Case Report: Neurologic signs following rattlesnake envenomation

Rattlesnake envenomation is a common emergency in horses in California. Rattlesnakes belong to a group of venomous snakes: pit vipers. The Northern Pacific Rattlesnake (Crotalus oreganus oreganus), a subspecies of the Western Rattlesnake, is the most widespread rattlesnake in California (1). A 5-year-old miniature horse mare presented for a presumed Western Rattlesnake bite. The owners found the horse the morning of presentation with severe facial swelling and the horse was housed in an area where rattlesnakes are commonly observed. The horse was reported to be normal the day prior to presentation. On blood examination, severe thrombocytopenia, elevated AST, and elevated creatine kinase (CK) were identified. On physical examination the horse was noted to have severe facial swelling, to be dribbling urine, and to have a hypermetric gate in the hind limbs. Treatment was initiated with antivenom, bethanechol, and supportive care. After 6 days of hospitalization, the horse regained urinary function, the facial swelling significantly improved, the neurologic gait resolved, and the horse was discharged. This is the first case report describing neurologic manifestations from a presumed Western Rattlesnake bite.