Snake venom is the cause of many injuries and deaths to humans each year. The affect that snake venom has on the human body varies based on the species of snake and the type and amount of venom that is injected. Each species of snake injects a different venom and knowing the type of snake involved in a snakebite incident can be vital in saving a person’s life.
How does snake venom affect the human body?
Snake venom falls into four categories, Hemotoxic venom, Cytotoxic venom, Proteolytic venom and Neurotoxic venom. Each of these venom types target different systems within the body and cause different symptoms. All of these types of venom will need treatment to deactivate the affects.
Snake venom falls into four categories, Hemotoxic venom, Cytotoxic venom, Proteolytic venom and Neurotoxic venom. Each of these venom types target different systems within the body and cause different symptoms. All of these types of venom will need treatment to deactivate the affects.
Hemotoxic venom attacks and damages red blood cells. This disrupts the body’s ability to clot blood and causes widespread damage to organs and tissue. The most obvious damage is done to the heart and cardiovascular system which pumps the venom around the body. Hemotoxic venom causes intense pain and will eventually result in death if not treated. In some cases the bitten limb is lost or needs to be amputated due to damage caused by the venom. Pit vipers are an example of the snakes that employ this type of venom. Hemotoxic venom does not cause instant onset of symptoms in humans. It may take up to a couple of hours before a human begins to experience nausea, disorientation and headache.
Cytotoxic venom attacks the cells of the body. There are a number of reactions that cells may undergo when injected with cytotixic venom. The cells may begin to suffer necrosis where the cell membranes fail and the cells die quickly. The cells may stop growing and multiplying or they can activate a genetic process in which the cells simply die. The symptoms in humans tend to be extreme swelling at the site of the bite. In extreme cases the area may bleed and blister causing death of the surrounding tissue.
Proteolytic venom causes the molecular structure of the cells in the surrounding area to breakdown. It disintegrates proteins which are the building blocks of cells. Proteolytic venoms break down the muscle tissue in the area surrounding the bite.
Neurotoxic Venom attacks the nervous system and the brain. The venom disrupts the normal function of the nervous system causing the death of neutrons. The most common symptoms in humans include limb weakness or numbness, loss of memory, vision, headache and paralysis.
Did you know?
The venom of proteroglyphous snakes such as the sea snake, mambas, king cobra, red-bellied black snake, tiger snake and death adders usually affect the nervous system. They cause respiratory paralysis and are deadly to humans.
The venom of proteroglyphous snakes such as the sea snake, mambas, king cobra, red-bellied black snake, tiger snake and death adders usually affect the nervous system. They cause respiratory paralysis and are deadly to humans.
The venom of vipers causes the blood to coagulate and clot in the main artery to the heart. Once bitten the area surrounding the bite swells, becomes discolored and is extremely painful. Within a few hours the victim will begin to vomit. The blood pressure drops and the pulse becomes weak and erratic. If a person survives through these stages including the severe drop in blood pressure they may survive the snake bite. Very toxic vipers require immediate attention or death will occur.
Rear fanged snakes such as boomslangs and vine snakes have venom that destroys blood cells and thins the blood. The early symptoms of a bite from a rear fanged snake include headaches, nausea, diarrhea, lethargy, mental disorientation, bruising and bleeding at the site and from all body openings. Most commonly death is caused by internal bleeding and hemorrhage.
When talking about venomous snakes and other animals with similar stings, there are two main types of venoms these animals use in order to attack its pray or in acts of defense to save itself. One of these venoms acts on the nervous system while the other acts directly on tissues or else on the components of the blood. Due to its effect on the blood components and its function, the latter type of toxin is given the name ‘
Effect of Venom.
hemotoxic venom’ and it is the topic of this article which will discuss its mechanism of action after it enters the body through bite wounds or through any other means.
