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Snakes: Etiology

Crotaline Snakes

Crotaline snakes are also known as pit vipers. They are identified by their triangular head, elliptical pupils, and fangs. The fangs are connected to venom sacs that inject venom. They can also retract on a hinge-like mechanism. The fangs have been reported to envenomate victims even after the snake's death. In addition, the undersurface of the snake has a single row of caudal plates or scales, as opposed to the double row found on non-venomous varieties.7, 8

Crotaline snakes account for 99% of venomous snakebites in the United States. The remaining 1% result from bites of elapid (coral snake) and exotic species. Rattlesnakes account for 65% of crotaline snakebites while copperheads are responsible for 25%; the remaining 10% are from water moccasins.9,10 Rattlesnakes, in addition to having the longest fangs, have rattles at the end of their tails which are occasionally heard prior to a strike. Water moccasins or cottonmouths (Agkistrodon piscivorous) are semiaquatic and have a distinctive white oral mucosa. They are reported to be aggressive and can bite
underwater. Copperheads (Agkistrodon contortrix) are known for their coppery brown color and hourglassshaped bands on their bodies.

Elapid Snakes

The coral snakes (Micruroides and Micrurus spp.) have distinctive red, yellow, and black bands. There are many mimickers of the coral snake, including the California king snake. The misidentification of coral snakes is a common reason for envenomation.

In a study with 39 victims, nine patients were envenomated because they believed that they were dealing with the nonpoisonous scarlet king snake. The king and coral snake can be distinguished by the spacing of their colored rings and the color of their snouts. Coral snakes have black snouts and king snakes have red snouts. The red, yellow, and black rings are in different sequences. In the coral snake, the red and yellow rings touch while, in the king snake, the red and black rings touch. This has lead to the common saying, "Red on yellow, kill a fellow; red on black, venom lack."11, 12

Envenomations by these snakes are not as frequent as crotaline bites because the venom apparatus is not as efficient for venom delivery and the snake's small mouth size makes it difficult to maintain a large aperture. Coral snakes are a non-aggressive species of snake and live mostly underground. Most of the bites occur when the snakes are being handled.11,13

The coral snake relies on a chewing action to deliver its venom through hollow, short, anterior maxillary fangs which measure about 2 mm in length. It is generally thought that the snake must maintain its bite-hold for a prolonged period of time in order to administer a significant amount of venom. In most cases, fang marks will be evident at the site of injury, but there have been case reports of apparent coral snake envenomation where no marks were evident at the site of the bite. It has been estimated that envenomation occurs in less than 40% of coral snake bites.12, 14

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