“TREATMENT FOR SNAKEBITE IN US NAVAL UNITS DEPLOYED ASHORE AND THE USE OF ANTIVENIN”

Situation: A few US Naval Medical personnel who deployed ashore in Kuwait and Iraq during Operation Iraqi 
Freedom, Phase I, observed that “selected USN medical units forward deployed in direct support of ground combat 
elements should have venomous snake antitoxin in order to initiate immediate treatment of venomous snakebites.”

Observation: The US Military Medical Officers and Epidemiologists consulted on this issue determined it is NOT a 
good Force Health Protection measure to provide antitoxin (antivenin) to Hospital Corpsmen and Medics and Level I
and II medical care units. All did agree that, although venomous snakebite have posed a small-to-moderate 
medical threat to modern militaries worldwide, the threat can be reduced by medical planning which must include:

	• Briefing preventive (snake avoidance) measures before and during deployments to areas in 
	which venomous snakes live.

	• Ensuring personnel are trained and equipped to provide first aid to victims known or suspected 
	to have been bitten by a venomous snake

	• Establishing a dedicated casualty evacuation plan for the area of operations that ensures known 
	or suspected snakebite victims are rapidly transferred from the field to a ICU-capable medical 
	treatment facility capable of administering species-specific or polyvalent antitoxin, if indicated, and 
	diagnosing and treating life-threatening complications of the venom itself and possible allergic 
	reactions to any antitoxin administered.

A more detailed discussion is in order:
	
	• First, although envenomation can be a life-threatening emergency and the care and evacuation 
	of victims of poisonous snakebite must be planned for in U.S. Military operations in areas where 
	poisonous snakes or arthropods are found, poisonous snakebite has not been a major medical 
	problem for U.S. Forces:

		- Per discussions in April 2004, with the Mortality Surveillance Division, Office of 
		the Armed Forces Medical Examiner, Armed Forces Institute of Pathology (AFIP), 
		in the U.S. Military, snakebites are not a significant cause of mortality in U.S. active 
		duty personnel in the continental United States and overseas, and only a rare 
		cause of hospitalization:

			- - There have been no U.S. Military deaths due to snakebite over 
			the last six years, according to the DOD Mortality Register, which 
			contains detailed cause and manner of death of all U.S. active duty 
			personnel since 1998.

			- - There have been no reported U.S. Military deaths due to snakebite 
			since 1978, as indicated by the AFIP mortality files, which contain 
			“unusual cases” and all autopsies performed by Armed Forces Medical 
			Examiner – approximately 1/3 of all active duty deaths.

			- - From 1994 to 2003, four U.S. active duty personnel (two Air Force, 
			two Marine Corps) were admitted to U.S. Military medial treatment facilities 
			(MTF) for snakebite (ICD-9 Code: 905.0), as determined by a review of 
			the DOD Medical Surveillance System.

[Note: The U.S. Military physicians consulted on this issue are “pretty sure that some bites never make into the DOD Medical Surveillance System.” 
For instance, one USAF physician was involved in the treatment of two snakebite injuries at Eglin AFB from 1997-2001: one involved an Army 
Ranger Instructor bitten by a “Timber Rattler” at the Ranger Jungle School on the Eglin reservation; the other was an Air Force Combat Controller 
who was bitten by his “pet Western Diamondback.” The same physician also treated an Airman at Brooke Army Medical Center in 2002. The four 
snakebites indicated above as being recorded in the DOD Medical Surveillance System could include these two USAF personnel, but would not 
include the USA Ranger.]

Likewise, data shows that venomous snakebites have posed a small-to-moderate medical problem to modern 
militaries worldwide:

		- A retrospective study of soldiers in field units of the Israeli Defense Forces between 
		the years 1993-1997 reports a yearly rate of 32-52 (mean 43.6) physician visits per 
		100,000 soldier years for snakebites – and 1370-1729 (mean 1478) physician visits 
		per 100,000 soldier years for arthropod bites. There were no fatal envenomations 
		during the study period. The paper does not indicate the extent of physician 
		intervention, the number of evacuations, or the number of bites that required antivenin. 
		The authors do conclude that poisonous animals pose a significant threat to field 
		soldiers, in that their bites are painful, often debilitating and potentially life-threatening. 

		[Haviv et al, “Poisonous Animal Bites in the Israeli Defense Forces,” Public Health Review (Israel) 1998; 26: 237-245.] 

