Venomous Snakes of Texas

[ Natural History ]

Venomous Snakes of Texas

A Field Guide

By Andrew H. Price

A thoroughly revised and updated edition of Price's Poisonous Snakes of Texas.



33% website discount price


4.5 x 7.5 | 130 pp. | 10 line drawings, 11 maps, 20 color photos, 2 tables

ISBN: 978-0-292-71967-5

Look Inside

Texas has about one hundred twenty native species and subspecies of snakes, fifteen of which are venomous. Since 1950, Texans have turned to the Poisonous Snakes of Texas pamphlet series published by the Texas Parks and Wildlife Department for help in identifying these snakes and for expert advice on preventing and treating snakebite. Venomous Snakes of Texas, a thoroughly revised and updated edition of Poisonous Snakes, carries on this tradition as a one-stop, all-you-need-to-know guide to Texas's rattlesnakes, copperheads, cottonmouths, and coral snakes.

In this authoritative field guide, you'll find:

  • Full-color photographs and a county-by-county distribution map for each species.
  • Each species' common and scientific name, description, look-alikes, and a summary sketch of its habitat, behavior, reproduction, venom characteristics, predator-prey relationships, and fossil record.
  • Up-to-date advice on recognizing venomous snakes and preventing and treating snakebite, both at home and in the field.
  • A glossary of terms and an extensive bibliography.

A special feature of this guide is an expanded treatment of the ecological and evolutionary context in which venomous snakes live, which supports Price's goal "to lessen the hatred and fear and to increase the understanding, the respect, and even the appreciation with which venomous snakes should be regarded."

  • Preface
  • Introduction
    • Precautions at Home
    • Protection in the Field
    • Recognizing Venomous Snakes
    • Venom
    • Snakebite
    • First Aid
    • Medical Treatment
  • Pit Vipers
  • Genus Agkistrodon
    • Copperhead (Agkistrodon contortrix)
    • Cottonmouth (Agkistrodon piscivorus)
  • Rattlesnakes
    • Western Diamondback Rattlesnake (Crotalus atrox)
    • Timber Rattlesnake (Crotalus horridus)
    • Rock Rattlesnake (Crotalus lepidus)
    • Blacktailed Rattlesnake (Crotalus molossus)
    • Mojave Rattlesnake (Crotalus scutulatus)
    • Western Rattlesnake (Crotalus viridis)
    • Massasauga (Sistrurus catenatus)
    • Pygmy Rattlesnake (Sistrurus miliarius)
  • Family Elapidae
    • Harlequin Coral Snake (Micrurus fulvius)
  • A Word about Conservation
  • Useful Sources of Information
  • Glossary
  • References
  • Index

Although it is clear from the biological evidence that snakes and lizards are closely related, as reflected in the placement of the two groups within the same taxonomic category (the reptilian order Squamata), the precise origin of snakes remains uncertain. Snakes and lizards could have evolved as separate lineages from within an ancient group called the Lepidosauria, or they could have evolved from a common lepidosaurian ancestor. The most likely scenario is that snakes evolved from lizards, the earliest representatives of which appear in the fossil record some 230 million years ago, during the Paleozoic-Mesozoic transition. The earliest unambiguous snake fossil dates from the early Cretaceous, about 135 million years ago. Diversification of the snake clade (the group that includes all descendants of a common snake ancestor) occurred by the late Cretaceous-Paleocene transition (70-65 million years ago), and by the Miocene (22.5 million years ago), the dominant modern families (Colubridae, Elapidae, and Viperidae) were present. Most biologists believe that ancestral snakes were adapted to a secretive or semiburrowing existence, as reflected by their descendants' possession of characteristics such as body elongation; modification of internal organs, including extreme elongation or loss of paired structure; loss of limbs; extreme reduction or loss of supporting pectoral and pelvic girdles; replacement of movable eyelids with a transparent cap over the eye; rearrangement and increased complexity of jaw and head muscles; and complete separation of mandibular symphyses, allowing each half of the lower jaw to be moved independently. There is some recent fossil evidence suggesting that the lizard ancestors of snakes may have been aquatic, seagoing forms, probably related to the mosasaurs—a group of giant marine lizards that became extinct at the same time as the dinosaurs. Many of the features listed above could just as readily be explained as aquatic adaptations. Whatever snakes' original line of descent, their ability to capture prey through constriction or the use of venom were later developments. Today, snakes, along with lizards, are the dominant reptiles on earth, and can be found on all continents except Antarctica and inhabit many oceans.

