![Vipera berus - Venom delivery apparatus](https://upload.wikimedia.org/wikipedia/commons/1/1d/Vipera_berus_-_Venom_delivery_apparatus.JPG)
Snake venom is a highly toxic
saliva
Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be ...
containing
zootoxins that facilitates in the immobilization and digestion of
prey
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...
. This also provides defense against threats. Snake venom is injected by unique
fang
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 fang ...
s during a
bite
Biting is a common zoological behavior involving the active, rapid closing of the jaw around an object. This behavior is found in toothed animals such as mammals, reptiles, amphibians and fish, but can also exist in arthropods. Myocytic con ...
, whereas some species are also able to spit
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 sti ...
.
[
The glands that secrete zootoxins are a modification of the ]parotid salivary gland
The parotid gland is a major salivary gland in many animals. In humans, the two parotid glands are present on either side of the mouth and in front of both ears. They are the largest of the salivary glands. Each parotid is wrapped around the man ...
s found in other vertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
and are usually located on each side of the head, below and behind the eye, and enclosed in a muscular sheath. The venom is stored in large glands called alveoli Alveolus (; pl. alveoli, adj. alveolar) is a general anatomical term for a concave cavity or pit.
Uses in anatomy and zoology
* Pulmonary alveolus, an air sac in the lungs
** Alveolar cell or pneumocyte
** Alveolar duct
** Alveolar macrophage
* ...
in which it's stored before being conveyed by a duct to the base of channeled or tubular fangs through which it's ejected.[
Venom contains more than 20 different compounds, which are mostly proteins and ]polypeptides
Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides.
A p ...
. The complex mixture of proteins, enzymes, and various other substances has toxic and lethal properties.[ Venom serves to immobilize prey.] Enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
s in venom play an important role in the digestion of prey, and various other substances are responsible for important but non-lethal biological effects. Some of the proteins in snake venom have very specific effects on various biological functions, including blood coagulation, blood pressure regulation, and transmission of nerve or muscle impulses. These venoms have been studied and developed for use as pharmacological or diagnostic tools, and even drugs.
Chemistry
Proteins
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
constitute 90-95% of venom's dry weight and are responsible for almost all of its biological effects. The hundreds, even thousands, of proteins found in venom include toxins, neurotoxin
Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature ner ...
s in particular, as well as nontoxic proteins (which also have pharmacological properties), and many enzymes, especially hydrolytic
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolysis ...
ones.[ Enzymes (]molecular weight
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...
13-150 KDa) make up 80-90% of viperid
The Viperidae (vipers) are a family of snakes found in most parts of the world, except for Antarctica, Australia, Hawaii, Madagascar, and various other isolated islands. They are venomous and have long (relative to non-vipers), hinged fangs tha ...
and 25-70% of elapid
Elapidae (, commonly known as elapids ; grc, ἔλλοψ ''éllops'' "sea-fish") is a family of snakes characterized by their permanently erect fangs at the front of the mouth. Most elapids are venomous, with the exception of the genus Emydoceph ...
venoms, including digestive hydrolase
Hydrolase is a class of enzyme that commonly perform as biochemical catalysts that use water to break a chemical bond, which typically results in dividing a larger molecule into smaller molecules. Some common examples of hydrolase enzymes are este ...
s, L-amino-acid oxidase
In enzymology, an L-amino acid oxidase (LAAO) () is an enzyme that catalyzes the chemical reaction
:an L-amino acid + H2O + O2 \rightleftharpoons a 2-oxo acid + NH3 + H2O2
The enzyme was first described in 1944 by A. Zeller and A. Maritz. Not onl ...
, phospholipase
A phospholipase is an enzyme that hydrolyzes phospholipids into fatty acids and other lipophilic substances. Acids trigger the release of bound calcium from cellular stores and the consequent increase in free cytosolic Ca2+, an essential step in ...
s, thrombin
Thrombin (, ''fibrinogenase'', ''thrombase'', ''thrombofort'', ''topical'', ''thrombin-C'', ''tropostasin'', ''activated blood-coagulation factor II'', ''blood-coagulation factor IIa'', ''factor IIa'', ''E thrombin'', ''beta-thrombin'', ''gamma- ...
-like pro-coagulant, and kallikrein
Kallikreins are a subgroup of serine proteases, enzymes capable of cleaving peptide bonds in proteins. In humans, plasma kallikrein (encoded by ''KLKB1 gene'') has no known paralogue, while tissue kallikrein-related peptidases (''KLKs'') encode a f ...
-like serine proteases
Serine proteases (or serine endopeptidases) are enzymes that cleave peptide bonds in proteins. Serine serves as the nucleophilic amino acid at the (enzyme's) active site.
They are found ubiquitously in both eukaryotes and prokaryotes. Serin ...
and metalloproteinases
A metalloproteinase, or metalloprotease, is any protease enzyme whose catalytic mechanism involves a metal. An example is ADAM12 which plays a significant role in the fusion of muscle cells during embryo development, in a process known as myogen ...
(hemorrhagins), which damage vascular endothelium
The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...
. Polypeptide toxins (molecular weight 5-10 KDa) include cytotoxin
Cytotoxicity is the quality of being toxic to cells. Examples of toxic agents are an immune cell or some types of venom, e.g. from the puff adder (''Bitis arietans'') or brown recluse spider (''Loxosceles reclusa'').
Cell physiology
Treating cells ...
s, cardiotoxin
Cardiotoxicity is the occurrence of heart dysfunction as electric or muscle damage, resulting in heart toxicity. The heart becomes weaker and is not as efficient in pumping blood. Cardiotoxicity may be caused by chemotherapy (a usual example is th ...
s, and postsynaptic
Chemical synapses are biological junctions through which neurons' signals can be sent to each other and to non-neuronal cells such as those in muscles or glands. Chemical synapses allow neurons to form circuits within the central nervous sys ...
neurotoxins (such as α-bungarotoxin and α-Cobratoxin
α-Cobratoxin is a substance of the venom of certain ''Naja'' cobras. It is a nicotinic acetylcholine receptor (nAChR) antagonist which causes paralysis by preventing the binding of acetylcholine to the nAChR.
Sources
α-Cobratoxin is a neur ...
), which bind to acetylcholine receptor
An acetylcholine receptor (abbreviated AChR) is an integral membrane protein that responds to the binding of acetylcholine, a neurotransmitter.
Classification
Like other transmembrane receptors, acetylcholine receptors are classified according ...
s at neuromuscular junctions. Compounds with low molecular weight (up to 1.5 KDa) include metals, peptides, lipids, nucleosides
Nucleosides are glycosylamines that can be thought of as nucleotides without a phosphate group. A nucleoside consists simply of a nucleobase (also termed a nitrogenous base) and a five-carbon sugar (ribose or 2'-deoxyribose) whereas a nucleotide ...
, carbohydrates, amines, and oligopeptides
An oligopeptide, often just called peptide ('' oligo-'', "a few"), consists of two to twenty amino acids and can include dipeptides, tripeptides, tetrapeptides, and pentapeptides. Some of the major classes of naturally occurring oligopeptides incl ...
