What are snake bites?
Snakes bite either to capture prey or in self-defense. Snakes that are poisonous voluntarily emit venom when they bite. Because snakes can control the amount of venom they discharge, some bites are "dry" and only 50% - 70% of venomous snake bites result in envenoming, or poisoning.
Even so it is best to treat all snake bites as a medical emergency unless one is certain the bite came from a non-venomous snake. Any delay in treatment following the bite of a venomous snake could result in death or serious injury.
Different species of venomous snakes carry different types of venom. In general, the major categories of venom are:
- Cytotoxins: Cause swelling and tissue damage in the area of the bite.
- Haemorrhagins: Cause disruption to blood vessels.
- Anti-clotting agents: Prevent the blood from clotting.
- Neurotoxins: Cause paralysis or other damage to the nervous system.
- Myotoxins: Break down muscles.
How common are snake bites?
According to the World Health Organization, at least 421,000 bites and 20,000 deaths occur each year from venomous snake bites. These figures could actually be as high as 1,841,000 venomous bites and 94,000 deaths per year.
The highest rates of venomous snake bites occur in rural areas of South Asia, Southeast Asia, and sub-Saharan Africa, where populations often do not have access to health care services or antivenoms.
In North America, most snakes are not venomous. Those that are include the rattlesnake, water moccasin, coral snake, and copperhead.
What are the symptoms of snake bites?
The symptoms that result from the bite of a venomous snake will depend on the type of snake involved. Some common reactions include the following:
- Two puncture wounds at the site of the bite. Other teeth marks may also be present.
- A sharp, throbbing pain at the site of the bite. However, pain is not always a symptom. For example, a bite from a coral snake can be nearly painless at first but still deadly.
- Redness, swelling and damaged tissue in the area of the bite
- Abnormal blood clotting and bleeding
- Low blood pressure and shock
- Nausea and vomiting
- Difficulty breathing, or in serious cases not being able to breathe at all
- Blurred vision
- Increased production of saliva
- Heavy sweating
- Numb feeling in the face or limbs
What causes snake bites?
The two major groups of venomous snakes are:
- Elapids (cobra family): There are about 300 venomous species of Elapidae, including kraits, mambas, coral snakes, and sea snakes. They have short fangs in the front of the upper jaw and strike downward, followed by chewing. Their venom is mainly neurotoxic but it can also harm body tissues or blood cells. Death from paralysis of the heart and lungs can occur quickly.
- Vipers: There are more than 200 species of the snake family Viperidae, which includes pit vipers (e.g., rattlesnakes, copperheads, water moccasins, or cottonmouths) and Old World vipers (adders). They have long, hollow, venomous fangs attached to movable bones in the upper jaw. The fangs fold back in the mouth when not in use.