Snake Bites
Medical Author: Melissa Conrad Stoppler, MD
Medical Editor: Jay W. Marks, MD
Introduction to snake bites
Although venomous (poisonous) snakes are relatively common in the U.S., bites
from venomous snakes are a rare cause of death in this country. While there are
about 8,000 venomous snake bites reported each year in the U.S., no more than 12
deaths were reported each year from 1960-1990 as a result of poisonous snake
bites. About half of all reported snake bites occur in children.
Pit vipers are a family of snakes whose scientific name is Crotalidae. This
group, which is responsible for 99% of poisonous snake bites in the U.S.,
includes the rattlesnakes, copperheads, and water moccasins (cottonmouths).
Within this group, rattlesnakes have the most deadly venom and cause the
majority of snakebite-related deaths. Rattlesnakes can be found in both the
Eastern and Western areas of the country. In particular, the Mojave rattlesnake has one of the most potent venoms of all rattlesnakes. Copperheads, common in the Eastern
U.S., have a milder venom than that of rattlesnakes. Water moccasins live around
natural waters in the Southeast; their venom has an intermediate potency between
that of the rattlesnakes and copperheads. Coral snakes found in the southern
U.S., related to the Asian cobras and not part of the pit viper family, are a
rare cause of poisonous snake bites in the U.S.
What are the symptoms of a poisonous snake bite?
Symptoms of snake bites are dependent upon the type and
size of the snake, the location of the bite on the body, and the age, size, and
health of the victim. Children are more likely to have severe symptoms because
they receive a larger concentration of venom due to their smaller body size.
Also, not all snake bites involve the discharge of venom into the victim (known as
evenomation). At least 25% of poisonous snake bites do not result in
evenomation.
Snake venoms are either hemotoxic (causing damage to
blood and other tissues)
or neurotoxic (causing damage to nerves). The pit vipers, with the exception of
some Mojave rattlesnakes, have hemotoxic venom. The extremely potent venom of the Mojave rattlesnake has neurotoxic activity. Coral snakes also have neurotoxic venom.
Pit viper bites often show two characteristic fang marks at the site of the
bite. Intense pain usually results at the site within five minutes of the bite,
and swelling is common. Other symptoms that may result from pit viper hemotoxin
include:
Bites from snakes such as coral snakes and their exotic
relatives whose venom is neurotoxic may result in minimal pain and no visible
marks on the skin.
Instead of pain and swelling, these bites often cause local numbness along with
a number of other symptoms including:
Next: What is appropriate first aid for poisonous snake bites? »
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