Recurrent Airway Obstruction


Recurrent airway obstruction (RAO) is a reversible inflammatory disease causing narrowing of the bronchioles and airways in the horse.

Often horses involved are genetically predisposed to general hypersensitivity reactions and are usually 7 years of age or older when their first incident of RAO occurs. Horses may have an episode of recurrent airway obstruction, but if managed correctly, can stay in remission without further problems much later on.

Causes for such an exaggerated immune reaction include dust and mould spores in hay and bedding, pollens or seasonal weather changes and forage mites in feed containers. Occasionally RAO cases are triggered after a previous respiratory virus or infection.

RAO cases range from the mild bout to the more serious and possibly life threatening reactions to specific allergens. Signs in mild cases in horses may show coughing, exercise intolerance and an increased respiratory rate at rest, while more severe cases can include fever, mucus nasal discharge, flared nostrils and audible wheezes. Chronic cases can develop a ‘heave line’ due to abdominal muscle enlargement and may also lose condition and bodyweight.

Treating RAO can be challenging. Most horses with mild cases respond well to treatment and as long as preventative measures are taken to stop recurrence, continue to do well with few or no problems later on. Larger hypersensitivity reactions can be more difficult to treat and require strict routine management to stop any later recurrence.

Medical treatment often involves a course of steroids, either short or long depending on severity, to suppress the immune reaction and the addition of a bronchodilator to increase airflow in the lungs. Systemic treatment is normally initiated first, but the use of an equine inhaler may be necessary. This ensures localised uptake of the medication into the lungs and reduces side affects from any long term oral steroid administration.

Environmental management is as important as initial medical treatment. Dust is a major cause of these reactions. Bedding in stables can be very dusty and could trigger an allergic reaction that could last for weeks. Minimising stabling time where possible or swapping bedding to dust extracted shavings, rubber matting or shredded paper, can reduce the chances of your horse having an RAO episode. Nearby stables, particular if in an American barn, should ideally be managed on a similar basis and there should be adequate ventilation at all times. Soaking hay can reduce the amount of dust present compared to dry hay, but does not remove fungal or mould spores. Often soaked hay is enough of a change to reduce dust content, but if not then Haylage may help to reduce the amount inhaled during feeding. Lightly damping feed concentrates and nuts can also benefit your horse’s exposure to allergens.

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