Histologic identification of intraocular Cytauxzoon felis in three cats

CASE SERIES SUMMARY: A 5-month-old male intact domestic shorthair (DSH) cat (cat 1), a 1-year-old male neutered DSH cat (cat 2) and a 1.5-year-old female spayed DSH cat (cat 3) were submitted for gross necropsy after acute death, with the clinical suspicion of cytauxzoonosis. All three cats displayed signs of rapidly progressive clinical deterioration, including lethargy, anorexia, and hyper- or hypothermia. Cat 1 was euthanized owing to the grave prognosis for survival, whereas cats 2 and 3 were found dead 1–4 days after the onset of clinical signs. Remains were submitted to the Kansas State University Veterinary Diagnostic Laboratory for gross necropsy. In all three cats, general examination findings included icterus of the mucous membranes, multifocal pulmonary parenchymal hemorrhages, and splenic reddening and enlargement. Histologic examination revealed macrophages laden with protozoal schizonts diffusely distributed within blood vessels and vascular spaces of all affected organs, including the blood vessels of the uveal tract. The ciliary body within the anterior uveal tract was most affected. RELEVANCE AND NOVEL INFORMATION: This is the first description of cytauxzoonosis affecting the eyes of infected cats. This report confirms involvement of ocular blood vessels similar to the classic lesions of the lungs, spleen and liver. In cats presenting with a history and clinical findings suggestive of cytauxzoonosis, complete ophthalmic examination is indicated to confirm or rule out ocular involvement.