, which inhibit angiotensin-converting enzyme
Angiotensin-converting enzyme (), or ACE, is a central component of the renin–angiotensin system (RAS), which controls blood pressure by regulating the volume of fluids in the body. It converts the hormone angiotensin I to the active vasoconstr ...
(ACE) and potentiate bradykinin (BPP). Inter- and intra-species variation in venom chemical composition is geographical and ontogenic.[ ]Phosphodiesterase
A phosphodiesterase (PDE) is an enzyme that breaks a phosphodiester bond. Usually, ''phosphodiesterase'' refers to cyclic nucleotide phosphodiesterases, which have great clinical significance and are described below. However, there are many oth ...
s interfere with the prey's cardiac system, mainly to lower the blood pressure
Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure" r ...
. Phospholipase A2
The enzyme phospholipase A2 (EC 3.1.1.4, PLA2, systematic name phosphatidylcholine 2-acylhydrolase) catalyse the cleavage of fatty acids in position 2 of phospholipids, hydrolyzing the bond between the second fatty acid “tail” and the glyce ...
causes hemolysis
Hemolysis or haemolysis (), also known by several other names, is the rupturing (lysis) of red blood cells (erythrocytes) and the release of their contents (cytoplasm) into surrounding fluid (e.g. blood plasma). Hemolysis may occur in vivo o ...
by lysing the phospholipid
Phospholipids, are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids typ ...
cell membranes
The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...
of red blood cells
Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek language, Greek ''erythros'' for "red" and ''k ...
. Amino acid oxidase
In biochemistry, an oxidase is an enzyme that catalyzes oxidation-reduction reactions, especially one involving dioxygen (O2) as the electron acceptor. In reactions involving donation of a hydrogen atom, oxygen is reduced to water (H2O) or hydro ...
s and protease
A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the ...
s are used for digestion. Amino acid oxidase also triggers some other enzymes and is responsible for the yellow colour of the venom of some species. Hyaluronidase
Hyaluronidases are a family of enzymes that catalyse the degradation of hyaluronic acid (HA). Karl Meyer classified these enzymes in 1971, into three distinct groups, a scheme based on the enzyme reaction products. The three main types of hyal ...
increases tissue permeability to accelerate the absorption of other enzymes into tissues. Some snake venoms carry fasciculin
Fasciculins are a class of toxic proteins found in certain snake venoms, notably some species of mamba. Investigations have revealed distinct forms in some Eastern green mamba, green mamba venoms, in particular FAS1 and FAS2 Fasciculins are so cal ...
s, like the mamba
Mambas are fast moving highly venomous snakes of the genus ''Dendroaspis'' (which literally means "tree Asp (reptile), asp") in the family Elapidae. Four Neontology, extant species are recognised currently; three of those four species are essen ...
s (''Dendroaspis''), which inhibit cholinesterase
The enzyme cholinesterase (EC 3.1.1.8, choline esterase; systematic name acylcholine acylhydrolase) catalyses the hydrolysis of choline-based esters:
: an acylcholine + H2O = choline + a carboxylate
Several of these serve as neurotransmitters ...
to make the prey lose muscle control.[ ]
Snake toxins vary greatly in their functions. The two broad classes of toxins found in snake venoms are neurotoxin
Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature ner ...
s (mostly found in elapids) and hemotoxin
Hemotoxins, haemotoxins or hematotoxins are toxins that destroy red blood cells, disrupt blood clotting, and/or cause organ degeneration and generalized tissue damage. The term ''hemotoxin'' is to some degree a misnomer since toxins that damage ...
s (mostly found in viperids). However, exceptions occur – the venom of the black-necked spitting cobra
The black-necked spitting cobra (''Naja nigricollis'') is a species of spitting cobra found mostly in sub-Saharan Africa. They are moderately sized snakes that can grow to a length of in length. Their coloration and markings can vary considera ...
(''Naja nigricollis
The black-necked spitting cobra (''Naja nigricollis'') is a species of spitting cobra found mostly in sub-Saharan Africa. They are moderately sized snakes that can grow to a length of in length. Their coloration and markings can vary considerab ...
''), an elapid, consists mainly of cytotoxin
Cytotoxicity is the quality of being toxic to cells. Examples of toxic agents are an immune cell or some types of venom, e.g. from the puff adder (''Bitis arietans'') or brown recluse spider (''Loxosceles reclusa'').
Cell physiology
Treating cells ...
s, while that of the Mojave rattlesnake
''Crotalus scutulatus'' (common names: Mojave rattlesnake,Crothier, B.I. ''et al''. 2003. Scientific and standard English names of amphibians and reptiles of North America north of Mexico: Update. ''Herpetological Review'' 34:196–203 Stebbins ...
(''Crotalus scutulatus''), a viperid, is primarily neurotoxic. Both elapids and viperids may carry numerous other types of toxins.
Toxins
Neurotoxins
The beginning of a new neural impulse goes as follows:
# An exchange of ions (charged atoms) across the nerve cell membrane sends a depolarizing current towards the end of the nerve cell (cell terminus).
# When the depolarizing current arrives at the nerve cell terminus, the neurotransmitter acetylcholine
Acetylcholine (ACh) is an organic chemical that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Part ...
(ACh), which is held in vesicles
Vesicle may refer to:
; In cellular biology or chemistry
* Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane
* Synaptic vesicle
; In human embryology
* Vesicle (embryology), bulge-like features o ...
, is released into the space between the two nerves (synapse). It moves across the synapse to the postsynaptic receptors.
# ACh binds to the receptors and transfers the signal to the target cell, and after a short time, it's destroyed by acetylcholinesterase.
;Fasciculins
:These toxins attack cholinergic
Cholinergic agents are compounds which mimic the action of acetylcholine and/or butyrylcholine. In general, the word "choline" describes the various quaternary ammonium salts containing the ''N'',''N'',''N''-trimethylethanolammonium cation. F ...
neurons (those that use ACh as a transmitter) by destroying acetylcholinesterase (AChE). ACh, therefore, cannot be broken down and stays in the receptor. This causes tetany
Tetany or tetanic seizure is a medical sign consisting of the involuntary contraction of muscles, which may be caused by disorders that increase the action potential frequency of muscle cells or the nerves that innervate them.
Muscle cramps cause ...
(involuntary muscle contraction), which can lead to death. The toxins have been called fasciculins since after injection into mice
A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...
, they cause severe, generalized and long-lasting (5-7 h) fasciculation
A fasciculation, or muscle twitch, is a spontaneous, involuntary muscle contraction and relaxation, involving fine muscle fibers. They are common, with as many as 70% of people experiencing them. They can be benign, or associated with more serio ...
s (rapid muscle contractions).
:Snake example: found mostly in the venom of mamba
Mambas are fast moving highly venomous snakes of the genus ''Dendroaspis'' (which literally means "tree Asp (reptile), asp") in the family Elapidae. Four Neontology, extant species are recognised currently; three of those four species are essen ...
s (''Dendroaspis'' spp.) and some rattlesnake
Rattlesnakes are venomous snakes that form the genera ''Crotalus'' and ''Sistrurus'' of the subfamily Crotalinae (the pit vipers). All rattlesnakes are vipers. Rattlesnakes are predators that live in a wide array of habitats, hunting small anim ...
s (''Crotalus'' spp.)
