Envenomation is the process by which

venom Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a st ...

is injected by the bite or sting of a venomous animal. Many kinds of animals, including mammals (e.g., the

northern short-tailed shrew The northern short-tailed shrew (''Blarina brevicauda'') is the largest shrew in the genus ''Blarina'', and occurs in the northeastern region of North America. It is a semifossorial, highly active, and voracious insectivore and is present in a v ...

, ''Blarina brevicauda''), reptiles (e.g., the king cobra),

spider Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...

s (e.g., black widows),

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three ...

s (e.g.,

wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. ...

s), and fish (e.g., stone fish) employ venom for hunting and for self-defense. Waspstinger1658-2

In particular, snakebite envenoming is considered a neglected tropical disease resulting in >100,000 deaths and maiming >400,000 people per year.

Mechanisms

Some venoms are applied externally, especially to sensitive tissues such as the eyes, but most venoms are administered by piercing the skin of the victim. Venom in the saliva of the

Gila monster The Gila monster (''Heloderma suspectum'', ) is a species of venomous lizard native to the Southwestern United States and the northwestern Mexican state of Sonora. It is a heavy, typically slow-moving reptile, up to long, and it is the only ve ...

and some other reptiles enters prey through bites of grooved teeth. More commonly animals have specialized organs such as hollow teeth (

fangs A fang is a long, pointed tooth. In mammals, a fang is a modified maxillary tooth, used for biting and tearing flesh. In snakes, it is a specialized tooth that is associated with a venom gland (see snake venom). Spiders also have external fa ...

) and tubular

stinger A stinger (or sting) is a sharp organ found in various animals (typically insects and other arthropods) capable of injecting venom, usually by piercing the epidermis of another animal. An insect sting is complicated by its introduction of ve ...

s that penetrate the prey's skin, whereupon muscles attached to the attacker's venom reservoir squirt venom deep within the victim's body tissue. For example, the fangs of venomous snakes are connected to a venom gland by means of a duct. Death may occur as a result of bites or stings. The rate of envenoming is described as the likelihood of venom successfully entering a system upon bite or sting. Snake Venom Delivery System Diagram

Mechanisms of Snake Envenomation

Snakes administer venom to their target by piercing the target's skin with specialized organs known as fangs.

Snakebite A snakebite is an injury caused by the bite of a snake, especially a venomous snake. A common sign of a bite from a venomous snake is the presence of two puncture wounds from the animal's fangs. Sometimes venom injection from the bite may occu ...

s can be broken into four stages; strike launch, fang erection, fang penetration, and fang withdrawal. Snakes have a venom gland connected to a duct and subsequent fangs. The fangs have hollow tubes with grooved sides that allow venom to flow within them. During snake bites, the fangs penetrate the skin of the target and the fang sheath, a soft tissue organ surrounding the fangs, is retracted. The fang sheath retraction causes an increase in internal pressures. This pressure differential initiates venom flow in the venom delivery system. Larger snakes have been shown to administer larger quantities of venom during strikes when compared to smaller snakes. Snake envenomation events are usually classified as either predatory or defensive in nature. Defensive envenomation events result in much larger quantities of venom being expelled into the target. Defensive envenomation can occur with 8.5 times greater venom flow rates and 10 times greater venom mass than predatory strikes. The need to quickly neutralize a target during a defensive strikes explains these higher venom quantities. Predatory strikes are quite different than defensive strikes. In predatory strikes, the snake strikes and envenomates the target, and then quickly releases the target. Releasing the target prevents retaliatory damage to the snake or it's venom delivery system. Once released, the target animal runs away until the venom induces death of the target. Snake venom has a scent that is easily recognized by the snake, allowing the snake to relocate its prey once it has run away and become deceased. While not all snake species in every situation release their prey after envenomation, venom generally assists in prey relocation. Venomous snakes have also been shown to be aware of the relative size of prey. Juvenile Rattlesnakes were experimentally shown to have the ability to adapt the volume of venom they expelled based on prey size. Once experienced, the juvenile Rattlesnakes consistently expelled more venom when attacking larger mice. This ability allows the snake to inject a sufficient quantity of venom to euthanize the prey while also conserving their venom supply for subsequent strikes. The economical use of venom is an important factor as it is a metabolically expensive resource.

Diagnosis and treatment

Diagnosing snake envenomation is a crucial step in determining which

antivenom Antivenom, also known as antivenin, venom antiserum, and antivenom immunoglobulin, is a specific treatment for envenomation. It is composed of antibodies and used to treat certain venomous bites and stings. Antivenoms are recommended only if th ...

is to be applied. Each year there are around 2 million cases of snake envenomation and up to 100,000 deaths worldwide. Various anti-venom treatments exist, typically consisting of antibodies or antibody fragments, which neutralize the

. Certain snakes require certain treatments, such as pit vipers and

coral snakes Coral snakes are a large group of elapid snakes that can be divided into two distinct groups, the Old World coral snakes and New World coral snakes. There are 16 species of Old World coral snakes, in three genera ('' Calliophis'', ''Hemibungarus' ...

. Anti-venom therapy is designed to treat the hemorrhaging and coagulation effects that venom has on humans.

References

External links

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Mechanisms

Mechanisms of Snake Envenomation

Diagnosis and treatment

See also

References

External links