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Rattlesnakes are pit vipers and include the genera Crotalus and Sistrurus. Pit vipers may be identified by a heat-sensing pit anteroinferior to the eye. Rattlesnakes may be identified in all but one species by a rattle at the tip of the tail. Rattlesnakes are indigenous from North America to South America. Only about 15% of the 3000 species of venomous snakes throughout the world are considered poisonous to humans. In the USA, about 25 species of snakes are venomous or have toxic salivary secretions. Poisonous snakes are native to every state except Alaska, Maine, and Hawaii. Although in the USA more than 8000 people per year are bitten by poisonous snakes, fewer than 6 deaths a year occur, mostly in children, the elderly, members of religious sects who handle venomous snakes, and untreated or undertreated cases. Rattlesnakes account for most venomous snakebites and for almost all deaths. Most other venomous snakebites are by copperheads and, to a lesser extent, cottonmouths (water moccasins). Coral snakes account for less than 1% of all bites. Imported species of venomous snakes, found in zoos, schools, snake farms, and amateur and professional collections, account for about 100 bites a year. Most victims are young males, of whom 50% are intoxicated and deliberately handling or molesting the snake. Most bites occur on the extremities.

Southern California Species:

Red Diamond Rattlesnake (Crotalus ruber)

This large, brick red snake is primarily a Baja California species, including several islands, and extends only into the corner of the United States. It is common in the low hills within a kilometer of the campus. Red diamond rattlesnakes can exceed 1.5 m in length but tend to have a rather passive disposition compared to many other rattlesnake species.

Southern pacific rattlesnake (Crotalus helleri)

Found throughout Southern California's densely populated coastal valleys and foothills, this dangerous snake is responsible for most of the rattlesnake bites in the greater Los Angeles basin. It was considered a subspecies of Crotalus viridis (Western rattlesnake, found mostly in the mid-west) for many years, but recent genetic analyses have led to systematic revisions of these taxa, with some researchers classifying helleri as part of the Crotalus oreganus (North Pacific rattlesnake) group while others elevate it to full species status. It can exceed 1.5 m in length.

Western diamondback rattlesnake (Crotalus atrox)

It inhabits a large portion of the arid southwestern United States and northern México, including the southeastern corner of California. Adults can exceed 2.0 m in length and are the largest rattlesnake species in the western United States. They are notoriously nervous and quick to rattle, often assuming a dramatic defensive pose when bothered by creatures as large as humans. The western diamondback's range in California encompasses sparsely populated areas where they encounter few people.

Mohave rattlesnake (Crotalus scutulatus)

This rattlesnake is common around many high-desert communities. It produces one of the most toxic venoms of any North American rattlesnake. Called "Mohave Greens" by the locals, they seem to have achieved "urban legend" status with a greatly exaggerated reputation for aggressiveness. Like other rattlesnakes, they prefer to remain still in hopes of going unnoticed. But if bothered, they will defend themselves enthusiastically. Length rarely exceeds 1 m in this area.

Sidewinder (Crotalus cerastes)

California's smallest rattlesnake species, this elegant snake rarely reaches 0.75 m in length. Famous for their specialized method of moving efficiently over loose sand by pushing straight down in only two places at a time, they can also be common on firmer substrates. Due to their small size (and, therefore, low venom yield) and comparatively low venom potency, their bites are usually not as serious as bites by other species. Two subspecies occur nearby, the Mohave Desert sidewinder (C. c. cerastes) and the Colorado Desert sidewinder (C. c. laterorepens).

Southwestern speckled rattlesnake (Crotalus mitchelli pyrrhus)

This snake is a rocky hillside specialist in the deserts. South towards San Diego, however, this species inhabits coastal hills and valleys. Probably due to their habitat preferences, they seem to suffer fewer encounters with people than other species that inhabit flatter terrain. The dorsal coloration of speckled rattlesnakes can vary greatly from gray to tan and even burnt orange. They are relatively small but occasionally exceed 1.25 m in length.

