Snakebites from Pit Vipers (rattlesnakes, water moccasins and copperheads)
Dr. Dawn Ruben
Bites by poisonous snakes, also referred to as snake envenomization, affect over 150,000 dogs and cats per year in North America. In the United States, there are two primary families of venomous snakes, Crotalidae and Elapidae. The southwestern and southeastern United States have a greater incidence of snakebites due to a higher population of venomous snakes. Rapid swelling at the site of the bite
Crotalidae is the most prevalent family of poisonous snakes in the United States. These include rattlesnakes, water moccasins and copperheads. These snakes have broad triangular heads with elliptical pupils, prominent curving fangs and a deep pit located between the nostril and the eye. For this reason they are commonly called "pit vipers." It is believed that pit viper account for approximately 99% of all venomous snake bites to pets.
Even though a venomous snake may have bitten your pet, not all bites contain venom. In fact, less than half of all snakebites result in signs associated with envenomation. The risk of snakebite toxicity is based on the type of snake, the size of the animal bitten and the amount of venom injected in the bite. The type, effect and amount of venom can vary with the age and type of snake and can even vary within families of snakes.
Pit viper venom is not yet fully understood and the toxicity of the venom varies from species to species. For example, copperhead venom is much less toxic than rattlesnake venom.
Most snakebites occur in large breed primarily outdoor dogs with the majority of bites located on the legs or head, especially the muzzle. Most bites occur during the spring and summer seasons. It is estimated that 90% of bites occur between April and mid October. Bites from these snakes are generally the result of aggressive or curious actions while playing in snake-infested areas.
What to Watch For
A common scenario is a pet that is in the woods, near a thick grassed area or by a wood pile that suddenly cries out after which you notice a swelling on the legs or muzzle.
Other signs include:
Fang marks (can be difficult to identify in some animals)
Tissue swelling is often worse 24 to 48 hours after the bite. Wound may drain and bleed for several days. Most snake bites require veterinary care.
Diagnosis is based on physical exam findings supportive of a recent venomous snake bite as well as the potential exposure to venomous snakes.
Blood work may be done to evaluate coagulation times on a blood sample taken from an affected animal. Prolonged clotting times can indicate exposure to pit viper venom.
With rapid treatment, most pets with Crotalidae snakebites recover. Treatment varies depending on which species of snake was responsible for the bite as well as the signs of toxicity displayed by the pet.
Antivenin (polyvalent Crotalidae) is available and recommended for rattlesnake bites. Antivenin is a product created from antibodies produced by an animal purposely exposed to snake venom. It helps to counteract the venom on the pets system. It is a human product and availability may be limited in certain geographic areas. It can also be very expensive ($300 to $400 per vial with each pet needed 1 to 3 vials) and may cause allergic reactions in some pets. For this reasons, pets are hospitalized and closely monitored.
For copperhead bites, antivenin is generally not recommended and rarely needed.
Diphenhydramine is typically given to reduce some signs of allergic reaction associated with the snakebite.
If the bite occurs in the area of the throat, airway support may be needed, including a temporary tracheotomy or ventilator.
Hospitalization with continuous intravenous fluids may be recommended in severe cases.
Treatment for pain and infection is also important.
After a venomous snakebite, DO NOT use a tourniquet. This will affect the circulation to the area significantly and may result in serious tissue damage.
Do not try to suck the venom out of the bite. Human saliva contains many bacteria and may result in severe infection.
The most helpful and important thing to do is to limit your pet's activity severely after the snakebite. The quieter and calmer he/she is, the less effect the venom will have.
Rapid treatment by a veterinarian is also strongly recommended.
After treatment for Crotalidae snakebite, you may notice oozing from the bite site for several days. The swelling in the area of the bite may take up to a week to subside.
The prognosis in a pet with a pit viper bite is generally good with prompt treatment. Copperheads are the least toxic and generally require time for skin wound healing but are not fatal.
The best way to prevent Crotalidae snakebites is to restrict access to Crotalidae infested areas. Snakes prefer to live in quiet and dark areas and woodpiles are popular nesting sites.
If a venomous snake bites your pet, it is unlikely that he will learn from the experience and he probably won't voluntarily avoid snakes in the future. Future venomous snakebites may result in much more severe toxic signs and might even result in death.