They and other authors conclude this threat can be reduced by proper common-sense preventive measures and 
that such measures should be stressed during Force Health Protection briefings before and during operations in 
areas where poisonous snakes live. The preventive measures advocated include:

		- Do not enter snake-infested areas without adequate protective clothing: calf-high 
		footwear, thick socks and fully-extended pant legs – full-length sleeves rolled down and 
		gloves only offer partial protection.

		- Do not put hands or feet in places that cannot be seen clearly, and do not put them in 
		places without first looking

		- Do not overturn or lift rocks, boulders or fallen branches or trees with unaided hands; 
		use entrenching tools or sticks or some other tool or use your foot if your ankle and leg 
		are properly protected; use careful techniques for digging fighting holes and trenches 
		and filling sandbags

		- Do not step over an obstacle (log, bush or boulder) if the other side is not visible; rather, 
		step on the obstacle and ensure it is safe before stepping down

		- Do not sit down before looking around carefully

		- Do not put sleeping bags near rocks, rubbish plies or cave entrances

		- Do not handle, antagonize or otherwise disturb snakes

		- Do not handle freshly killed venomous snakes.

	[Murdock et al, “Prevention and Emergency Field Management of Venomous Snakebites during Military Exercises,” 
	Military Medicine, 1990; 155, 12:587; Ismail and Memish, “Venomous Snakes of Saudi Arabia and the Middle East; 
	a keynote for travelers, International Journal of Antimicrobial Agents, 2003, 21: 164-169.]

	[Note: One U.S. Military physician stressed that the majority of snakebites in the U.S. involve young adult males who
	are bitten while “playing” with the snake. Alcohol is frequently involved. His experience in “treating more than 50 
	snakebite victims over the years has been that most victims (approximately 40 of 50) were intoxicated and messing 
	with the snake.” His number one rule in preventing snakebites in young active duty males is: “Don’t Mess With The 
	Snake!”]

	• Second, although all bites by poisonous snakes must be considered medical emergencies until it is 
	proven that envenomation has not occurred, many such bites will prove not to be life threatening - 
	no envenomation occurs in approximately 20% of documented bites by New-World pit vipers - 
	rattlesnake, copperhead, water moccasin, and fer-de-lance. An even higher percentage of bites 
	inflicted by other snake families (e.g., up to 50% for cobras and 75% for sea snakes) are “dry.” 

	[Harrison’s Principles of Internal Medicine, 15th Edition, 2001; 2616-2617.] 

	This is due to the circumstances of the bites, which are usually defensive in nature, and the species 
	of the snake - some having more prominent fangs, or being more aggressive biters and more likely 
	to envenomate than others. In a one-year (July 1999-July 2000) prospective study of snake bites in 
	Australia, which has 40% of the world’s neurotoxic snakes and 23% of all venomous snakes, 70 
	patients from the general population admitted to the emergency department with a diagnosis of 
	snake bite, 35 (36%) had no signs of envenomation; of the remaining 45, only three (4.3%) were 
	considered severe and required antivenin. 

	[Isbister and Curry, “Suspected Snakebite: One Year Prospective Study of Emergency Department Presentations,” Emergency 
	Medicine (2003), 15, 160-169.]

	[Note: All U.S. Military physicians consulted agree that snakebite in the field must be considered a medical emergency until it is 
	PROVEN that the bite was a “dry strike” or a hit from a non-venomous snake; that is, given snakebite in the field, it best to 
	assume that envenomation has occurred. This DOES NOT mean to give antivenin every time. Indeed, antivenin should be given 
	only when there are appropriate clinical signs and symptoms. It DOES mean that “medical planning should include rapid 
	evacuation to a medical facility with ER or ICU capability where the casualty can be observed for at least six-to-eight hours in the 
	case of New-World pit viper or Old-World viper bites, and up to 24 hours for Elipidae family bites (cobras and coral snakes) and 
	Hydrophidae Family bites (sea snakes).]

	• Third, healthy young adults are most likely to survive envenomation – with the likelihood of survival 
	increasing with proper first aid and rapid transport to a high-level medical treatment facility where 
	intensive care can be rendered and species-specific antivenin can be administered safely. In the 
	United States, human mortality in the general population due to snake envenomation remains low,
	where 20 of the more than 120 species of snakes are poisonous:

		- In 1994, Gold and Wingert estimated approximately 8,000 poisonous snakebites 
		annually, resulting in about nine to fifteen fatalities, [“Snake venom poisoning in the 
		United States: a review of therapeutic practice,” South Med J 1994; 87:579-589.]

