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!

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Just as many humans start to sneeze in the fall, horses can also be affected by seasonal allergies and also equine asthma. Sometimes this is apparent by coughing, but other times, according to Laurent Couëtil, professor of Large Animal Internal Medicine in Purdue University’s College of Veterinary Medicine, the only sign is that their performance suffers.

Couëtil has spent much of his career treating and researching equine respiratory disease, and he collaborated with three other researchers to argue for the adoption of equine asthma as an official diagnosis in the Equine Veterinary Journal. Equine asthma can flare up as a result of allergies, especially during the fall, which is when many of the traditional spring horse races were moved. Couëtil’s research shows that the causes of equine asthma are largely environmental.

“We tend to see an increase in horses showing signs of equine asthma during crop harvest season,” he said. “Horses pastured near fields where crops are harvested may be exposed to the dust generated by the combine harvesting crops.”

Horses affected by these allergies may develop signs like coughing or increased breathing efforts within a few days of exposure to the dust or allergens and may show impaired performance.

“Other horses with asthma tend to show signs when pollen and molds peak again in the fall,” Couëtil said. “So, the triggers may be different, but horses will show similar symptoms.”

One reason for so many allergy and asthma flare-ups in the fall has to do with feeding. As grass becomes sparse toward the end of the summer or early fall and horses are supplemented with dry hay, more susceptible horses may develop asthma flare-ups.

“Most asthmatic horses are allergic to hay dust,” Couëtil said, “and, therefore, they usually develop clinical signs when fed hay in the barn during the winter months.”

Additionally, feeding round bales is associated with more severe signs because horses are exposed to higher dust levels compared with eating from square bales.

“This is especially true when round bales are left in the field uncovered as they tend to become moldy from exposure to rain and moisture,” Couëtil said.

Couëtil has found that often, less severe asthma signs improve when horses are on grass pasture, but during the fall months, this isn’t always possible. Feeding low-dust forages can help horses recover and also prevent flare-ups.

“Our recent research demonstrated that athletic horses, such as racehorses, benefit from being fed steamed hay or haylage instead of dry hay,” he said. “These forages result in lower exposure to dust as compared to dry hay, and this translates in lower levels of airway inflammation. Haylage appears to have the strongest beneficial effect, and this effect seems to be linked to higher omega-3 fatty acid content.”

Additional supplementation with nutrients rich in omega-3 fatty acids, like EPA and DHA found in fish oil and algae, can help keep asthmatic horses healthy.

Avoiding exposure to allergy triggers, such as by feeding low-dust forages, can help horses stay healthy and perform at peak levels. During crop harvest season, this might mean keeping the horse in the barn while crops around the stable are harvested.

“If horses continue to show signs of asthma despite environmental management, your veterinarian may prescribe treatment with aerosolized corticosteroids,” Couëtil said.

Taking preventive measures can help minimize horses’ exposure to allergens and prevent asthma flare-ups, keeping horses healthy and performing at their best levels.

Couëtil’s research is supported by the Grayson Jockey-Club Research Foundation, the state of Indiana and the Purdue Veterinary Medicine research account.

About Purdue University

Purdue University is a top public research institution developing practical solutions to today’s toughest challenges. Ranked the No. 6 Most Innovative University in the United States by U.S. News & World Report, Purdue delivers world-changing research and out-of-this-world discovery. Committed to hands-on and online, real-world learning, Purdue offers a transformative education to all. Committed to affordability and accessibility, Purdue has frozen tuition and most fees at 2012-13 levels, enabling more students than ever to graduate debt-free. See how Purdue never stops in the persistent pursuit of the next giant leap at www.purdue.edu.

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Latex exposure could be detrimental to a horse’s respiratory health. That’s the surprising discovery from Morris Animal Foundation-funded research at the Royal Agricultural University and University of Nottingham. While further investigation is needed, researchers say latex could be among the allergens responsible for causing severe equine asthma (sEA), a serious horse ailment with limited treatment options. The team published their findings in the Nature journal Scientific Reports.

The finding came from a larger study that applied a new, more comprehensive microarray platform to determine the precise allergens within horses’ stable dust that elicit sEA. Researchers tested nearly 400 extracts and proteins associated with the equine environment on blood samples from 138 horses from Switzerland, France, the United States, and Canada.

The study revealed several previously suspected allergens, such as pollen, mold and insect proteins, are likely involved in sEA, but the most surprising finding was the implication that natural rubber latex allergies might also play a role in equine asthma. In fact, four of the five most significant allergens associated with sEA were latex proteins. The fifth was a protein from Aspergillus fumigatus, a common fungus previously linked with sEA. Until now, latex had not been tested due to limitations associated with classical allergen assessment methods.

“Research to date has generally implicated fungi and bacteria as the predominant allergens associated with sEA, so this was a little unexpected,” said the lead author on the paper, Samuel White, Ph.D., senior lecturer at Nottingham Trent University. “We would need to learn more about how these allergens affect actual predisposed horses, but avoidance of latex allergens may still be beneficial.”

