Mild and Severe

Working in the show horse mecca of Wellington, Fla., Meg Miller Turpin, DVM, DACIVM, of Rood & Riddle Equine Hospital, routinely treats horses with equine asthma.

Miller Turpin explains that mild to moderate equine asthma is also referred to as inflammatory airway disease (IAD), while severe asthma is best described as recurrent airway obstruction (RAO).

“Mild and moderate [IAD] are the earlier forms of the disease, which we tend to see in young and middle-aged horses,” she explains. “If caught early, it can be reversible. When aggressive treatment and essential management changes are applied to these reactive horses, then many will completely recover. In the sport horse world, we’ve improved our early diagnostic measures, which allows treatment before the condition becomes severe and irreversible.

“Unfortunately, when the disease progresses to severe [RAO], there are lung changes that are irreversible, so then we must rely on figuring out the best way to manage the symptoms,” Miller Turpin adds.

In the past, this airway condition was known as chronic obstructive pulmonary disease (COPD) or “heaves.” Many horse owners still refer to such respiratory conditions as heaves.

“The terms are often used interchangeably, but they all mean basically the same thing: mucous plugs in a hypersensitive airway,” explains Miller Turpin.

Clinical Signs of Equine Asthma

Signs of equine asthma can include:

• Coughing
• Nasal discharge
• Wheezing
• Flared nostrils when breathing normally
• Increased respiratory effort/heavy breathing
• Increased respiratory rate, even at rest
• Poor performance
• Resistance to work
• Exercise intolerance
• Anhidrosis (partial or total inability to sweat)
• Elevated heart rate during exercise or recovery
• Prolonged recovery after exercise

“We see a lot of horses with anhidrosis in Florida,” says Miller Turpin. “I’ve found that many horses with mild or moderate asthma [IAD] stop sweating, so that’s a double whammy. Sometimes you can get them to start sweating again once you get the airway issues under control.”

She finds that horses suffering from equine asthma can take much longer to recover from exercise—as long as 30 to 60 minutes to start breathing normally.

When a horse’s heart rate is much higher than it should be for the rate at which he’s working, this can indicate a lung problem is preventing the heart from getting enough oxygen to pump to the rest of the body, including muscles required for action.

Affected horses can have elevated respiratory rates as high as 50 to 90 (or more!) breaths per minute. Keep in mind, normal respiration for an adult horse is 8 to 20 breaths per minute.

Dramatically high respiratory rates combined with hot weather can be life threatening.

Causes and Triggers of Equine Asthma

Equine asthma is typically related to inhaled allergens and irritants. These can be year-round, such as dust, mold and fungal spores found in hay, straw and poorly ventilated or closed-up barns.

Other horses may only be susceptible to seasonal allergens, such as pollen encountered during specific times of year, typically spring and summer, or sometimes fall. Seasonal allergies can be easier to manage because you know when to expect a problem.

Miller Turpin finds that if horses have had a respiratory virus or a bacterial infection of the airway, this can make them more vulnerable to irritants that act as triggers.

It is believed that some horses may have a genetic predisposition to developing asthma, and when faced with environmental triggers, like dust, they will develop clinical signs.

Sensitive horses that often get hives and are very reactive to topical products and/or vaccines may be more likely to develop equine asthma.

“Horses that are stalled in cold climates in the winter with windows closed are set up for even more reactions to dust and molds,” says Turpin Miller. “Ammonia levels from urine in the stall can be toxic to the airways in a closed environments with poor ventilation. In tropical Florida, we have all this growth, bloom and mold, so even if horses receive additional turnout, there are still triggers in different grasses [and the] hay that is delivered from different areas of the United States and Canada.”

Those inhaled allergens and irritants cause inflammation, which leads to airway constriction as the tissue lining the small airways in the lungs narrows and becomes thickened. The smooth muscle surrounding these airways also constricts and tightens. Thick, sticky mucous accumulates in the airways, which also obstructs breathing.

As a result, inhaling and expelling air from the lungs becomes an effort for the horse. When the condition goes untreated, lung tissue can suffer permanent damage, resulting in irreversible loss of lung function.

Over time, horses can develop what is known as a “heave line” along the bottom of the rib cage on both sides as the abdominal muscles enlarge due to the continued effort of exhaling.

Diagnosing Equine Asthma

When a horse exhibits clinical signs that point to equine asthma, the veterinarian should do a thorough physical exam, including ultrasound of the lungs and a resting airway scope of the upper respiratory tract.

