Snakebites

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

A snakebite is a bite inflicted by a snake. Snakes often bite their prey when feeding, but occasionally, they bite humans. People can avoid and treat snakebites by knowing their etiology, along with prevention tips, and first-aid and hospital treatment.

Every state but Maine, Alaska and Hawaii is home to at least one of 20 domestic poisonous snake species. About 8,000 people a year receive venomous bites in the United States; nine to 15 victims die. Some experts say that because victims can’t always positively identify a snake, they should seek prompt care for any bite, though they may think the snake is nonpoisonous. Some deaths are sudden, however in fact it is uncommon to die within four hours of a snake bite. In the 1900’s, the untreated death rates were as high as 40% to 50%. Improved supportive treatment and the availability of effective antivenoms has reduced this considerably.

Recovery is usually complete, though the patient usually develops a sensitivity to equine immunoglobulin. If the patient develops serum sickness, the severity is reduced by steroid administration (eg. prednisolone 1mg/kg every 8 hours) until resolution occurs. A course of steroids is recommended in all patients who receive polyvalent antivenoms.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

• Two families of venomous snakes are native to the United States. The vast majority are pit vipers, of the family Crotalidae, which include rattlesnakes, copperheads and cottonmouths (water moccasins). Pit vipers get their common name from a small “pit” between the eye and nostril that allows the snake to sense prey at night. The vipers are generally considered to be the most advanced family of snakes since they possess a very sophisticated venom delivery system. Large tubular fangs are placed in the front of the mouth and they are hinged, allowing them to be folded back when not in use.
• About 99 percent of the venomous bites in this country are from pit vipers. Some–Mojave rattlesnakes or canebrake rattlesnakes, for example–carry a neurotoxic venom that can affect the brain or spinal cord. Copperheads, on the other hand, have a milder and less dangerous venom that sometimes may not require antivenin treatment.
• The other family of domestic poisonous snakes is Elapidae, which includes two species of coral snakes found chiefly in the Southern states. The Elapidae contains some of the world’s most dangerous snakes including cobras, mambas and sea snakes. In North America, three species of elapids are found, the Eastern and Western coral snakes and the Yellow bellied sea snake. The coral snakes are relatively small snakes that spend most of their time underground. Their primary food is other snakes. Despite their small size and small fangs, their venom is extremely toxic. Coral snakes have small mouths and short teeth, which give them a less efficient venom delivery than pit vipers. People bitten by coral snakes lack the characteristic fang marks of pit vipers, sometimes making the bite hard to detect.
• Though coral snakebites are rare in the United States–only about 25 a year by some estimates–the snake’s neurotoxic venom can be dangerous. A 1987 study in the Journal of the American Medical Association examined 39 victims of coral snakebites. There were no deaths, but several victims experienced respiratory paralysis, one of the hazards of neurotoxic venom.
• Some nonpoisonous snakes, such as the scarlet king snake, mimic the bright red, yellow and black coloration of the coral snake. This potential for confusion underscores the importance of seeking care for any snakebite (unless positive identification of a nonpoisonous snake can be made).
• The bites of both pit vipers and coral snakes can be effectively treated with antivenin. But other factors, such as time elapsed since being bitten and care taken before arriving at the hospital, also are critical.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Most snakebites are caused by non-venomous snakes. Of the roughly 3,000 known species of snake found worldwide, only 15 percent are considered dangerous to humans. Snakes are found on every continent except Antarctica. The most diverse and widely hihpihh distributed snake family, the Colubrids, has only a few members which are harmful to humans. Of the 120 known indigenous snake species in North America, only 20 are venomous to human beings, all belonging to the families Viperidae and Elapidae. However, in the United States, every state except Maine, Alaska, and Hawaii is home to at least one of 20 venomous snake species.

Since the act of delivering venom is completely voluntary, all venomous snakes are capable of biting without injecting venom into their victim. Such snakes will often deliver such a “dry bite” (about 50% of the time) rather than waste their venom on a creature too large for them to eat. Some dry bites may also be the result of imprecise timing on the snake’s part, as venom may be prematurely released before the fangs have penetrated the victim’s flesh. Even without venom, some snakes, particularly large constrictors such as those belonging to the Boidae and Pythonidae families, can deliver damaging bites; large specimens often causing severe lacerations as the victim or the snake itself pulls away, causing the flesh to be torn by the needle-sharp recurved teeth embedded in the victim. While not normally as life-threatening as a bite from a venomous species, the bite can be at least temporarily debilitating and could lead to dangerous infections if improperly dealt with.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Poisonous snake bites include bites by any of the following:

• Cobra
• Copperhead
• Coral snake
• Cottonmouth (water moccasin)
• Rattlesnake
• Various snakes found at zoos

All snakes will bite when threatened or surprised, but most will usually avoid people if possible and only bite as a last resort.

Snakes found in and near water are often mistaken as being poisonous. Most species of snake are harmless and many bites are not life-threatening, but unless you are absolutely sure that you know the species, treat it seriously.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Every state but Maine, Alaska and Hawaii is home to at least one of 20 domestic poisonous snake species. About 8,000 people a year receive venomous bites in the United States; nine to 15 victims die. Some experts say that because victims can’t always positively identify a snake, they should seek prompt care for any bite, though they may think the snake is nonpoisonous. Some deaths are sudden, however in fact it is uncommon to die within four hours of a snake bite. In the 1900’s, the untreated death rates were as high as 40% to 50%. Improved supportive treatment and the availability of effective antivenoms has reduced this considerably.

Since reporting is not mandatory, many snakebites go unreported. Consequently, no accurate study has ever been conducted to determine the frequency of snakebites on the international level. However, some estimates put the number at 2.5 million bites per year, resulting in perhaps 125,000 deaths.^[1] Worldwide, snakebites occur most frequently in the summer season when snakes are active and humans are outdoors.^[2] Agricultural and tropical regions report more snakebites than anywhere else.^[1] Victims are typically male and between 17 and 27 years of age.^[2]

A late 1950s study estimated that 45,000 snakebites occur each year in the United States.^[3] Despite this large number, only 7,000 to 8,000 of those snakebites are actually caused by venomous snakes, resulting in an average of 10 deaths. This puts the chance of survival at roughly 499 out of 500. The majority of bites in the United States occur in the southwestern part of the country, in part because rattlesnake populations in the eastern states are much lower.^[4]

Most snakebite related deaths in the United States are attributed to eastern and western diamondback rattlesnake bites. Children and the elderly are most likely to die (Gold & Wingert 1994). The state of North Carolina has the highest frequency of reported snakebites, averaging approximately 19 bites per 100,000 persons. The national average is roughly 4 bites per 100,000 persons.^[5]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Recovery is usually complete, though the patient usually develops a sensitivity to equine immunoglobulin. If the patient develops serum sickness, the severity is reduced by steroid administration (eg. prednisolone 1mg/kg every 8 hours) until resolution occurs. A course of steroids is recommended in all patients who receive polyvalent antivenoms.

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