In today's society, where information about almost any subject is readily available, knowledge about venomous snakes and snakebite remains a relative mystery to most people. More than one recent survey has revealed that snakes in general possess a higher "fear quotient" for respondents than almost any other group of organisms, which probably reflects a relationship extending well into human prehistory. Given the abundance and diversity of snakes in Texas, and the increasing frequency with which Texans and visitors are exploring the outdoors, it is essential that accurate knowledge be available about the identification, distribution, and biological characteristics of the state's venomous reptiles, the relative risks of snakebite, and how to prevent it or treat it should it occur.

The first major study of the incidence of venomous snakebite in Texas was reported in 1927 by Afranio do Amaral, then director of the Antivenom Institute of America. During the twelve-month period from July 1926 to June 1927, a total of 150 cases of snakebite envenomation were known to have occurred in Texas, 28 of them fatal. A subsequent survey by R. H. Hutchison showed that 163 cases of snakebite were reported in 1928, 9 of which resulted in death. John Werler of the Houston Zoo recorded 1,318 snakebites in Texas during the five-year period 1949-1953, 18 of them fatal.

Henry M. Parrish reported on 559 snakebite cases seen by Texas physicians in 1958-1959. Of those, 461 were detailed enough to extract information. Rattlesnakes were involved in 47% of the cases, followed by copperheads (22%), cottonmouths (7%), coral snakes (1%), and a high number of unidentified venomous snakes (23%). Bites were less frequent in the sparsely populated western third of the state, and particularly high around larger cities (Austin, Beaumont, El Paso, Dallas/Fort Worth, Houston, Port Arthur, and San Antonio). Ninety-seven percent of all snakebites reported in the survey occurred during the months of April through November, when snakes are most active and when people are more likely to be outdoors. The largest number of bite victims (46%) were under 20 years of age, highlighting the importance both of supervising young children closely when they are in areas where venomous snakes are known to occur, and of instructing older children and teenagers in matters of snakebite prevention.

Most recently, T. G. Glass reported on 175 snakebite cases he personally treated in the San Antonio area from 1966 to 1975. The victims ranged in age from eighteen months to eighty-five years, with males being bitten more than twice as often as females (121 versus 54). The snakes inflicting the bites were western diamondback rattlesnakes (Crotalus atrox; 135, or 77%), copperheads (Agkistrodon contortrix; 30, or 17%), cottonmouths (Agkistrodon piscivorus; 5, or 3%), and coral snakes (Micrurus fulvius; 5, or 3%). Of those, 101 (75%) western diamondback, 19 (63%) copperhead, and 3 (60%) cottonmouth bites were treated surgically based on the appearance of local symptoms such as swelling or tenderness. This level of surgical intervention is considered unnecessary by most medical personnel today. Debridement (surgical removal of damaged tissue) revealed obvious signs of intramuscular injection of venom in 69 (56%) cases. Bites occurred most often on the leg (33%), followed by foot or ankle (28%), finger (20%), and hand or arm (15%). Fourteen patients developed blood-clotting problems, 16 were treated with antivenom, 13 developed serum sickness, and one eighty-five-year-old woman died from complete defibrination of the plasma resulting in a cerebral hemorrhage.

In general surveys of more than 1,300 snakebite cases from southern states during the 1960s and 1970s by L. H. S. Van Mierop and Henry Parrish and colleagues, 25% of the cases were "dry bites"—fang marks were present, but there was little if any pain because little or no venom was injected—and no medical treatment was necessary. Mild envenomation with slight swelling and pain occurred in 39% of the cases, requiring minimal medical treatment and usually no administration of antivenom. Moderate envenomation accompanied by pain, swelling, nausea, and other symptoms of shock occurred in 22%, requiring medical attention and the administration of antivenom. Finally, severe envenomation with heightened symptoms, including unconsciousness in some cases, occurred in 14%, requiring hospitalization and treatment with high levels of antivenom.

Snakebites are relatively rare when compared to accidents resulting from other outdoor-related activities, as shown by data from the Bureau of Vital Statistics, Texas Department of Health, in Table 1.

