Snakes bite either to capture prey or as a defense. In venomous species, the discharge of venom is voluntary. Venom is stored in glands on either side of the head behind the eyes, and is expelled through muscular action. The venom passes through two ducts leading to hollow fangs located in the forward portion of the upper jaw (maxilla). Each fang possesses a small opening near the tip through which the venom is injected into the site of the bite (Fig. 1). This action is similar to forcing drops of fluid through a hypodermic syringe and needle.
Because injection of venom is voluntary, venomous snakes may occasionally deliver a "dry" bite in which no venom is injected. This can occur when snakes produce a superficial bite or are panicked. About one in five bites to humans from venomous snakes are in this category. At other times only a specific amount of venom is injected. Due to the spongy nature of the glands it is nearly impossible for a snake to expel all of its venom. When most of the venom is expelled from the glands, between 15 and 20 days are required for the secretory tissue to refill the glands. However, secretion appears to be rapid during the first few days, so that venomous snakes may possess dangerous quantities of venom within a day or two of its expulsion.
Bites from venomous snakes exhibit a distinctive pattern (Fig. 2). Typically only one or two fang punctures are evident on the skin, although smaller scratches or punctures may be evident from small teeth within the snake's mouth. Bites from non-venomous snakes display markings from small teeth only, typically seen in rows. Sharp, throbbing pain usually results immediately when venom is injected from the pit vipers, and will immediately indicate envenomation. However, pain is not always a symptom, even from potentially lethal bites. Bites from coral snakes may be nearly painless, or exhibit limited pain near the bite. Bites from nonvenomous snakes produce superficial pain, if any at all.
Bites from pit vipers are hemorrhagic, that is, they break down vascular tissue by enzymatic action. Upon entering the body, the venom travels through lymphatic vessels and sometimes the bloodstream, binding with the victim's tissues as it goes. This results in severe pain and swelling, and can produce secondary results such as dizziness, nausea, headache and shock. Short-term results from bites may include discoloration and eventual tissue loss. In fatal bites, death usually results from loss of blood pressure and volume through destruction of vascular tissue.
Coral snake venom is neurotoxic and effects the central nervous system. Thus, there may be little pain or swelling from the bite. However, effects on the nervous system can cause the arrest of involuntary muscle activity that normally controls breathing and heartbeat. Envenomation may cause symptoms of drowsiness or anxiety. It is important to note that subtle symptoms from coral snake bite may not be apparent for several hours.
Individuals may react differently to venomous snake bites, just as some people are more susceptible to bee stings than others. Successive bites may initiate some immunity which can reduce the negative impact of bites. However, successive bites often increase sensitivity to venom, producing the opposite effect -- people who have experienced two or three previous bites may go into shock if subsequently bitten.
Snakebite is a rare occurrence, even among people who spend a great deal of time outdoors. Prior to the mid-1960s, approximately one in 10,000 people were bitten by venomous snakes each year in Louisiana. The incidence of snakebite to Louisiana citizens is now likely reduced. The people at greatest risk of being bitten are those who handle snakes, including individuals who keep venomous snakes as pets, or are in the habit of killing or skinning venomous snakes. Such individuals account for roughly 40% of venomous snake bites. Surprisingly, the incidence of snakebite for children playing outdoors is relatively low. Fatality from snake bites has become a rare occurrence: about one in 600 reported bites are fatal following medical treatment, and in some species such as the Copperhead, the fatality rate is near zero. The fatality rate without medical treatment is about one in 40.
The first step in snakebite treatment is to avoid panic and seek medical attention. The very low death rate from snakebites should be reassuring. Several treatments have been recommended for field first aid, but the most important step is to seek medical attention immediately. Call local hospitals to determine which ones are prepared to treat snakebite victims.
What to do:
- Remain calm; snakebite is rarely fatal.
- Seek immediate medical attention. Call ahead to the hospital so that emergency personnel will be ready upon your arrival.
- Keep the bitten body part immobilized (i.e., if a hand is bitten, suspend the arm in a sling).
Remove jewelry and clothing that may become constrictive as swelling progresses.
The following steps are optional for rattlesnake, copperhead and cottonmouth bites only. No first aid for coral snakes is recommended beyond steps 1-4 above.
- If medical attention is less than 20 minutes away, apply a wide constricting band just above the bite (use only if the bite is on a limb). This band should be loose enough so that a finger can easily be slipped between it and the skin, and should never be tight enough to cut off circulation.
- If medical attention is more than 20 minutes away, and the bite is less than 10 minutes old, small incisions may be made just above the bite (in the direction of the trunk). These should be no more than 3/8 inch long and 1/8 inch deep. Fluid may be sucked from the bite and incisions during the next half-hour. Fluid should never be sucked orally if open sores are present on or in the mouth. Incisions are ineffective if the bite is over 15 minutes old, as the venom will have dispersed within the lymphatic system.
What not to do:
- Never apply ice packs.
- Never apply a tourniquet that restricts blood circulation.
- Never attempt to excise the wound or "cut-out" the venom.
- Never allow the victim to drink alcohol or take aspirin or other blood thinners.
- Never apply electric shock to the bitten area.
Never give antivenin in the field -- antivenin is, itself, a toxin that may cause anaphylactic shock.
Snake bite can be avoided in a number of ways:
- Be cautious about where hands and feet are placed. Do not put hands in holes or under objects (i.e., lumber, scrap metal, overturned boats) without first being sure that a snake is not located underneath.
- Do not lay your head down or sit down in vegetation or other situations where there may be any doubt about the presence of venomous snakes.
- Wear proper foot gear such as hightop leather boots when walking through dense vegetation.
- Do not attempt to capture, tease, handle or keep venomous snakes. Involuntary nervous activity may allow snakes to bite for up to an hour after they have been ?killed.?
- Camp away from swamps, stream banks, brush piles, tall vegetation, trash and other areas likely to be inhabited by venomous snakes.
- Do not walk barefoot at night.