POISONOUS SNAKES AND SNAKEBITES

Red diamondback rattlesnake , near Soboba Hot Springs, San Jacinto Valley, California. Photographed and copyrighted © by Arthur G. Sylvester, April 1984.

POISONOUS SNAKES IN THE USA - Poisonous snakes bite about 8,000 people annually in the USA, but according to most estimates, only 12 to 15 of these bites are fatal. Much more commonly, such bites cause severe pain, necrosis, residual paresthesias, diminished function and, rarely, loss of a limb. In most cases, permanent damage after a snakebite is due not to the snake's venom but to overreactions in application of first aid.

About 20 species of poisonous snakes are in the USA. Most are rattlesnakes, cottonmouths (water moccasins), and copperheads; all are called Òpit vipersÓ because they have deep pits lined with heat receptors in the cheeks between the eyes and nostrils. These receptors are thought to detect the presence of prey and guide the direction of the strike. Pit vipers are widely distributed throughout the USA, but most bites occur in southern and southwestern states between the months of April and October. Rattlesnake bites are the most serious; copperhead envenomation usually does not cause major systemic injury, but cottonmouth venom poisoning is intermediate in severity. About 20% of bites by pit vipers are ÒdryÓ; no venom is injected.

Coral snakes, found in the southern and southwestern states, rarely bite people; when they do, they rarely inject enough venom to cause major damage, because they are small snakes. Coral snake bites can be treacherous, however, because they are relatively painless and hard to detect, and severe symptoms can appear many hours after the bite.

CLINICAL EFFECTS - Snake venoms are highly complex mixtures of many proteins and peptides, including some enzymes; these may cause local effects such as inflammation, damage to vascular epithelium, and tissue necrosis. Venoms can also cause neurotoxicity and interfere with blood clotting.

The effects of rattlesnake bites are extremely variable and depend on the following factors: 1) the age, size vigor, and health of the victim; 2) the susceptibility of the victim to protein poisoning; 3) the emotional condition of the victim -- extreme fear will affect heart action and therefore the rate of venom absorption; 4) the site of the bite; 5) the nature of the bite -- whether a direct strike with both fangs, or a glancing blow or scratch; 6) the number of bites; 7) the length of time the snake holds on, because it may withdraw or be torn loose before injection; 8) the extent of the snake's fear or anger -- the snake's natural tendency is to withhold venom for its next prey, but if hurt or violently excited, it will probably inject most of its venom; 9) the species, size and age of the snake, the venom quality, and depth of envenomation; 10) the condition of the venom glands -- whether full or partially depleted because of recent feeding, defense, or ill health; 11) the condition of the fangs, whether broken, lately renewed, or ready for shedding; 12) the presence of toxic microorganisms in the snake's mouth -- this is the main source of poison in the gila monster, the only poisonous lizard in the USA.

Pit viper envenomation may cause severe pain, usually occurring almost immediately after the bite, but it may also be painless. Swelling, erythema, and ecchymosis may occur locally, and later, blebs may form near the puncture site and spread along the swollen limb. Regional effects, as with a bite on a hand or foot (the most common locations), often include edema of the arm or leg (which may be massive), ecchymosis, and lymphadenopathy. Systemic signs and symptoms can include weakness, sweating, chills, numbness, and paresthesias of the tongue and perioral region, nausea and vomiting (which can be so severe that the esophagus ruptures), muscle fasciculations, bleeding hypotension, convulsions, respiratory depression, and renal failure.

TREATMENT FOR RATTLESNAKE BITE - The first-aid procedure recommended by the Australian Serum Institute seems sensible, and some case reports suggest that it has been effective: a broad, firm, Ace bandage is applied immediately over the bitten area and around the limb, bandaging as much of the limb as possible; the limb is then splinted. If the patient is faint, give strong coffee or tea. Do not give any alcoholic drink, unless the victim wants to die happy.

Incision and suction over the wound is generally not an effective way of removing venom and can cause permanent damage. Tourniquets can cause necrosis and loss of a limb. Complete stoppage of the circulation is unnecessary and dangerous.

