Envenomation

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Envenomation
Specialty Toxicology

Envenomation is the process by which venom is injected by the bite or sting of a venomous animal. [1]

Contents

Many kinds of animals, including mammals (e.g., the northern short-tailed shrew, Blarina brevicauda), reptiles (e.g., the king cobra), [2] spiders (e.g., black widows), [3] insects (e.g., wasps), and fish (e.g., stone fish) employ venom for hunting and for self-defense.

A droplet of venom on the stinger of a wasp Waspstinger1658-2.jpg
A droplet of venom on the stinger of a wasp

In particular, snakebite envenoming is considered a neglected tropical disease resulting in >100,000 deaths and maiming >400,000 people per year. [4]

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 and some other reptiles enters prey through bites of grooved teeth. More commonly animals have specialized organs such as hollow teeth (fangs) and tubular stingers 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. [4] 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.[ citation needed ]

Diagram of a snake's venom penetration system Snake Venom Delivery System Diagram.jpg
Diagram of a snake's venom penetration system

Mechanisms of snake envenomation

Snakes administer venom to their target by piercing the target's skin with specialized organs known as fangs. Snakebites 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 initiates an increase in internal pressures. This pressure differential initiates venom flow in the venom delivery system. [5] Larger snakes have been shown to administer larger quantities of venom during strikes when compared to smaller snakes. [6] 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. [7] 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 its 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 died. While not all snake species in every situation release their prey after envenomation, venom generally assists in prey relocation. [8] 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. [6] This ability allows the snake to inject a sufficient quantity of venom to dispatch the prey while also conserving their venom supply for subsequent strikes. The economical use of venom is important as it is a metabolically expensive resource.[ citation needed ]

Diagnosis and treatment

Diagnosing snake envenomation is a crucial step in determining which antivenom is to be applied. Each year there are around 2 million cases of snake envenomation end up to 100,000 deaths worldwide. [2] Various anti-venom treatments exist, typically consisting of antibodies or antibody fragments, which neutralize the venom. Certain snakes require certain treatments, such as pit vipers and coral snakes. Anti-venom therapy is designed to treat the hemorrhaging and coagulation effects that venom has on humans. [9]

See also

Related Research Articles

<span class="mw-page-title-main">Venom</span> Toxin secreted by an animal

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 stinger, in a process called envenomation. Venom is often distinguished from poison, which is a toxin that is passively delivered by being ingested, inhaled, or absorbed through the skin, and toxungen, which is actively transferred to the external surface of another animal via a physical delivery mechanism.

<span class="mw-page-title-main">Antivenom</span> Medical treatment for venomous bites and stings

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 there is significant toxicity or a high risk of toxicity. The specific antivenom needed depends on the species involved. It is given by injection.

<span class="mw-page-title-main">Rattlesnake</span> Group of venomous snakes of the genera Crotalus and Sistrurus

Rattlesnakes are venomous snakes that form the genera Crotalus and Sistrurus of the subfamily Crotalinae. All rattlesnakes are vipers. Rattlesnakes are predators that live in a wide array of habitats, hunting small animals such as birds and rodents.

<span class="mw-page-title-main">Viper</span> Family of snakes

Vipers are snakes in the family Viperidae, found in most parts of the world, except for Antarctica, Australia, Hawaii, Madagascar, New Zealand, Ireland, and various other isolated islands. They are venomous and have long, hinged fangs that permit deep penetration and injection of their venom. Three subfamilies are currently recognized. They are also known as viperids. The name "viper" is derived from the Latin word vipera, -ae, also meaning viper, possibly from vivus ("living") and parere, referring to the trait viviparity common in vipers like most of the species of Boidae.

<span class="mw-page-title-main">Snakebite</span> Injury caused by bite from snakes

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 occur. This may result in redness, swelling, and severe pain at the area, which may take up to an hour to appear. Vomiting, blurred vision, tingling of the limbs, and sweating may result. Most bites are on the hands, arms, or legs. Fear following a bite is common with symptoms of a racing heart and feeling faint. The venom may cause bleeding, kidney failure, a severe allergic reaction, tissue death around the bite, or breathing problems. Bites may result in the loss of a limb or other chronic problems or even death.

<span class="mw-page-title-main">Snake venom</span> Highly modified saliva containing zootoxins

Snake venom is a highly toxic saliva containing zootoxins that facilitates in the immobilization and digestion of prey. This also provides defense against threats. Snake venom is usually injected by unique fangs during a bite, though some species are also able to spit venom.

<span class="mw-page-title-main">Inland taipan</span> Venomous snake native to Australia.

