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"Red touch yellow, kills a fellow; red touch black, venom lack." Of all the childhood rhymes we've grown up learning, this one might be high on the list of ones to remember if you live in coral snake country. If you aren't familiar with this saying, it refers to distinguishing the venomous coral snake from its nonvenomous look-alikes (e.g., the king snake, shovel-nosed snake, and milk snake). It's important to note that this general rule doesn't apply to non-native coral snake species, which might have different patterns. Coral snakes are members of the Elapidae family, which includes cobras. Coral snakes usually have a pattern of red, black, yellow (or white) colored rings that span their bodies. For the purposes of this article, we'll focus primarily on the three species found in the US, which are:
- Eastern coral snake (Micrurus fulvius) - Found in Florida and the southeastern US
- Texas coral snake (Micrurus tener) - Found in Texas and northwestern Mexico
- Arizona or Sonoran coral snake (Micruroides euryxanthus) - Found in southeastern US, and Sonora, Mexico)
By nature, coral snakes are reclusive and seldom bite unless they're provoked or threatened. Compared to their pit viper counterparts (e.g., rattlesnakes), coral snake bites are uncommon and represent only about 2% of snake bites reported to US Poison Centers annually. Of the three species in the US, bites by the eastern coral snake tend to be the most severe, while those of the Arizona/Sonoran coral snake aren't generally considered medically significant and have not been shown to produce severe toxicity.
Coral snakes have small, fixed fangs, and when they bite they tend to latch onto their prey and "chew" for a few seconds in order to deliver their venom. Compared to other venomous snakes, their bite marks can be easily missed, often showing no significant local tissue damage, obvious injury, or pain. However, the venom contains very potent neurotoxins that can cause severe illness or death if left untreated. The neurotoxic venom blocks an important neurotransmitter called acetylcholine, which is important for the activation of muscles in the body. Blockade of acetylcholine after envenomation can lead to weakness and paralysis and even complete respiratory failure in severe cases. The effects of the venom are usually delayed (up to 13 hr) but progress rapidly once they develop. Symptoms of a coral snake envenomation can include nausea, vomiting, paresthesias (abnormal sensations), slurred speech, double vision, ptosis (drooping eye), muscle twitching, weakness, and paralysis. The major cause of death from coral snake envenomations is respiratory failure as a result of neuromuscular weakness.
Given the potentially serious outcomes after a coral snake bite, all people with a suspected envenomation should be seen in a hospital immediately and observed for at least 24 hours. The traditional treatment for coral snake envenomation has been a horse-derived IgG antibody antivenom produced by Wyeth Pharmaceuticals (now a subsidiary of Pfizer, Inc.) called the North American Coral Snake Antivenin. However, the manufacturer stopped production in 2006. The remaining available antivenom has passed the manufacturer-assigned expiration date of 2008, but FDA continues to provide information on expiration date extensions based evaluation of stability data. Because having a supply of the antivenom is uncommon in most hospitals, healthcare providers need to work with their regional Poison Control Center to locate a source of supply. If the antivenom is available, if and when to start is decided on a case-by-case basis after careful risk/benefit assessment as antivenom administration is not without dangers. If the antivenom is unavailable, management of the patient is focused on supportive care, which includes airway management with mechanical ventilation. There are other treatment options that have been shown to possibly provide benefit for certain coral snake bites, like the anticholinesterase drug neostigmine. However, data on its efficacy is limited and inconsistent. In all cases, discussion among the healthcare providers, Poison Control Centers, and toxicologists is key to providing optimal care for each patient.
If you or someone you know has been bitten by a coral snake, seek medical attention by calling 911 or Poison Control (1-800-222-1222), or use the webPOISONCONTROL® online tool for guidance.
Kristina Yee, PharmD
Certified Specialist in Poison Information
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