North America is unique in that it is home not only to venomous snakes, but also to the world's only known venomous lizards. Fortunately, bites by venomous reptiles in North America are relatively uncommon, although precise statistics are not available. The only systematic attempt to evaluate the incidence of venomous snakebite in the United States was done in the late 1960s by Dr. Henry Parrish. He estimated that there were approximately 7000 bites by venomous snakes, of which approximately 15 ended in death. The incidence of venomous snakebite may have changed significantly since Parrish's study, but given that snakebite is not a reportable "disease," no mechanism exists for obtaining reliable data. The incidence of snakebite in Canada is lower than that in the United States because fewer snakes species are found farther north up the continent. In Mexico, however, snakebite takes on increasing medical importance because this country has more venomous snake species than any other nation in the New World. As many as 150 deaths may be caused by snakebite in Mexico each year.
[...] Although Parrish and Khan estimated that fewer than 20 coral snake bites occurred in the United States each year, the 1998 report of the American Association of Poison Control Centers (AAPCC) Toxic Exposure Surveillance System listed 61 cases. The only two known species of venomous lizards in the world are found in North America and belong to the genus Heloderma. The Gila monster (Heloderma suspectum, with two subspecies) is found in the southwestern United States (Arizona, western New Mexico, southeastern California, southern tip of Nevada, extreme southwestern Utah) and northwestern Mexico. [...]
[...] The medically important North American venomous snakes all fall into the families Viperidae (subfamily Crotalinae, the crotalines or pit vipers) and Elapidae (elapids, the coral snakes). Although there are reports of human envenoming by a handful of species of Colubridae—the family of snakes traditionally regarded as harmless—the cases from North America have all been relatively minor and non-life threatening. Pit vipers are widely dispersed throughout most of North America below southern Canada (south of 55 degrees north latitude).In the United States, for example, all 48 contiguous states except Maine have at least one pit viper species. [...]
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