;Dendrotoxins
:Dendrotoxin
Dendrotoxins are a class of presynaptic neurotoxins produced by mamba snakes (''Dendroaspis'') that block particular subtypes of voltage-gated potassium channels in neurons, thereby enhancing the release of acetylcholine at neuromuscular junctions. ...
s inhibit neurotransmissions by blocking the exchange of positive and negative ions across the neuronal membrane lead to no nerve impulse, thereby paralyzing the nerves.
:Snake example: mamba
Mambas are fast moving highly venomous snakes of the genus ''Dendroaspis'' (which literally means "tree Asp (reptile), asp") in the family Elapidae. Four Neontology, extant species are recognised currently; three of those four species are essen ...
s
;α-neurotoxins
:Alpha-neurotoxin
α-Neurotoxins are a group of neurotoxic peptides found in the venom of snakes in the families Elapidae and Hydrophiidae. They can cause paralysis, respiratory failure, and death. Members of the three-finger toxin protein family, they are antago ...
s are a large group; over 100 postsynaptic neurotoxins having been identified and sequenced. α-neurotoxins attack the Nicotinic acetylcholine receptor
Nicotinic acetylcholine receptors, or nAChRs, are receptor polypeptides that respond to the neurotransmitter acetylcholine. Nicotinic receptors also respond to drugs such as the agonist nicotine. They are found in the central and peripheral ne ...
s of cholinergic neurons. They mimic the shape of the acetylcholine molecule, and so fit into the receptors, where they block the ACh flow, leading to a feeling of numbness and paralysis.
:Snake examples: king cobra (''Ophiophagus hannah'') (known as hannahtoxin containing α-neurotoxins), sea snakes
Sea snakes, or coral reef snakes, are elapid snakes that inhabit marine environments for most or all of their lives. They belong to two subfamilies, Hydrophiinae and Laticaudinae. Hydrophiinae also includes Australasian terrestrial snakes, where ...
(Hydrophiinae) (known as erabutoxin), many-banded krait
The many-banded krait (''Bungarus multicinctus''), also known as the Taiwanese krait or the Chinese krait, is a venomous species of elapid snake found in much of central and southern China and Southeast Asia. The species was first described by t ...
(''Bungarus multicinctu''s) (known as α-bungarotoxin), and cobras (''Naja'' spp.) (known as cobratoxin
α-Cobratoxin is a substance of the venom of certain ''Naja'' cobras. It is a nicotinic acetylcholine receptor (nAChR) antagonist which causes paralysis by preventing the binding of acetylcholine to the nAChR.
Sources
α-Cobratoxin is a neurot ...
)
Cytotoxins
;Phospholipases
:Phospholipase
A phospholipase is an enzyme that hydrolyzes phospholipids into fatty acids and other lipophilic substances. Acids trigger the release of bound calcium from cellular stores and the consequent increase in free cytosolic Ca2+, an essential step in ...
is an enzyme that transforms the phospholipid molecule into a lysophospholipid (soap) → the new molecule attracts and binds fat and ruptures cell membranes. Phospholipase A2
The enzyme phospholipase A2 (EC 3.1.1.4, PLA2, systematic name phosphatidylcholine 2-acylhydrolase) catalyse the cleavage of fatty acids in position 2 of phospholipids, hydrolyzing the bond between the second fatty acid “tail” and the glyce ...
is one specific type of phospholipases found in snake venom.
:Snake example: Okinawan habu (''Trimeresurus flavoviridis'')
;Cardiotoxins / Cytotoxins
:Cardiotoxin
Cardiotoxicity is the occurrence of heart dysfunction as electric or muscle damage, resulting in heart toxicity. The heart becomes weaker and is not as efficient in pumping blood. Cardiotoxicity may be caused by chemotherapy (a usual example is th ...
s are components that are specifically toxic to the heart. They bind to particular sites on the surface of muscle cells and cause depolarisation → the toxin prevents muscle contraction. These toxins may cause the heart to beat irregularly or stop beating, causing death. An example is the three-fingered cardiotoxin III
Cardiotoxin III (CTX III, also known as cytotoxin 3) is a sixty amino-acid polypeptide toxin from the Taiwan Cobra Naja atra. It is an example of a group of snake cardio/cytotoxins (), which are made up of shorter snake venom three-finger toxins.
...
from Chinese cobra
The Chinese cobra (''Naja atra''), also called the Taiwan cobra, is a species of cobra in the family Elapidae, found mostly in southern China and a couple of neighboring nations and islands. It is one of the most prevalent venomous snakes in Ch ...
, an example of the short three-fingered family ().
: Snake example: mamba
Mambas are fast moving highly venomous snakes of the genus ''Dendroaspis'' (which literally means "tree Asp (reptile), asp") in the family Elapidae. Four Neontology, extant species are recognised currently; three of those four species are essen ...
s, and some ''Naja
''Naja'' is a genus of venomous elapid snakes commonly known as cobras (or "true cobras"). Members of the genus ''Naja'' are the most widespread and the most widely recognized as "true" cobras. Various species occur in regions throughout Afric ...
'' species
; Hemotoxins
:Hemotoxin
Hemotoxins, haemotoxins or hematotoxins are toxins that destroy red blood cells, disrupt blood clotting, and/or cause organ degeneration and generalized tissue damage. The term ''hemotoxin'' is to some degree a misnomer since toxins that damage ...
s cause hemolysis, the destruction of red blood cells (erythrocytes), or induce blood coagulation (clotting, e.g. mucrocetin). A common family of hemotoxins includes snake venom metalloproteinases such as mucrolysin
Mucrolysin (, ''Trimeresurus metalloendopeptidase A'', ''mucrotoxin A'') is an enzyme. This enzyme catalyses the following chemical reaction
: Cleavage of Ser9-His, His10-Leu, Ala14-Leu, Leu15-Tyr and Tyr16-Leu bonds in insulin B chain
This end ...
.[
:Snake examples: most ]vipers
The Viperidae (vipers) are a family of snakes found in most parts of the world, except for Antarctica, Australia, Hawaii, Madagascar, and various other isolated islands. They are venomous and have long (relative to non-vipers), hinged fangs tha ...
and many cobra species: The tropical rattlesnake ''Crotalus durissus
''Crotalus durissus'', known as the South American rattlesnake, tropical rattlesnake,Mehrtens JM. 1987. Living Snakes of the World in Color. New York: Sterling Publishers. 480 pp. and by other names, is a highly venomous pit viper species foun ...
'' produces convulxin Convulxin is a snake venom toxin found in a tropical rattlesnake known as ''Crotalus durissus terrificus''. It belongs to the family of hemotoxins, which destroy red blood cells or, as is the case with convulxin, induce blood coagulation.
It cause ...
, a coagulant.
