title: More than meets the eye: subretinal aspirate from an acutely blind dog.
abstract: A 14-year-old, spayed female Cocker Spaniel was presented to the Boren Veterinary Medical Teaching Hospital at Oklahoma State University with acute loss of vision in the right eye and a history of intermittent bloody diarrhea of unknown duration. Small, white, plaque-like lesions in the retina and subretina were visualized by direct ophthalmic examination, and aspirated with ultrasound-guidance. A direct smear of the subretinal fluid was highly cellular and contained large numbers of pleomorphic organisms consistent with Prototheca sp. The structures were round, oval, or elongated, 4-6 microm width and 8-16 microm in length and surrounded by a thin, clear cell wall. Small, central, pink to purple nuclei were observed in some organisms, but in most, the nuclei were obscured by a deeply basophilic, granular cytoplasm. Some organisms contained endospores. Negatively-stained structures of similar size and shape were considered to be empty casings (theca) of ruptured sporulating and nonsporulating forms of the organism. Protothecosis usually is a disseminated, fatal disease in dogs. The Prototheca organisms observed in this case showed characteristic morphology, illustrating the ability to diagnose protothecosis in cytologic samples.
authors.affiliation: Department of Pathobiology, Oklahoma State University, Stillwater, OK, USA. theresa.rizzi@okstate.edu
authors.forename: Theresa E
authors.initials: TE
authors.lastname: Rizzi
authors.forename: Rick L
authors.initials: RL
authors.lastname: Cowell
authors.forename: James H
authors.initials: JH
authors.lastname: Meinkoth
authors.forename: Margi A
authors.initials: MA
authors.lastname: Gilmour
mesh_terms: D000208:Acute Disease; D000818:Animals; D001766:Blindness / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*; D004283:Dog Diseases / Q000175:diagnosis / Q000473:pathology*; D004285:Dogs; D005123:Eye / Q000473:pathology; D005260:Female; D007239:Infections / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*; D011525:Prototheca / Q000302:isolation & purification*