The veterinarian may also wish to perform a scope while the horse is exercising to rule out a mechanical cause, such as a displaced palate or abnormal epiglottis.

Should the horse’s heart rate be abnormally elevated, the veterinarian may use an exercise EKG to evaluate the horse under exercise.

Skin allergy testing may also be used to determine specific allergens that might be associated with inflammatory airway disease.

When equine asthma seems likely after these exams, the veterinarian will likely use a procedure known as bronchoalveolar lavage (BAL) to better define the diagnosis.

The BAL can be done without taking the horse to a clinic. While the horse is sedated, a special tube is passed through the nostril into the trachea and down into part of the lung. Sterile saline is flushed in and suctioned back out, drawing cells and mucous out with the fluid. These samples are then submitted for cytological analysis to pinpoint the most effective treatment.

Treatment Protocol

The traditional medical approach is to address inflammation with corticosteroids and, if necessary, open the airways with a bronchodilator.

The duration and amount of medication used is tailored to the specific horse.

Although systemic steroids have been the gold standard to relieve inflammation and asthma signs, these drugs can suppress the immune system and carry risks, such as laminitis.

Administering steroids via nebulizer or inhaler, instead of orally or by injection, may reduce the risk of side effects by targeting the steroids directly to the lungs.

“With competition horses, you also have to consider competition regulations and withdrawal times,” says Miller Turpin.

Some regenerative medicines are being used with promise, including stem cells. Another innovative treatment uses a patented process to filter alpha-2-macroglobulin (A2M) from the horse’s own blood. This protein has powerful anti-inflammatory properties and can be administered via a nebulizer. (Studies are still necessary to prove the efficacy of these medications.)

Supplements may also help. Miller Turpin notes that both high doses of Vitamin C and omega-3 fatty acids have lung health benefits.

It also appears that acupuncture can help breathing function in some horses with equine asthma.

The Importance of Management

Owners need to be very aware of their horse’s environment and any individual triggers. For the horse to experience ongoing relief, management changes are a crucial part of treatment protocol.

“You can treat aggressively with medications in the early stages and the horses may respond well, but if you don’t take away the triggers causing the allergy or reactive airway, then as soon as you stop the medication, the symptoms will come back, and often they will be exacerbated,” cautions Miller Turpin.

Depending on which allergens/irritants are to blame, your horse may do better when kept outside as much as possible. On the other hand, horses battling seasonal allergens may have less exposure if they’re not turned out as much that time of year.

Air quality is key. Eliminate dust and mold as much as possible. Reduce allergen/irritant exposure by:

• Using the stall with the most airflow (usually an end stall).
• Reconsider bedding (straw is often the worst choice; peat moss or cardboard may be better).
• Remove the affected horse from the barn whenever cleaning stalls, sweeping, or using a blower.

Forage Considerations

Obviously, forage is the main part of the equine diet. For asthmatic horses, however, hay can be a primary source of allergens and irritants.

Some owners find that dampening or steaming hay helps. Dry hay is not recommended, and round bales are an absolute no-no due to their high levels of dust, fungal and mold spores.

“These horses do better when you replace hay with chopped forage, pellets or complete feed,” says Miller Turpin.

Case History

The first indication Natalie Pai’s Oldenburg stallion, Mister-C, had respiratory issues was a hacking cough at the beginning of his workouts.

After Pai imported the stallion to Florida, she found he was also very sensitive to topical products, often breaking out in hives.

Miller Turpin examined Mister-C and did a series of skin allergy tests, which showed he was reactive to a wide array of allergens. She also performed airway endoscopy and a BAL. He was diagnosed with equine asthma due to severe allergies.

A2M and steroid/bronchodilator treatments through a nebulizer are part of his routine. He also gets allergy shots administered subcutaneously every two weeks. His hay is steamed to remove any dust.

“His breathing is very well managed now,” says Pai, who understands the frustration of breathing problems since she herself has allergy-induced asthma.

Key Takeaway

When a horse has breathing abnormalities, especially combined with skin sensitivities, have your veterinarian conduct an exam for possible equine asthma. Being proactive with early treatment and management changes may keep the condition from becoming severe and irreversible.

Further Reading
◆ Horse Respiratory Issues: Management of Asthma and Other Disorders
◆ Horse Allergies: Symptoms, Treatment, and Prevention

This article about equine asthma appeared in the July 2024 issue of Horse Illustrated magazine. Click here to subscribe!