Myotoxins
The of crotamine ()">tertiary structure of crotamine ()
Myotoxin
Myotoxins are small, basic peptides found in snake venoms (e.g. rattlesnakes) and lizard venoms (e.g. Mexican beaded lizard). This involves a non-enzymatic mechanism that leads to severe muscle necrosis. These peptides act very quickly, causing in ...
s are small, basic peptide
Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides.
A ...
s found in rattlesnake
Rattlesnakes are venomous snakes that form the genera ''Crotalus'' and ''Sistrurus'' of the subfamily Crotalinae (the pit vipers). All rattlesnakes are vipers. Rattlesnakes are predators that live in a wide array of habitats, hunting small anim ...
and lizard
Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...
(e.g. Mexican beaded lizard
The Mexican beaded lizard (''Heloderma horridum'') is a species of lizard in the family Helodermatidae
The Helodermatidae or beaded lizards are a small family of lizards endemic to North America today, but formerly more widespread in the ancien ...
) venoms. This involves a non-enzymatic mechanism that leads to severe skeletal muscle
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...
necrosis
Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
. These peptides act very quickly, causing instantaneous paralysis
Paralysis (also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, roughly 1 in 50 ...
to prevent prey
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...
from escaping and eventually death due to diaphragmatic
The thoracic diaphragm, or simply the diaphragm ( grc, διάφραγμα, diáphragma, partition), is a sheet of internal skeletal muscle in humans and other mammals that extends across the bottom of the thoracic cavity. The diaphragm is the mo ...
paralysis.
The first myotoxin to be identified and isolated was crotamine
Crotamine is a toxin present in the venom of the South American rattlesnake ('' Crotalus durissus terrificus''). It is a 42-residue long protein containing 11 basic residues (9 lysines, 2 arginines) and 6 cysteines. It has also been isolated from t ...
, discovered in the 1950s by Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
ian scientist
A scientist is a person who conducts Scientific method, scientific research to advance knowledge in an Branches of science, area of the natural sciences.
In classical antiquity, there was no real ancient analog of a modern scientist. Instead, ...
José Moura Gonçalves
José Moura Gonçalves (January 5, 1914– October 18,1996), Brazilian physician, biomedical scientist, biochemist and educator, one of the pioneers of biochemistry in the country.
Moura Gonçalves studied medicine in Belo Horizonte. While a stude ...
from the venom of tropical South American rattlesnake ''Crotalus durissus terrificus
''Crotalus'' is a genus of venomous pit vipers in the family Viperidae, known as rattlesnakes or rattlers. Wright AH, Wright AA (1957). ''Handbook of Snakes of the United States and Canada''. Ithaca and London: Comstock Publishing Associates (7t ...
''. Its biological actions, molecular structure
Molecular geometry is the three-dimensional arrangement of the atoms that constitute a molecule. It includes the general shape of the molecule as well as bond lengths, bond angles, torsional angles and any other geometrical parameters that determ ...
and gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
responsible for its synthesis were all elucidated in the last two decades.
Determining venom toxicity (LD50)
Snake venom toxicity is assessed by a toxicological test called the median lethal dose
In toxicology, the median lethal dose, LD50 (abbreviation for "lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a toxin, radiation, or pathogen. The value of LD50 for a substance is the ...
, LD50, (abbreviated as "lethal dose, 50%"), which determines the concentration of a toxin required to kill half the members of a tested population. The potency of wild snake venom varies considerably because of assorted influences such as biophysical environment
A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...
, physiological status, ecological variables, genetic variation (either adaptive
Adaptation, in biology, is the process or trait by which organisms or population better match their environment
Adaptation may also refer to:
Arts
* Adaptation (arts), a transfer of a work of art from one medium to another
** Film adaptation, a ...
or incidental), and other molecular and ecological evolutionary factors. This is true even for members of one species. Such variation is smaller in captive populations in laboratory settings, though it cannot be eliminated. However, studies to determine snake venom potency must be designed to minimize variability.
Several techniques have been designed to this end. One approach is to use 0.1% bovine serum albumin (also known as "fraction V" in Cohn process
The Cohn process, developed by Edwin J. Cohn, is a series of purification steps with the purpose of extracting albumin from blood plasma. The process is based on the differential solubility of albumin and other plasma proteins based on pH, ethanol ...
) as a diluent in determining LD50 values. It results in more accurate and consistent LD50 determinations than using 0.1% saline as a diluent. For example, fraction V produces about 95% purified albumin (dried crude venom). Saline as a diluent consistently produces widely varying LD50 results for nearly all venomous snakes. It produces unpredictable variation in precipitate purity (35-60%). Fraction V is structurally stable because it has seventeen disulfide bonds
In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In ...
; it's unique in that it has the highest solubility and lowest isoelectric point
The isoelectric point (pI, pH(I), IEP), is the pH at which a molecule carries no net electrical charge or is electrically neutral in the statistical mean. The standard nomenclature to represent the isoelectric point is pH(I). However, pI is also u ...
of major plasma proteins. This makes it the final fraction to be precipitated from its solution. Bovine serum albumin
Bovine serum albumin (BSA or "Fraction V") is a serum albumin protein derived from cows. It is often used as a protein concentration standard in lab experiments.
The nickname "Fraction V" refers to albumin being the fifth fraction of the origin ...
is located in fraction V. The precipitation of albumin is done by reducing the pH to 4.8, near the pH of the proteins, and maintaining the ethanol concentration at 40%, with a protein concentration of 1%. Thus, only 1% of the original plasma remains in the fifth fraction.
When the ultimate goal of plasma processing is a purified plasma component for injection
Injection or injected may refer to:
Science and technology
* Injective function, a mathematical function mapping distinct arguments to distinct values
* Injection (medicine), insertion of liquid into the body with a syringe
* Injection, in broadca ...
or transfusion, the plasma component must be highly pure. The first practical large-scale method of blood plasma fractionation was developed by Edwin J. Cohn
Edwin Joseph Cohn (December 17, 1892 – October 1, 1953) was a protein scientist. A graduate of Phillips Academy, Andover 911 and the University of Chicago 914, PhD 1917 he made important advances in the physical chemistry of proteins, and was r ...
during World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
. it's known as the Cohn process
The Cohn process, developed by Edwin J. Cohn, is a series of purification steps with the purpose of extracting albumin from blood plasma. The process is based on the differential solubility of albumin and other plasma proteins based on pH, ethanol ...
(or Cohn method). This process is also known as cold ethanol fractionation, as it involves gradually increasing the concentration
In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', ''molar concentration'', ''number concentration'', an ...
of ethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...
in the solution
Solution may refer to:
* Solution (chemistry), a mixture where one substance is dissolved in another
* Solution (equation), in mathematics
** Numerical solution, in numerical analysis, approximate solutions within specified error bounds
* Soluti ...
at 5 °C and 3 °C. The Cohn Process exploits differences in plasma proteins properties, specifically, the high solubility
In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution.
