Rhinofacial pythiosis with basilar empyema in a lamb

A 2-month-old male suckling lamb presented with spontaneous early weaning, hyporexia, weight loss, swelling of the nostrils and upper lip, fever, lethargy, recumbency and death. Necropsy revealed enlargement and deformity of the nasal region, ulceration of the upper lip, a rostral oronasal fistula and extensive ulceration of the hard palate. Mid-sagittal sectioning of the head showed a necrotic, yellow-black, irregularly shaped, friable mass extending through the mucocutaneous region of the nostrils, hard palate and nasal septum. Additionally, yellow purulent exudate was observed in the sella turcica at the basisphenoid bone, from which Klebsiella sp was isolated. Histological examination demonstrated marked multifocal pyogranulomatous rhinitis associated with negatively stained hyphal profiles. The hyphae stained with Grocott's methenamine silver stain and immunolabelled with anti-Pythium insidiosum antibody. The pituitary region contained extensive liquefactive necrosis, a myriad of bacteria and fibrinosuppurative inflammation. Based on epidemiological, clinical, anatomopathological, immunohistochemical and microbiological findings, a diagnosis of rhinofacial pythiosis with secondary basilar empyema was established. Nasal lesions caused by P. insidiosum in sheep may serve as a portal for opportunistic bacterial infections and precipitate basilar empyema.