Shrub or tree of family Rhamnaceae, Karwinskia humboldtiana commonly called Coyotillo or Tullidora. Found in arid southwestern U.S. environments; uncharacterized neurotoxin with high toxicity; single intake of just 0.05-0.3% by body weight in plant material; fruit is particularly toxic. Impaired cerebellar and peripheral nerve function is characteristic; clinical signs include hypersensitivity, tremors, abnormal gait, progressing to paralysis especially in hind quarters; pulmonary edema in some cases also. Toxin produces progressive polyneuropathy through segmental demyelination and degenerative changes in axons of peripheral nerves, followed by myodegeneration.polyneuropathy.