The extent of the solubil ...
and low pI of albumin. As the ethanol concentration is increased in stages from 0 to 40%, the pH declines from neutral (pH ~ 7) to about 4.8, which is near the pI of albumin. At each stage, proteins are precipitated out of the solution and removed. The final precipitate
In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...
is purified albumin. Several variations to this process exist, including an adapted method by Nitschmann and Kistler that uses fewer steps, and replaces centrifugation
Centrifugation is a mechanical process which involves the use of the centrifugal force to separate particles from a solution according to their size, shape, density, medium viscosity and rotor speed. The denser components of the mixture migrate ...
and bulk freezing with filtration
Filtration is a physical separation process that separates solid matter and fluid from a mixture using a ''filter medium'' that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filter ...
and diafiltration. Some newer methods of albumin purification add additional purification steps to the Cohn process and its variations. Chromatographic albumin processing emerged in the 1980s, however, it was not widely adopted until later due to the scarity of large-scale chromatography
In chemical analysis, chromatography is a laboratory technique for the separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it through a system (a ...
equipment. Methods incorporating chromatography generally begin with cryo-depleted plasma undergoing buffer exchange via either diafiltration
Diafiltration is a dilution process that involves removal or separation of components (permeable molecules like salts, small proteins, solvents etc.,) of a solution based on their molecular size
A molecule is a group of two or more atoms h ...
or buffer exchange chromatography, to prepare the plasma for following ion exchange chromatography
Ion chromatography (or ion-exchange chromatography) separates ions and polar molecules based on their affinity to the ion exchanger. It works on almost any kind of charged molecule—including large proteins, small nucleotides, and amino acid ...
steps. After ion exchange, generally purification steps and buffer exchange occur.
However, chromatographic methods began to be adopted in the 1980s. Developments were ongoing between when Cohn fractionation started emerge in 1946, and when chromatography
In chemical analysis, chromatography is a laboratory technique for the separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it through a system (a ...
emerged, in 1983. In 1962, the Kistler and Nistchmann process was created as a spin-off of the Cohn process. In the 1990s, the Zenalb and the CSL Albumex processes were created, which incorporated chromatography with variations. The general approach to using chromatography for plasma fractionation for albumin is: recovery of supernatant I, delipidation, anion exchange chromatography
Anion-exchange chromatography is a process that separates substances based on their charges using an ion-exchange resin containing positively charged groups, such as diethyl-aminoethyl groups (DEAE). In solution, the resin is coated with positive ...
, cation exchange chromatography, and gel filtration chromatography. The recovered purified material is formulated with combinations of sodium octanoate and sodium N-acetyl tryptophanate and then subjected to viral inactivation procedures, including pasteurization at 60 °C. This is a more efficient alternative than the Cohn process because:
* smooth automation and a relatively inexpensive plant was needed,
* easier to sterilize equipment and maintain a good manufacturing environment
* chromatographic processes are less damaging to the albumin protein
* a more successful albumin result can be achieved.
Compared with the Cohn process, albumin purity increased from about 95% to 98% using chromatography, and the yield increased from about 65% to 85%. Small percentage increases make a difference in regard to sensitive measurements such as purity. The big drawback has to do with the economics. Although the method offered efficient, acquiring the necessary equipment was difficult. Large machinery is necessary, and for a long time, the lack of equipment availability limited its widespread use.
Evolution
Venom evolved just once among all Toxicofera
Toxicofera (Greek for "those who bear toxins") is a proposed clade of scaled reptiles (squamates) that includes the Serpentes (snakes), Anguimorpha (monitor lizards, gila monster, and alligator lizards) and Iguania (iguanas, agamas, and chamel ...
about 170 million years ago, and then diversified into the huge venom diversity seen today. The original toxicoferan venom was a very simple set of proteins that were assembled in a pair of glands. Subsequently, this set of proteins evolved independently in the various lineages of toxicoferans, including Serpentes
Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more joints ...
, Anguimorpha
The Anguimorpha is a suborder of squamates. The group was named by Fürbringer in 1900 to include all autarchoglossans closer to '' Varanus'' and '' Anguis'' than ''Scincus
''Scincus'' is a genus of skinks, lizards in the family Scincidae. Th ...
, and Iguania
Iguania is an infraorder of squamate reptiles that includes iguanas, chameleons, agamids, and New World lizards like anoles and phrynosomatids. Using morphological features as a guide to evolutionary relationships, the Iguania are believed t ...
. Several snake lineages have since lost the ability to produce venom, often due to a change in diet or a change in predatory tactics. In addition to this, venom strength and composition has changed due to changes in the prey of certain snake species. For example, the venom of the marbled sea snake (''Aipysurus eydouxii'') became significantly less toxic after the diet of this species changed from fish to strictly fish eggs. The evolution of venom is thought to be responsible for the enormous expansion of snakes across the globe.
The mechanism of evolution in most cases has been gene duplication
Gene duplication (or chromosomal duplication or gene amplification) is a major mechanism through which new genetic material is generated during molecular evolution. It can be defined as any duplication of a region of DNA that contains a gene. ...
in tissues unrelated to the venom. Pre-existing salivary proteins are the likely ancestors of most venom toxin genes. Expression of the new protein in the venom gland followed duplication. Then proceeded natural selection
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Charle ...
for adaptive traits
Adaptation, in biology, is the process or trait by which organisms or population better match their environment
Adaptation may also refer to:
Arts
* Adaptation (arts), a transfer of a work of art from one medium to another
** Film adaptation, a ...
following the birth-and-death model, where duplication is followed by functional diversification, resulting in the creation of structurally related proteins that have slightly different functions. The study of venom evolution has been a high priority for scientists in terms of scientific research, due to the medical relevance of snake venom, in terms of making antivenom and cancer research. Knowing more about the composition of venom and the ways it can potentially evolve is very beneficial. Three main factors that affect venom evolution have been closely studied: predators of the snake that are resistant to snake venom, prey that are in an evolutionary arms race
In evolutionary biology, an evolutionary arms race is an ongoing struggle between competing sets of co-evolving genes, phenotypic and behavioral traits that develop escalating adaptations and counter-adaptations against each other, resembling an a ...
with snakes, and the specific diets that affect the intraspecific evolution of venom. Venoms continue to evolve as specific toxins and are modified to target a specific prey, and toxins are found to vary according to diet in some species.
Rapid venom evolution can also be explained by the arms race between venom-targeted molecules in resistant predators, such as the opossum
Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 93 species in 18 genera. Opossums originated in South America and entered North ...
, and the snake venom that targets the molecules. Scientists performed experiments on the opossums and found that multiple trials showed replacement to silent substitutions in the von Willebrand factor (''vWf'') gene that encodes for a venom-targeted hemostatic blood protein. These substitutions are thought to weaken the connection between vWf and a toxic snake venom ligand (botrocetin), which changes the net charge and hydrophobicity. These results are significant to the venom evolution because it's the first citation of rapid evolution in a venom-targeted molecule. This shows that an evolutionary arms race may be occurring in terms of defensive purposes. Alternative hypotheses suggest that venom evolution is due to trophic adaption, whereas these scientists believe, in this case, that selection would occur on traits that help with prey survival in terms of venom evolution instead of predation success. Several other predators of the pit viper (mongooses and hedgehogs) show the same type of relationship between snakes, which helps to support the hypothesis that venom has a very strong defensive role along with a trophic role. Which in turn supports the idea that predation on the snakes can be the arms race that produces snake venom evolution.
