Extended Survival in a Dog With Disseminated Protothecosis

A 5-year-old Basenji Mix achieved extended survival with treatment for disseminated protothecosis. The dog originally presented with iridal hyperemia and ocular ultrasonographic examination revealed a mass effect. Histopathology revealed ocular protothecosis and staging confirmed disseminated protothecosis. Treatment with itraconazole and amphotericin B (AmB) infusions resulted in remission. Four years later, restaging revealed recurrence of infection in colonic biopsy samples. An extended AmB protocol was restarted for a cumulative dose of 84 mg/kg and the dog received isavuconazole based on susceptibility testing. The dog was euthanized 4 years and 8 months after initial diagnosis due to decline of neurologic status. Necropsy confirmed the presence of disseminated protothecosis in multiple arteries, multiple lymph nodes, the pituitary gland, thyroid glands, kidneys, colon, cecum, right eyelid, right eye, heart, brain, and periosteum of one bone associated with the middle ear. This report documents the extended survival of a dog with widespread disseminated protothecosis after prolonged administration of AmB.