One aim of the 1998 edition of this book was to reduce the incidence of snakebite by educating people about the nature of venomous snakes and by showing them how to be better prepared to deal with such a contingency during outdoor activities. I again urge every Texan to obtain a thorough working knowledge of the correct first-aid treatment for snakebite so that proper action may be taken if it becomes necessary. Preventing a bite from happening is at least equally important, and a necessary step toward attaining this goal is to acquire knowledge about the habits, distribution, behavior, and identification of venomous snakes. A further step is to understand the evolutionary adaptations of venomous snakes and their ways and, in a larger sense, to reintegrate humankind with the natural world. This book is intended to be a small contribution toward that goal.

Precautions at Home

Statistics show that a large percentage of all bites occur near the home. Although a few of these are inflicted upon small children playing in their own backyards, many are what physicians refer to as "illegitimate bites," resulting from people taking unnecessary or foolish risks with venomous snakes. Every year, zoos, animal control officers, and other wildlife-agency personnel receive calls from distressed homeowners who have discovered rattlesnakes or copperheads beneath their houses, in garages, or under trash piles. They ask for assistance in removing the snakes and preventing them from coming back. Unfortunately, as human populations grow, cities expand into snake habitats, and since greater numbers of people want to live near "natural" or "pristine" areas, such incidents will become only more frequent. Venomous snakes are a fact of life in Texas; encounters can be managed and minimized but not eliminated. Unfortunately, none of the commercially available "snake-proofing" devices, chemical or mechanical, have ever been demonstrated to be completely reliable.

Snakes, including the venomous kinds, frequent human areas for two basic reasons: food and shelter. Snakes are found in or underneath objects either because those objects also attract their prey, such as rodents, or because the snakes are escaping inhospitable weather conditions. One can therefore minimize the attractiveness of a dwelling to a venomous snake by moving the objects which attract rodents and other prey items, such as trash dumps, brush piles, and wood piles, and by constructing barns and livestock sheds as far away from dwellings as possible. Overturned boats, trailers, tarps, and similar objects may provide temporary shelter for a snake moving through the area. Snakes are adept at getting through seemingly impossibly tiny openings, which should be kept in mind when attempting to close off a basement, a detached garage, or a shed. Keep such areas as neat and tidy as possible, and remember that snakes seek out such areas for peace and quiet, and so are likely to be tucked away somewhere instead of lying in the middle of the floor.

Charles M. Bogert, late curator of herpetology at the American Museum of Natural History, once suggested the use of a quarter-inch mesh wire fencing to keep snakes off residential property. A yard-high, snakeproof fence would placed around the house much like an ordinary picket fence, except that the bottom must be set about six inches down into the ground to prevent snakes from forcing their way beneath it. In addition, all gates must be provided with close-fitting sills on the bottoms and sides to ensure a completely tight enclosure. Experiments with fences of this kind were made to determine their effectiveness and to seek possible improvements in their construction, with the result that one important change was made. Copperheads and small rattlesnakes could not get over the vertically straight fence, but a six-foot rattlesnake used in the experiment was able to climb over. When the same fence was tilted outward at a 30-degree angle, not even the largest snake was able to reach the top. Although such fences are expensive and difficult to keep in good repair, they may be desirable under extreme circumstances.

Electrical fences have been tried in certain situations, such as the invasion of the Pacific island of Guam by the brown tree snake (Boiga irregularis), with some success. These fences are at least 2 feet (60 cm) high, and all vegetation is cleared away an equal distance from both sides of them. They are usually constructed of vinyl netting or similar material, and are most effective if several electrical strands are embedded in it.

Protection in the Field

In rural areas, where venomous snakes are more common, they present a greater hazard to human life than elsewhere. Consequently, farmers, ranchers, hunters, fishermen, hikers, campers, and others who spend a great deal of time outdoors should take extra care in avoiding a bite. Because most snakebites are inflicted on the arms or legs, they require special protection. The use of a little caution when placing hands and feet where snakes may be partially or completely hidden from view is the best protection. This is particularly true when climbing on rocky ledges, where one's hands may reach a ledge before the eyes do. In some parts of the state, rattlesnakes and copperheads are common on rocky hillsides, where, especially during the warm days of early spring or late fall, they coil and sun themselves.

