Canine ocular protothecosis: A review of 14 cases

Purpose To examine a series of 14 cases of canine ocular protothecosis from archived cases from the Comparative Ocular Pathology Laboratory of Wisconsin ( COPLOW ), and compare gross and histologic findings. Methods Archival records from COPLOW were searched for canine cases of ocular protothecosis. Fourteen cases that contained matching criteria were identified, and gross and histologic findings, and clinical records for each case were tabulated, examined, and compared (2001–2013). Results Of the 14 cases identified, six had evidence of systemic disease, as per clinical history. Two of the 14 cases had Prototheca identified via cytology of ocular fluid or retinal exudate; in the remainder of cases, Prototheca identified via cytology of ocular fluid or retinal exudate in the remaining 12 cases, Prototheca was identified upon histologic examination of the submitted globe(s). Presenting ocular clinical signs were variable and nonspecific. Duration of ocular clinical signs varied from days to months. Fundoscopically, white membranes or plaques were identified on or around the retina in five cases. Retinal detachment was identified in 13 of the 14 submitted globes on gross examination following fixation and sectioning. The predominant histologic finding was granulomatous chorioretinitis with retinal detachment, with variable numbers of Prototheca within the inflammatory infiltrate. Conclusions Due to the nonspecific nature of the ocular signs, a diagnosis of protothecosis generally is not made until enucleation and histopathologic examination of the globe(s). Retinal detachment and blindness were common. Cytologic sampling of retinal plaques and exudate may provide a rapid way to identify Prototheca .