Acute lymphoblastic leukemia in a juvenile southern black rhinoceros (Diceros bicornis minor)

A 21-mo-old female southern black rhinoceros (Diceros bicornis minor) devel oped acute upper respiratory dyspnea in association with lymphadenopathy an d marked immature lymphocytosis. A diagnosis of acute lymphoblastic leukemi a was reached on the basis of the morphologic and cytochemical characterist ics of peripheral lymphoblasts. Antineoplastic chemotherapy included admini stration of cytarabine, cyclophosphamide, vincristine, and doxorubicin, wit h clinical remission achieved 19 days after initiation of treatment. The rh inoceros died, however, of congestive heart failure, presumably secondary t o doxorubicin cardiotoxicity and a particular sensitivity of rhinoceros myo cardial tissue to free hydroxyl radicals. The pharmacologic effects of any therapeutic agent need to be carefully considered before use in the black r hinoceros, especially within the context of the unique physiology of this s pecies.