Moccasin Envenomation
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Moccasins are new world pit vipers (family Viperidae, subfamily Crotalinae), which may be identified by a heat-sensing pit anteroinferior to each eye, elliptical pupils, a triangular head, and undivided subcaudal scales. See the image below.
Moccasins comprise the genus Agkistrodon, which includes the cottonmouth (Agkistrodon piscivorus) and copperhead (Agkistrodon contortrix) in the southeastern United States; the cantil (Agkistrodon bilineatus) in Mexico and Central America; the mamushi (Agkistrodon blomhoffii), Siberian pit viper (Agkistrodon halys), and Central Asian pit viper (Agkistrodon intermedius) in central and northeastern Asia; and the Malayan pit viper (Calloselasma rhodostoma) and hundred-pace snake (Deinagkistrodon acutus) in southeastern Asia. See the image below.
Envenomation occurs when the moccasin injects venom via hollow movable fangs located in the anterior mouth. The effects of moccasin envenomation are generally similar to rattlesnake envenomation. However, in most cases, moccasin envenomation is less serious than envenomation by rattlesnakes. For further discussion of more severe pit viper envenomation, see Rattlesnake Envenomation.
Moccasin venom is complex, with nearly 50 identified components. These can be broken down into four major categories [1] :
Proteolytic enzymes that directly destroy tissue, as happens in digestion of prey animals
Inflammatory mediators, including histamine- and bradykinin-like factors, that cause pain, erythema, swelling, and occasionally distributive shock
Fibrinolytic enzymes that cleave fibrin into ineffective D-dimers, resulting in coagulopathy
Antiplatelet factors that cause thrombocytopenia
Although neurotoxic factors can be detected in moccasin venom, clinically significant neurotoxicity does not occur with envenomation by copperheads or cottonmouths.
United States
Approximately 5,000 snakebites are reported to poison centers each year. Of the venomous snakebites for which the species is known, moccasins are responsible for 42%. The vast majority of these (86%) are copperhead envenomations. In portions of the southeastern United States, copperheads account for 85% of all reported snake envenomations. [2, 3] See the image below.
International
An estimated 300,000-400,000 venomous snakebites occur per year worldwide. The proportion of these caused by Agkistrodon species is not known.
Incidence of snakebite is higher in males than in females.
Young adults are bitten most commonly. [4]
The American Association of Poison Control Centers (AAPCC) previously reported only one death from moccasin envenomation since its first annual report in 1983; however, the latest (2014) report includes 1 reported copperhead envenomation death. [5] Prospective studies of morbidity from moccasin envenomation have not been conducted. [6] However, in two retrospective studies of copperhead victims, patients missed a median of 2 or 6 weeks of work.
Nearly all patients fully recover after moccasin envenomation.
Some patients have long-term problems with limb pain and/or swelling, particularly after physical exertion. The proportion of patients that develop these sequelae and the impact of antivenom therapy on this incidence are not known.
Call professionals, such as animal control, to move snakes.
Never attempt to handle, possess, or kill venomous reptiles.
For patient education resources, see the patient education article Snakebite.
Wingert WA, Pattabhiraman TR, Cleland R, Meyer P, Pattabhiraman R, Russell FE. Distribution and pathology of copperhead (agkistrodon contortrix) venom. Toxicon. 1980. 18(5-6):591-601. [Medline].
Sullivan JB, Wingert WA, Norris RL Jr. North American venomous reptile bites. PS Auerbach, ed. Wilderness Medicine: Management of Wilderness and Environmental Emergencies. St. Louis: Mosby-Year Book; 1995. Vol 2: 680-709.
Thorson A, Lavonas EJ, Rouse AM, Kerns WP 2nd. Copperhead envenomations in the Carolinas. J Toxicol Clin Toxicol. 2003. 41(1):29-35. [Medline].
Bush SP, Thomas TL, et al. Envenomations in children. Pediatr Emerg Med Rep. 1997. 2:1-12.
Mowry JB, Spyker DA, Brooks DE, McMillan N, Schauben JL. 2014 Annual Report of the American Association of Poison Control Centers’ National Poison Data System (NPDS): 32nd Annual Report. Clin Toxicol (Phila). 2015. 53 (10):962-1147. [Medline].
Spiller HA, Bosse GM. Prospective study of morbidity associated with snakebite envenomation. J Toxicol Clin Toxicol. 2003. 41(2):125-30. [Medline].
Scharman EJ, Noffsinger VD. Copperhead snakebites: clinical severity of local effects. Ann Emerg Med. 2001 Jul. 38(1):55-61. [Medline].
Bush SP, Hegewald KG, Green SM, Cardwell MD, Hayes WK. Effects of a negative pressure venom extraction device (Extractor) on local tissue injury after artificial rattlesnake envenomation in a porcine model. Wilderness Environ Med. 2000 Fall. 11(3):180-8. [Medline].
Bush SP. Snakebite suction devices don’t remove venom: they just suck. Ann Emerg Med. 2004 Feb. 43(2):187-8. [Medline].
