A description of cutaneous-subcutaneous pythiosis in fifteen dogs

Abstract

Information regarding signalment, duration of clinical signs, history of swimming, results of CBC and serum biochemical analyses, biopsy findings and mycological results, together with treatments and outcome, was retrieved from the medical records of 15 dogs with a diagnosis of pythiosis made between 1985 and 1995 at the Colleges of Veterinary Medicine, North Carolina State University and the University of Florida. Most of the dogs were young (median age 22 months) and represented larger breeds (>20 kg). Lesions were characteristically chronic, ulcerated, and nodular with multiple draining tracts on the limbs, thoracic wall or perineal regions. The median duration of these lesions was 3 months with a range of 2 weeks–6 months. Seven dogs had a history of swimming. Peripheral eosinophilia was observed in 14 of the dogs. Cytological evaluation of discharge, aspirates, or impression smears made from biopsy specimens revealed hyphae in five of 11 dogs (45%). Histopathological evaluation using the Gomori Methenamine-Silver (GMS) stain was the most useful test for providing presumptive evidence of cutaneous pythiosis. Immunotherapy or antifungal therapy using either amphotericin B, liposomal nystatin, itraconazole, or ketoconazole were all unsuccessful. The only dog to survive underwent amputation of the affected limb; thus, the prognosis for cutaneous pythiosis in the dog is poor.