Background

Approximately 40-50 species of venomous coral snakes exist in North America and South America, with the greatest variety from Mexico to northern South America. A number of African and Asian coral snake species also exist. All coral snakes belong to the family Elapidae; Micrurus fulvius (eastern coral snake) and Micrurus tener (Texas coral snake) are the most important species in the United States.

Another US coral snake, Micruroides euryxanthus (Sonoran or Arizona coral snake), is a relatively innocuous snake, and no deaths have been attributed to its bite.

Coral snakes tend to be relatively shy creatures, and bites are uncommon. Coral snakes account for less than 1% of venomous snakebites in the United States. Most people bitten by coral snakes are handling them intentionally. Most bites occur in the spring or fall.

Pathophysiology

The coral snake venom apparatus is composed of a pair of small, fixed, hollow fangs in the anterior aspect of the upper jaw through which the snake injects venom via a chewing motion (see the image below). Unlike pit vipers, such as rattlesnakes, copperheads, and cottonmouths, which strike quickly, coral snakes must hang on for a brief period to achieve significant envenomation in humans.

Coral snake skull.

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Coral snake venoms tend to have significant neurotoxicity, inducing neuromuscular dysfunction. They have little enzymatic activity or necrotic potential compared with most vipers and pit vipers. These venoms tend to be some of the most potent found in snakes, yet the venom yield per animal is less than that of most vipers or pit vipers. Because of the relatively primitive venom delivery apparatus, as many as 60% of those bitten by North American coral snakes are not envenomed (ie, they receive a "dry bite").

Frequency

United States

There were 76 alleged coral snake bites reported to the American Association of Poison Control Centers in 2015.^[1]

International

No accurate information on international incidence is available, but there are no regions of the world where coral snake bites would be considered common.^{[2, 3]}

Prognosis

With sound supportive care (eg, prevention of aspiration) and appropriate antivenom administration, when available, prognosis following coral snake envenomation is excellent; expect a full recovery. This is generally true, even in the absence of an available, appropriate antivenom,^[4]but the overall clinical course (including the need for prolonged intubation and respiratory support) will be longer. Patients who survive the bite may require respiratory support for up to a week and may suffer persistent weakness for weeks to months.

A single death has been reported due to a coral snake bite in the United States in the last 40 years (roughly, since coral snake antivenom became available).^[5]Before that time, the estimated case-fatality rate was 10%, and the cause of death was respiratory or cardiovascular failure.

Patient Education

For patient education resources, see the patient education article Snakebite.

Clinical Presentation

Mowry JB, Spyker DA, Brooks DE, Zimmerman A, Schauben JL. 2015 Annual Report of the American Association of Poison Control Centers' National Poison Data System (NPDS): 33rd Annual Report. Clin Toxicol (Phila). 2016 Dec. 54 (10):924-1109. [Medline].
de Roodt AR, De Titto E, Dolab JA, Chippaux JP. Envenoming by coral snakes (Micrurus) in Argentina, during the period between 1979-2003. Rev Inst Med Trop Sao Paulo. 2013 Jan-Feb. 55(1):13-8. [Medline].
Pardal PP, Pardal JS, Gadelha MA, Rodrigues Lda S, Feitosa DT, Prudente AL. Envenomation by Micrurus coral snakes in the Brazilian Amazon region: report of two cases. Rev Inst Med Trop Sao Paulo. 2010 Nov-Dec. 52(6):333-7. [Medline].
Wood A, Schauben J, Thundiyil J, Kunisaki T, Sollee D, Lewis-Younger C, et al. Review of Eastern coral snake (Micrurus fulvius fulvius) exposures managed by the Florida Poison Information Center Network: 1998-2010. Clin Toxicol (Phila). 2013 Sep-Oct. 51 (8):783-8. [Medline].
Norris RL, Pfalzgraf RR, Laing G. Death following coral snake bite in the United States--first documented case (with ELISA confirmation of envenomation) in over 40 years. Toxicon. 2009 May. 53(6):693-7. [Medline].
Cardwell MD. Recognizing dangerous snakes in the United States and Canada: a novel 3-step identification method. Wilderness Environ Med. 2011 Dec. 22 (4):304-8. [Medline].
German BT, Hack JB, Brewer K, et al. Pressure-immobilization bandages delay toxicity in a porcine model of eastern coral snake (Micrurus fulvius fulvius) envenomation. Ann Emerg Med. 2005 Jun. 45(6):603-8. [Medline].
Gray S. Pressure immobilization of snakebite. Wilderness Environ Med. 2003 Spring. 14(1):70-1. [Medline].
Simpson ID, Tanwar PD, Andrade C, et al. The Ebbinghaus retention curve: training does not increase the ability to apply pressure immobilisation in simulated snake bite--implications for snake bite first aid in the developing world. Trans R Soc Trop Med Hyg. 2008 May. 102(5):451-9. [Medline].
U.S. Food and Drug Administration. Expiration Date Extension for North American Coral Snake Antivenin (Micrurus fulvius) (Equine Origin) Lot L67530 through January 31, 2018. Available at https://www.fda.gov/BiologicsBloodVaccines/SafetyAvailability/ucm538841.htm. February 1, 2017; Accessed: August 2, 2018.
Norris RL, Bush SP. North American venomous reptile bites. Auerbach PS, ed. Wilderness Medicine. 4th ed. St. Louis: Mosby; 2001. 896-926.
Norris RL, Dart RC. Apparent coral snake envenomation in a patient without visible fang marks. Am J Emerg Med. 1989 Jul. 7(4):402-5. [Medline].
Norris RL, Ngo J, Nolan K, et al. Physicians and lay people are unable to apply pressure immobilization properly in a simulated snakebite scenario. Wilderness Environ Med. 2005. 16(1):16-21. [Medline].