Burch JM, Agarwal R, Mattox KL, Feliciano DV, Jordan GL Jr. The treatment of crotalid envenomation without antivenin. J Trauma. 1988 Jan. 28(1):35-43. [Medline].
Whitley RE. Conservative treatment of copperhead snakebites without antivenin. J Trauma. 1996 Aug. 41(2):219-21. [Medline].
Dart RC, McNally JT, Spaite DW, Gustafson R. The Sequelae of Pitviper Poisoning in the United States. Campbell JA, Brooks DE, editors. Biology of the Pitvipers: Tyler, TX: Selva; 2002. 395-404.
Gold BS, Wingert WA. Snake venom poisoning in the United States: a review of therapeutic practice. South Med J. 1994 Jun. 87(6):579-89. [Medline].
Walter FG, Stolz U, Shirazi F, Walter CM, McNally J. Epidemiology of the reported severity of copperhead (Agkistrodon contortrix) snakebite. South Med J. 2012 Jun. 105(6):313-20. [Medline].
Lavonas EJ, Ruha AM, Banner W, Bebarta V, Bernstein JN, Bush SP, et al. Unified treatment algorithm for the management of crotaline snakebite in the United States: results of an evidence-informed consensus workshop. BMC Emerg Med. 2011 Feb 3. 11:2. [Medline]. [Full Text].
Lavonas EJ, Gerardo CJ, O’Malley G, Arnold TC, Bush SP, Banner W Jr, et al. Initial experience with Crotalidae polyvalent immune Fab (ovine) antivenom in the treatment of copperhead snakebite. Ann Emerg Med. 2004 Feb. 43(2):200-6. [Medline].
Dart RC, Seifert SA, Carroll L, Clark RF, Hall E, Boyer-Hassen LV, et al. Affinity-purified, mixed monospecific crotalid antivenom ovine Fab for the treatment of crotalid venom poisoning. Ann Emerg Med. 1997 Jul. 30(1):33-9. [Medline].
Lawrence WT, Giannopoulos A, Hansen A. Pit viper bites: rational management in locales in which copperheads and cottonmouths predominate. Ann Plast Surg. 1996 Mar. 36(3):276-85. [Medline].
Ruha AM, Curry SC, Beuhler M, Katz K, Brooks DE, Graeme KA, et al. Initial postmarketing experience with crotalidae polyvalent immune Fab for treatment of rattlesnake envenomation. Ann Emerg Med. 2002 Jun. 39(6):609-15. [Medline].
Dart RC, Seifert SA, Boyer LV, Clark RF, Hall E, McKinney P, et al. A randomized multicenter trial of crotalinae polyvalent immune Fab (ovine) antivenom for the treatment for crotaline snakebite in the United States. Arch Intern Med. 2001 Sep 10. 161(16):2030-6. [Medline].
Gerardo CJ, Lavonas EJ. The Efficacy of Early Fab Antivenom Versus Placebo Plus Optional Rescue Therapy on recovery From Copperhead Snake Envenomation. Toxicon. Jul 2016. 117:102.
Jurkovich GJ, Luterman A, McCullar K, et al. Complications of Crotalidae Antivenin Therapy. Journal of Trauma. 1998. 28:1032-1037.
Sean P Bush, MD, FACEP Professor of Emergency Medicine, The Brody School of Medicine at East Carolina University
Sean P Bush, MD, FACEP is a member of the following medical societies: American College of Emergency Physicians, International Society on Toxicology, Society for Academic Emergency Medicine, Wilderness Medical Society
Disclosure: Nothing to disclose.
Eric J Lavonas, MD, FACEP Associate Director, Rocky Mountain Poison and Drug Center; Assistant Professor, University of Colorado School of Medicine
Eric J Lavonas, MD, FACEP is a member of the following medical societies: Alpha Omega Alpha, American Academy of Clinical Toxicology, Phi Beta Kappa, American College of Emergency Physicians, American College of Medical Toxicology, Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.
John T VanDeVoort, PharmD Regional Director of Pharmacy, Sacred Heart and St Joseph’s Hospitals
John T VanDeVoort, PharmD is a member of the following medical societies: American Society of Health-System Pharmacists
Disclosure: Nothing to disclose.
David Eitel, MD, MBA Associate Professor, Department of Emergency Medicine, York Hospital; Physician Advisor for Case Management, Wellspan Health System, York
David Eitel, MD, MBA is a member of the following medical societies: American College of Emergency Physicians, American Society of Pediatric Nephrology, Society for Academic Emergency Medicine, Society of Critical Care Medicine
Disclosure: Nothing to disclose.
Joe Alcock, MD, MS Associate Professor, Department of Emergency Medicine, University of New Mexico Health Sciences Center
Joe Alcock, MD, MS is a member of the following medical societies: American Academy of Emergency Medicine
Disclosure: Nothing to disclose.
Robert L Norris, MD Professor, Department of Emergency Medicine, Stanford University Medical Center
Robert L Norris, MD is a member of the following medical societies: American College of Emergency Physicians, Wilderness Medical Society
Disclosure: Nothing to disclose.
Moccasin Envenomation
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