Systemic protothecosis in a dog: pathological description of a case

Abstract

A case of systemic protothecosis in a dog is reported. The diagnosis was based on the morphological aspects as well as the ultrastructural features of the microorganism under a light microscope. The patient was a 9 year-old, female Poodle, which initially presented torticollis and a presumptive diagnosis of left external otitis. The dog was referred to the University Hospital, Universidad Nacional, Heredia, Costa Rica. On physical examination the animal presented horizontal nistagmos, left side torticollis, proprioceptive deficit of the front right limb and blindness. The dog died two days after admission. On macroscopic examination, the heart, kidneys and liver presented white yellow areas up to 1.0 cm in diameter with clear borders. Microscopically, the areas consisted of necrosis with moderate inflammatory reaction, predominantly with histiocytes and plasma-cells. Pleomorphic microorganisms (which stained positively with P.A.S. and Grocott ) were observed in the necrotic areas and were identified as Prototheca sp. The diagnosis was corroborated by electron microscopy.