Description of hemotoxic venom
Although the term hemotoxic suggest that the particular type of toxin only acts on the blood components and its functionality, the same toxin can also act directly on the tissues that lies in its path. Thus, the term hemotoxic venom is a misnomer to a certain extent, although the most notable and the earliest effects of the said toxin may indeed be associated with the blood and its functionality.
Hemolytic effect of hemotoxic venom
When discussing how hemotoxic venom affects various body tissues and blood, destruction of the red blood cells could be highlighted as one of the main mechanisms. Thus, within a few minutes to a few hours of its entry to the blood circulation, the hemotoxic venom can cause ‘hemolysis’ of red blood cells which can eventually lead to a depletion of red blood cells in the circulation. When there aren’t enough red blood cells, the oxygen carrying capacity of the blood would also deplete and many body organs including the brain, heart, liver and the kidneys will suffer as a result. At the same time, the lungs may have to exert an extra effort in order to maintain the oxygen supply, which would manifest as breathlessness and sometimes as chest discomfort due to an overworking heart.
Disseminated intravascular coagulation
Another mechanism that the hemotoxic venom affects within the animal body is the clotting mechanism. A derailment of the clotting mechanism would eventually lead to uncontrollable bleeding within body tissues and to a process known as ‘disseminated intravascular coagulation’ in which the blood clots abruptly within the blood vessels. Such clots can travel to various organs in the body and lead to fatal outcomes such as strokes, pulmonary embolism, heart attack…etc.
Cellular destruction
Although hemotoxic venom is known to act mainly on the blood, it can also act on the tissues that are lying in its path both directly as well as indirectly. However, when a toxin acts directly on the tissues or body cells it is known as ‘cytotoxic’ while it is believed that hemotoxic venom has both properties to a certain extent.
Other characteristics of hemotoxic venom
While these are the main methods in which hemotoxic venom acts on the body, it takes relatively long time before it reaches its full potential compared to other types of venoms such as neurotoxic venom. However, the hemotoxic venom is said to be rather painful as it exerts its actions, although neurotoxins are relatively swift and pain-free in its interference with the nerve activity.
Neroutoxic Venom
The term neurotoxic venom refers to any biogenic molecule that interferes with the normal function of a neuron, sometimes culminating in cell death. The animals most often associated with neurotoxic venom are snakes and spiders. As we shall see, however, many aquatic species also produce neurotoxins, including puffer fish, jellyfish, sea anemones, scorpion fish, cone shells, and octopods. This article will focus on the different mechanisms of action of neurotoxins and briefly discuss the treatments available for people bitten or stung by these creatures.
Cobras are one of the most well known venomous snakes. The neurotoxic component of cobra venom paralyzes skeletal muscles by blocking the nicotinic acetylcholine receptor, much like curare and certain anesthetic drugs. The diaphragm is a skeletal muscle, meaning it contains nicotinic acetylcholine receptors activated in response to acetylcholine released by the phrenic nerves. Death can occur up to several hours after a bite from respiratory muscle paralysis.
The treatment for a cobra bite is elapid antivenin purified from horse serum. This preparation contains equine antibodies to the toxins present in cobra venom. Since these are not human derived antibodies, however, repeated injections of antivenin will trigger an immunological response called an Arthus reaction or serum sickness. For patients suffering from respiratory muscle paralysis, mechanical ventilation is necessary.
After a spider bite, this toxin travels through the bloodstream where it enters cholinergic neurons and causes a massive burst of acetylcholine release. This neurotransmitter causes sustained contraction, or tetany, of respiratory and skeletal muscles followed by paralysis. Tissue necrosis also occurs at the bite site. Treatment consists of airway support (in the form of a mechanical ventilator) along with an injection of antibodies to black widow spider venom.
In Japan, puffer fish, also known as fugu, is a risky delicacy. Chefs who prepare puffer fish must be specially licensed; still, approximately 50 Japanese die annually after eating puffer fish. The reason is that female puffer fish produce a chemical called tetrodotoxin (TTX) in their ovaries. Some TTX can also be found in the fish's liver and skin. TTX has no distinct taste or odor but acts as a powerful blocker of voltage gated sodium channels, stopping the propagation of action potentials along neuronal axons.