The post What is Equine Asthma? appeared first on Horse Illustrated Magazine.

Ask anyone with asthma what it’s like to have an attack and words like “suffocating,” “drowning,” and “an elephant on my chest” are a common refrain. The Asthma and Allergy Foundation of America explains that asthma is a “long-term disease that causes inflammation and swelling of the airways,” meaning that the asthmatic truly cannot get enough air into their lungs. Asthma in humans has been on the rise in recent years, and it certainly seems that more horse owners are also battling the disease and other respiratory issues among their horses. Being able to identify asthma triggers is an important part of keeping people—and horses—healthy.

Once asthma triggers like dust, pollen and animal dander are identified, many human asthmatics make lifestyle changes to minimize their exposure, giving them the best chance to remain healthy. While it would seem intuitive that similar lifestyle changes would be warranted in horses, a recent study conducted by the University of Lisbon found that the majority of horse owners and managers were reluctant to implement any kind of adjustment to the horse’s routine.

Knowing that these changes are imperative to—quite literally—being able to breathe, why are some horse owners slow to adopt management changes?

Clinical Signs and Diagnosis

Lais Rosa Costa, MedVet, Ph.D., DACVIM, DABVP, director of operations for the Veterinary Emergency Response Team at the UC Davis School of Veterinary Medicine, is a boarded large animal internist whose clinical and research work has focused on respiratory diseases, especially severe equine asthma.

Though equine respiratory disease ranks second only to musculoskeletal disease in disorders that limit performance horses, signs of pulmonary disease often come on slowly, causing them to be unnoticed by owners and farm managers until clinical signs are severe.

According to Costa, signs a horse may be suffering from pulmonary disease include exercise intolerance and increased respiratory rate or increased respiratory effort. A horse suffering from asthma will often cough from increased mucus production. Any of the chronic or recurrent pulmonary diseases will cause a horse to work harder to breathe, leading to poor performance and weight loss, she notes.

It’s imperative that the root cause of horse’s health issue be defined and differentiated from other conditions, such as cardiac diseases, Costa says. This will require getting a thorough history, along with a detailed clinical examination.

“The lungs have limited ways to deal with insults, so many of these conditions manifest similarly, but the trigger is specific for the condition,” she explains.

Additional respiratory diagnostics may be needed to narrow down the source of a horse’s problem, says Kate Christie, DVM, DACVIM, an associate veterinarian with Rood and Riddle Equine Hospital in Lexington, Ky., who has a special interest in respiratory disease.

“Diagnostics are aimed at determining whether the problem is in the upper or lower airway, as well as whether the problem is infectious or inflammatory in nature,” says Christie. “The answer to these questions helps us come up with a treatment and management plan for each individual horse.”

Additional diagnostics may include bloodwork, diagnostic imaging (ultrasound examination and chest radiographs), specific airway diagnostics like endoscopy, and—if equine asthma is suspected—bronchoalveolar lavage, she explains.

Management

Once the trigger is identified, management changes to reduce or eliminate the issues causing breathing distress are imperative for the horse’s health. This can be tricky—especially in cases of inflammatory airway disease, according to Christie.

Though the “gold standard” of care would be to remove all dust and allergens from a horse’s environment, it’s simply not possible to completely eradicate these, as horses are expected to be ridden in arenas, to eat forage, and often to sleep on some form of bedding.

“Although it’s really difficult, environmental management is the cornerstone of treating inflammatory conditions of the lower airway,” says Christie. “You could provide the horse with all the medication in the world, but if the environment isn’t improved, the horse won’t respond as well [to treatment]. Our recommendations for environmental management are all aimed at decreasing exposure to airborne allergens, including dusts and molds.”

Some of the modifications need not be as overwhelming as they initially appear.

Horse Respiratory Health Myth No. 1: All horses with allergy issues should have wet hay.

Reality: Wetting hay is not the cure-all solution it was once believed to be.

“[Wetting hay] actually increases the amount of mold and exacerbates conditions like equine asthma,” says Costa. “Washing the hay, or—better yet—steaming the hay are effective ways to decrease organic particulate matter.”

Management change: While not everyone will be able to afford a hay steamer or the time to go to the barn twice a day to make cleaning the hay a reality, there are other ways to make a forage change work, according to Costa. A complete pelleted diet, pelleted hay, and haylage are a few options to consider, but no diet change should be done without the input of a veterinarian or an equine nutritionist to be sure the horse receives adequate and appropriate fiber and nutrients.

