Q: How is asthma diagnosed in horses, and what is the treatment?

A: Clinical signs of asthma occur when a genetically susceptible horse inhales an allergen to which they’re allergic. This results in airway spasm and the production of inflammatory cells and mucus within the airway. Dust in forage or the stable environment is frequently implicated as the allergen, but some horses develop asthma associated with pollens from summer pasture.

Affected horses can show increased breathing rate and effort, coughing, and decreased exercise tolerance. White or cream mucus may be seen in the nostrils, and abnormal chest sounds, like wheezing, might be heard through a stethoscope. If clinical signs are only seen during exercise, the vet may ask you to ride or lunge your horse during the examination.

Asthma is often diagnosed based on historical findings as well as a positive response to treatment.

Blood or swabs may also be taken, but full confirmation is based on the laboratory analysis of samples of airway fluid, usually taken following an endoscopic examination of the airway.

Treatment of asthma is centred on relieving airway spasm and inflammation using drug therapy, usually via either an oral or inhaled route. Management changes will also be recommended, such as improving ventilation in the stable, steaming or soaking hay to reduce dust exposure and potentially changing bedding if this is a contributing factor.