Death occurs over the course of hours due to respiratory paralysis.
Certain species of mussels produce saxitoxin, a chemical with the same mechanism of action as TTX. It is estimated that the poison from a single mussel can kill 50 people.
Found mainly in the Pacific Ocean and Australian coastal waters, the blue ringed octopus produces TTX like the puffer fish. Since there is no specific antidote for TTX, a bite can be fatal in a matter of minutes.
Jellyfish and sea anemones
These sea creatures contain specialized stinging cells called nematocysts that inject venom in a manner similar to a harpoon. Compared to snake venom, jellyfish venom is less well characterized. From numerous reports, however, scientists know that jellyfish venom can interfere with respiratory muscle function and cardiac conduction. As far as danger to humans goes, the most notorious jellyfish include the box jelly and the Portuguese man-of-war. Anemones are relatively stationary and, unlike jellyfish, present little danger to swimmers or scuba divers.
These mollusks produce a poison called omega conotoxin, which acts as a powerful calcium channel blocker. Within a few seconds of exposure to this toxin, neurons stop releasing neurotransmitters. The reason is that although the neuronal axons can still conduct action potentials, (mediated by sodium ion influx and potassium ion efflux through voltage gated ion channels), neurotransmitter release requires an influx of calcium ions into the axonal terminal. Once conotoxin reaches the phrenic nerves, they stop releasing acetylcholine; the diaphragm muscle stops contracting; and death from respiratory muscle paralysis occurs a few minutes later.
A neurotoxin is a substance which inhibits the functions of neurons. Neurons are found throughout the brain and nervous system, and the function of these unique cells is critical for a variety of tasks, ranging from autonomic nervous system jobs like swallowing to higher-level brain function. Neurotoxins can work in a variety of ways, with the danger of exposure varying, depending on the neurotoxin involved and the dosage.
In some cases, neurotoxins simply severely damage neurons so that they cannot function. Others attack the signaling capability of neurons, by blocking releases of various chemicals or interfering with the methods of reception for such transmissions, and sometimes telling neurons to send false signals. A neurotoxin may also destroy neurons altogether.
The body actually generates some neurotoxins; many of the neurotransmitters produced to send messages across the nervous system can be dangerous in high amounts, for example, and sometimes the body produces neurotoxins as it responds to a threat to the immune system. Neurotoxins are also present in large numbers in the natural environment; some venomous animals produce neurotoxins, while heavy metals such as lead are also neurotoxins. Neurotoxins are also used by some governments for crowd control and warfare, in which case they are usually known as nerve agents.
Exposure to neurotoxins can cause dizziness, nausea, loss of motor control, paralysis, difficulty with vision, seizures, and strokes. In extreme cases, the results of exposure may include coma and eventual death as the nervous system shuts down. Especially when a neurotoxin inhibits the function of the autonomic nervous system, the body quickly starts to break down, because a number of important tasks are not being performed.
In the case of acute exposure, someone is exposed suddenly to a dose of a neurotoxin. Asnake bite is an example of acute exposure. Chronic exposure involves slow exposure over time; heavy metals poisoning often takes the form of chronic exposure, with the unwitting victim taking in a small amount each day. The problem with heavy metals is that they build up in the body, rather than being expelled, so at a certain point, the victim will become sick.
A variety of techniques can be used to treat neurotoxin exposure. Many focus on supportive care, performing tasks which the body isn't doing until the patient is stable. In these cases, the patient may recover, but he or she will often experience side-effects related to the exposure later in life. Sometimes, chemicals can be used to block the function of a neurotoxin, or to help flush it from the body. In other cases, there is no cure for exposure, and the goal is to keep the patient comfortable.
