asthma | Horse Racing Free Tips

Heaves And Heart Failure: Is There A Connection?

A new study out of Canada shows that uncontrolled respiratory disease in horses may put them at risk for pulmonary artery changes that lead to heart failure.

People with severe asthma can have thickening of the pulmonary arteries, which leads to pulmonary hypertension. Severe equine asthma, like asthma in humans, presents as airway inflammation, coughing and labored breathing; therefore it's feasible that equine asthma can also lead to pulmonary artery thickening, reports EQUUS magazine.

Often called “heaves,” this condition is triggered by mold or dust in hay or the environment. The affected horse must be managed so exposure to these environmental triggers is minimized. Best management practices for horses with heaves include as much turnout as possible, removing horses from stalls when they are cleaned and rebedded, and soaking hay.

Dr. Serena Ceriotti and other researchers at the University of Montreal looked at multiple post-mortem lung samples from 18 horses — six that were in heaves episodes when they died; six with heaves that was in remission because of management practices; and six with no history of heaves.

The scientists measured arterial thickness and found that the horses experiencing active heaves episodes had thicker arteries than the other horses.

Though it's unclear why the arteries thicken, experiments in rodents suggest the low oxygen content and inflammation may increase smooth muscle in the arterial wall. This increase in the muscle decreases the area for blood to flow and may increase muscle contractions, which leads to pulmonary hypertension, minimizing blood flow and limiting cardiac function. This condition can eventually lead to the enlargement and failure of the right ventricle of the heart.

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A second portion of the study tested two potential pulmonary hypertension treatments on live horses. One involved reducing the horse's exposure to dust for an entire year and on using hay alternatives. The second used the medication fluticasone for six months then added in dust-control strategies for an additional six months.

The researchers found that both treatments lead to a reversal in artery wall thickness, but this could only be seen once the dust control measurements were enacted. The team notes that hay is the main trigger for heaves; often just changing the horse's diet to include a forage alternative is enough to control the disease.

They conclude that arterial wall remodeling is reversible, but only with strict dust control measures. Inhaled corticosteroids can rapidly improve a horse in experiencing a heaves flareup, but an improved environment is the only way to manage the condition long term.

Peat Moss Or Wood Shavings: Bedding For Asthmatic Horses

The natural dust and molds found in bedding material often intensify the clinical signs of horses with asthma. Bedding materials differ in the inhalable and respirable particles they release, just as they have variable absorptive qualities and aesthetic appeal. While horsemen the world over use straw and wood shavings extensively, the popularity of peat moss often coincides with where it is easily obtained, such as in Nordic and Baltic countries. Finnish researchers recently investigated if the use of wood shavings and peat moss as bedding had different effects on the respiratory health of horses.

Researchers chose 32 clinically healthy riding-school horses for this study. The daily schedule of the horses included 18 hours in a stall, 2 to 3 hours of exercise in an indoor arena, and 3 to 4 hours outside in sandy paddocks. Horses were stabled in identically sized stalls with a common airspace and with the same level of ventilation. Researchers maintained bedding at a depth of approximately 4 inches, with new bedding added each day after stall cleaning to keep the depth consistent. Horses stayed on each bedding material for 35 days. Diets consisted of haylage and pelleted concentrate. Horses ate the haylage off the stall floor. Researchers performed lower airway endoscopy and sampling (tracheal wash and bronchoalveolar lavage fluid) for cytological examination at the end of each bedding period.

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While researchers found no differences in respiratory rate or tracheal mucus accumulation between treatments, horses bedded on wood shavings had more neutrophils in their tracheal washes and bronchoalveolar lavage fluid. The researchers concluded that “between the two bedding materials used in this study, peat caused less neutrophilic lower airway inflammation in horses.”

Asthmatic horses should be kept outside as much as possible, a management strategy that keeps many horses from having severe symptoms of asthma. High-performance horses must often be stabled to accommodate training and competition schedules. In these instances, medical management of asthma should be guided by a veterinarian well versed in the respiratory care of horses. Management decisions are often based on reducing inhalable dust and molds, which includes careful selection of bedding and forages.