Some of the various adaptations produced by this process include venom more toxic to specific prey in several lineages, proteins that pre-digest prey, as well as a method to track down prey after a bite. Though venom function has evolved to be specific to prey class (e.g. particular coagulatory effects), the evolution of broad toxicological effects (e.g. neurotoxicity or coagulotoxicity) does not appear to be broadly affected by prey type. The presence of digestive enzymes
Digestive enzymes are a group of enzymes that break down polymeric macromolecules into their smaller building blocks, in order to facilitate their absorption into the cells of the body. Digestive enzymes are found in the digestive tracts of anim ...
in snake venom was once believed to be an adaptation to assist digestion. However, studies of the western diamondback rattlesnake
The western diamondback rattlesnake or Texas diamond-backWright AH, Wright AA. (1957). ''Handbook of Snakes''. Comstock Publishing Associates. (7th printing, 1985). . (''Crotalus atrox'') is a rattlesnake species and member of the viper family, ...
(''Crotalus atrox''), a snake with highly proteolytic
Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Uncatalysed, the hydrolysis of peptide bonds is extremely slow, taking hundreds of years. Proteolysis is typically catalysed by cellular enzymes called proteases, ...
venom, show that venom has no impact on the time required for food to pass through the gut. These various adaptations of venom have also led to considerable debate about the definition of venom and venomous snakes.
Injection
Vipers
In viper
The Viperidae (vipers) are a family of snakes found in most parts of the world, except for Antarctica, Australia, Hawaii, Madagascar, and various other isolated islands. They are venomous and have long (relative to non-vipers), hinged fangs tha ...
s, which have the most highly developed venom-delivery apparatus, the venom gland is very large and is surrounded by the masseter
In human anatomy, the masseter is one of the muscles of mastication. Found only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter. The most obvious muscle of mastication is the masseter muscle, since it ...
or temporal muscle
In anatomy, the temporalis muscle, also known as the temporal muscle, is one of the muscles of mastication (chewing). It is a broad, fan-shaped convergent muscle on each side of the head that fills the temporal fossa, superior to the zygomatic a ...
, which consists of two bands, the superior arising from behind the eye, the inferior extending from the gland to the mandible. A duct carries venom from the gland to the fang. In vipers and elapids, this groove is completely closed, forming a hypodermic needle-like tube. In other species, the grooves are not covered, or only partially covered. From the anterior extremity of the gland, the duct passes below the eye and above the maxillary bone
The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The tw ...
, to the basal orifice of the venom fang, which is ensheathed in a thick fold of mucous membrane
A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...
. By means of the movable maxillary bone hinged to the prefrontal bone and connected with the transverse bone, which is pushed forward by muscles set in action by the opening of the mouth, the fang is erected and the venom discharged through the distal orifice. When the snake bites, the jaws close and the muscles surrounding the gland contract, causing venom to be ejected via the fangs.
Elapids
In the proteroglyphous
A snake skeleton consists primarily of the skull, vertebrae, and ribs, with only vestigial remnants of the limbs.
Skull
The skull of a snake is a very complex structure, with numerous joints to allow the snake to swallow prey far larger than ...
elapid
Elapidae (, commonly known as elapids ; grc, ἔλλοψ ''éllops'' "sea-fish") is a family of snakes characterized by their permanently erect fangs at the front of the mouth. Most elapids are venomous, with the exception of the genus Emydoceph ...
s, the fangs are tubular, but are short and do not possess the mobility seen in vipers.
Colubrids
Opisthoglyphous
A snake skeleton consists primarily of the skull, vertebrae, and ribs, with only vestigial remnants of the limbs.
Skull
The skull of a snake is a very complex structure, with numerous joints to allow the snake to swallow prey far larger than it ...
colubrid
Colubridae (, commonly known as colubrids , from la, coluber, 'snake') is a family of snakes. With 249 genera, it is the largest snake family. The earliest species of the family date back to the Oligocene epoch. Colubrid snakes are found on ever ...
s have enlarged, grooved teeth situated at the posterior extremity of the maxilla
The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...
, where a small posterior portion of the upper labial or salivary gland produces venom.
Mechanics of biting
Several genera, including Asian coral snakes (''Calliophis''), burrowing asps (''Atractaspis''), and night adders (''Causus''), are remarkable for having exceptionally long venom glands, extending along each side of the body, in some cases extending posterially as far as the heart. Instead of the muscles of the temporal region serving to press out the venom into the duct, this action is performed by those of the side of the body.
Considerable variability in biting behavior is seen among snakes. When biting, viperid snakes often strike quickly, discharging venom as the fangs penetrate the skin, and then immediately release. Alternatively, as in the case of a feeding response, some viperids (e.g. ''Lachesis'') bite and hold. A proteroglyph or opisthoglyph may close its jaws and bite or chew firmly for a considerable time.
Differences in fang length between the various venomous snakes are likely due to the evolution of different striking strategies. Additionally, it has been shown that the fangs of different species of venomous snakes have different sizes and shapes depending on the biomechanical properties of the snake's prey.
Mechanics of spitting
Spitting cobras
A spitting cobra is any of several species of cobras that can defensively spray a toxic secretion - functioning as both a venom (that can be injected via a wound) and a toxungen (that can be sprayed on the target surface) - from their fangs in ...
of the genera ''Naja
''Naja'' is a genus of venomous elapid snakes commonly known as cobras (or "true cobras"). Members of the genus ''Naja'' are the most widespread and the most widely recognized as "true" cobras. Various species occur in regions throughout Afric ...
'' and '' Hemachatus'', when irritated or threatened, may eject streams or a spray of venom a distance of 4 to 8 ft. These snakes' fangs have been modified for the purposes of spitting; inside the fangs, the channel makes a 90° bend to the lower front of the fang. Spitters may spit repeatedly and still be able to deliver a fatal bite.
Spitting is a defensive reaction only. The snakes tend to aim for the eyes of a perceived threat. A direct hit can cause temporary shock and blindness through severe inflammation
Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...
of the cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power ...
and conjunctiva
The conjunctiva is a thin mucous membrane that lines the inside of the eyelids and covers the sclera (the white of the eye). It is composed of non-keratinized, stratified squamous epithelium with goblet cells, stratified columnar epithelium ...
. Although usually no serious symptoms result if the venom is washed away immediately with plenty of water, blindness can become permanent if left untreated. Brief contact with the skin is not immediately dangerous, but open wounds may be vectors for envenomation.
Physiological effects
The four distinct types of venom act on the body differently:
* Proteolytic
Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Uncatalysed, the hydrolysis of peptide bonds is extremely slow, taking hundreds of years. Proteolysis is typically catalysed by cellular enzymes called proteases, ...
venom dismantles the molecular surroundings, including at the site of the bite.
* Hemotoxic
Hemotoxins, haemotoxins or hematotoxins are toxins that destroy red blood cells, disrupt blood clotting, and/or cause organ degeneration and generalized tissue damage. The term ''hemotoxin'' is to some degree a misnomer since toxins that damage ...
venom acts on the cardiovascular system, including the heart and blood.