There is general agreement that victims of serious poisonous snakebite should receive antivenom, except possibly, asymptomatic patients. Some experienced clinicians use antivenom for all bites cause by the eastern coral snake and the Mojave green rattlesnake if the snake has been positively identified. The location of antivenoms for rare species of poisonous snake, names and telephone numbers of experts on venomous bites, and of local and regional Poison Control Centers can be obtained 24 hours from the Oklahoma City Poison Control Center (405-271-5454).

SAFETY FIRST - The best rule is: Watch where you put your hands and feet. Do not put them in places without looking, and do not put them in places where you can't look.

1) Don't lift a stone, plank, log, or any other object under which a rattler might be hidden, by placing your hand or fingers under it. Move it first with a stick.

2) Don't gather firewood in the dark.

3) Don't reach into a hole, whether in the ground or in a tree.

4) As you walk in grass, brush, cactus, or rocks, stay in cleared areas as much as possible, make noise, tromp heavily, and keep a sharp lookout for snakes that may lie concealed in or beside your path.

5) Don't believe stories that rattlers are out only in hot weather; they are always hidden in the shade when it is hot. They are most active in the early evening when the temperature is moderate.

6) Don't take too literally the tales that they shun high attitudes. They are found up to 3800 m or more in the southwest and up to 4800 m in central Mexico. Rattlesnakes can climb trees and bushes, and they are superb swimmers.

7) Learn to glance frequently at your path in the field to avoid stepping on a rattler. And remember that the leader of a file is not the one most exposed to snakebite; the leader may disturb a hidden snake that will strike one of the followers.

8) Don't walk around your camp in darkness, because rattlers are nocturnal most of the season. If you must move about, wear your boots and use a flashlight.

9) Step on a log, never over it. The rattler may be on the other side keeping cool in the shade of the log.

10) Don't reach above your head for a handhold in climbing among rocks, and avoid placing your hands near crevices into which you can't see. Poke your hammer in there, first. When you crawl under a fence, do so in a cleared area; if there is grass or brush, beat it with a stick so that a rattler will escape or make its presence known.

11) Look before you sit or squat.

12) When you hear the sudden rattle of a snake, don't move until you know where it is; you may step on it rather than away from it.

13) Rattlers usually strike at moving objects. When you back away from one snake, be sure all is clear behind you.

14) Pitch your tent in a clearing.

15) Don't handle an injured or dead rattlesnake. Don't touch the head of a decapitated rattlesnake. Bury it. If you collect rattles, bury the head first. The head of a rattler has been known to bite as much as an hour after it was completely severed from the body.

16) If you collect rattlesnakes or like to play with them, don't grab the tail of a snake as it is going down a hole; the other end may already have turned and be facing you.

TALL TALES

1) Rattlesnakes do not remove their fangs or venom glands temporarily to take a drink.

2) A rattlesnake does not die from the venom spilled in its own mouth after a strike.

3) Rattlesnakes are harmful after coming out of hibernation.

4) Rattlesnakes are harmful if deprived of water for some time.

5) Alcohol is not an antidote for snake venom.

6) If a drunk person is bitten, the snake will not die.

7) A person does not develop immunity after several rattlesnake bites. (One man died on his 22nd bite)

8) Rattlesnakes will crawl over any kind of a rope

9) Rattlesnakes do not swallow their young for protection.

10) Rattlesnakes do not always rattle before striking; occasionally one will have lost its rattles through an accident.

CONCLUSIONS - The idea that rattlesnakes are the quintessence of evil and that their continuous and sole purpose in living is to wreak havoc and vengence on all living creatures (especially geologists) is unfounded. Unless injured, attacked, surprised, or brought to bay, rattlers are relatively inoffensive and timorous, seeking to hide unnoticed or to escape to some secluded refuge. Unfortunately, their food-getting mechanisms - fangs and venom - make them dangerous creatures all out of proportion to their size, but they are not innately vicious. One exception to this may be the Mojave green rattlesnake which has developed a reputation for being an especially nasty snake.

A poisonous snakebite is an emergency that should be treated with restraint; first aid is usually best limited to bandaging and immobilization of the bitten part. Serious bites by poisonous snakes should be treated with antivenom.

Modified by A. G. Sylvester from The Medical Letter 24 (#619), 87-89; and from R. V. Fisher with his modifications from Klauber, L. M., 1956: Rattlesnakes, University of California Press.