Ovine nasal zygomycosis caused by Conidiobolus incongruus.

About 700 sheep died on 52 farms in north-western New South Wales and south-western Queensland over a 3 mo period. Affected animals had a marked asymmetrical swelling of the face, extending from the nostril to just anterior to the eyes. They lost condition rapidly and died within 7 to 10 days. At necropsy there was a unilateral severe necrogranulomatous rhinitis with extension of inflammation into the adjacent subcutaneous tissue, nasal septum and hard palate. Metastatic lesions were present in the draining lymph nodes and in the thorax. Histological changes consisted of a granulomatous reaction with numerous eosinophilic foci of necrosis and a diffuse, heavy, mixed inflammatory cell response. Many vessels had segmental necrosis and thrombosis. Fungal hyphae were numerous, particularly within or associated with necrotic foci. Conidiobolus incongruus was isolated from nasal tissues, parotid and submandibular lymph nodes and pulmonary lesions.