Horses primarily come into contact with natural rubber latex on artificial riding surfaces, like arenas and racetracks. Urbanized environments, which also have higher levels of breathable latex from car tires, have been identified as a risk factor in sEA, as well.

The high level of breathable dust associated with equines training on artificial surfaces has already been linked with chronic bronchitis, inflammation and oxidative stress in riding instructors, and latex allergies have long been associated with a variety of respiratory conditions in humans, including asthma.

Severe equine asthma, which closely resembles human asthma, is a debilitating and chronic allergic respiratory condition. Diagnosed in all breeds, it affects 14% of horses in the northern hemisphere. When exposed to allergens, these horses can experience inflammation and constriction of the airways, as well as excessive mucus production. sEA also is known as heaves, recurrent airway obstruction (RAO) and chronic obstructive pulmonary disease (COPD).

“This new finding highlights the need to better understand the potential health effects of the environments we expose our horses to,” said Janet Patterson-Kane, BVSc, Ph.D., FRCVS, who is the Morris Animal Foundation’s chief scientific officer. “It’s crucial that we identify which allergens might cause them distress so we know what to avoid, as well as develop appropriate treatments.”

The team plans to conduct further research to establish exposure levels of latex in a horse’s daily environment and demonstrate the benefit of avoiding latex.

Morris Animal Foundation is funding other studies to address equine asthma. One is investigating if targeting a specific protein is a viable new therapeutic strategy to treat the condition. Another is examining differences in mast cell subtypes found in the airways of healthy and asthmatic horses to help identify better diagnostic and treatment strategies for equine asthma.

Morris Animal Foundation’s mission is to bridge science and resources to advance the health of animals. Founded by a veterinarian in 1948, it has funded and conducted critical health studies for the benefit of all animals. Learn more at www.morrisanimalfoundation.org.

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Learn more about the differences between terms used for respiratory disease in the horse, such as heaves, chronic obstructive pulmonary disorder (COPD), bronchiolitis, small airway disease, recurrent airway obstruction (RAO), inflammatory airway disease (IAD), and most recently, equine asthma.

For nearly as long as horses have been domesticated, the relationship between barn confinement and respiratory disease, such as equine asthma, in the horse has been recognized. This relationship is intuitive, especially when we consider that deep in the lung, where the blood takes up oxygen, the barrier between the outside air and the horse’s circulation is as thin as a couple of cells.

The surface area of this gas-exchange region of the lung has on average a surface area of 2,500 square meters (26,900 square feet), equal to nearly half a football field. The response of the lung’s immune system to inhaled air results in a number of diseases in both humans and horses. Many of the occupational respiratory diseases in humans are associated with agriculture due to exposure to organic dusts. Dust in agricultural settings, including the horse barn, are rich in substances such as endotoxin and fungi that can drive inflammation.

Depending on when the conversation took place, owners consulting their veterinarians about respiratory disease in their horse will have heard many terms applied to this problem: broken wind, heaves, chronic obstructive pulmonary disorder (COPD), bronchiolitis, small airway disease, recurrent airway obstruction (RAO), inflammatory airway disease (IAD), and most recently, equine asthma. Along the way, distinctions have been drawn between those horses that develop difficulty breathing at rest (heaves, RAO, severe equine asthma) and those that do not (IAD, mild equine asthma). While potentially leading to confusion for the horse owner, the changing terminology actually reflects improvements in veterinary knowledge.

While the term COPD was applied to reflect the obstruction or blocked airflow that can occur in severe cases, this term was discarded due to the differences with the human disease. In humans, COPD is mainly a consequence of cigarette smoke and is characterized by structural changes within the lung that are absent in the horse. While the terms recurrent airway obstruction and inflammatory airway disease are descriptively accurate, they are not necessarily terms that immediately help the horse owner to understand the disease process.

A More Relatable Term for Respiratory Disease

Due to its many similarities with the human disease, the term equine asthma has most recently been adopted. Like human asthma, equine asthma is triggered by inhalation of dust that contains allergens and other irritants, and like human asthma, the cough and difficulty breathing can be reversed in the short term by medications, often delivered by inhalers, or in the long term by removal from the offending dust. Also similar to asthma in humans, the response of the horse’s airway to inhaled dust can vary widely. In some highly susceptible horses, inhalation of even small amounts of dust in the barn environment or airborne allergens (e.g., pollen, molds) at pasture can cause severe inflammation and difficulty breathing due to the accumulation of mucus and narrowing of the airways. There is no known cure for these “severely asthmatic” horses, and they require special management for the duration of their life span.

In other horses, the inflammation is milder, with occasional coughing and decreased performance. Respiratory problems in these “mildly asthmatic” horses often become apparent only when the horse is asked to perform athletically and may resolve over time. Those horses with mild asthma do not necessarily go on to become severely asthmatic.

While susceptibility varies widely, any horse (or person) exposed to enough dust will develop inflammation in the airway. In the case of stabled horses, dust exposure is mostly due to hay. Those horses with severe asthma often require that hay be completely removed from the diet and that the horses be removed from confinement to the barn altogether.

