Wilderness Medical Society snowmass 2005 Page 253
83
Chapter 20
REPTILE ENVENOMATION
Recommendations are considered Category 1B, except where indicated 1A, by the WMS
Panel of Expert Reviewers
I. GENERAL INFORMATION
There are approximately 300,000 human snakebites worldwide each year from 2700
known species. In the United States it is estimated that there are 45,000 bites of humans
with 8000 envenomations and 5 to 12 deaths per year. The incidence of bites and fatality
rates may be much higher in other parts of the world. In general, fatalities are more
frequent where the snakes are more venomous, e.g., Australia, or where lay knowledge
regarding venomous bites and access to medical care is lacking, e.g., parts of Asia and
Africa. Venomous snakes can be broadly divided into Crotalidae (pit vipers--including
rattlesnakes, cottonmouths and copperheads) and the family Elapidae (which includes
coral snakes and all venomous Australian snakes). There are about 3000 known species
of lizards, but only members of the family Helodermatidae (including Gila monsters) are
considered venomous. They are found exclusively in the southwestern United States and
Mexico. Lizards rarely cause human fatalities. Fatalities from U.S. crotalid
envenomation are not common, but complications may be severe.
A. Pit Vipers: Crotalids have a triangular head, cat-like vertical pupils, hinged fangs, and
a heat-sensitive "pit" on each side of the head between the tip of the nose and the eye.
Rattlesnakes have a variable number of rattles depending upon age and number of molts.
They sometimes strike without rattling. About 60% of this country's venomous bites are
attributed to rattlesnakes. Cottonmouths (water moccasins) and copperheads are the other
two commonly encountered North American pit vipers. Copperhead and cottonmouth
venoms are quite similar and weaker than most rattlesnake venoms. Bites by
cottonmouths tend to be more serious than copperhead bites because it is a bigger snake.
B. Elapidae: These species are widely distributed, most particularly in the Southern
Hemisphere. They are notable for bites that cause profound systemic effects such as
neuromuscular paralysis and coagulopathy and myonecrosis, but often with minimal local
effects. Identification of species even by trained observers is notoriously difficult and is
not to be used to guide therapy. The several species of coral snakes are brightly colored,
with black noses and alternating red-yellow-red-black bands around their bodies
(remember "red on yellow can kill a fellow"). They have relatively small mouths with
fixed fangs. From southern Mexico through tropical South America the rules for
distinguishing coral snakes are highly unreliable. Unless you are a knowledgeable
herpetologist, it is best not to pick up colorful snakes in tropical America.