Horse Respiratory Health Myth No. 2: Bedding doesn’t matter if the horse isn’t in the stall when it’s cleaned.

Reality: A horse stalled on any type of bedding that contains contaminants that trigger a pulmonary response is at risk, and not just when the stall is being cleaned. Simply walking around in the stall can stir up enough dust to cause breathing issues.

While no horse should be kept in the stall while it’s being cleaned, asthmatic horses must be removed before the stall is mucked, and should remain out of the barn for at least one hour after cleaning.

Management change: Straw is one of the dustiest (and moldiest) types of bedding that can be used, with rice hulls and sawdust not far behind. Good quality wood shavings are not as bad.

“Severely asthmatic horses have to be bedded on shredded cardboard bedding or rubber mats with no bedding at all,” says Costa.

An even better solution? Turn the horse out 24/7.

“Many horses resolve [their breathing issues] completely with 24-hour turnout alone,” says Christie. The only time this recommendation varies is when horses are diagnosed with summer pasture associated recurrent airway obstruction (SPARAO). This condition is more common in the southeastern United States and is characterized by difficulty breathing when pastured in the summer. Pollens and other seasonal allergens are suspected to be the cause, according to Christie.

Similar to the barn-associated equine asthma, implementation of management changes is crucial for effective care of SPARAO, and without them, these horses do not respond to medical therapies, Costa says. This is a seasonal recurrent condition that can be controlled successfully with management changes and minimal medical therapies.

Horse Respiratory Health Myth No. 3: Stall location doesn’t matter.

Reality: Similar to a real estate expert, the owner of a stalled horse with breathing issues should be concerned with one thing: Location, location, location. While owners may think stalls located near doors are more uncomfortable for the horse in cold, blustery weather, the reality is the more airflow, the better.

Management change: Though horse and barn owners can get stuck in routines that are hard to change, this adjustment is one of the easier ones to implement. Moving a horse closer to a doorway, away from the indoor arena or even to a stall with a window can offer some immediate relief to the afflicted equine.

Equine asthma is a lifelong condition for which there is no cure. But be assured that even small changes can make a big impact for a horse that has a difficult time breathing.

“I often stress that [owners] can spend a lot of money on medical therapies, but these won’t make a difference if the environment is not controlled,” says Christie. “If people are able to adhere to environmental changes and keep flare-ups to a minimum, it’s less likely that the horse’s condition will progress to recurrent airway obstruction (RAO) or heaves—a much more serious and severe category of equine asthma.”

Costa also feels that management should be the No. 1 priority.

“Our job as veterinarians is to help owners and caretakers understand the importance, although sometimes challenging, of implementing management changes [that go hand-in-hand with treatment],” says Costa. “The management changes have to be realistic. Sometimes we have to be creative. The best [way to handle the situation] is to keep a positive outlook and do the best that is possible.”

While these changes may take some planning to implement, the horse’s quality of life can quite literally depend on it.

Smoke Inhalation Horses affected by barn fires and wildfires face a different set of issues that those with equine asthma and other airway diseases. Lais Rosa Costa, MedVet, Ph.D., DACVIM, DABVP, a veterinarian at the UC Davis School of Veterinary Medicine in California, has seen multiple horses affected by smoke inhalation from wildfires. “Smoke inhalation affects both the upper airways and the lower respiratory tract,” Costa explains. “Much of the acute signs of smoke inhalation injury are associated with toxic compounds released upon combustion [plus] inhalation thermal injury. “ The immediate concern is treating the acute smoke inhalation injury, which entails managing acute respiratory distress, decreasing inflammation, and preventing secondary infection. Kate Christie, DVM, DACVIM, an associate veterinarian with Rood and Riddle Equine Hospital in Lexington, Ky., notes that horses involved in fires can be severely affected by smoke and particulate inhalation—sometimes days after the initial insult to their lungs. “A massive inflammatory response may be initiated [by smoke and particulate inhalation] that causes severe pulmonary disease,” she says. “This response can be delayed from the initial exposure and is a huge problem for horses that survive barn fires. Permanent damage from smoke inhalation is also possible, and these horses may have prolonged respiratory disease that is difficult to manage.”

This article about management of horse respiratory issues like asthma appeared in the September 2022 issue of Horse Illustrated magazine. Click here to subscribe!

The post Horse Respiratory Issues: Management of Asthma and Other Disorders appeared first on Horse Illustrated Magazine.