Fast Five Quiz: Snakebite Facts vs Fiction

Richard H. Sinert, DO


July 12, 2021

Of the approximately 3000 snake species worldwide, only 10%-15% are believed to be venomous. Most venomous snake species are viperids (eg, rattlesnakes, Gaboon vipers) or elapids (eg, cobras, taipans). Although most snakes in the Colubridae family are nonvenomous, some (eg, boomslang) are venomous and responsible for significant morbidity and mortality.

Four types of venomous snakes are native to the United States: copperheads, cottonmouths (water moccasins), rattlesnakes, and coral snakes. The first three are crotalids in the family Viperidae. Approximately 25 species of rattlesnakes are included in the genera Crotalus and Sistrurus. The genus Agkistrodon has both copperheads (Agkistrodon contortrix, Agkistrodon laticinctus) and cottonmouths (Agkistrodon piscivorus, Agkistrodon conanti). Collectively, these crotalids, also known as pit vipers, account for more than 95% of all native snake envenomations.

Crotalids are characterized by large, triangular heads, comparatively small eyes, large and retractable fangs, and a thermoreceptor "pit" located between the eye and the nostril. Pit vipers also have a single row of subcaudal plates distal to the anus, and rattlesnakes have one or more keratin buttons that compose the "rattle" at the distal end. Although some references recommend using the pupil shape as a way of distinguishing pit vipers from noncrotalids, it should be noted that all snakes can have round or elliptical pupils, depending on the amount of ambient light. Additionally, many nonvenomous snakes can flatten their heads into a triangle shape when they feel threatened. Experts recommend that people learn to recognize the venomous species in their vicinity rather than rely on mnemonics.

Crotalid venom is produced and stored in paired glands below the eyes. Crotalids have hollow, mobile, relatively long fangs located in the front of the upper jaw and are capable of delivering venom quite efficiently. Only 20%-25% of crotaline snakebites are dry, meaning there is no venom deposition.

Coral snakes are the only elapids that are native to the Western hemisphere, and the three species of US coral snakes account for less than 5% of all native envenomations. Coral snakes have shorter, fixed, front fangs and a smaller mouth, which make them deliver venom less efficiently. In the wild, snakes often hang onto their prey until the venom takes effect. However, despite the persistent myth, coral snakes do not need to "chew" in order to envenomate.

It is a common misconception that most snakebite victims are under the influence of intoxicating substances when they are envenomated. In a study of snakebite reports to the American Association of Poison Control Centers, only 608 (0.7%) of 92,751 snakebites were associated with concomitant drug or alcohol use.

Read more on the etiology of snakebites.


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