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What is Snake Bite?

It is not surprising that many snakes found in the United States are capable of causing great harm to a horse. Thankfully, due to their size and body weight, horses are unlikely to be killed by most snake bites, though serious injury may occur. A variety of factors affect the outcome of a snake bite in a horse. Of course, the type of venom is at the top of this list. Some snakes are far deadlier than others. The location of the bite is another determining factor; bites to the head and face, as well as other areas of major blood supply cause more serious injury than bites to the limbs and general body area. The deadliest spots for a snake bite to occur on the horse include the muzzle, head and neck. While fatalities do happen following venomous snake bites, the sheer size of the horse typically sends most snakes slithering away to another location. Typically, the snake will try and avoid a run-in with a large-sized animal and will give the horse the courtesy of a few seconds to change direction.

If, however, the snake strikes and appears to bite the horse, it’s important for the human to stay calm and take the following steps: try to prevent the horse from looking down at the snake. If riding, signal to the horse to slowly back away. If possible, get a look at the snake for identification purposes, but focus more on the care of the horse. Even the slightest descriptors, such as the color or markings on the top of the snake, can help determine the proper type of antiserum/antivenin. 

Horse owners, especially those in regions populated by poisonous snakes, should have a plan and some sort of emergency preparedness kit before setting out on a trail. The quality and type of care administered to the horse in the first hour following the bite may make the difference between life and death. Primary goals include delaying the spread of venom, countering any already absorbed venom, and addressing cardiorespiratory health.  If there is any suspicion of a bite from a poisonous snake, arrange for immediate veterinary care. In the meantime, keep the horse as calm as possible. If in an area populated by poisonous snakes, your veterinarian may suggest a dose of epinephrine be kept on hand in case of anaphylaxis.

Horses are one of the most sensitive animals when it comes to snakes bite, followed by sheep, cows, goats and pigs.

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Symptoms of Snake Bite in Horses

  • Pain
  • Shock
  • Swelling at site
  • Puncture wounds/fang marks
  • Sloughing of tissues near site
  • Extensive or minor bleeding
  • Cardiac arrhythmias
  • Collapse
  • Paralysis
  • Respiratory distress
  • Sudden death

Causes of Snake Bite in Horses

The snakes that pose the greatest risk to horses in the United States include rattlesnakes, copperheads, and water moccasins. The greatest risk, including the threat of a possible fatality, accompanies the bite of a Diamondback rattler. Horses will typically come across such a snake on the trail. If the horse steps on the snake, it can release all of its venom into the horse. This not only kills the snake, but also may lead to an immediate breakdown of tissues and blood vessels in the horse. Blood clotting is impaired, and the heart is either damaged or stopped. In the best case scenario, the bite is “dry,” meaning it contains no venom.

Diagnosis of Snake Bite in Horses

As with most animals, it’s difficult to find the “bite site” on the horse due to hair, as well as resistance to even the briefest examination due to pain, fear or shock. The site of the bite should begin to swell and bleed within minutes of the strike, and a close look may reveal fang marks. The most common reaction to a snake bite is shock. Swelling, particularly if bitten on the nose or muzzle, can impede breathing through the nostrils. The horse may experience severe pain, nausea, muscle weakness, and shock directly following the bite. Anxiety can spike the blood pressure, and an increased heart rate will speed the spread of venom throughout the body.  

For the veterinarian, diagnosis of the snake bite is straightforward if observed by the owner. Otherwise, a bitten horse will present with additional symptoms that may include a very swollen limb, bleeding at the wound site or signs of shock.

Treatment of Snake Bite in Horses

Pre-veterinary Intervention

A compression wrap/tourniquet may help slow the spread of venom, though tourniquets on the face are not indicated. Keep the horse calm and the heart pumping naturally until veterinary care comes available. If possible, wash the wound with soap and water. Applying hot or cold compresses is not recommended.

Veterinary Intervention

Antivenin is key to the treatment of a poisoned horse, and is effective when administered within 24 hours of the incident. If the bite was observed, any details about the snake’s appearance will guide the choice of product.  Veterinary treatment will include fluid therapy, corticosteroids, pain medication, wound care, tetanus and antibiotics.

Recovery of Snake Bite in Horses

Once past the acute phase of treatment, the horse should be checked every 3-6 months for subsequent complications such as heart or kidney damage, anemia, or respiratory problems. The horse remains at risk for cardiac failure in the months following the original incident. Vigilance should be maintained during exercise; shortness of breath, exercise resistance and weakness may suggest heart failure.