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Observation
What you see. The starting point for addressing any equine health related issue is your observation.

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Snakebite, Witnessed or Presumed

Summary

You saw a snake bite your horse. Or you saw a snake near your horse, and you notice a wound or swelling on the horse (usually on the muzzle, face or legs) that you assume resulted from a snake bite. Now what?

Generally, poisonous snakes are divided into two broad groups: Pit Vipers (vipers, adders and rattlesnakes), and Neurotoxic snakes (coral snake, mambas, and their relatives). In the United States we have Rattlesnakes, Copperhead, Water Moccasin and the small Coral Snake. Rattlesnakes usually rattle, but not always.

Some non-venomous species emulate rattlesnakes by buzzing their tails or hissing. Rarely, certain species of large non-venomous snake may bite a horse when cornered. I know of at least one young horse bitten by an angry, cornered Bull Snake. DO YOU KNOW WHAT KIND OF SNAKE IT IS?

The severity of a snake bite depends on the species involved, the amount of venom injected, and location of the bite. In some cases, very little or no venom is injected - a dry bite.

A venomous snakebite usually results in local swelling and pain within 30 minutes. Usually there are two small bleeding puncture wounds that correspond to the fangs, although there may be only one. These bite wounds can be difficult to see on dark skinned horses or horses with a thick coat. Many times I have not been able to find snakebite wounds on horses until I clipped the hair off and looked very carefully.

  • Code Red

    Call Your Vet Immediately, Even Outside Business Hours

your role

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What To Do

If possible, take a photo of the snake and share it with your vet or someone that can identify the snake species. If the snake is dead, save it for later identification. If it is a non-venomous species, its likely that no treatment (other than monitoring) will be needed.

If you know or suspect that the horse has been bitten by a venomous snake, keep yourself and the horse calm, and immediately call your vet. Most horses bitten by (North American) poisonous snakes will not die, so do not panic.

Assess the bite area for swelling and perform the Whole Horse Exam (WHE), paying particular attention to attitude, heart rate and rectal temperature. If you have medications (anti-inflammatories, antibiotics, steroids) that you think might be helpful, tell your vet. They may suggest giving a medications prior to their arrival, but only give these under your vet's direction.

If the bite is near or on the nose or face, it may rapidly swell. If the nasal passages swell and begin to close, you will notice increasingly loud snoring sounds with breathing. Rarely, pit viper bites on the face can cause severe enough facial swelling to cause a horse's nasal passages to swell closed leading to difficulty breathing.

One common recommendation (found on the Internet and elsewhere) is for a horse owner to cut short tubes from a garden hose and stuff them up the horse's nose. I do not recommend this practice. In my experience, it is rare for a rattlesnake (pit viper) bite to cause sufficient swelling that tubes must be placed in the nose. Likewise, I have seen inexperienced but well-meaning people attempt to stuff tubes up their horse's nose, resulting in additional and unnecessary stress to the horse.

Bites to the limbs usually cause severe swelling and lameness. In rare cases, a joint or tendon sheath could be involved in the bite, which causes further complications.

If you are positive that the snake was non-venomous, monitor your horse for 6-12 hours to ensure that they are well. In rare cases, resulting small wounds could become locally infected requiring some treatment. If you notice significant swelling at the site or any other abnormalities, call your vet immediately.

What Not To Do

If possible, do not force the horse to move. Exercise causes increased blood flow, which moves the venom more quickly through the horse's body.

Do not cut open the wound, squeeze the wound, try to suction out the venom, or try to suck out the venom yourself. Do not apply ice or any other topicals to the site of injury without consulting your vet.

Do not try to place anything up the horse's nasal passage without a strong sense that the horse truly cannot breathe (loud snoring respiration and obvious, increasing distress).

Do not kill non-venomous snakes. They control rodents, and may reduce the population of venomous snakes in a location.

Venomous snakes, too, have their place. But not around horses or other domestic animals. When I was young, I would kill venomous snakes. Now I prefer to catch them and relocate them to an area where they are less likely to cause problems.

your vet's role

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Your vet assesses the horse's general health and implements first aid and nursing care as needed. Prompt treatment with anti-inflammatories, steroids or antihistamines often reduce pain and swelling.

Anti-venom (antivenin) can be a useful treatment. Historically, the only one available was cost-prohibitive. Now, however, there is at least one commercial vet product that can potentially be very helpful for rattlesnake and pit viper bite.

Severe bites may require hospitalization and varying levels of nursing care.
Questions Your Vet Might Ask:
  • What species of snake bit the horse?
  • Did you actually see it happen?
  • When did this happen?
  • Does your horse seem normal otherwise?
  • Is there bleeding or swelling at the bite site?
  • Where is the bite wound located?
  • What are the results of the Whole Horse Exam (WHE)?
  • What is the age and breed of the horse?

Author: Doug Thal DVM Dipl. ABVP