Fatal extraintestinal toxoplasmosis in a young male cat with enlarged mesenteric lymph nodes.

A 22-month-old indoor/outdoor neutered male domestic short-haired cat had a history of progressive lethargy, vomiting, and decreased appetite. Abdominal ultrasound revealed an irregular hyperechoic mass in the mid-abdomen. He was unresponsive to symptomatic medical management and was euthanized after 3 days of hospitalization. A diagnosis of disseminated extraintestinal toxoplasmosis was made based on the finding of intracytoplasmic protozoan parasites on histopathological examination of mesenteric lymph nodes, hepatic and intestinal samples, and on immunohistochemistry.