Pack rat middens and armadillo burrows also make excellent shelters for rattlesnakes, and it is foolhardy to reach into one of these holes. Yet, during one year in South Texas alone, two people were bitten by rattlesnakes when they reached into armadillo holes searching for small game animals.

Another way to invite snakebite is to turn over a log or similar object thoughtlessly with bare hands or to step over one without first looking to see if a snake is coiled on the other side. Many snakes, particularly copperheads and coral snakes, often hide beneath or within decaying logs, and such habitats should be considered a potential snake haven. If a log must be moved, use a long stick or garden tool. Stepping over a log will be less risky if boots or high-top shoes are worn, but even then it is safer to first see what is on the other side.

Several types of footwear offer good protection against the bites of most snakes, especially high-top leather shoes, riding boots, rubber boots, or a combination of army "paratrooper shoes" and heavy leather puttees. For protection of the legs above the knees, snakeproof trousers are available that weigh little more than those of ordinary duck. They consist of three thicknesses of duck material and one layer of fine wire mesh, flexible enough to allow easy knee movement. Snakeproof leggings made of a similar material can be purchased for safeguarding just the lower legs. Aluminum or plastic leggings furnish good protection in many cases, but some brands may be thin and easily damaged, while others are simply uncomfortable.

If an active venomous snake is discovered nearby, the best response is to remain as still as possible until the snake has moved away. It should be remembered that a snake might be quick to strike at a moving object, so to step away at such a moment may stimulate the snake to strike. If a rattlesnake is heard nearby but cannot be located, do not make a wild dash for safety. The location of the snake may be misjudged, and a person fleeing the area may walk into rather than away from it. Again, remain still until the snake is sighted. When it is certain the reptile is at least five or six feet distant and is the only snake in the vicinity, slowly back away. If you must move away before locating the snake, do it as slowly as possible.

Because native venomous snakes are mostly nocturnal in their activities, usually remaining hidden during the day and emerging at night to search for food, a flashlight should be used by persons who find it necessary to travel on foot through snake country after dark. This precaution should be taken even around one's own home, particularly for those living in newly expanding suburbs or in rural areas. During the cooler days of spring and autumn, however, these daily habits are often reversed: snakes will be out during the day, searching for warm spots in which to sun themselves, and by nightfall they will again be under cover.

None of the types of venomous snakes found in Texas ordinarily can strike farther than a distance equal to three-quarters of its body length unless it has a firm backing or is striking downward on an incline. Certainly, none has the ability to jump at a target, a feat often attributed to rattlesnakes. A snake on the defensive is coiled, with the forward part of the body in a loose S position. When a snake strikes, this coil is straightened out and the head is thrust forward. It is not necessary for a snake to strike from a coil in order to bite; if picked up, it may simply turn and bite the hand that is holding it.

Recognizing the Venomous Kinds of Snakes

It is evident that the ability to differentiate harmless from venomous snakes is an important component of managing the risk and treatment of snakebite. Only 15 of the approximately 120 different kinds of snakes native to Texas are dangerous to humans, and some of these are so infrequently encountered that they are not much of a threat. In addition to these, several species of smaller Texas snakes known as opisthoglyphs ("rear-fanged") possess a relatively mild venom and a set of small, grooved fangs set far back on the upper jaw. They are considered harmless to humans because of their unaggressive behavior, weak and limited supply of venom, and small fangs, which are poorly adapted for injecting venom into large animals. Most of these, such as the black-headed snakes (genus Tantilla), which are found throughout the state, are less than 15 inches (38 cm) long and thinner than a pencil. The slightly larger night snake (Hypsiglena torquata) of west and central Texas has enlarged but ungrooved teeth in the upper jaw. Two Mexican species found as far north as the King Ranch (Norias Division) are somewhat larger: the black-striped snake (Coniophanes imperialis) reaches about 20 inches (50 cm), and the cat-eyed snake (Leptodeira septentrionalis) reaches about 36 inches (90 cm). Another rarely seen (but not rare) species is the lyre snake (Trimorphodon biscutatus) from extreme west Texas.

