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What is it?
In stabled horses, the primary culprits for respiratory airway obstruction (RAO) are dust, pollens, moulds, and endotoxins found in hay and straw. Horses that spend time in fields and develop the summer pasture-associated form appear to be more sensitive to field pollens. Prolonged exposure to these triggers is responsible for the chronic nature of the disease.
Cause
Typically, the disease is initiated by the inhalation of allergens. In stabled horses, the primary culprits are dust, pollens, moulds, and endotoxins present in hay and straw. Horses residing in fields and developing the summer pasture-associated form seem more susceptible to field pollens. It's this prolonged exposure to these triggers that leads to the chronicity of the disease.
Consequences
RAO is characterised by inflammation in the lower respiratory airways. The condition involves an increase in inflammatory cells and mucus production, which can result in chronic structural changes in the lungs, such as airway thickening. Furthermore, airway constriction occurs as a consequence of inflammation, limiting the flow of air and preventing normal breathing in horses.
Symptoms
Common symptoms include:
- A cough, often accompanied by mucus production.
- Occasional nasal discharge.
- Dilated nostrils, an increase in breathing effort and rate.
- Exercise intolerance, especially during faster gaits.
These symptoms are usually more pronounced when the horse engages in mild to moderate physical activity, and they typically do not accompany a fever.
Tests
Routine examinations
Your veterinarian will begin with a thorough clinical examination of your horse, assessing vital parameters, general appearance, and demeanour. They will then evaluate the horse's respiratory system, checking for any nasal discharge and monitoring the effort and rate of breathing. Listening to the horse's lungs helps identify abnormal sounds. Don't be concerned if your veterinarian uses a bag on your horse's nostrils; this technique allows them to assess your horse's response to increased breathing effort and to detect any abnormal sounds more clearly.
Complementary examinations
To confirm the diagnosis, your vet may perform additional diagnostic tests, such as:
- Endoscopy to examine the respiratory tract.
- Bronchoalveolar lavage to retrieve cells from the bronchi and lungs.
- Less frequently, venous and arterial oxygen and CO2 measurements and other functional tests to assess lung ventilation.
Treatments
Basic principles to follow
To prevent an RAO episode, it's crucial to minimise the inhalation of environmental allergens. Horses that are allergic to field pollens and live outside may need to be stabled or have limited access to the field during allergy seasons. If overwintering your horse indoors is not feasible, measures must be taken to reduce dust and mould in the stable. Here are some examples:
- Select high-quality hay.
- Dampen dusty hay for at least 30 minutes before feeding it.
- Use a hay net.
- Regularly remove dust from the stable, including the ceiling. Ensure you do this when the horse is not inside.
- Opt for a dust-free type of bedding.
Treatment principles
If the symptoms are severe, your veterinarian may prescribe medications and management techniques. These may include anti-inflammatories and bronchodilators. In cases of severe distress, these products can be administered intravenously and followed up with oral or inhaled forms over an extended period.
In parallel or for prevention, it is possible to provide nutritional support with ingredients that meet the increased demands on the respiratory system. There are products specifically designed for horses in dusty or pollen-rich environments that contain suitable plant-based components. An example is nigella, also known as 'black cumin,' which has proven efficacy.
For further veterinary advice, please consult your vet.
