injury caused by the mouth parts of a snake, usually from
venom. It is estimated that the worldwide number of deaths from venomous snakebites may be as high as 50,000 annually, with the greatest number being reported in the Indian subcontinent. In North America most poisonous snakes are
pit vipers (
rattlesnakes,
copperheads, and
water moccasins). A few species of
coral snakes are found from the southern and southwestern United States southward into Mexico and Central America. Major groups found in other parts of the world include the
cobras and the
adders.
Not many snakebite deaths occur annually in North America; there are far more deaths from hypersensitivity to
insect bites and stings. Practices that increase the incidence of snakebites include failure to wear protective covering for the feet and legs, sleeping outdoors on the ground, and the ritual handling of venomous snakes in some religious ceremonies.
Recognition of Venomous Snakebite. The accurate diagnosis of venomous snakebite is greatly enhanced by capturing or killing the snake and correctly identifying it. Lacking this information, one must depend on clinical manifestations, which can be varied and confusing. One should not depend on visual inspection of the pattern of marks left on the skin. Local swelling may blur the pattern of fang marks; sometimes only one fang of the venomous snake has entered the skin. Nonvenomous snakebites usually do not produce much local swelling or pain, and they bleed freely. These symptoms may, however, also occur in some types of venomous snakebites.
Symptoms. In general, venomous snakebites of the type found in the United States produce severe local pain, swelling that spreads from the site of puncture, and involvement of the lymph glands. The patient may experience nausea and vomiting, thirst, sweating, and a low grade fever. If no other symptoms develop, the prognosis is excellent. More serious symptoms indicating poisoning by a
neurotoxin include numbness and tingling of the face, hypotension, convulsions, and visual disturbances. If the snake is the type whose venom contains a
hemotoxin, the bite may produce hemorrhaging with hemoptysis, hematuria, and increased prothrombin time.
Treatment. There are conflicting opinions among experts as to the value of incisions over the fang marks and suctioning of venom from the wound if this is done outside a medical facility or by someone other than a specially trained health care provider. Some continue to recommend emergency treatment consisting of immediate application of a tourniquet, deep incisions over the fang marks, and suctioning. Others feel that the application of a tourniquet to reduce peripheral circulation and packing the affected part in ice to reduce absorption of the venom is the best first aid treatment. Some, however, do not recommend use of ice. In any case, the victim is kept calm and as physically inactive as possible and is quickly transported to a medical facility where adequate débridement of the wound and mechanical removal and neutralization of the venom can be done. This also minimizes the danger of introducing infectious agents into the wound.
In addition to local wound treatment, which may require skin grafting at a later date, treatment is concerned with administration of an immune serum (
antiserum or
antivenin), counteraction of the specific pharmacologic effects of the venom, symptomatic relief, and prevention of complications.
Prevention of Snakebite. Most snakebites are inflicted on people who handle snakes or are foolishly careless in areas where there are known to be venomous snakes. Certain common-sense precautions should be taken when visiting such an area. Important facts to keep in mind are that most snakes are active in the early evening, that they often congregate on rocky slopes facing south or west in order to bask in the sunlight (especially in the spring and fall), and that they are not active at temperatures below 10°C (50°F).