No single, general rule can be used to safely identify venomous snakes in Texas at a glance. For example, it is a mistaken idea that all venomous snakes have broad triangular heads. In fact, anyone applying this rule could mistake many of our harmless snakes for venomous ones. Hognose snakes (genus Heterodon), water snakes (genus Nerodia), and garter snakes (genus Thamnophis) can all flatten their heads by laterally expanding their jaw muscles as part of their defensive display, whereas the coral snake has a small, narrow head. The characteristic rattle of a rattlesnake may be missing under some circumstances, rendering identification more difficult. A rattlesnake may be coiled so that the rattle is hidden beneath the snake's body, and therefore the snake must be recognized by different means. Rattlesnakes frequently do not rattle before initially striking, so don't expect a warning—it might not come.

Disregard all of the so-called easy rules by which venomous snakes can be identified, and instead learn to know each one by the combination of its most characteristic features. For example, to identify the cottonmouth, look for a relatively short, stout body and a broad, flat head. Ignore the light color of the inside of the mouth. Also, look for a body color of black, dark brown, or olive and a pattern of ten to fifteen wide, usually indistinct crossbands that are generally lighter in the center than on the edges. The upper jaw below the eye and the lower jaw will be light colored, in contrast to the dark color of the remainder of the head. Together, these characteristics will make identification quite certain at a reasonable distance. Remember that the young of this species are colored differently from the adults and that you may not be able to identify the juveniles in the same manner as adults.

An additional complicating factor in identification occurs when a snake's markings are temporarily obscured, making recognition more difficult. Approximately ten days before snakes shed their skins, the eyes and color pattern appear milky and opaque (the so-called "blue" phase), clearing again a few days before they shed. During this period, when the snake's pattern and colors are dulled, identification may not be easy. Incidentally, venomous snakes are generally more irritable than usual at this time and may be more prone to strike, since they are essentially blind and may be physiologically stressed. Consider also that snakes with abnormal features of color and pattern—including all-white specimens, all-yellow ones, or those that are completely black—sometimes occur among populations of normal-looking individuals. Such aberrant individuals are rare; even so, the more you familiarize yourself with the normal colors, markings, and overall appearance of a species, the easier it will be to recognize the occasional abnormally pigmented specimen.


Snake venoms are complex substances, containing a large number of proteins with multiple lethal enzyme fractions, the specific composition of which varies among species and sometimes among individuals within a species (see, for example, the accounts for the timber rattlesnake and the Mojave rattlesnake). The importance of understanding the effects of specific enzyme components of venom, along with being able to identify the venomous species that occur naturally in Texas, cannot be overemphasized in the management and treatment of snakebite. Among lethal venom components are the following: neurotoxins, which interfere with the chemical communication between nerve cells (and thus nerve function) or between nerves (including those responsible for regulating breathing) and muscle cells at neuromuscular junctions, and which usually cause death from asphyxiation; proteolytic enzymes, which destroy blood-plasma proteins such as those involved in blood clotting, as well as collagen and other elastic connective tissues, the destruction of which results in local tissue damage; myonecrotic enzymes, which specifically destroy the functional microanatomy of muscles, perhaps through a massive disruption of the ability of the sarcolemma (the membrane surrounding a muscle) to regulate the influx of sodium ions, and through the disruption of ion-regulation functions in general; hemorrhagic enzymes, which cause blood to leak through vessel walls, and hemolytic enzymes, which destroy red blood cells, the effects of both of which reduce blood pressure and disrupt the delivery of oxygen to tissues; cardiovascular enzymes, which specifically attack heart muscle, decreasing cardiac output and perturbing blood pressure ratios; and cytolytic enzymes, which disrupt cellular function and destroy other cells in the body. Several major enzyme constituents of snake venom, such as phospholipase A2, may be present in multiple isoforms (functionally similar forms) in the venom of a particular species or an individual snake, each isoform contributing to one of the major lethal effects just outlined.

Individual snakes possess a limited quantity of venom at any one time, and what they have is energetically expensive to make. This may help explain why little or no venom is injected in 20%-40% of human venomous-snakebite cases in Texas ("dry bites"); venom is a precious commodity, since it is the primary means whereby a snake obtains a meal, and a snake is not going to waste it on anything else unless absolutely necessary. If venom is injected, the yield and toxicity depend on a number of variables: for the snake, these include the time interval since it last expended venom (which can take up to four days to resynthesize); the snake's age, size, and general health; environmental and seasonal effects; geographic location; and individual variation (genetic effects). Many of these same factors are also important in determining the outcome of a venomous snakebite for a victim. A given snakebite is likely to be more serious for the very young or very old, or for someone whose physiology is already compromised by disease or illness. In addition, the location of the bite on the body is important: bites on the extremities are less life-threatening and more easily treated than those closer to or on the trunk. The most important factor in the seriousness of a venomous snakebite, however, is the timeliness and quality of medical care provided to the victim.

