Pit Viper Envenomation In The United States: Rattlesnake, Copperhead, Water Moccasin

Pit-viper-poisonous-venomous-rattlesnake

It is early August and once again you are on an all too familiar trail, heading to your favorite fishing hole to try your luck for smallmouth bass. As you round the corner, a sound stops you right in your tracks. “BZZZZZZZZZZZZZ”. It’s a primal sound that strikes at something deep inside, cautioning that you go no further. There, auspiciously perched along a nearby log, sits a beautiful yellow timber rattlesnake snake upset that its morning hunt has been intruded upon. While this encounter was harmless, unfortunately this is not always the case. In the United States, approximately 5,000 snakebites are reported to poison control centers each year, with about half attributed to pit vipers.  It’s important to always know that when in snake country, a simple trip and fall or a misplaced step could result in a snakebite.

Statistically, most bites occur in young adult males or children during the summer. Alcohol is often involved. There are, however, some steps you can take to minimize encounters and reduce your risk. Always make noise if able when walking and carry a stick to move brush and plants out of your path for a clear view. This gives the snake an opportunity for escape and you the best chance at seeing it. Consider investing in a good pair of chaps or snake boots, especially if in an area known for snakes in the summer. If an encounter happens, simply back away and find another route. Be extra cautious however, as more snakes could be hidden nearby. Keep in mind that a rattlesnake can often strike nearly 2/3 of its body length when in full striking position. This means that a 60-inch snake can strike out to 40 inches! Never provoke or mess around with a snake, alive or dead, as this is often why bites occur.  Every year people are bitten by supposedly “dead” snakes.  In the words of an old friend, “That snake may be dead, it just doesn’t know it yet”.  Snakes are cold blooded. Because of this, they often retain their striking and envenomation mechanism for 6+ hours after killed or even decapitated.

Pit Viper Venom

Pit viper venom is a unique mixture of compounds meant to quickly kill its prey. Interestingly, this venom can vary in its makeup, even within the same species. Snakes separated by only a few miles or fed a different diet can have venom differing in potency and make up. With this in mind, snakebites may present different symptoms.  Immediately upon entering the body it begins breaking down blood as well as muscle tissue. This not only leads to possible bleeding issues, but can cause low pressure, rapid heart rate and trouble breathing.  The venom can also cause nausea, vomiting, and heavy sweating. Neurologic symptoms such as confusion, weakness, seizures, facial numbness and twitching can also occur in some instances. Nearly all bites will have local tissue injury with significant swelling, bruising and excruciating pain.

Pit Viper Identification

  • Rattle on the tail for rattlesnakes
  • Triangular head and narrow neck
  • Cat-like elliptical pupils
  • Two prominent fang marks on bite
  • Do not rely on the pattern or color

If bitten, immediately move out of harm’s way and attempt to identify the snake, but DO NOT put yourself or others in danger to do so. It isn’t worth a second bite. Pit vipers have a few unique characteristics (besides the obvious rattle on rattlesnakes) to help in their identification.  First, they have a triangular head and a more narrow neck (see illustration). This is secondary to their large venom glands. Second, they have cat-like elliptical pupils (see illustration). Do not rely on the pattern or color of the snake. This can often be deceiving. Lastly, one can evaluate the bite itself. Semicircular bites with multiple punctures suggest a nonvenomous snake. If two prominent fang marks are present, it is likely the bite was delivered by a pit viper (see Fang Marks in illustration). When bitten by a pit viper, about 25% of the time, venom is not injected. This is known as a “dry bite”.

Snakebite First Aid

  • Identify the snake and move to safe area
  • Evaluate the bite
  • Stay as calm as possible
  • Remove all body accessories to prepare for swelling (jewelry, watches, etc.)
  • Immobilize body part and raise or lower it as close to the level of the heart
  • Clean the wound if able
  • Do not make incisions, do not attempt to suck out the venom (commercial suction or by mouth), do not apply a tourniquet, do not take ibuprofen or naproxen, do not ice, and do not drink alcohol

After a pit viper bite, it is important to stay calm. This may be easier said than done, but keep in mind by increasing your heart rate, you increase the venom’s circulation. Quickly remove all jewelry, watches, etc. in preparation for severe swelling. Immobilize the body part as best as possible at the level of the heart if able. This is an attempt to balance the local venom effects with the systemic effects. Clean the wound if able, but do not make incisions, attempt to suck the venom out, or apply a tourniquet. Commercial suction devices have only been shown to reduce the total venom load by approximately 2%, making it not worthwhile. Tourniquets can cause increased damage to the limb by keeping all of the venom in one place.  Do not take ibuprofen or naproxen as this increase bleeding effects. Don’t ice the area or drink any alcohol.

CroFab®, an antivenom producer, has a useful free phone app called Snakebite911 that not only has resources regarding snake identification, steps to take and even hospitals nearby that carry antivenom. It is certainly worth considering if you often find yourself in snake country.

Once at a hospital, physicians need to work quickly to evaluate for these processes and determine the need for antivenom.

There are now two antivenoms in the US market: CroFab® and recently approved Anavip®. Antivenom can bind and neutralize the proteins in snake venom, halting the damage caused.  It also can quickly reverse bleeding, reduce swelling and muscle breakdown, and decrease pain and other symptoms. With the advent of antivenom, the risk of death today from a snakebite is only about .06%. This risk increases with rattlesnake bites (more potent venom on average), or with bites to the face, neck or trunk.

Conclusion

While snakebites are generally rare, they can and do happen. We take this risk any time we enter snake country. Armed with some general knowledge on avoidance and identification, you can drastically improve your odds of never being on the receiving end of a venomous snakebite, and if you or someone you know is unfortunate enough to be bitten, taking some simple treatment steps in the field can help prevent loss of a limb or even save a life.

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In early 2019, Dr. Kyle Yebernetsky presented his research on pit viper envenomation in the United States to a group of over 30 medical doctors. He followed up his research by writing this short, yet comprehensive article for the lay adventurer who might encounter a venomous snake.

Kyle Yebernetsky MD is an emergency medicine resident in central Pennsylvania.

The Author disclaims any liability from injury that may result from the use, proper or improper, of the information contained in this article. All the information in this article comes directly from highly trained professionals in emergency medicine, but does not guarantee that information contained herein is complete, safe, or accurate, nor should it be considered a substitute for your good judgement and common sense.

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