Media Gallery

Snake envenomations, coral. Comparison of the harmless Lampropeltis triangulum annulata(Mexican milksnake) (top) with Micrurus tener(Texas coral snake) (bottom). Photo by Charles Alfaro.
Coral snake skull.
The Australian pressure immobilization technique: Step 1. This technique has been shown to be helpful in delaying systemic absorption of elapid venoms. A broad pressure bandage is immediately wrapped, beginning distally, around as much of the extremity as possible. No effort should be spent removing clothing prior to bandage application. The bandage is wrapped snugly, as for a severely sprained ligament. A splint (or sling when applied to the upper extremity) is then placed, and the victim is carried from the scene. The victim should expend no effort in getting to definitive care. Pressure immobilization should remain in place until the victim has reached medical care. The doctor will decide when to remove the bandages. If venom has been injected, it will move into the bloodstream quickly once the bandages are removed. The doctor should leave the bandages and splint in position until appropriate antivenom is available whenever possible. Used with permission from Commonwealth Serum Laboratories.
The Australian pressure immobilization technique: Step 2. This technique has been shown to be helpful in delaying systemic absorption of elapid venoms. A broad pressure bandage is immediately wrapped, beginning distally, around as much of the extremity as possible. No effort should be spent removing clothing prior to bandage application. The bandage is wrapped snugly, as for a severely sprained ligament. A splint (or sling when applied to the upper extremity) is then placed, and the victim is carried from the scene. The victim should expend no effort in getting to definitive care. Pressure immobilization should remain in place until the victim has reached medical care. The doctor will decide when to remove the bandages. If venom has been injected, it will move into the bloodstream quickly once the bandages are removed. The doctor should leave the bandages and splint in position until appropriate antivenom is available whenever possible. Used with permission from Commonwealth Serum Laboratories.
The Australian pressure immobilization technique: Step 3. This technique has been shown to be helpful in delaying systemic absorption of elapid venoms. A broad pressure bandage is immediately wrapped, beginning distally, around as much of the extremity as possible. No effort should be spent removing clothing prior to bandage application. The bandage is wrapped snugly, as for a severely sprained ligament. A splint (or sling when applied to the upper extremity) is then placed, and the victim is carried from the scene. The victim should expend no effort in getting to definitive care. Pressure immobilization should remain in place until the victim has reached medical care. The doctor will decide when to remove the bandages. If venom has been injected, it will move into the bloodstream quickly once the bandages are removed. The doctor should leave the bandages and splint in position until appropriate antivenom is available whenever possible. Used with permission from Commonwealth Serum Laboratories.
The Australian pressure immobilization technique: Step 4. This technique has been shown to be helpful in delaying systemic absorption of elapid venoms. A broad pressure bandage is immediately wrapped, beginning distally, around as much of the extremity as possible. No effort should be spent removing clothing prior to bandage application. The bandage is wrapped snugly, as for a severely sprained ligament. A splint (or sling when applied to the upper extremity) is then placed, and the victim is carried from the scene. The victim should expend no effort in getting to definitive care. Pressure immobilization should remain in place until the victim has reached medical care. The doctor will decide when to remove the bandages. If venom has been injected, it will move into the bloodstream quickly once the bandages are removed. The doctor should leave the bandages and splint in position until appropriate antivenom is available whenever possible. Used with permission from Commonwealth Serum Laboratories.
The Australian pressure immobilization technique: Step 5. This technique has been shown to be helpful in delaying systemic absorption of elapid venoms. A broad pressure bandage is immediately wrapped, beginning distally, around as much of the extremity as possible. No effort should be spent removing clothing prior to bandage application. The bandage is wrapped snugly, as for a severely sprained ligament. A splint (or sling when applied to the upper extremity) is then placed, and the victim is carried from the scene. The victim should expend no effort in getting to definitive care. Pressure immobilization should remain in place until the victim has reached medical care. The doctor will decide when to remove the bandages. If venom has been injected, it will move into the bloodstream quickly once the bandages are removed. The doctor should leave the bandages and splint in position until appropriate antivenom is available whenever possible. Used with permission from Commonwealth Serum Laboratories.