A snakebite is an injury caused by the bite of a snake, especially a venomous snake. Of over 3,000 known snake species, only about 400 are venomous. Venomous snakes inject venom using modified salivary glands. During envenomation, venom is passed into the fangs through a duct from the venom gland, and is injected into a prey with a bite. Not all bites lead to envenomation. Snakes can regulate whether to release venom and how much to release. Dry Bites – a bite where no venom is injected – occur in up to fifty percent of snake bites.
Snake venom is a combination of numerous toxins that produces different effects in the body. The major components can be divided into 4 categories namely – cytotoxins, hemotoxins, neurotoxins and cardiotoxins.
The number of snakebites and the number of fatalities from these bites vary markedly by geographic region. Snakebites are more common in tropical regions and in areas that are primarily agricultural. In these areas, large numbers of people coexist with numerous snakes. Reporting of snakebites is not mandatory in many areas of the world, making it difficult to accurately determine the number of bites.
Symptoms of Snakebite
Bites by venomous snakes result in a wide range of effects. Effects following a venomous snakebite can be misleading. A victim can have no initial significant symptoms, and then suddenly develop breathing difficulty and go into shock.
Common signs and symptoms seen following a snakebite can be grouped into these categories:
1. Local effects: These include effects on skin and tissue surrounding the area of bite. Bites by vipers and some cobras are painful and tender. They can be severely swollen and can bleed and blister. Some cobra venoms can also kill the tissue around the site of the bite.
2. Bleeding: Bites by vipers and some elapids can cause changes in the victim’s hematologic system causing bleeding. This can be localized or diffuse. A victim may bleed from the bite site or bleed spontaneously from the mouth or old wounds. Unchecked bleeding can cause hemorrhagic shock or even death.
3. Nervous system effects: Nervous system effects can be local or widespread. Venom from elapids and sea snakes can have widespread effects. Cobra and mamba venom can act particularly quickly to stop the breathing muscles, resulting in death if appropriate intervention is not instituted. Victims may also experience visual problems, speaking and breathing difficulties, and numbness close to or distant to the bite site.
4. Muscle death: Venom from Russell’s vipers, sea snakes, and some elapids can directly cause muscle deaths. This can manifest as a local muscle death (necrosis), or involvement of a distant group of muscles (rhabdomyolysis). The debris from dead muscle cells can clog the kidneys, which try to filter out the proteins. This can lead to kidney failure.
5. Eyes: Spitting cobras and ringhals (cobra-like snakes from Africa) can actually eject their venom quite accurately into the eyes of their victims, resulting in direct eye pain and damage.
Most Venomous (Poisonous) Snakes to Humans
Two major families of snakes account for most venomous snakes dangerous to humans.
1. The elapid family – cobras, mambas, the coral snakes, tiger snakes, king brown snakes, and death adders.
2. The viper family – rattlesnakes, vipers and puff adders.
Diagnosis is usually made based on the history of the event. Identification or description of the snake can be helpful in developing a treatment plan as not all snakes are venomous, and different kinds of anti-venom exist for different species of snakes. There may be evidence of fang marks or local trauma at the site of bite. Pain and swelling accompany most bites, venomous or not.
First Aid for Snakebite
Any snakebite victim should go to a hospital emergency department as soon as is possible. Safely and rapidly transport the victim to an emergency medical facility. Individuals were possible can provide emergency medical care within the limits of their training.
Identification of the snake as venomous or non-venomous should not be used as criteria whether to seek medical care. Bites by nonvenomous species require proper wound care. Victims should receive a tetanus booster if they have not had one within the last 5 years. Wash the wound with large amounts of soap and water. Inspect the wound for broken teeth or dirt.
Identify or be able to describe the snake, but only if it can be done without significant risk for a second bite or a second victim. Do not try to catch the snake as this can lead to additional victims or bites. Snakes can continue to bite and inject venom with successive bites until they run out of venom.
Remove constricting items on the victim, such as rings or other jewelry, which could cut off blood flow if the bite area swells. If a person has been bitten by a dangerous elapid and has no major local wound effects, a pressure immobilizer may be applied. Wrap a bandage at the bite site and up the extremity with a pressure at which you would wrap a sprained ankle. Then immobilize the extremity with a splint, with the same precautions concerning limiting blood flow. This technique may help prevent life-threatening systemic effects of venom, but may also worsen local damage at the wound site if significant symptoms are present there.
While applying mechanical suction has been recommended by many authorities in the past, it is highly unlikely that it will remove any significant amount of venom, and it is possible that suction could actually increase local tissue damage. This technique is, in general, no longer recommended.
‘Do Nots’ in Snakebite
1. Do NOT cut and suck. Cutting into the bite site can damage underlying tissues and organs, increase the risk of infection and sucking on the bite site does not result in venom removal.
2. Do NOT use ice. Ice does not deactivate the venom and can cause frostbite.
3. Do NOT use electric shocks. The shocks are not effective and could cause burns or electrical problems to the heart.
4. Do NOT use alcohol. Alcohol may deaden the pain, but it also makes the local blood vessels bigger, which can increase venom absorption.
5. Do NOT use tourniquets or constriction bands. These have not been proven effective, may cause increased tissue damage, and could cost the victim a limb.
Treatment of Snakebite
Treatment for shock, breathing problems, shock, and/or immediately life-threatening injuries is vital even before a full workup is complete. Bite wound should be cleaned and examined.
If a patient has symptoms, the doctor will likely send blood and urine samples to the laboratory to look for evidence of bleeding, problems in the blood clotting system, kidney problems, or muscle death. These problems may not be initially apparent, but can have dire consequences if missed.
The patient is monitored to look for worsening symptoms at the wound site, or worsening systemic symptoms in the respiratory or cardiovascular systems. Anti-venim may be administered as appropriate if available.
Prognosis and Outcomes
Most people that are bitten by snakes can recover completely with appropriate first aid and emergency care. The availability of emergency medical care and, most important, antivenin can affect how well the victim recovers. Majority of bites are dry and there is no envenomation. Most common complications of a nonvenomous bite are a retained tooth in the puncture wounds or a wound infection (including tetanus). Snakes do not carry or transmit rabies.
Snakes are mostly scared of humans and bite when cornered or frightened. Giving the snake the opportunity to escape prevents most bites.
Do not attempt to handle, capture, or tease venomous snakes or snakes of unknown identity. A large percent of snakebites occur when the victim tries to capture a snake or handles a snake carelessly.
Wearing boots while working where snakes may live can also reduce snakebites. Long pants can also reduce the severity of a bite. When in snake country, be cautious where you place your hands and feet (for example, when gathering firewood or collecting berries), and never walk barefooted.
References – WHO, Wikipedia, Mayo Clinic
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