PD is a respiratory problem caused by allergens and effects health and performance in many horses.
Chronic obstructive pulmonary disease (COPD), also known as “heaves” or recurrent airway obstruction (RAO), occurs in horses that are allergic to environmental dust allergens. The allergic reaction causes inflammation and narrowing of the airways creating breathing difficulties.
Affected horses have allergic reactions to environmental allergens such as fungal spores (from Microsporum faenii or Aspergillus fumigatus) or pollen. These fungal spores are associated with dusty environments and bedding, or mouldy hay and straw. This is why; COPD is more common in stabled horses where dust and fungal spores is prevalent.
Upon inhalation of the allergen, an affect horse develops an allergic reaction in the small airways. This allergic reaction, increases mucus production with inflammatory cells and, constricts the airways via bronchospasm. These combine to reduce the airway diameter making it harder to breathe. The airways can even completely collapse during expiration, making breathing out particularly difficult.
COPD typically affects older, stabled horses however, it can occur at any age and even in horses at pasture. It is associated with dusty environments and feeding mouldy hay. As it takes time for an allergy to develop, COPD is usually gradual in onset. The initial signs however, are mild and can be inapparent. As the allergy becomes established continued exposure to the allergen leads to more attacks of greater severity. Once an allergy has developed, it remains for life.
Signs of COPD:
- Forcefully breathing or double expiration
- “Heave” line
- Chronic cough
- Reduced exercise tolerance/performance
- Increased mucus
- Increased respiratory rate
The clinical signs of COPD are non-specific and can also occur due to respiratory infections. A veterinary surgeon can diagnose COPD from the clinical history, clinical signs associated with the illness and examination of the horse. Further testing, such as endoscopic examination of the airways of bronchoalveolar lavage (BAL) may be necessary in some cases.
Once established, COPD is a lifelong condition. The most successful solution to COPD is to eliminate the cause by turning affected horses out to pasture full time
Where this is not possible mould and dust must be removed from the horse’s stable environment
- Dust free bedding material
- Mould free forage
- Soak hay, by immersing it in water for one hour
Your veterinary surgeon may prescribe bronchodilators to aid in acute attacks of the condition or corticosteroids to help reduce inflammation in long term cases. Delivery of either of these drugs by nebuliser is also possible. Bronchodilators and corticosteroids however, are not suitable for use in competition horses.
Nutritional supplements designed to loosen mucus, open up airways and help with coughing can help alleviate some symptoms.
As COPD is an allergic reaction, supplements which balance and aid the immune system and act as natural anti-inflammatories can also be of benefit.