What is Asthma?
The inflammatory airway disease, equine asthma, has had quite a few names over the years. Once called heaves (due to the heaving of the chest and abdominal muscles associated with labored breathing), the condition has also been called broken wind, COPD (chronic obstructive pulmonary disease), SPAOPD (summer pasture associated obstructive pulmonary disorder) and RAO (recurrent airway obstruction). Just like human asthma, equine asthma manifests as difficulty breathing due to an inflamed, obstructed airway, excessive mucus secretion and bronchial muscle contraction (bronchospasm). It is a non-infectious, incurable lung disease typified by wheezing, breathlessness, chronic coughing and nasal discharge.
Due to acute risk, as well as the long-term impact on respiratory and overall health, the horse must receive treatment upon earliest observation of such symptoms. Long-term management of equine asthma is necessary, and outcome will also depend upon the complexity and severity of each case. Air hygiene is mandatory to reduce clinical signs. If treatment is not given, airway obstruction will worsen and breathing will become progressively difficult. Irreversible damage may be done to the lungs.
Equine asthma is a complicated respiratory disease that involves several factors. Factors include genetic predisposition, respiratory tract infections, ineffective lung clearance, seasonal allergies, environmental conditions and exposure to aggravating, breathable particles such as fungal spores in hay, particles of bedding, skin flakes from grooming, mold spores and pollens. The disease is reported most commonly in southeastern regions of the United States, especially Florida, Georgia, Louisiana and Mississippi, although it has been described in other parts of the world such as England and Scotland. Affected horses are commonly over six years of age, and kept in pasture for more than 12 hours a day. There is some breed disposition documented, but thus far not proven. However, cases among Arabians, Appaloosa and Paint horses were over-represented in one major survey.
An inflammatory airway disease, equine asthma manifests as difficulty breathing, excessive mucus secretion, and bronchial muscle contraction.
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Symptoms of Asthma in Horses
- Exercise resistance and intolerance
- Weight loss
- Forced respiration
- Runny nose
- Flared nostrils
- Heave line (abnormal abdominal muscle development caused by coughing and labored breathing)
The first type of equine asthma, barn heaves (or chronic obstructive pulmonary disease (COPD), occurs in the stable. Allergens include dust, mold, and mildew. Sources include the hay flakes used for food, bedding, skin flakes from grooming, and dust and dirt on the floors, walls, and ceilings. Barn heaves are more common in colder climates during the winter when horses are more likely to be kept indoors all day.
The second type of equine asthma, summer heaves (summer pasture-associated obstructive pulmonary disease (SPAOPD), occurs outdoors where horses spend most of their time. In SPAOPD, the horse develops a response to the pollen released by the trees and grasses growing in the pasture. Summer heaves are most common in warmer climates during summer months when pollen counts are high and horses are usually outdoors.
Causes of Asthma in Horses
- Inhalation of environmental pollutants
- Mold spores and pollen
- Exposure to dust from hay, grain, straw, bedding
- Respiratory-tract infections
- Food allergies
- Confinement to enclosed barns
- Breed-linkage possible
- Long hours of trailering
- Close quarters at competitions
- Stress and anxiety
- Weather extremes
Diagnosis of Asthma in Horses
Various methods are used to diagnose equine asthma. Your horse will undergo a physical examination, with observations made before, during and after exercise, and before and after a rebreathing bag is placed over the nostrils. Blood testing will rule out other respiratory problems like infections. Other diagnostics may include:
- Bronchoalveolar lavage (BAL)
- Blood gas measurement
- Chest x-rays
- Lung biopsy
- Lung function tests
Treatment of Asthma in Horses
Successful treatment of your horse depends on the identification of the cause and severity of asthma. Once investigated and determined, allergens and other triggering agents must be minimized, or removed from the equine’s environment.
Allopathic therapy is known to be an effective treatment. This is administered to equines through the use of corticosteroids, bronchodilators and mucolytics, sometimes accompanied by antibiotics to combat secondary infections. Inhalers equipped with special masks fit over the nose of the horse and enable open airways and normal breathing.
Recovery of Asthma in Horses
Allergens must be continually managed and reduced. Keeping the stable and barn areas clean and free of excessive dust and other pollutants is key to treating equine asthma. Changing bedding from hay to paper which has been shredded or quality wood shavings has been known to reduce the amount of mold spores in the stable. Large animal and equine veterinarians recommend soaking hay flakes or switching to feeds that come in pellet form to cut down on mold, fungal spores and dust.