Clean It Up! Addressing Environment Critical to Protecting Equine Respiratory Health

Tuesday, February 2, 2021
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Emerging from a year when COVID-19 made human respiratory health a perennial front page news item, horses may end up benefitting from their owners' increased understanding how harmful microscopic airborne particles can be.

One positive to emerge is a better understanding of how the horse's respiratory system works, its vulnerabilities, how it can be protected and the subtle and not-so-subtle signs of trouble.

Respiratory function is greatly affected by particulate matter. Microscopic bits of dust, fungi and bacteria found in a normal barn environment are big problems.

"Particles above 5 microns in size can usually be filtered out of by natural defense mechanisms in the horse's upper airway," explains Dr. Phoebe Smith of Riviera Internal Medicine and Consulting in Santa Ynez, California.

The trachea, or windpipe, transports air from the nostrils to the lower airway passages in the horse's lungs. Built-in defenses consist of a mucus membrane and tiny, hair-like cilia that can usually trap and transport the 5-micron and bigger particles back out the nose or send to the esophagus to be swallowed. These particles are about the size of a human hair.

Smaller particles slip past and infiltrate the thin lining of the lung. There they irritate the surface and cause inflammation, impeding the transfer of oxygen to the bloodstream. Horses' bodies are 60 muscle and muscles need oxygen to function, as do all cells in the body.

Fortunately, the most effective way to safeguard the respiratory system is easy: cleaning up the horse's living environment. Renowned Belgium sporthorse vet Dr. Emmanuelle Van Erck Westergren starts any case of suspected or diagnosed respiratory issue with an assessment of the horse's habitat.

"We do measurements of dust levels and samples of contaminants," she explains of a typical barn visit for this purpose. "Some are easy to see. Have you seen someone sweep dust from the barn aisle, then stash that in the horse's stall? Or seen mold stains on barn walls or ceilings?

"A condition called Sick Building Syndrome exists in human medicine and it can apply to horses, too. They may not be coughing or having nasal discharge, but they clearly don't feel well. That can often be linked to the amount of contaminants growing inside the building.

"Horses were designed to live outside, but many horses spend 23 hours a day in the barn. Living inside, they're exposed to 50 times more inhalable irritants! Even if they live outside, if they're getting hay with contaminants, it's still a problem."

Hay and bedding are big contributors to unhealthy barn air. Because most horses do best when the majority of their diet is forage, Dr. Van Erck Westergren advocates Haygain Steamed Hay. It reduces up to 99% of the dust, fungi, bacteria and other allergens found even in hay of top nutrient quality. This is a special problem because hay puts these particulates right in the horse's breathing zone.

On the stall bedding front, flooring that seals to the stall wall to prevent urine seepage and accumulation of harmful ammonia odors is ideal. Haygain's ComfortStall is a top brand to feature that component and its layer of therapeutic foam reduces the need for bedding to only the amount required to absorb urine.

Low dust bedding is another key environmental improvement. AirLite Bedding is emerging as a leader in this product category. Made of unused cardboard and subjected to a dust extraction process, AirLite is proven effective in absorbing another common airway irritant: ammonia that arises from accumulated urine. Because the cardboard hasn't been used first for other purposes, it does not bring chemicals or contaminants into the barn.

Fear Fungi
Found in hay, straw bedding and elsewhere in the barn, fungi is increasingly recognized as a major risk factor in respiratory health. "It can be very allergenic because it has proteins that can trigger a very strong reaction," Dr. Van Westergren explains. "It can become infectious and start to grow inside the horse's airways. That process can produce toxins and irritations to the respiratory mucosa, which can ultimately affect the throat muscles. Fungi can also trigger inflammatory responses that manifest as rhinitis and sinusitis.

"The role of fungi, aka mold, is not yet broadly recognized in the veterinary world," she continues. "When a fungal infection is suspected or diagnosed, current treatments often include corticosteroids to address inflammation. Those further depress the immune system, enhancing the opportunity for fungal infection.

"In our study of 731 horses referred for suspected respiratory issues and/or poor performance, 88% were found to have Inflammatory Airway Disease. Horses with fungal elements in their airway were 2.1 times as likely to have IAD.

"In a study we did on sport horses, we detected a link between fungi in the airways and the likelihood of Exercised Induced Pulmonary Hemorrhage: a horse is seven times more likely to bleed from the lungs, through the nose, during extreme exertion when they have fungi in the airways. In the United States, this could get a lot of attention as racetracks are in the process of phasing out Lasix, the medication that reduces EIPH."

Trouble Signs
An occasional throat-clearing cough at rest or when beginning to exercise is normal in healthy people but not in healthy horses. It's often an early sign of conditions on the mild end of the Equine Asthma Spectrum. Caught at that stage, irritation and inflammation can be undone by reducing the horse's exposure to its causes. Untreated, it can progress to more severe and potentially irreversible conditions, like Severe Equine Asthma, which can only be managed, not cured.

"Other subtle signs include nostril flair and a higher than normal respiratory rate," says Dr. Smith. "Normal is 12-24 breaths per minute, and a rate above 30 can be a symptom of trouble. Also, your horse might just seem a little off." Many veterinarians consider respiratory challenges to be the top performance limiter after soundness. This is one of many areas where knowing what's normal for your horse is essential, the California veterinarian adds.

Diagnostic tests include a rebreathing exercise in which the vet listens to lung sounds, an endoscopic exam of the airways and a bronchoalveolar lavage (lung wash) to count the number of nutrophils, inflammation indicators, that come out of the lungs.

As in any health concern, the horse's regular veterinarian is the first source for protecting respiratory safety, diagnosing the specific issue and recommending treatments and management.