Case Report: Neurologic signs following rattlesnake envenomation.

Neurologic signs can occur in horses following rattlesnake envenomation, a common emergency in California, and appropriate treatment including antivenom can lead to recovery. This case report documents the first known instance of neurologic symptoms after a Western Rattlesnake bite in a miniature horse.

Background on Rattlesnake Envenomation in Horses

• Rattlesnake bites are a frequent emergency issue affecting horses in California.
• Rattlesnakes belong to the pit viper family, known for their venomous bites.
• The Northern Pacific Rattlesnake, a subspecies of the Western Rattlesnake, is the most common rattlesnake species encountered in California.

Case Presentation

• A 5-year-old miniature horse mare was suspected to have been bitten by a Western Rattlesnake.
• The horse was found with severe facial swelling, a location known for rattlesnake activity.
• Prior to this, the horse appeared normal without any obvious signs of distress or illness.

Clinical Findings

• Blood tests revealed severe thrombocytopenia (low platelet count), elevated aspartate aminotransferase (AST), and elevated creatine kinase (CK), indicating muscle and liver involvement/damage.
• Physical examination showed:
  • Severe facial swelling, consistent with envenomation effects.
  • Urinary dribbling, signifying neurological dysfunction affecting bladder control.
  • A hypermetric gait in the hind limbs, a neurological sign indicating abnormal coordination or proprioception.

Treatment and Clinical Course

• The horse was treated with:
  • Antivenom to neutralize the snake venom.
  • Bethanechol, a medication used to stimulate bladder function and improve urine control.
  • Supportive care, including monitoring and symptomatic treatment during hospitalization.
• Over 6 days, the horse showed significant improvement:
  • Return of urinary function.
  • Reduction of facial swelling.
  • Resolution of the abnormal gait and neurological signs.
• The horse was eventually discharged in good condition.

Significance and Novelty of the Case

• This is the first documented case report describing neurologic signs following a presumed Western Rattlesnake bite in a horse.
• The presence of neurologic manifestations such as urinary incontinence and hypermetric gait expands the clinical understanding of rattlesnake envenomation effects in equine patients.
• The report highlights the importance of recognizing neurologic symptoms promptly to provide targeted treatment and improve outcomes.
• Successful treatment with antivenom and adjunct therapies demonstrates the potential for recovery even when neurologic signs are present.