The following table, taken from Russell (1983), illustrates the variation just discussed.

[table omitted from this excerpt]


Texas snakes, including the venomous ones, are successful components of the ecosystems to which they belong; their ability to remain inconspicuous to potential enemies, including humans, is a part of this success. Sensing danger, a snake that is awake and alert is more likely to move off without first being detected by the average person outdoors. Failing that, a snake is mostly likely to remain hidden or stationary and to rely upon crypsis (camouflage) or threatening behavior, such as striking with a closed mouth, vibrating the tail, flattening or inflating the body, hissing, or rattling (in the case of rattlesnakes). Only from an acute sense of danger is a snake likely to bite. On the other hand, any snake is likely to bite if startled or surprised, such as if stepped on while asleep; in such cases, rattlesnakes are likely to bite without rattling first. Although snakebite is an unlikely event, it just makes sense to have a contingency plan: prior planning can be the most important contribution to surviving a venomous snakebite.


  1. Learn to recognize the snakes that are likely to occur in the area in which you are or will be. This can have important consequences should treatment be necessary, and can render unnecessary the killing of harmless snakes.
  2. Minimize the chances for an unfortunate encounter with a venomous snake by learning about their habits, when and where they are likely to be active, and under what conditions they are likely to strike.
  3. Be sensible. Don't walk around after dark in snake country collecting firewood or engaging in other activities without a light. Check before putting your hands or feet in places that might conceal a snake. Don't sit down on the ground without inspecting the area nearby. Don't crawl beneath fences without first looking underneath them carefully. Don't sleep near wood or rubbish piles, at the entrance to a cave, or near swampy areas.
  4. Be careful. Dress appropriately; wear boots, shoes, long pants, or other protective clothing where encounters are likely. A normal defensive strike by a pit viper at ground level is unlikely to penetrate boots or canvas pants, and a number of "snakeproof" leggings are commercially available.
  5. Be smart. Don't play around with live or dead venomous snakes; "dead" ones have been known to bite and inject venom. Physicians emphasize that approximately half of the bites treated annually are "illegitimate"; that is, they result from interactions between humans and snakes that are premeditated by the former.
  6. Be prepared. Know what to do (and not to do) when engaging in activities where encounters with venomous snakes are a possibility.
  7. First Aid

    Recommended measures:

    • Assume envenomation has occurred, especially if initial symptoms are present. Initial symptoms of pit viper bites include fang puncture marks (Fig. 1) and almost always include immediate burning pain at the bite site, immediate and usually progressive local swelling within five minutes, and local discoloration of the skin (ecchymosis) due to the destruction of blood vessels and red blood cells. Initial symptoms of coral snake bites include tremors, slurred speech, blurred or double vision, drowsiness or euphoria, and a marked increase in salivation within four hours; however, life-threatening effects from coral snake envenomation may not be evident for twenty-four hours or longer.
    • Identifying the species of venomous snake inflicting the bite may provide useful information for emergency medical personnel attempting to judge the onset and severity of symptoms, but is not necessary to ensure proper clinical treatment. Appropriate precautions should be taken in attempting to identify the snake in order to avoid another person being bitten.
    • Keep the victim as calm as possible. This helps reduce the spread of venom and delay the onset of shock to a stressed physiological system.
    • Keep yourself and any other members of the group calm as well. This will help reassure the victim and ensure that the appropriate first-aid measures are followed. It may also prevent anyone else from becoming injured.
    • Know and be alert for the symptoms of shock, and institute the proper treatment if it ensues. Respiratory distress or renal shutdown are frequent symptoms of envenomation.
    • Wash the bite area with a disinfectant, if available.
    • Remove jewelry such as rings and watches, as well as tight-fitting clothes, before the onset of swelling.
    • Reduce the movement of or immobilize a bitten extremity, using a splint if possible; this helps decrease the spread of venom. Position the extremity below the level of the heart for the same reason.
    • Get the victim to a medical facility as soon as possible and begin treatment there with intravenous (IV) antivenom, crystalloid solutions, and antibiotics. Antivenom treatment is generally most effective within the first four hours of envenomation and ineffective after eight to ten hours.

