A five year old, male castrated zebra (Equus quagga), presented to Cornell’s Emergency Service on 1/18/2015 after being found down in the pasture. He was observed to be normal that morning, but by the afternoon, the zebra was laterally recumbent and mentally obtunded. He was brought to Cornell immediately. The zebra had a history of weight loss and being a poor-doer, which was attributed to heavy parasite burden (ascarids). Daily deworming was used as a preventative and treatment for the parasite burden. The zebra’s diet consisted of hay, a handful of grain per day, and fresh grass seasonally. He received a vitamin E/selenium supplement and had access to a mineral block. The zebra had been in the care of his current owners since he was 7 months old and he shared a pasture with a male castrated donkey.
On presentation, the zebra was obtunded and experiencing hypovolemic shock, hypothermia, and lacked a response to painful stimuli. Patient side blood work showed hypoglycemia, hypokalemia, hypocalcemia, and muscle damage. When the profound weakness and recumbency persisted after the resolution of the hypothermia and hypoglycemia, diagnostics to look for a neurologic or muscular condition were pursued. Initially, there was motor function in the hind limbs and he was able to bear weight on his hind legs when supported in a sling. The front legs were non-weight bearing with minimal motor function. Patellar reflexes were present bilaterally, triceps reflexes were absent bilaterally. Cranial nerve reflexes were intact. Eventually, the zebra became tetraparetic, unable to lift his head, and dysphagic. During the course of his stay, the zebra developed tricavitary effusion, severe hypertension, tachycardia, acidemia, and hypoxia. When he failed to improve despite extensive supportive care, he was euthanized.
Our top differentials for the primary problems of persistent recumbency and generalized weakness were white muscle disease (WMD), other myopathy, neuroborreliosis, equine protozoal myelitis (EPM), cervical trauma, and encephalitis. Cervical radiographs were within normal limits. Cerebrospinal fluid was negative for neuroborreliosis and EPM. Selenium results were above normal and vitamin E was within normal limits. Gross necropsy and histological findings were supportive of a myopathy.