		- Langley and Morrow (1997) estimated 700-8000 bites per year, resulting in five to 
		six deaths, [“Deaths resulting from animal attacks in the United States,” Wilderness & Environmental 
		Medicine 1997; 8:8-16.]

	Per Gold and Barish, “The ultimate severity of any venomous snakebite depends on the health of the 
	person bitten and the quantity and comparative toxicity of the venom injected. These factors are 
	determined by the size and species of the snake, the number and depth of fang punctures, and the 
	age, size, and underlying medical condition of the victim.” [“Venomous Snakebites: current concepts in diagnosis, 
	treatment and management,” Emergency Medical Clinics of North America, 1992; 249-267.] 

	All studies show that, although the preponderance of American victims of snakebite are young 
	(between 17-27 years of age), the majority of the deaths occur in those with systemic disease and in 
	the very young and very old - outside the U.S. Military active duty age group. Worldwide, there are 
	some 3000 identified species of snakes, of which some 15% (450) are considered dangerous to 
	humans. However, estimates of death due to snakebite in general populations are either unavailable 
	or highly unreliable, as many serious envenomations and deaths occur in medically underserved or
	non-served populations and areas.

	• Fourth, it is virtually impossible to procure, distribute, and store potent species-specific antivenin (for 
	the different venomous snakes and arthropods in a given operating area) or polyvalent antivenin at 
	lower level medical units, forward deployed ashore in direct support of ground combat elements. 

	Dr. Otten, CAPT, MC, USNR, an Emergency Physician and Toxicologist, University of Cincinnati, reports 
	that, “In Desert Storm we deployed troops with antivenin for pit vipers (mostly New World rattlesnake, 
	copperhead, water moccasin, fer-de-lance), which was worthless because the antivenin was absolutely 
	no good against any of the snakes found in S.W. Asia.” [Otten, “Scenario Seven: Snakebite,” Wilderness & 
	Environmental Medicine, Volume 9, 99-103 (1998).]

	• Fifth, a definitive diagnosis of snakebite poisoning requires identification of the snake and signs and 
	symptoms of envenomation. It is essential not to mistake autonomic reactions in response to the bite 
	for actual envenomation, thereby leading to unwarranted treatment. [Harrison’s Principles of Internal Medicine, 
	15th Edition.] 

	Unless the person who is bitten knows the snake to be non-poisonous (e.g., the North American garter 
	snake or king snake), the initial symptom of snakebite is usually related to a “terror reaction,” 
	characterized typically by autonomic discharge: nausea, vomiting, diarrhea, dizziness, fainting, 
	dyspnea, tachycardia, and cold, clammy skin. Conversely a casualty may enter a stage of lethargy and 
	withdrawal.

	[Note: The U.S. Military physicians who reviewed this paper agreed that such “terror reactions” to bites by non-venomous snakes 
	usually “sort themselves out early in the clinical course.” The signs and symptoms characteristic of envenomation by the families 
	Viperidae (Old-World vipers that include puff adders, desert adders and true vipers) and Crotalidae (New-World pit vipers such as 
	the rattlesnake, copperhead, and cottonmouth) result from the primarily hemotoxic effect of the venom: severe pain, progressive 
	swelling and ecchymosis beginning at the bite site, a metallic taste in the mouth, ptosis, and thrombocytopenia.]

	[Note: The Mojave Rattlesnake (Crotalus scutalus) is a particularly dangerous species for U.S Military personnel in the field in the 
	U.S. Southwest. It is renowned over most of its range – the desert of California, Nevada and Arizona and Mexico - for its ability to
	inflict severe, even fatal, injury without any appreciable degrees if pain or swelling; patients bitten by the Mojave Rattlesnake 
	often do not exhibit these signs and symptoms because its venom is more neurotoxic than that of the average pit viper.]

	One expert regards bites by Elapids (cobras, mambas, craits, and coral snakes) as “clinically more 
	interesting,” in that, “Early on, it is difficult to determine if the nausea, dyspnea and fainting are due to 
	venom or fear. It is important to look for other neurological signs, and, if any are positive, one must 
	treat for a significant envenomation.”

	• Sixth, MEDICAL PLANNING MUST PROVIDE for the rapid transfer of a proven envenomation victim 
	to a Level III or higher facility that can diagnose, monitor and treat life-threatening emergencies 
	(multiple organ and system failures) and administer large doses (many vials) of species-specific or 
	polyvalent antivenin. Planning must also provide for the distribution to designated higher-level facilities 
	of antivenin from a source approved by the Commander of the Geographical Command.