Measures absolutely to AVOID:

  1. DO NOT make incisions over the bite marks. This can significantly damage already traumatized tissue, damage intact structures such as nerves and blood vessels, enhance bleeding caused by the anticoagulant components of venom, and enhance the rapid spread of venom throughout the body if the circulatory system is compromised. A suction device, such as the Sawyer Extractor/TM, may be used and may remove significant quantities of venom, although its efficacy has yet to be conclusively determined.
  2. DO NOT use a tourniquet or other constricting band except in extreme cases of envenomation, and then only if properly trained in the technique. Such devices are of no value if applied more than thirty minutes after the bite, and if improperly used, they can restrict vital blood flow to the traumatized tissue and possibly result in the amputation of an extremity. Unbearable pain can also result, and the improper loosening of such devices can allow sudden systemic absorption of venom.
  3. DO NOT use cryotherapy (including cold compresses, ice, dry ice, chemical ice packs, spray refrigerants, and freezing) for the same reasons as above and because it can increase the area of necrosis (dead tissue).
  4. DO NOT use electroshock therapy, a method popularized following the publication of a letter from a missionary in South America, who reported its effectiveness in treating bites from snakes of uncertain identity. Several controlled clinical trials and at least one on humans have failed to demonstrate any positive result. The potential negative results from the uncontrolled use of an electric charge should be obvious.
  5. DO NOT drink alcohol, since it dilates blood vessels and increases absorption from the circulatory system, and thus helps spread venom faster.
  6. DO NOT use aspirin or similar medications to relieve pain, because they increase bleeding. A pain reliever not containing aspirin may be used.
  7. DO NOT, when treating pit viper bites, use the pressure-immobilization technique, which consists of firmly wrapping the entire limb with an elastic bandage and then splinting. The theory behind this treatment is to confine the venom to the area of the bite until a medical facility is reached, but studies have shown the technique to be ineffective or worse with venoms that produce local swelling and tissue damage.
  8. DO NOT administer antivenom in the field unless properly trained in the procedure, unless evacuation to a medical facility will take many hours or even days, or unless extreme envenomation has occurred. Intramuscular (IM) or subcutaneous (SC) application of antivenom has proved to be much less effective than IV administration, and in some cases even ineffective. Acute allergic reactions to antivenom can occur, and the contemplated field administration of antivenom should include provision for a sufficient supply of epinephrine (Adrenalin) to counteract any such effects.
  9. Medical Treatment

    Long-term care and recovery, the details of which will vary in each case, are best left to the discretion of trained and experienced medical personnel. Patients may take several weeks to recover from severe envenomations, and symptoms may appear or recur anytime during this period, especially in cases in which antivenom therapy is contraindicated. The prognosis is generally good in cases of muscle or tissue damage, provided that blood circulation and nerve connections to the affected area remain good and infection doesn't set in. Surgery is generally not called for except to relieve intramuscular compartmental pressure from swelling. Antivenom therapy can be greatly enhanced through the use of specific enzyme immunoassays of the patient's blood and other body fluids. Secondary complications, such as kidney failure, hypotension (low blood pressure), or anaphylaxis (allergic shock), are common, and must be anticipated in treatment.

    In cases of envenomation by coral snakes, antivenom therapy is only one component of successful treatment. Patients should be observed for at least twenty-four hours because paralysis from bites may not occur immediately. In cases of severe paralysis, only an endotracheal intubation with mechanical ventilation will save the patient, since administration of antivenom will not reverse paralysis. Pneumonia, brain damage, or death may result if ventilation is not performed quickly and appropriately; with proper ventilation, the neuromuscular blockade will gradually decrease and the patient will ultimately return to normal.

By Andrew H. Price

Andrew H. Price was until recently a Natural Resources Scientist in the Wildlife Diversity Program of the Texas Parks and Wildlife Department. He is also a Research Fellow of the Texas Memorial Museum at the University of Texas at Austin.