* Neurotoxic
Neurotoxicity is a form of toxicity in which a biological, chemical, or physical agent produces an adverse effect on the structure or function of the central and/or peripheral nervous system. It occurs when exposure to a substance – specificall ...
venom acts on the nervous system, including the brain.
* Cytotoxic
Cytotoxicity is the quality of being toxic to cells. Examples of toxic agents are an immune cell or some types of venom, e.g. from the puff adder (''Bitis arietans'') or brown recluse spider (''Loxosceles reclusa'').
Cell physiology
Treating cells ...
venom has a localized action at the site of the bite.
Proteroglyphous snakes
The effect of the venom of proteroglyphous
A snake skeleton consists primarily of the skull, vertebrae, and ribs, with only vestigial remnants of the limbs.
Skull
The skull of a snake is a very complex structure, with numerous joints to allow the snake to swallow prey far larger than ...
snakes (sea snakes
Sea snakes, or coral reef snakes, are elapid snakes that inhabit marine environments for most or all of their lives. They belong to two subfamilies, Hydrophiinae and Laticaudinae. Hydrophiinae also includes Australasian terrestrial snakes, where ...
, kraits
''Bungarus'' is a genus of venomous elapid snakes, the kraits ("krait" is pronounced , rhyming with "kite"), found in South and Southeast Asia. The genus ''Bungarus'' has 16 species.
Distribution
Kraits are found in tropical Asia, from near Ir ...
, mamba
Mambas are fast moving highly venomous snakes of the genus ''Dendroaspis'' (which literally means "tree Asp (reptile), asp") in the family Elapidae. Four Neontology, extant species are recognised currently; three of those four species are essen ...
s, black snakes
''Black Snakes'' is a collaboration between the experimental rock band Red Krayola and the conceptual art group Art & Language. It was released in 1983 by RecRec Music. The album was adopted by Drag City and re-issued on CD in 1997.
Critical re ...
, tiger snakes, and death adders) is mainly on the nervous system
In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes th ...
, respiratory paralysis
Paralysis (also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, roughly 1 in 50 ...
being quickly produced by bringing the venom into contact with the central nervous mechanism that controls respiration; the pain and local swelling that follow a bite are not usually severe. The bite of all the proteroglyphous elapids, even of the smallest and gentlest, such as the 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' ...
, is, so far as known, deadly to humans. However, some mildly venomous elapids remain, such as the hooded snakes (''Parasuta
''Suta'' is a genus of venomous snakes in the Family (biology), family Elapidae. The genus is Endemism, endemic to mainland Australia.
Species
*''Suta dwyeri'' – Dwyer's snake, variable black-naped snake, whip snake – New South Wales, Que ...
''), bandy-bandies ('' Vermicella''), etc.
Vipers
Viper venom (Russell's viper
Russell's viper (''Daboia russelii''), is a venomous snake in the family Viperidae native to the Indian subcontinent and one of the big four snakes in India. It was described in 1797 by George Shaw and Frederick Polydore Nodder, and named afte ...
, saw-scaled vipers, bushmasters, and rattlesnakes
Rattlesnakes are venomous snakes that form the genera ''Crotalus'' and ''Sistrurus'' of the subfamily Crotalinae (the pit vipers). All rattlesnakes are vipers. Rattlesnakes are predators that live in a wide array of habitats, hunting small anima ...
) acts more on the vascular system, bringing about coagulation of the blood and clotting of the pulmonary arteries; its action on the nervous system is not great, no individual group of nerve-cell
A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. No ...
s appears to be picked out, and the effect upon respiration is not so direct; the influence upon the circulation explains the great depression, which is a symptom of viperine envenomation. The pain of the wound is severe and is rapidly followed by swelling and discoloration. The symptoms produced by the bite of the European vipers are thus described by Martin and Lamb:
The Viperidae differ much among themselves in the toxicity of their venoms. Some, such as the Indian Russell's viper (''Daboia russelli'') and saw-scaled viper (''E. carinatus''); the American rattlesnakes (''Crotalus'' spp.), bushmasters (''Lachesis'' spp.), and lanceheads (''Bothrops'' spp.); and the African adders (''Bitis'' spp.), night adders (''Causus'' spp.), and horned vipers (''Cerastes'' spp.), cause fatal results unless a remedy is speedily applied. The bite of the larger European vipers may be very dangerous, and followed by fatal results, especially in children, at least in the hotter parts of the Continent; whilst the small meadow viper (''Vipera ursinii''), which hardly ever bites unless roughly handled, does not seem to be possessed of a very virulent venom, and although very common in some parts of Austria
Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...
and Hungary
Hungary ( hu, Magyarország ) is a landlocked country in Central Europe. Spanning of the Carpathian Basin, it is bordered by Slovakia to the north, Ukraine to the northeast, Romania to the east and southeast, Serbia to the south, Croatia a ...
, is not known to have ever caused a serious accident.
Opisthoglyphous colubrids
Biologists had long known that some snakes had rear fangs, 'inferior' venom injection mechanisms that might immobilize prey; although a few fatalities were on record, until 1957, the possibility that such snakes were deadly to humans seemed at most remote. The deaths of two prominent herpetologists, Robert Mertens
Robert Friedrich Wilhelm Mertens (1 December 1894 – 23 August 1975) was a German herpetologist. Several taxa of reptiles are named after him.Beolens, Bo; Watkins, Michael; Grayson, Michael (2011). ''The Eponym Dictionary of Reptiles''. Baltimore ...
and Karl Schmidt, from African colubrid bites, changed that assessment, and recent events reveal that several other species of rear-fanged snakes have venoms that are potentially lethal to large vertebrates.
Boomslang
The boomslang (, , or ; ''Dispholidus typus'') is a large, highly venomous snake in the family Colubridae.
Taxonomy and etymology
Its common name means "tree snake" in Afrikaans and Dutch – ''boom'' meaning "tree", and ''slang'' meaning "sna ...
(''Dispholidus typus'') and twig snake
The twig snakes (genus ''Thelotornis''), also commonly known as bird snakes or vine snakes, are a genus of rear-fanged venomous snakes in the family Colubridae. The genus is native to Africa. All species in the genus have a slender and elongat ...
(''Thelotornis'' spp.) venoms are toxic to blood cells and thin the blood (hemotoxic, hemorrhagic). Early symptoms include headaches, nausea, diarrhea, lethargy, mental disorientation, bruising, and bleeding at the site and all body openings. Exsanguination
Exsanguination is death caused by loss of blood. Depending upon the health of the individual, people usually die from losing half to two-thirds of their blood; a loss of roughly one-third of the blood volume is considered very serious. Even a sing ...
is the main cause of death from such a bite.
The boomslang's venom is the most potent of all rear-fanged snakes in the world based on LD50. Although its venom may be more potent than some vipers and elapids, it causes fewer fatalities owing to various factors (for example, the fangs' effectiveness is not high compared with many other snakes, the venom dose delivered is low, and boomslangs are generally less aggressive in comparison to other venomous snakes such as cobras and mambas). Symptoms of a bite from these snakes include nausea and internal bleeding, and one could die from a brain hemorrhage
Intracerebral hemorrhage (ICH), also known as cerebral bleed, intraparenchymal bleed, and hemorrhagic stroke, or haemorrhagic stroke, is a sudden bleeding into the tissues of the brain, into its ventricles, or into both. It is one kind of bleed ...
and respiratory collapse.
