Idiopathic Eosinophilic Pneumonia with Associated Pulmonary Vasculitis in Horse: A Case Series

Various eosinophilic lesions and their association with diseases have been described in horses. Multisystemic Eosinophilic Epitheliotropic Disease (MEED) characterized by eosinophilic granulomas in various organs represent the most diffuse manifestation. In the present study, we describe the gross and microscopic lesions of idiopathic eosinophilic pneumonia with associated pulmonary vasculitis in 11 horses without systemic involvement. Lungs were enlarged, pale pink, poorly collapsed with white-reddish nodules, randomly distributed throughout the parenchyma. Histologically the lesions ranged from mild eosinophilic bronchointerstitial pneumonia to severe eosinophilic lobular bronchopneumonia associated with eosinophilic necrotizing vasculitis affecting small to medium-size vessels. There was no histologic evidence of parasites within the lesion of any of these horses. Eosinophilic pneumonia with vasculitis and without intralesional parasites have not been previously reported in horses. The current histologic findings are similar to pathologic lung findings observed in Churg-Strauss syndrome of man.