hemorrhage needs rest.

Treating Horses Legally

Many of the corticosteroids veterinarians use to treat airway inflammation are on the Fédération Equestre Internationale’s (FEI) banned or controlled substances list. Dexamethasone and fluticasone, for instance, are both considered controlled substances for which the treating veterinarian must provide a withdrawal time.

Ter Woort cautioned veterinarians to calculate these withdrawal periods carefully, adding in a couple-day safety margin. Although the FEI provides detection times for some drugs, many commonly used medications have no official FEI detection time. In these cases, the veterinarian might have to work with a clinical pharmacologist or research the published or pharmacokinetic data behind the drug to come up with these calculations. Then, she recommended being extremely clear about whether the drug can cause a doping positive and for how long and writing that information on the medication box or label.

Nonmedication Options

With a big show coming up, however, what nonmedication options do owners have?

One easy option, said ter Woort, is omega-3 supplementation. She described a recent study that showed supplementing horses with omega-3s improved the clinical signs associated with severe asthma.

Another option is to use inhaled essential oils, which researchers have shown reduces airway inflammation in humans and mice. In fact, she did a clinical study on some of these essential oils and found one that resulted in a significant difference in neutrophil numbers on tracheal wash but not BAL.

“What that shows me is these essentials oils aren’t going to do anything for your severe equine asthma cases where the inflammation is in the lower airways, but in cases where the problem is that they’re just breathing in all these particles and traveling a lot, the essential oil is a really good option to use,” she said.

Lastly, ter Woort emphasized the importance of routine follow-up exams and prevention over treatment.

“Once we’ve identified these horses that have sensitive lungs and have gotten them through the show, we always schedule a follow-up about six months later,” she said. “We try to pick a time when they have a break in the competition schedule. Then we can find things that are subclinical before they become clinical and treat them before the next show.”