Aside from forage type (haylage versus dry hay) or treatment (soaking versus high-temperature steaming), another nutritional consideration is the use of long-chain omega-3 fatty acids, particularly docosahexaenoic acid (DHA). In a consensus statement from the American College of Veterinary Internal Medicine, experts recommend the use of omega-3 fatty acids as a way to control airway inflammation.^° The most potent sources of omega-3 fatty acids available for horses are marine-derived oils, such as EO-3.

^*Monki, J., M. Sasstamoinen, N. Karikoski, M. Rajamaki, M. Roaekallio, J. Junnila, S. Sarkjarvi, M. Norring, A. Valros, S. Oranen Ben Fatma, and A. Mykkanen. 2021. Effects of bedding material on equine lower airway inflammation: A crossover study comparing peat and wood shavings. Frontiers in Veterinary Science 8:656814.

Owner Diligence Key To Equine Asthma Management, But Many Won’t Implement Management Changes

Scientists in Portugal have discovered that many horses suffering from equine asthma aren't given a fair shake at disease management for one reason: their owners are reluctant to follow vet advice to reduce the horse's exposure to environmental irritants, reports EQUUS magazine.

Dr. Joana Simões and a team of scientists examined 39 horses that were diagnosed with severe equine asthma (SEA), also known as heaves. Heaves is triggered by environmental factors like dust and mold, and is characterized by coughing, labored breathing, and airway inflammation. Reduction of exposure to triggers normally allows the symptoms to subside.

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The horses' owners were given a questionnaire asking how the horse was housed and fed, and what respiratory issues he showed. A veterinarian then offered six management recommendations, which included things like soaking hay before feeding and turning horses out as much as possible. Each strategy was directly correlated with equine asthma improvement.

One year later, the researchers contacted the horse owners again to see if they had followed through on the veterinary recommendations. They discovered that only three of the 38 owners had implemented all six recommended strategies for keeping their horse healthy, and only six owners were utilizing five of the recommended measures. About half of the owners had adopted one or two control strategies. Horses that did not have management changes remained symptomatic and required medical treatment.

Simões notes that it may be difficult to implement every suggested control strategy, like increased barn ventilation, but some of the strategies required only that a horse owner change their daily routine. Some horse owners responded that implementing things like soaking the affected horse's hay was too time consuming or that they could not get the horse's caretaker to comply.

The scientists believe that some lack of compliance may be because the disease can only be managed and not cured – there is no quick fix or pill to solve severe equine asthma. The research team suggests that horse owners may be more inclined to better manage the condition if they understood the disease and its progression more completely.

Horses, Humans Have Similar Reactions To Allergic Dermatitis

The intense itchiness caused by allergic dermatitis can make horses scratch to the point where they harm themselves, breaking the skin as they scratch in an attempt to relieve the itching. This inflammatory disease often affects a horse's ears, face, and other hair-free areas, and it can be caused by insect or environmental allergies. Humans also experience atopic dermatitis, often called eczema.

Dr. Rosanna Marsella reviewed literature on the current understanding of atopic dermatitis in dogs, cats, horses, and people to try to improve understanding of the disease and develop new treatments. In people and horses, allergy-related disease often first shows itself as dermatitis, but respiratory disease can occur later. Some atopic horses develop heaves and some affected humans can develop food allergies, rhinitis and asthma.

Atopic dermatitis is often diagnosed by analyzing the patient's history and clinical signs, though serology testing can be done to create a definitive diagnosis. Affected horses are often given glucocorticoids and antihistamines, but controlling triggers for itchiness is crucial to the success of therapy, Marsella says.

Allergen specific immunotherapy is recommended for horses that suffer from the disease and has a success rate of between 64 and 84 percent. Most improvement is seen after the first year of treatment. Some horses require other medical interventions while receiving immunotherapy, but the amounts of these medications may decrease the longer immunotherapy is administered. Interleukin-31, which causes intense itchiness, may be a target for therapy.

Though understanding of atopic dermatitis is limited, affected horses seem to suffer similarly to humans affected by the disease. Treatment has evolved from suppressing the immune system to a more holistic restoration of the immune system, often through allergen-specific immunotherapy.

Read the review here.