Researchers are studying the different ingredients in snake venom, in hopes that some of them might be used to make new drugs. These might help treat brain injuries, strokes and other illnesses.
Several snake venom polypeptides have been isolated and characterized. These include Kunitz-type inhibitors, ANP/BNP natriuretic peptides and cathelicidins. These peptides have a conserved structure but differ in their functionalities.
Symptoms
Most snakes bite only to capture prey or for self-defense. However, a few of them can release poison into the victim when they bite. These are called venomous snakes, and they include pit vipers like rattlesnakes, copperheads and cottonmouths in North America and coral snakes and water moccasins (also known as moccasins) worldwide. Venom can cause severe injury and even death unless treated promptly with antivenom, which must be given within hours of the bite.
Venom from snakes contains complex mixtures of destructive substances, such as cytotoxins that cause swelling and damage to tissue; anticoagulants that prevent the blood from clotting; and neurotoxins that affect the nerves. Symptoms of a venomous snake bite vary according to the type of snake that bit the person and the amount of venom injected. They may include a tingling or metallic taste in the mouth, swelling and bruising of the bitten area, pain, numbness, weakness and drooping of the eyelids. A sudden drop in blood pressure can cause faintness and shock.
Reassure the victim and keep them calm, and do not try to suck out the venom. Move the person to the nearest hospital as soon as possible. Restrict movement, and splint or sling the affected limb. Avoid using tourniquets, which can increase the bleeding and occlude the blood flow in the limb, and can delay absorption of the antivenom. The person should be kept warm, but not hot, and should not drink any caffeinated or alcoholic beverages. Monitor pulse, blood pressure and respiration hourly.
Treatment
The venom of many snakes contains multiple bioactive compounds. The peptides and proteins in these venoms have been shown to exert neurotoxic, haemotoxic and cytotoxic effects. Venom composition varies between snake species and within the same species; however, secreted phospholipases A2 (PLA2s) and three-finger toxin (3FTxs) are commonly major constituents of these venoms, although venoms from Dendroaspis genus (mambas) and some Australian snakes lack PLA2. The myotoxic action of 3FTxs involves a sequence with mixed positive and hydrophobic segments in the C-terminal domain, such as the KKYRYYLKPLCKK sequence found in MT-II from the venom of the coral snake (Bothrops asper): this sequence destabilizes the sarcolemma and triggers an influx of Ca2+ ions into muscle cells that results in contractions and hyperpolarization.
Muscarinic acetylcholine receptor (mAChR) binding toxins have been characterized with high selectivity for distinct subsets of mAChR. These venom-derived Kunitz-type inhibitors exhibit subtle structural differences in the canonical and secondary binding loops, resulting in unique functional properties.
Defibrase is a venom-derived serine protease purified from the Brazilian lancehead pit viper (Bothrops moojeni) that induces defibrinogenation and is marketed in China for the treatment of stroke, coronary artery disease and vascular occlusive diseases. Crotamine is a small defensin purified from the venom of the southern neotropical rattlesnake (Crotalus durissus). This toxin shows low myotoxicity and neurotoxicity. It is a basic, amphipathic 42-residue peptide with a three disulfide bonds and folds similar to human a-defensins and b-defensins.
Prevention
Getting the right type of treatment in time can prevent serious illness and, sometimes, death. Early access to health facilities that can treat snakebite envenoming is crucial.
Snakebite prevention options include education and training for medical staff in countries where snakebite occurs. Medical and nursing schools should include substantive modules on snakebite. This can help to prevent the need for expensive and complex treatment such as limb amputation.
A bite from a viper (Elaphetidae) or other venomous snake is a medical emergency requiring hospitalisation. Bites from spitting cobras, mambas or other elapid snakes can squirt venom into the eyes of the victim, leading to conjunctivitis and corneal ulceration or erosion and, in severe cases, blindness.
Antivenom is made by immunising horses or sheep against the venom of a specific snake species and is available in some places. There are also antivenoms that treat bites from a range of snakes found in a geographic region (polyspecific antivenoms).
All snakebites should be treated as a medical emergency and a patient should be taken to a hospital emergency department unless they are certain the snake was non-venomous and has not bitten them before. Victims should also have a tetanus booster shot, especially if it has been a long time since they last had one. It is important that the patient knows what kind of snake bit them, where and on which part of their body, as this can help in determining which anti-venom to give them.
Prognosis
The outcome of a snake bite depends on many factors, including the type of snake and the availability of antivenom treatment. The majority of venomous snake bites in the United States are not fatal. If a person is bitten by a viper (like a rattlesnake or copperhead) or a coral snake, immediate medical care is essential.
A venomous snake may bite without injecting any venom, called a dry bite. This usually occurs when a snake strikes at something that is not alive, such as a rock or piece of wood. Typically, the person will not have any obvious marks on their skin from the bite. The venom of the coral snake contains neurotoxic toxins that can cause weakness, paralysis and breathing difficulties. It blocks an important neurotransmitter called acetylcholine, which activates muscles in the body.
It is a good idea to call triple zero (000) if a person is bitten by a snake, especially if the bitten area looks pale or cold. They should also use their adrenaline autoinjector if they have one and follow an ASCIA allergy action plan if not already doing so. If the person is not breathing normally, they will need cardiopulmonary resuscitation. St John Ambulance Australia has a great resource on first aid resuscitation.
The global snakebite crisis is due to a number of issues, including poor data on the incidence of snake bites and deficient distribution policies for antivenoms. WHO urges regulators, researchers, clinicians and community organisations to work together to address these problems.