VENOMOUS SNAKES

Of the 33 snake species in California, 6 are poisonous--all of them rattlesnakes. 10 to 15 deaths are reported each year from venomous snake bites. Snake venom, which is mostly protein, acts as a neurotoxin (attacking the nervous system) and/or hemotoxin (attacking the circulatory system).

Venom facts for rattlesnakes found in California:

Sidewinder -- Venom is of moderate toxicity. Human lethal dose is 40 mg and people have died from envenomation. Average venom delivered per bite is 20-63 mg. Venom is still lethal to mice and cats after 27 years of storage. Venom causes deep tissue necrosis at site of bite.

Speckled rattlesnake -- Venom is very potent. Minimum lethal dosage for 350 gram pigeon is 0.002-0.04 mg, for mice 0.05-0.12 mg. Adults contain up to 227 mg of venom (dry weight) but inject 0.16 mg. Dried venom potency undiminished after 27 years storage.

Red diamond rattlesnake -- Long fangs (over 1/2 inch). Low in toxicity compared to other rattlesnakes but this is a large species capable of delivering large amounts of venom. Lethal dose for people is about 100 mg and 150-350 mg (up to 1.65 ml) is delivered per bite. People have died from envenomation. Lethality of venom decreases only slightly after 27 years, producing complete neuromuscular block of a cat diaphragm in 22 minutes. Tissue damaging properties of venom are 6-15 times greater in adults than juveniles.

Southern Pacific rattlesnake (western rattlesnake) -- Venom primarily hemorrhagic (affecting blood) but some subspecies contain neurotoxic components. Toxicity of venom is greater than some larger species such as the western diamondback. This coupled with the high irritability of some individuals makes this a dangerous snake. Hemorrhagic, neurologic and proteolytic activity can all result from the same bite. Hemorrhagic activity in 18 minutes accompanied by some paralysis. Death in untreated cases may occur in 18 hours or up to 5 days. Lethal venom dose for humans is 70-160 mg and adults can produce up to 112 mg of venom (dried). Dried venom toxic to mice for at least 27 years.

Western diamond back rattlesnake -- Fangs over 1/2 inch in length. Venom highly hemorrhagic. 53% of the enzymes cause breakdown of the circulatory system, 17% are neurotoxic, and 30% digest proteins. Hemorrhaging from vascular breakdown occurs in only 6 minutes. Stored venom loses little potency after 17 years. Lethal dose to humans is about 100 mg and snakes may contain up to 300 mg (dried). One snake yielded 1,145 mg (3.9 ml liquid)! This species probably responsible for more human deaths than any other snake in the U.S. Symptoms following bites include intense burning, vomiting, breathing difficulties, lowered blood pressure, increased heart rate, and secondary gangrene infection.

Mojave rattlesnake -- Neurotoxic venom is extremely virulent (10 times more toxic than any other rattlesnake in the U.S.), affecting heart, skeletal muscles and neuromuscular junctions. One bite sufficient to kill a human: lethal dose is only 10-15 mg and one adult can yield 141 mg (dried). Death occurs in a high frequency of untreated cases.

1. Keep the victim calm and reassured. Allow him or her to lie flat and avoid as much movement as possible. If possible, allow the bitten limb to rest at a level lower than the victim's heart.

2. (If pump extractor is available) Identify the bite site, looking for fang marks, and apply the Sawyer Pump extractor with the largest cup possible over the bite site. If there are two or more fang marks noted on the limb, apply the pump extractor over at least one fang mark. If more than one pump extractor is available, they may be applied to the additional fang marks.

3. Immediately wrap a large constricting band snugly about the bitten limb at a level just above the bite site, i.e. between the bite site and the heart. The constricting band should be as tight as one might bind a sprained ankle, but not so tight as to constrict blood flow.

4. DO NOT remove the constricting band until the victim has reached the hospital and is receiving antivenom.

Sources:
http://www.werc.usgs.gov/cc/snake.html
http://www-surgery.ucsd.edu/ent/DAVIDSON/Snake/Crotalus.htm

Back to CEHS website:
http://www.envtox.ucdavis.edu/CEHS/Index.htm