	[Note: U.S. Military physicians agree, “Yes! Medical planning must include the capability to get these patients out of the field and to 
	an ICU-capable facility ASAP!]

	• Finally, Administration of antivenin is the only effective treatment for moderate to severe 
	envenomations. Its effectiveness is both dose- and time-related, with its greatest effect occurring 
	during the first four hours. It is less effective after 12 hours, but has reversed coagulopathies after 
	24 hours. [Gold, “Snake Venom Poisoning,” Conn’s Current Therapy, 1167-1170 (1999); Gold and Barish, Emergency 
	Medical Clinics of North America, (1992).]

	• Antivenins are derived from the serum of different animals: some countries use horses, some use 
	goats, others sheep. The original Wyeth Crotalid polyvalent antivenin was made from horse serum; 
	the newer CroFab Crotalid antivenin is derived from sheep and considered the safer of the two in 
	that it has a significantly lower incidence of severe allergic reactions. However, it must be stressed 
	that anyone administering antivenin must be alert to possible immediate or delayed 
	antivenin-precipitated anaphylactic reactions in 15-25% of patients. They must also be prepared to 
	deal with serum sickness days after administration of antivenin which, in a retrospective study of 
	snakebites in Arizona over a five-year period, occurred in 34%, 36%, 88% and 100% cases when 
	patients received fewer than 20, 20 to 29, 30 to 39, or 40 or more vials of polyvalent antivenin 
	respectively to presumed victims of Rattlesnake bites. [Lo Vecchio et al, “Serum Sickness Following 
	Administration of Antivenin (Crotalidae) Polyvalent in 181 Cases of Presumed Rattlesnake Envenomation,”  Wilderness & 
	Environmental Medicine, Volume 14, 220-221 (2003).] 

	A snakebite expert at Loma Linda lost a patient to snakebite last year, despite progressive, 
	appropriate antivenin therapy. The patient had a cerebral vascular attack (CVA) two days into his 
	course of therapy. It remains unknown if the CVA was due to the envenomation, the administration 
	of antivenin, or just a coincidence. Dr. Edward Otten notes, “The problems involved with using 
	antivenin are much more serious than the benefits of using them in the field.” [Otten, “Scenario Seven: 
	Snakebite,” Wilderness & Environmental Medicine, 1998, Volume 9, 99-103.]

Analysis/Mission Impact:
	• Venomous snakebites do not occur in significant numbers in U.S Military personnel in the United 
	States or overseas. Many young American males of active duty age are bitten by poisonous snakes 
	while handling, antagonizing or attempting to kill the animals; in approximately 50 percent of the 
	cases, the young men have consumed alcohol.

	• It is not practical to add species-specific or polyvalent antivenin to the Authorized Medical Allowance 
	List (AMMAL) of forward-deployed Level I and II medical facilities.

	• Although the vast majority of venomous snake - and arthropod - bites sustained by US Military 
	personnel are not life-threatening, medical support plans for US combat forces should include:

		- Force Health Prevention briefings regarding snake avoidance and snakebite 
		prevention

		- First responder training to evaluate bites to determine if poisoning has occurred, 
		and, when confronted with envenomation, provide effective first responder (tactical 
		field) care. The basic elements of first responder aid are:

		-- Move the victim and rescuers to a place of safety, keep the casualty as inactive 
		as possible to limit the systemic spread on venom, and rapidly transport them to 
		definitive medical care.

		-- The injured part (usually a limb) should be immobilized in a functional position below 
		the level of the heart and a pressure wrap placed proximal to the bite – if it can be 
		placed within 30 minutes of the bite. The wrap should be just tight enough to impede 
		lymphatic flow, thereby delaying the systemic absorption and circulation of the venom - 
		but not so tight to restrict venous or arterial circulation. If placed, pressure wraps 
		should be left in place until arrival at the treating facility, probably until after the 
		administration of antivenin.

[Note: Some providers strongly advocate the use of pressure-immobilization techniques only for snakebites caused by elapid or 
neurotoxic-predominant species. However, other providers advocate pressure-immobilization for all venomous snakebites. 
Current research projects addressing this issue are expected to be completed soon.]

[Note: Use of the Extractor Pump has been deleted from US SPECOPS protocols after recent studies showed it is not 
effective and may, in some cases, cause severe necrosis at the suction site. ]

		-- Potentially constricting items, such as watches, rings, and tight clothing should be 
		removed prior to the onset of edema.

