We’ve all been there. It’s a spring day of good weather, perfect for a ride. As you amble to the barn to saddle up, you hear coughing. Turning the corner, you see the coughing culprit is your horse.

In another barn, a rider grabs the grooming kit to brush her horse in preparation for the saddle. As she runs her hand over his neck, she feels, and then sees, numerous bumps, some of which have merged to form large bumps.

What is going on with these horses? Allergies.

A Teeming World of Horse Allergies

Unseen by the naked eye, the world is abundant in proteins and substances that can incite an allergic response. These allergens may be inhaled, ingested, or may affect a horse through topical contact. You’ll be tipped off to signs of trouble when you notice your horse has itching, hives, or breathing problems.

Allergies are common throughout the human and animal world, and horses are no exception. Usually, horses manage in their environment just fine without developing obvious signs that microscopic compounds are affecting them. Horse allergies happen when a horse’s immune system overreacts to a foreign protein, goes on the offense and becomes over-sensitized.

Sometimes it takes months or years of accumulated exposure for a horse to become hypersensitive; sometimes the response is more immediate and acute. Whatever specific protein causes the reaction, it sets up a cascade of inflammatory events that release prostaglandins and histamines to create obvious skin or respiratory allergic signs.

Skin Allergies in Horses

Horse allergies that manifest in the skin may result from topical contact, but also may develop from oral ingestion or inhaled particles. Aerosolized dust, mold, pollen, bedding, and insect bites are just a few of the sources that can cause itching and/or hives.

A major cause of itching starts with the bite of insects called Culicoides, also known as midges or no-see-ums. While the midges tend to feed on the abdomen, a horse displays an allergic response to the midge saliva by aggressively rubbing his tail, hindquarters, neck and mane due to intense itching. Those areas become raw, crusty, and inflamed, with substantial hair loss.

Some breeds and lines of horses tend to be particularly allergic to midges, such as Morgans, Icelandics and Arabians. The solution relies on moving the horse away from areas favorable to midge breeding, like ponds, wetlands and slow-moving streams.

Fly sheets are important, but they should have belly bands of netting material. Bringing a horse inside at dusk and dawn also helps to reduce midge exposure, as that is their preferred feeding time.

In contrast to an itching reaction (pruritus), hives aren’t typically itchy but herald a definite sign of exposure to some kind of allergen. Hives tend to be soft swellings that indent when you push in with your finger, called pitting edema.

They may be variable in size, sometimes coalescing into one big welt when several are close together. Inhaled allergens also can cause hives, referred to as atopic dermatitis.
Contact dermatitis is also not unusual. One example that occurs fairly commonly is hives from contact with pine bedding. If there is a suspicion that bedding is a problem, substitute paper bedding or a different source of pine bedding to see if the hives resolve.

Some shampoos or fly sprays can cause skin irritation and hives, as can laundry detergent residue or dirt on a saddle pad. On rare occasions, a horse with a fungal infection called ringworm may develop hive-like reactions around a fungal lesion.

Hives can develop acutely and disappear just as quickly. Sometimes they persist long after the allergen is removed from the environment. In difficult cases, it may be necessary to medicate the horse with a short course of a corticosteroid like dexamethasone or prednisolone, which are effective anti-inflammatory medications.

Certain feedstuffs can set off a skin reaction, although food allergies are not that common. If it is a food allergy, however, it’s often a challenge to determine the exact food or oral substance that is the culprit.

This may need to be done through a process of elimination: eliminate all food and supplements and start by feeding only grass hay, although diet changes may need to be done slowly. Check with your vet. After a couple of weeks with no signs of hive lesions, add in one more food element and wait a week or two before adding in another. This may help pinpoint the cause.

Supplements tend to be the likeliest culprit, far more than hay or feed materials, although alfalfa has been known to cause allergic reactions.

Respiratory Allergies in Horses

Respiratory allergies can affect horse performance by impacting breathing and comfort, especially during exercise. A horse with a respiratory allergy often has a dry cough or wheezing that amplifies when he is eating or exercising. There may be a chronic or intermittent nasal discharge, as well.

Respiratory health is at risk when horses are placed inside barns, especially those with poor ventilation, and/or are exercised in indoor arenas. Many toxic compounds are aerosolized to circulate in the air in those environments: endotoxin (part of the cell wall of Gram-negative bacteria) in manure, ammonia vapor from urine-soaked bedding, mold spores from hay, or hay dust filtering down when stored in lofts above the stalls or arena. Arena footing can also contribute to respiratory irritation.

The best solution is to minimize a horse’s time indoors and instead turn him out as much as possible. Better yet, arrange full-time outdoor living with run-in sheds to protect against inclement weather. Soaking or steaming hay before feeding helps tamp down dust and mold.

If barn living is all you have available, then implementing good ventilation is very important. Use appropriately placed fans, open windows, and open barn doors to keep fresh air circulating. Store hay in a building separate from horse housing.

Another important strategy for respiratory health is to keep your horse on a regular immunization schedule, especially against respiratory viruses. Equine influenza virus is known for causing long-term respiratory damage, including development of equine asthma. Discuss an appropriate vaccine schedule with your veterinarian.

Once a horse develops equine asthma, a variety of medications, including inhaled and/or oral bronchodilators, can help improve his comfort and ease of breathing. It is much easier and more effective to apply an ounce of preventive strategies for respiratory health than a pound of cure to treat after the fact.

Equine Anaphylaxis

In an instance where a horse’s immune system develops a profound and severe reaction, a horse can experience life-threatening anaphylaxis. With that in mind, it’s important to contact your vet immediately when seeing signs of an allergic response, particularly if your horse is having difficulty breathing and/or there is swelling of his face and muzzle or limbs and belly.

If your horse has a known allergy to a medication, such as penicillin or a non-steroidal anti-inflammatory drug (NSAID) like phenylbutazone or flunixin meglumine, it’s critical to place caution signs on the horse’s stall door and paddock to prevent accidental administration of potentially deadly drugs.

People with allergies wear neck tags or bracelets to convey this critical information, but for horses, it’s necessary to post signs in obvious places. Advise your barn manager and staff, friends and veterinarians who may deal with your horse.

Allergies can be troublesome to resolve, so observe and monitor every facet of your horse’s environment. With knowledge about potential problems, you can deter allergic problems before they begin.

The post Horse Allergies: Symptoms, Treatment, and Prevention appeared first on Horse Illustrated Magazine.

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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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.”

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