What are Allergic Bronchitis?
As horses suffering from this condition often struggle to effectively exhale and empty the lungs, over-inflation may occur, leading to emphysema. Without proper treatment and management this condition can lead to damage to the lung tissue and non-reversible reduced lung function.
Allergic bronchitis in horses, also known as heaves or recurrent airway obstruction, is a chronic, non-infectious airway condition that is caused following exposure to allergens such as pollen, dust or fungal spores. Common causes of exposure are hay and straw. This condition causes the airways to become obstructed, leading to difficulty breathing. This increased respiratory effort may lead to the development of a heave line due to enlargement of the abdominal muscles.
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Symptoms of Allergic Bronchitis in Horses
Often owners may first notice an occasional cough which often progresses to a frequent, deep cough. Other symptoms may include:
- Laboured breathing with dilated nostrils
- Excessive clear or white discharge from the nasal passages
The severity of clinical signs may vary. Often the horse may suffer from exercise intolerance while in more severe cases, the horse may suffer from dyspnea at rest.
Causes of Allergic Bronchitis in Horses
This is a non-infectious condition that is caused by an allergic reaction to inhaled allergens such as molds. The exposure to this allergen leads to the small airways of the lung tissue to become obstructed due bronchoconstriction. This is caused by the inflammation of the tissue lining these airways and the constriction of the smooth muscle surrounding them. The most common causes of allergies in horses are from reaction to hay and bedding.
Diagnosis of Allergic Bronchitis in Horses
Your veterinarian will first observe your horse from a distance to check for abnormalities that may not be visible while restrained, they will note your horse’s respiratory rate and watch the character of the respiration. As horses suffering from this condition often need to work harder to expel air due to the narrowed airways they may notice your horse appearing to heave in order to exhale air. Your veterinarian will then examine all the major organs and auscultate the lungs, heart and digestive system. If your horse is suffering from a severe case of allergic bronchitis, your veterinarian may make a diagnostic based on the symptoms alone. Further diagnostic tests may be deemed necessary; these tests may include:
- Collection of fluid sample via bronchoalveolar lavage to examine inflammatory cells
- Hematology to rule out diseases such as pneumonia, pleuritis, and cancers of the thorax
Treatment of Allergic Bronchitis in Horses
Your horse many require medical treatment. To support the recovery it is vital to make environmental changes to prevent relapse. Your veterinarian may prescribe anti-inflammatory medication such as corticosteroids and bronchodilators, these can be given orally, by injection or through aerosolized drug preparations. Aerosolized drug preparations have shown to be more effective than other forms of administration with reduced risk of adverse reactions.
Bronchodilators reduce inflammation, clear mucus and relieve the muscles in the airways, which may allow your horse to breath easier. Corticosteroids reduce or prevent the body from releasing inflammatory chemicals, therefore reducing inflammation.
Supportive care should include offering highly palatable food to prevent weight loss and provide energy for healing, and ensuring adequate hydration. Fresh fruit and vegetables should be offered to support the immune system. Provide your horse with a warm, dry environment to recover in. Ensuring the environment is at a good temperature will reduce the need for the respiratory system to provide thermoregulation, allowing the body to rest and recover.
Recovery of Allergic Bronchitis in Horses
Your horse’s long term recovery will depend on the management of his environment. While there is no cure for this condition, good environmental management can lead to full recovery.
Ideally your horse should be kept outdoors with access to fresh air and away from dust roads. However, if this is not possible the stable should be adequately managed to provide your horse with clean, dust free air.
- Ensure your horse’s environment has good ventilation, in some cases ceiling fans with particle filters to circulate the air may be beneficial
- As hay, grain and bedding may cause mold spores and particles to be released into the area, store away from your horse’s environment
- Provide your horse with rubber matting or shaved paper for bedding rather than straw or wood shavings to reduce inhalants
- Feed your horse a dust-free diet
- As poor quality hay can often be damp, causing mold, ensure only good-quality high with low moisture content is provided; good quality high should be sweet smelling, free of mold and dust, cut before maturity and green in colour
- Ensure excellent hygiene is maintained
- Muck stalls out daily to prevent ammonia or other air pollutant build up