		-- Do not give food, drink or aspirin-containing medicines; analgesia (e.g., morphine) 
		may be required

		-- During transport from the point of injury to Level I Care (e.g., a Battalion Aid Station) 
		the casualty must be given supportive care and reassurance that CASEVAC to definitive 
		care is forthcoming.

		- En route care to definitive treatment in a Level III or higher medical facility capable of 
		administering large amounts of antitoxin and treating its complications and the venom-
		induced multiple-organ failure.

		- Medical Planning to that includes a tactical CASEVAC plan to support the timely 
		evacuation as indicated above.

		- The source(s), approved by the U.S. Geographic Commander, from which snake and 
		arthropod antivenin can be provided to the facility where U.S. personnel will be treated for 
		proven envenomations.

	• Excellent sources regarding snakebite during wilderness and military operations are:

		- The proceedings of the Wilderness Medical Society workshop “Wilderness Medicine 
		Scenarios for Military Special Operations,” published as a special issue of “Wilderness
		and Environmental Medicine,” Volume 9, Number 2, Scenario Seven, “Snakebite,” 
		99-103, (1998).

		- Special Operations Forces Medical Handbook, Chapter 17: “Toxicology: Venomous 
		Snake Bite,” 5/142-5/145, (2001)

		- Anderson, “Rattlesnake Bite and the Art of Medicine - Sorting Out Therapies,” Journal 
		of Special Operations Medicine, Volume 4, Edition 1, 52-57 (2004).

		- “Wilderness Medicine,” 4th Edition, Auerbach, editor, (Mosby 2001).

		- “Field Guide to Wilderness Medicine,” Auerbach, Donner, and Weiss, (Mosby 2003); a 
		quick reference “handbook” associated with Auerbach’s Wilderness Medicine Textbook.

	• The initial symptom of most bites in which envenomation occurs is progressively intensive pain, which
	commonly starts within five to 30 minutes, with profound envenomation usually resulting in shorter time 
	of onset of symptoms. Systemic signs and symptoms follow, including evolving edema and erythema or 
	ecchymoses both proximally and distally as the venom spreads. Therefore rapid evacuation is required 
	to an MTF which can:

		- Treat the significant complications of envenomations - altered mental state, respiratory
		problems which can progress to arrest, hemolysis, rhabdomyolysis, and renal failure

		- Administer antitoxin that is species-specific whenever possible and acquired from 
		approved sources

		- Treat potentially life-threatening systemic reactions to antitoxin that occur in 15-25% of 
		all cases.

	• Treatment at a medical facility consists of initial evaluation and definitive care, if necessary. Initial 
	evaluation includes examination of the injured part of the body, as well as a full evaluation of the 
	neurologic, cardiovascular, and pulmonary systems. Laboratory evaluation is vital, including tests of 
	clotting function (whole blood clotting time is sensitive), renal function, and for hemolysis and 
	rhabdomyolysis. Treatment with antivenom is indicated for cases where systemic toxicity is present.

	• Finally, the treatment of clinically significant venomous snakebites is complicated. Antivenom should 
	not be administered in the field; it should only be administered in an intensive care setting, after 
	pre-medication, where hemodynamic and airway emergencies can be managed. The literature is clear 
	that the adverse effects of antivenin are significant – including anaphylactic reactions and serum 
	sickness. Note also that bites severe enough to warrant specific treatment often needed significant 
	amounts of antivenin; the experience from Arizona showed a mean of 38 vials administered, and 31% 
	received 40 or more vials of antivenin, There is a very significant risk of immediate effects, and with 
	doses needed to counteract a severe envenomation the risk of serum sickness approaches unity.

Plans/Recommendations:

	1. Medical personnel assigned to U.S. Naval units should conduct Force Health Prevention briefings 
	regarding snake avoidance and snakebite prevention before and during operations in areas where 
	poisonous snakes and arthropods live, with emphasis on the poisonous animals that live in the area of 
	operations.

	2. Medical personnel assigned to U.S. Naval units that will operate ashore in areas where poisonous 
	snakes and arthropods live should be capable of and equipped to administer effective first responder
	care to casualties suspected or know to have been envenomated by a poisonous snake or arthropod.

	3. Medical plans should include emergency CASEVAC of envenomation victims to designated upper 
	Level medical treatment facilities capable of administering intensive care and administering 
	species-specific antivenin, derived from sources approved by the Commander of the Geographical 
	Command.

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