Leukoencephalomalacia in a Neonatal Female Black Rhinoceros (Diceros bicornis): Report of a Fourth Case

Acute neurologic signs were observed in a 3-wk-old female black rhinoceros (Diceros bicornis) born at the Denver Zoological Gardens. The neonate's condition deteriorated after the first 24 hr. Following physical examination, the calf was separated from its mother and transferred to the zoo hospital for intensive care, additional diagnostics, and hand raising. Standard hematologic tests, serologic tests (including bile acids), urinalyses, and Leptospira titers failed to establish a diagnosis. There was no detectable serum vitamin E at the neonatal examination, but 3 wk later at the onset of illness the levels were normal. After consultation with a veterinary neurologist, the rhinoceros was transported to the Colorado State University Veterinary Teaching Hospital for diagnostic tests, including computed tomography of the brain, lumbar spinal taps, and portal venography. Hypodense areas compatible with edema, ischemia, necrosis, or malacia were seen in each cerebral hemisphere. Hemorrhage was seen in each caudate nucleus. No portosystemic shunt was observed. After hospitalization for 15 mo, the animal's condition deteriorated and it was euthanized. Gross necropsy and histopathologic evaluation confirmed a diagnosis of leukoencephalomalacia. This is the fourth female black rhinoceros to be diagnosed with this condition.