Idiopathic chronic eosinophilic pneumonia in 7 horses.
Authors: Bell S A, Drew C P, Wilson W D, Pusterla N
Journal: Journal of veterinary internal medicine
Summary
# Idiopathic chronic eosinophilic pneumonia in horses: recognising an uncommon but treatable condition Idiopathic chronic eosinophilic pneumonia remains poorly characterised in equine medicine, yet presents as a significant differential diagnosis for horses with persistent respiratory disease unresponsive to conventional management. Bell and colleagues conducted a retrospective analysis of seven adult horses (aged 8–20 years) with histologically confirmed eosinophilic pneumonia, documenting clinical signs, laboratory findings, imaging, and treatment responses to establish diagnostic criteria. All affected horses exhibited tachypnoea and abnormal lung sounds on physical examination, whilst thoracic radiography consistently revealed severe diffuse interstitial patterns of increased pulmonary density; bronchoalveolar lavage fluid analysis showed eosinophil predominance in all cases, with peripheral blood eosinophilia present in six of the seven horses, and lung biopsy confirming eosinophilic infiltration throughout. Dexamethasone administration in three horses produced short-term clinical improvement, suggesting potential therapeutic benefit, though the temporary nature of response warrants consideration of alternative or adjunctive management strategies. Practitioners should maintain a high index of suspicion for eosinophilic pneumonia in older horses presenting with chronic respiratory disease, particularly where imaging demonstrates diffuse interstitial changes and bronchoalveolar lavage identifies eosinophil predominance—two findings together that may prompt lung biopsy and consideration of corticosteroid therapy.
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Practical Takeaways
- •Suspect idiopathic eosinophilic pneumonia in adult horses (8-20 years) presenting with chronic respiratory disease, tachypnea, and diffuse interstitial lung patterns on radiographs
- •Bronchoalveolar lavage fluid analysis showing eosinophil predominance is a key diagnostic indicator; lung biopsy confirms diagnosis histologically
- •Corticosteroid therapy (dexamethasone) may provide temporary clinical relief but long-term efficacy is unclear based on this limited data
Key Findings
- •All 7 horses presented with tachypnea and abnormal respiratory sounds on physical examination
- •Thoracic radiography revealed severe diffuse interstitial patterns of increased pulmonary density in all horses
- •Six of 7 horses had peripheral blood eosinophilia with predominance of eosinophils in bronchoalveolar lavage fluid
- •Dexamethasone administration resulted in short-term clinical improvement in all 3 treated horses