Idiopathic chronic eosinophilic pneumonia in 7 horses

Idiopathic chronic eosinophilic pneumonia of horses is incompletely described.

To describe the physical examination, clinicopathologic, histopathologic, and radiographic features and response to corticosteroid treatment of idiopathic chronic eosinophilic pneumonia of horses.

Seven horses with eosinophilic pneumonia.

Retrospective, descriptive study.

Anamnesis, clinical signs, and clinicopathologic and radiologic findings in 7 adult horses with histologically confirmed eosinophilic pneumonia were reviewed. The horses were examined for signs of chronic respiratory disease. The horses ranged in age from 8 to 20 years. Significant findings on physical examination included tachypnea and abnormal respiratory sounds. Thoracic radiography revealed severe diffuse interstitial patterns of increased pulmonary density in all horses. There was a predominance of eosinophils in bronchoalveolar lavage fluid (BALF), and 6 of 7 horses had peripheral blood eosinophilia. Lung biopsies revealed eosinophilic infiltrates in all horses. Dexamethasone was administered to 3 horses and resulted in short-term clinical improvement in all three.

A diagnosis of idiopathic eosinophilic pneumonia should be considered in horses with a history of chronic pulmonary disease, diffuse interstitial pattern of increased pulmonary density on thoracic radiographs, and a predominance of eosinophils in BALF. Horses with this condition may show a temporary response to treatment with dexamethasone.