Thursday, December 1, 2011
Two major families of snakes account for most venomous snakes dangerous to humans.
1. The elapid family includes:
- the cobras (Naja and other genera) of Asia and Africa;
- the mambas (Dendroaspis) of Africa; the kraits (Bungarus) of Asia;
- the coral snakes (Micrurus) of the Americas; and the Australian elapids, which include the coastal taipan (Oxyuranus scutellatus),
- tiger snakes (Notechis), king brown snake (Pseudechis australis), and
- death adders (Acanthophis).
- Highly venomous sea snakes are closely related to the Australian elapids.
Pictures of snakes from the elapid family
Coral snake (Micrurus fulvius), a shy American elapid that accounts for only about 1% of venomous snakebites in the United States. Recognize it by this catch phrase: "Red on yellow, kill a fellow." Photograph by Joe McDonald.
Milk snake (Lampropeltis triangulum), a harmless mimic of the coral snake. "Red on black, venom lack," although this old saying becomes unreliable south of the United States. Photograph by Joe McDonald.
2. The viper family includes:
- the rattlesnakes (Crotalus) (Western diamondback rattlesnake and timber rattlesnake), moccasins (Agkistrodon), and lance-headed vipers (Bothrops) of the Americas;
- the saw-scaled vipers (Echis) of Asia and Africa;
- the Russell's viper (Daboia russellii) of Asia; and
- the puff adder (Bitis arietans) and Gaboon viper (Bitis gabonica) of Africa.
Northern copperhead (Agkistrodon contortrix), an American pit viper. Bites by this species tend to be less severe than rattlesnake or water moccasin bites but still require urgent medical attention. Photograph by Joe McDonald.
Most species of the most widely distributed and diverse snake family, the Colubrids, lack venom that is dangerous to humans. Some species, however, including the boomslang (Dispholidus typus), twig snakes (Thelotornis), the Japanese garter snake (Rhabdophis tigrinus), and brown tree snake (Boiga irregularis), can be dangerous. Other members of this family, including American garter snakes, kingsnakes, rat snakes, and racers, are harmless to humans.
Snakebite Self-Care at Home
Common sense, hopefully, will guide a person's efforts if they are bitten by a snake or are witness to someone else being bitten. Even a bite from a nonvenomous snake requires excellent wound care. The patient needs a tetanus booster if he or she has not had one within 5 years. Wash the wound with large amounts of soap and water. Inspect the wound for broken teeth or dirt.
Take the following measures:
- Prevent a second bite or a second victim. Do not try to catch the snake as this can lead to additional victims or bites. Snakes can continue to bite and inject venom with successive bites until they run out of venom.
- Identify or be able to describe the snake, but only if it can be done without significant risk for a second bite or a second victim.
- Safely and rapidly transport the victim to an emergency medical facility.
- Individuals should provide emergency medical care within the limits of their training.
- Remove constricting items on the victim, such as rings or other jewelry, which could cut off blood flow if the bite area swells.
- If a person has been bitten by a dangerous elapid (for example, sea krait [a type of sea snake], black and yellow sea snake) and has no major local wound effects, a pressure immobilizer may be applied. This technique is mainly used for Australian elapids or sea snakes. Wrap a bandage at the bite site and up the extremity with a pressure at which you would wrap a sprained ankle. Then immobilize the extremity with a splint, with the same precautions concerning limiting blood flow. This technique may help prevent life-threatening systemic effects of venom, but may also worsen local damage at the wound site if significant symptoms are present there.
- While applying mechanical suction (such as with a Sawyer Extractor) has been recommended by many authorities in the past, it is highly unlikely that it will remove any significant amount of venom, and it is possible that suction could actually increase local tissue damage. This technique is, in general, no longer recommended but is still listed as a treatment technique in many medical publications. If a person decides to try this technique, the instructions should be carefully followed.
- The two guiding principles for care often conflict during evacuation from remote areas.
- First, the victim should get to an emergency care facility as quickly as possible because antivenin (medicine to counteract the poisonous effects of the snake's venom) could be life-saving.
- Second, the affected limb should be used as little as possible to delay absorption and circulation of the venom.
A number of old first aid techniques have fallen out of favor. Medical research supports the following warnings:
- Do NOT cut and suck. Cutting into the bite site can damage underlying organs, increase the risk of infection, and sucking on the bite site does not result in venom removal.
- Do NOT use ice. Ice does not deactivate the venom and can cause frostbite.
- Do NOT use electric shocks. The shocks are not effective and could cause burns or electrical problems to the heart.
- Do NOT use alcohol. Alcohol may deaden the pain, but it also makes the local blood vessels bigger, which can increase venom absorption.
- Do NOT use tourniquets or constriction bands. These have not been proven effective, may cause increased tissue damage, and could cost the victim a limb.