A case of pythiosis in a donkey

Abstract

A case of crater-shaped granulomatous ulcer was observed in skin covering knee joint of right forelimb in 8 years old male donkey referred to Mansoura veterinary teaching hospital. Clinical examination of the lesion showed necrotic tissue with tumor appearance, abundant fibrinous-bloody exudation and yellowish-white caseous material (kunkers). Mycological isolation revealed white to off-white colonies at 37°C but not at 25°C. The colonies did not present aerial mycelium, and the mycelial growth penetrated the medium in all cultures. Histopathologically, the lesion with the hematoxylin-eosin (H&E) stain showed severe pyogranulomatous dermatitis, with abundant eosinophilic and neutrophilic inflammatory infiltrate and poorly stained thin septated hyphae. Immunohistochemistry showed positively stained hyphae inside the lesion using rabbit polyclonal antibody. The definitive diagnosis of the disease was based on the clinical features, mycological isolation, histopathological findings and immunohistochemical staining. This report described a case of pythiosis in a donkey.