Pathophysiology

 Venom is usually injected into subcutaneous tissue via hollow movable fangs located in the anterior mouth. Occasionally, intramuscular or (probably rarely) intravenous injection occurs. Rattlesnake venom is generally composed of several digestive enzymes and spreading factors, which result in local and systemic injury.

Clinically, local effects most commonly predominate, progressing from pain and edema to ecchymosis and bullae. Hematologic abnormalities, including defibrination with or without thrombocytopenia, may result, but serious bleeding is uncommon. Local or diffuse myotoxicity may result in complications such as compartment syndrome or rhabdomyolysis. Other general effects include shock, myokymia/fasciculations, taste changes, and vomiting. Rarely, direct cardiotoxicity or allergy to venom may occur. Some rattlesnakes may exhibit neurotoxicity with minimal local tissue effects.

Frequency

· In the US: Approximately 8,000 reptile bites were reported to the American Association of Poison Control Centers (AAPCC) in 2004. However, this figure is probably conservative because of underreporting. Rattlesnakes cause the majority of all bites by identified venomous snakes in the United States. Dry bite (ie, no clinical evidence of envenomation) occurs in between 10 and 50% of strikes.

Internationally: An estimated 300,000-400,000 venomous snakebites occur per year. Although rattlesnakes are not found naturally outside of North America, Central America, and South America, they are imported into zoos, museums, and private collections in other regions of the world.

Mortality/Morbidity: Fewer than half a dozen deaths occur per year as a result of snakebite in the United States; most are caused by rattlesnake bites. Estimates of deaths each year from snakebite range from 30,000-110,000 worldwide. Up to 5 times as many individuals experience permanent morbidity.

US mortality with administration of antivenin is approximately 0.28%. Without antivenin being administered mortality is approximately 2.6%.

Sex: Males are bitten more commonly than females.

Age: Young adults are bitten most commonly.

 

History

All or none of the following may be present. Note that symptoms are subject to change, and this change can be very rapid or very insidious. In addition, severity is generally guided by the most severely affected parameter.

· Pain around the bite site

· Swelling

· Taste changes (e.g., a metallic taste)

· Difficulty breathing

· Chest pain

· Nausea, vomiting, or diarrhea

· Hematemesis, hematochezia (blood in urine)

· Neurologic symptoms:

o Weakness

o Paresthesias (numbness)

o Syncope, near syncope (fainting)

 

Physical

· Fang marks - May be 1, 2, or more, or may be unable to discern

· Tenderness surrounding the bite site

· Local edema

o Use a pen to mark and time the border of advancing edema every 15-20 minutes initially. Once stabilization with antivenom has occurred, repeat measurements every 1-2 hours.

o Rapidly progressive swelling is usually indicative of a severe envenomation.

· Erythema

· Ecchymosis

· Bullae

· Bleeding

· Hypotension/hypertension

· Tachycardia

· Myokymia (muscle fasciculations)

· Neurologic effects

· Lethargy

Causes

 A large percentage of bites occur when a snake is handled, kept as a pet, or abused. These are considered intentionally interactive bites. Many bites are associated with alcohol use.

Prehospital Care

Call 9-1-1

· Lymphatic constriction bands and pressure immobilization techniques may inhibit the spread of venom, but whether they improve outcome is not clear. Limiting venom spread actually may be deleterious for pit viper envenomation if it increases local necrosis or compartment pressure. Tourniquets are not recommended.

· Maintain the extremity in a neutral position and keep the patient calm.

· First aid techniques that lack therapeutic value or are potentially more harmful than the snakebite include electric shock, alcohol, stimulants, aspirin, placing ice on the wound, and various folk and herbal remedies. Cost and risk of acute adverse reactions generally preclude field use of antivenom.

Attempts to capture or kill the snake cannot be recommended because of the risk of additional injury. If uncertainty exists about whether a particular snake is venomous, consider taking photographs of the snake from a safe distance of at least 6 feet away using a digital or Polaroid camera.

Rattlesnakes