In the milder cases, decreasing the dust released from hay by soaking or steaming may improve airway health. As soaking has a number of draw backs, high temperature steaming is becoming the preferred method to reduce exposure to the dust from hay. At Purdue University College of Veterinary Medicine, we use a Haygain hay steamer, which has been shown to reduce respirable dust by 98%.

Article provided by Haygain, manufacturers of Haygain Hay Steamers and ComfortStall Orthopedic Sealed Flooring. For more information, visit www.haygain.com.

Further Reading

• Breakthrough in Identifying Equine Asthma Allergens
• Waiting to Inhale
• Ask the Vet: Allergy Symptoms in Horses

The post Learn More About Respiratory Disease in the Horse for National Asthma and Allergy Awareness Month appeared first on Horse Illustrated Magazine.

An accurate diagnosis is the foundation for effective treatment of any equine health issue and especially so for allergic conditions that impact equine respiratory function, such as identifying equine asthma allergens. Haygain’s long-standing commitment to research has recently resulted in significant progress toward identifying which of various allergens trigger inflammatory responses and other allergy symptoms in the horse.

The study involved horses with severe equine asthma. As its name implies, this is the condition on the most severe end of the equine asthma spectrum, the umbrella term adopted by the veterinary community in 2016 to encompass the range of respiratory conditions. At the mild and moderate end of the spectrum is the much more common Inflammatory Airway Disease (IAD), known to affect over 80% of the active sport horse population. Horses with IAD are not necessarily more susceptible to contracting the more severe manifestations, but many do. Severe equine asthma is commonly referred to as Recurrent Airway Obstruction (RAO) or heaves. By any name, it’s a debilitating condition that affects 14% of horses in the Northern Hemisphere.

It’s common knowledge that allergens found in fungi, bacteria and arthropods (mites, etc.) cause this condition by triggering the body’s inflammatory responses.

Which Allergen or Allergens?

Samuel White, PhD candidate, MSc, BSc, and his co-researchers utilized the latest developments in computing power and robotic technology to produce a microarray, a microchip-based testing platform that enabled evaluation of almost 400 potential allergens at a single time. This was the largest scale allergen assessment in severe equine asthma in horses to date. The results established a wide range of previously unidentified allergens and highlighted fungi and mites as the main reactants.

This initial study established a sound platform for future diagnostics by providing a reliable, fast and repeatable method for screening of potential allergens. Crucially, it enables targeted allergen-avoidance regimes, which are the cornerstone to treatment.

Know Your Equine Asthma Allergens

White, the lead researcher, is an equine science faculty member at Nottingham Trent University in Nottingham, England. An applied immunologist, he specializes in equine asthma and allergies, focusing on the identification of biomarkers, protein allerginicity and the development of novel diagnostic techniques.

The study was accepted and published by The Journal of Veterinary Internal Medicine in July of 2019. “The last four years of my PhD have been both challenging and exciting in equal measures!” says White. “The funding provided by Haygain has enabled significant scientific advances in both the understanding and future diagnosis of severe equine asthma. It is very rewarding to see our initial development of this technique published in one of the highest-ranked veterinary journals globally. I look forward to publishing further aspects of this project in due course.”

White’s research supervisor, Professor Meriel Moore Colyer, is equally excited about the findings. “This research has produced a highly specific and accurate method by which to identify severe equine asthma allergens in horses and is definitely the way forward for better diagnosis and accurate treatment,” says Colyer. “The high number of allergens tested and the international aspect of the samples collection means that these results are applicable worldwide.

“Being able to identify what an individual horse is allergic to will help owners choose management regimes and employ the most effective pre-feeding treatments to minimize the horse-allergen interaction and reduce the negative impact of this performance-limiting condition.”

Collaboration is Critical

Haygain’s technical director Becky James explains the horse health company’s motivation for funding equine research in general and this study in particular: “Collaboration in research is important when pushing boundaries and using innovative techniques such as the microarrays,” says James. “It’s exciting that so many specialists from around the world were involved: a collective group from the UK, France, Switzerland and the U.S.”

Along with advancing management and treatment protocols for all horses with or at risk of severe equine asthma, the study results confirm earlier research that fungi are a major cause of equine respiratory problems. In addition to dust, mold and bacteria, high-temperature hay steaming greatly reduces fungi in hay.

“We are proud to have supported this research project to better understand which allergens cause Recurrent Airway Obstruction,” James notes. The broader context of the investigation is the reality that over 80% of active sporthorses suffer some degree of airway disease, often without obvious symptoms. “It’s important to support general understanding of all degrees of equine asthma,” James concludes. “It’s all part of our effort to prevent or successfully treat this all-too-common condition.”

For more information on Haygain, and its high-temperature hay steaming process and products, visit www.haygain.com.

Read the full study, “Development of a comprehensive protein microarray for immunoglobulin E profiling in horses with severe asthma.”

The post Breakthrough in Identifying Equine Asthma Allergens appeared first on Horse Illustrated Magazine.