The inland taipan, also commonly known as the western taipan, small-scaled snake, or fierce snake, is a species of extremely venomous snake in the family Elapidae. The species is endemic to semiarid regions of central east Australia. Aboriginal Australians living in those regions named the snake dandarabilla. It was formally described by Frederick McCoy in 1879 and then by William John Macleay in 1882, but for the next 90 years, it was a mystery to the scientific community; no further specimens were found, and virtually nothing was added to the knowledge of this species until its rediscovery in 1972.

A snake-stone, also known as a viper's stone, snake's pearl, black stone, serpent-stone, or nagamani is an animal bone or stone used as folk medicine for snake bite in Africa, South America, India and Asia.

<i>Crotalus scutulatus</i> Species of snake

Crotalus scutulatus is known commonly as the Mohave Rattlesnake. Other common English names include Mojave Rattlesnake and, referring specifically to the nominate (northern) subspecies: Northern Mohave Rattlesnake and Mojave Green Rattlesnake, the latter name commonly shortened to the more colloquial “Mojave green”. Campbell and Lamar (2004) supported the English name “Mohave (Mojave) rattlesnake” with some reluctance because so little of the snake’s range lies within the Mojave Desert.

<span class="mw-page-title-main">Eastern diamondback rattlesnake</span> Species of reptile endemic to the southeastern US

The eastern diamondback rattlesnake is a species of pit viper in the family Viperidae. The species is endemic to the Southeastern United States. It is one of the heaviest venomous snakes in the Americas and the largest rattlesnake. No subspecies are recognized.

<span class="mw-page-title-main">Venomous snake</span> Species of the suborder Serpentes that produce venom

Venomous snakes are species of the suborder Serpentes that are capable of producing venom, which they use for killing prey, for defense, and to assist with digestion of their prey. The venom is typically delivered by injection using hollow or grooved fangs, although some venomous snakes lack well-developed fangs. Common venomous snakes include the families Elapidae, Viperidae, Atractaspididae, and some of the Colubridae. The toxicity of venom is mainly indicated by murine LD50, while multiple factors are considered to judge the potential danger to humans. Other important factors for risk assessment include the likelihood that a snake will bite, the quantity of venom delivered with the bite, the efficiency of the delivery mechanism, and the location of a bite on the body of the victim. Snake venom may have both neurotoxic and hemotoxic properties. There are about 600 venomous snake species in the world.

Crotalidae polyvalent immune Fab (ovine), sold under the brandname CroFab, is a snake antivenin, indicated for North American crotalid (rattlesnake, copperhead and cottonmouth/water moccasin) snake envenomation.

<span class="mw-page-title-main">Western diamondback rattlesnake</span> Species of snake

The western diamondback rattlesnake or Texas diamond-back is a rattlesnake species and member of the viper family, found in the southwestern United States and Mexico. Like all other rattlesnakes and all other vipers, it is venomous. It is likely responsible for the majority of snakebite fatalities in northern Mexico and the greatest number of snakebites in the U.S. No subspecies are currently recognized.

<span class="mw-page-title-main">Tiger rattlesnake</span> Species of snake

The tiger rattlesnake is a highly venomous pit viper species found in the southwestern United States and northwestern Mexico. No subspecies are currently recognized. The specific name tigris,, refers to the many narrow dorsal crossbands, which create a pattern of vertical stripes when viewed from the side.

A dry bite is a bite by a venomous animal in which no venom is released. Dry snake bites are called "venomous snake bite without envenoming". A dry bite from a snake can still be painful, and be accompanied by bleeding, inflammation, swelling and/or erythema. It may also lead to infection, including tetanus.

<span class="mw-page-title-main">Epidemiology of snakebites</span>

Most snakebites are caused by non-venomous snakes. Of the roughly 3,700 known species of snake found worldwide, only 15% are considered dangerous to humans. Snakes are found on every continent except Antarctica. There are two major families of venomous snakes, Elapidae and Viperidae. 325 species in 61 genera are recognized in the family Elapidae and 224 species in 22 genera are recognized in the family Viperidae, In addition, the most diverse and widely distributed snake family, the colubrids, has approximately 700 venomous species, but only five genera—boomslangs, twig snakes, keelback snakes, green snakes, and slender snakes—have caused human fatalities.

<span class="mw-page-title-main">Evolution of snake venom</span> Origin and diversification of snake venom through geologic time

Venom in snakes and some lizards is a form of saliva that has been modified into venom over its evolutionary history. In snakes, venom has evolved to kill or subdue prey, as well as to perform other diet-related functions. While snakes occasionally use their venom in self defense, this is not believed to have had a strong effect on venom evolution. The evolution of venom is thought to be responsible for the enormous expansion of snakes across the globe.

<span class="mw-page-title-main">Snakebite in Latin America</span> Snake Attacks Causing Health Concern

Snakebite envenomation is considered a public health problem in Latin America, with an estimated 70,000 cases annually, but due to underreporting, these numbers may be even higher.

References

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