Clinicopathological findings of intestinal granulomatous pythiosis in a dog

Pythiosis is a chronic pyogranulomatous disease of subcutaneous tissue in humans and animals especially horses and dogs caused by the oomycete, Pythium insidiosum. Gastrointestinal tract phthisis was commonly reported in dogs and it was rarely observed in other animals. A one-year-old German Shepherd male dog was referred to Veterinary Clinical Complex, Veterinary College and Research Institute, Theni, Tamil Nadu with a history of hematochezia, tenesmus, dyschezia and progressive weight loss since three months. Transabdominal ultrasound examination revealed, approximately 1.5 cm thickened irregular walls in the distal third of caecum, colon and rectum, and narrow intestinal lumen with loss of the normal layered pattern and an additional discrete eccentric mass of approximately 1.14 × 0.39 cm in the ileal wall. Exploratory laparotomy was performed with the consent of the owner but the animal collapsed immediately opening the abdominal cavity. The caecum portion of the intestine tissue was preserved in 10% formalin and sent for histopathological examination. Histopathological examination of caecum revealed multifocal fungal granulomas areas on the muscularis layer consisting of central necrotic areas with fungal hyphae surrounded by epithelioid cells, macrophages, few neutrophils and eosinophils and lymphocytes. Histological examination with a special staining procedure with Grocott-Gomori’s Methenamine Silver (GMS) stain demonstrated the presence of black coloured fungal hyphae indistinguishable from the Pythium spp. within the necrotic areas. Based on the histopathological observations the case was confirmed as intestinal granulomatous pythiosis.