Updated: Jan 25
Chronic obstructive pulmonary disease is the most common cause. Pulmonary hypersensitivity to inhales allergens, such as Aspergillus fumigatus, may cause a chronic cough in horses. Marked neutrophilia in tracheal aspirates or bronchoalveolar lavage fluid suggests chronic obstructive pulmonary disease ( COPD ). Intradermal antigen testing is not useful in the diagnosis of COPD. Clinical features of 50 cases of COPD included nasal discharge ( 50% percent of cases ), expiratory effort ( 23% ), and abnormal respiratory sounds on auscultation ( 48% ). Elimination of casual mold allergens can result in permanent remission of COPD. This may be achieved by keeping affected horses on pasture.
Summer pasture-associated obstructed pulmonary disease is similar to COPD, but it affects pastured horses. The diagnosis is based on the history and finding of neutrophilia in the tracheal mucus. Chronic cough may result from a viral infection, because of airway epithelial damage or hypersensitivity. Lungworm infection is an uncommon cause of chronic cough and is usually seen in horses pastured with donkeys. The diagnosis is based on finding eosinophilia in tracheal mucus and response to anthelmintic therapy. Pulmonary abscessation and severe pneumonia may cause chronic cough, dyspnea, thoracic pain, lymphadenopathy, and purulent nasal discharge. Other causes of chronic cough are exercise-induced pulmonary hemorrhage, tracheal collapse, thoracic neoplasia, foreign bodies, eosinophilic interstitial pneumonia, and pulmonary infarction.