Updated August 13, 2014
It’s warm up out there and the creepy, crawly things are coming out, many of which bite and sting. And this includes those venom packing snakes common to the U.S.: rattlesnakes, copperheads, cottonmouth and coral snakes.
How does it feel to be bitten by a poisonous snake? Depends on whether you have yours with or without venom. Bites without injection of venom or dry bites are frequent but not without pain and a slight risk of infection. When venom is deposited, the amount of pain and damage is dependent on venom potency and the amount injected and whether the poison remains locally in the tissues or is picked up in significant amounts by the circulation.
Severity also depends on the type of venom. There are two broad categories for venomous snakes, those that are neurotoxic and those that are hemotoxic. This is a very simple division considering there are twenty or more toxins that are found in various combinations in poisonous snakes in the US and around the world.1,2 These toxic substances can produce major clinical problems such as paralysis, muscle damage, clotting dysfunction, bleeding, kidney damage, shock and tissue damage1. But not all toxins are present in a single snake species.
Common Types
The most common and widely distributed venomous snakes in North America are the Crotalidae family of pit vipers: rattlesnakes, copperheads and cottonmouths. Their “pits” are heat sensors located between the eyes and nostrils and are used to locate small warm blooded animals for food and on occasion any part of a large warm blooded animal that irritates or threatens them, accidentally or on purpose.
Pit vipers also have moveable front fangs which allow them to reach out and touch someone more effectively.2 Pit vipers typically cause local tissue damage but when envenomation is severe can cause shock from damage to capillaries that allows the intravascular fluid to leak out producing hypovolemia and may cause the body’s clotting mechanism to malfunction thus causing the victim to hemorrhage.
The coral snake is less common and is neurotoxic with the potential for inducing paralysis but may also cause local tissue damage.1 But coral snakes are not the only neurotoxic snake in our country. Some members of the Mojave or Mohave family of rattlesnakes in the southwest carry the Mojave toxin which is neurotoxic and can induce paralysis1.
Bite risk
Most snake bites occur on the extremities3 and victims are commonly young adult males involved with the use of alcohol (go figure) or folks working around their home.4 Also at risk are snake handlers (religious or professional), snake collectors and employees around snake farms, research centers, and zoos where exposure to domestic and foreign venomous snakes is possible.
Fortunately, most US snake bite victims survive. The death rate for US snakebites averages five deaths per year, mostly due to pit vipers5. Using the average snake bite data below, that’s only one death per 2,795 bites or an annual death rate of 0.18% (of course it’s 100% if you’re one of the).5
So what’s your bite risk? Below is US data reported to the National Poison Center Database from 2000 to 20076 (annual average in parenthesis).
- 9571 (1196) rattlesnake bites
- 7724 (965) copperhead (highland moccasin) bites
- 1362 (170) cottonmouth (water moccasin) bites
- 3063 (382) unknown pit viper bites
- 656 (82) coral snake bites
And these were only the reported numbers, which always means there were unreported bites.
Of interest, but no utility, the cottonmouth is sometimes called a water moccasin and the copperhead a highland moccasin. Why moccasin? It is unknown but one rumor has it that neither the cottonmouth nor the copperhead are equipped with rattles like their cousin, thus move about quietly as do humans wearing moccasins. And if you want to know how the venomous snakes really got their poison click here.
In case of bite
So what happens if you get bit? Or you are caring for the bitten? First, remind yourself or the patient that they are not going to die from the snakebite (almost 100% true) and to keep calm which lessens the increase in heart rate and decreases circulation which will help decrease the absorption of the venom.
Take care of any immediate threats. Make sure the offending snake is not close by and remember that dead snakes may still have a bite reflex. Assure the patient has an open airway and adequate respirations and be ready to intervene if necessary. If you are IV capable, start a line. Immobilize the bitten part if possible to slow absorption of venom.
Now, do you elevate the bitten part or keep it low?
Logic suggests that if the bite produces mostly local damage you would want to elevate above the heart to help prevent or decrease edema and additional tissue damage; but if the bite is producing systemic symptoms like shock or bleeding then perhaps the bitten part should be lowered to decrease venom absorption. Or perhaps the best bet is to keep the involved body part level with the heart. That may be the most logical position because we may not be able to determine if the bite will progress one way or the other.
Determine the time of the bite if possible. Mark a spot above and below the bite and measure the circumference, note the time and repeat the measurement every 10-15 minutes during transport if not too busy with more urgent treatment. Mark the leading edge of any bruising and/or swelling and note the time. The rate of progression of signs at the bite site and the development of systemic symptoms or signs will help determine if antivenom is indicated and the amount of antivenom administered.3 Crofab is the anitvenom for pit viper envenomation and is commonly available. However there is a dwindling supple of coral snake antivenom as the only company that manufactured the product has ceased production.7 Fortunately, another company has initiated production of a new anti-neurotoxin called Anacoral Antivenom and clinical trials by the University of Arizona will begin in June of this year.
Identify the snake without endangering yourself, like a cell phone photo or two. And if you have that capability, take a picture of the bite site and note the time, then repeat if there is change.
DO NOT cut, suck, shock, or freeze the bite site nor restrict blood or lymphatic flow in or out; these all makes it worse. However, for a neurotoxic snake bite it appears that a pressure immobilization wrap from below the bite to above the bite may be of benefit if done appropriately.9,10 But discuss this technique with your medical director before utilization.
So what have we learned?
- Don’t play with snakes while intoxicated
- Wear snake proof clothing when working in your yard
- Know what’s lurking in your neighborhood
- And if you do get bit, relax, it may hurt but you won’t die (most of the time)
References
1. White J. Snake Venoms and Coagulopathy. Toxicon. 2005;45:951-967.
2. Snake Venom. Available at http://www.chm.bris.ac.uk/webprojects2003/stoneley/types.htm. Accessed April 14, 2011.
3. Gold BS, Barish RA, Dart CD. North American Snake Envenomation: Diagnosis, Treatment, and Management. Emerg Med Clin N Am. 2004;22:423-443.
4. O’Neil ME, Mack KA, Gilchrist J, Wozniak EJ. Snakebite Injuries Treated in the United States Emergency Departments, 2001-2004. Wilderness and Environmental Medicine. 2007;18:281-287.
5. Bellman L, Hoffman B, Levick NR, Winkel KD. US Snakebite Mortality, 1979-2005. J Med Toxicol. 2008;4(1):45.
6. Spiller HA, Bosse,GN, Ryan ML. Use of Antivenom for snakebites reported to United States Poison Centers. Am J Emerg Med. 2010;28(7):780-85.
7. Seifert SA. Abstracts of the Coral Snake Antivenom Conference, January 28, 2009. Journal of Medical Toxicology. 2009;5(4):250-256.