Aglyphous snakes
Experiments made with the secretion of the parotid gland
The parotid gland is a major salivary gland in many animals. In humans, the two parotid glands are present on either side of the mouth and in front of both ears. They are the largest of the salivary glands. Each parotid is wrapped around the man ...
of ''Rhabdophis
''Rhabdophis'' is a genus of snakes in the subfamily Natricinae of the family Colubridae. Species in the genus ''Rhabdophis'' are generally called keelback snakes, and are found primarily in Southeast Asia.
Toxicity
''Rhabdophis'' is often thoug ...
'' and ''Zamenis
''Zamenis'' is a genus of Old World nonvenomous snakes in the Family (biology), family Colubridae.
Name
''Zamenis'' comes from Greek language, Greek ''wiktionary:ζαμενής, ζαμενής'' (Latin, lat. ''wiktionary:vehemens, vehemens'', ...
'' have shown that even aglyphous snakes are not entirely devoid of venom, and point to the conclusion that the physiological difference between so-called harmless and venomous snakes is only one of degree, just as various steps exist in the transformation of an ordinary parotid gland into a venom gland or of a solid tooth into a tubular or grooved fang.
Use of snake venoms to treat disease
Given that snake venom contains many biologically active ingredients, some may be useful to treat disease.
For instance, phospholipases type A2 (PLA2s) from the Tunisian vipers ''Cerastes cerastes
''Cerastes cerastes'', commonly known as the Saharan horned viperMallow D, Ludwig D, Nilson G. (2003). ''True Vipers: Natural History and Toxinology of Old World Vipers''. Malabar, Florida: Krieger Publishing Company. . or the desert horned viper ...
'' and ''Macrovipera lebetina
''Macrovipera lebetinus'', known as the blunt-nosed viper, Lebetine viper, Levant viper,Mallow D, Ludwig D, Nilson G. 2003. ''True Vipers: Natural History and Toxinology of Old World Vipers''. Malabar, Florida: Krieger Publishing Company. 359 pp. ...
'' have been found to have antitumor activity. Anticancer activity has been also reported for other compounds in snake venom. PLA2s hydrolyze phospholipids, thus could act on bacterial cell surfaces, providing novel antimicrobial (antibiotic) activities.
The analgesic
An analgesic drug, also called simply an analgesic (American English), analgaesic (British English), pain reliever, or painkiller, is any member of the group of drugs used to achieve relief from pain (that is, analgesia or pain management). It ...
(pain-killing) activity of many snake venom proteins has been long known. The main challenge, however, is how to deliver protein to the nerve cells: proteins usually are not applicable as pills.
Immunity
Among snakes
The question whether individual snakes are immune to their own venom has not yet been definitively settled, though an example is known of a cobra that self-envenomated, resulting in a large abscess
An abscess is a collection of pus that has built up within the tissue of the body. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pressed. The area of redness often extends b ...
requiring surgical intervention, but showing none of the other effects that would have proven rapidly lethal in prey species or humans. Furthermore, certain harmless species, such as the North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
n common kingsnake
''Lampropeltis getula'', commonly known as the eastern kingsnake,Roger Conant (herpetologist), Conant R (1975). ''A Field Guide to Reptiles and Amphibians of Eastern and Central North America, Second Edition''. (First published in 1958). Boston: ...
(''Lampropeltis getula'') and the Central
Central is an adjective usually referring to being in the center of some place or (mathematical) object.
Central may also refer to:
Directions and generalised locations
* Central Africa, a region in the centre of Africa continent, also known as ...
and South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...
n mussurana
Mussurana or musurana (Portuguese: ''muçurana'') is a common name which is used for several species of New World snakes, especially species in the genus ''Clelia''. ''Clelia'' is a genus of large snakes in the family Colubridae. The genus is e ...
(''Clelia'' spp.), are proof against the venom of the crotalines, which frequent the same districts, and which they are able to overpower and feed upon. The chicken snake (''Spilotes pullatus'') is the enemy of the fer-de-lance (''Bothrops caribbaeus'') in St. Lucia, and in their encounters, the chicken snake is invariably the victor. Repeated experiments have shown the European grass snake
The grass snake (''Natrix natrix''), sometimes called the ringed snake or water snake, is a Eurasian non-venomous colubrid snake. It is often found near water and feeds almost exclusively on amphibians.
Subspecies
Many subspecies are recogniz ...
(''Natrix natrix'') not to be affected by the bite of the European adder
''Vipera berus'', the common European adderMallow D, Ludwig D, Nilson G. (2003). ''True Vipers: Natural History and Toxinology of Old World Vipers''. Malabar, Florida: Krieger Publishing Company. . or common European viper,Stidworthy J. (1974). ...
(''Vipera berus'') and the European asp
''Vipera aspis'' is a Viperinae, viper species found in southwestern Europe.
Its common names include asp, asp viper,Mallow D, Ludwig D, Nilson G. 2003. ''True Vipers: Natural History and Toxinology of Old World Vipers''. Krieger Publishing Comp ...
(''Vipera aspis''), this being due to the presence, in the blood of the harmless snake, of toxic principles secreted by the parotid and labial glands, and analogous to those of the venom of these vipers. Several North American species of rat snakes, as well as king snakes, have proven to be immune or highly resistant to the venom of rattlesnake species. The king cobra, which does prey on cobras, is said to be immune to their venom.
Among other animals
The hedgehog
A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the eulipotyphlan family Erinaceidae. There are seventeen species of hedgehog in five genera found throughout parts of Europe, Asia, and Africa, and in New Zealand by introducti ...
(Erinaceidae), the mongoose
A mongoose is a small terrestrial carnivorous mammal belonging to the family Herpestidae. This family is currently split into two subfamilies, the Herpestinae and the Mungotinae. The Herpestinae comprises 23 living species that are native to so ...
(Herpestidae), the honey badger
The honey badger (''Mellivora capensis''), also known as the ratel ( or ), is a mammal widely distributed in Africa, Southwest Asia, and the Indian subcontinent. Because of its wide range and occurrence in a variety of habitats, it is listed ...
(''Mellivora capensis'') and the opossum
Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 93 species in 18 genera. Opossums originated in South America and entered North ...
are known to be immune to a dose of snake venom. Recently, the honey badger and domestic pig were found to have convergently evolved amino-acid replacements in their nicotinic acetylcholine receptor, which are known to confer resistance to alpha-neurotoxins in hedgehogs. Whether the pig
The pig (''Sus domesticus''), often called swine, hog, or domestic pig when distinguishing from other members of the genus '' Sus'', is an omnivorous, domesticated, even-toed, hoofed mammal. It is variously considered a subspecies of ''Sus s ...
may be considered immune is still uncertain, though early studies show endogenous resistance in pigs tested against neurotoxins. Though the pig's subcutaneous layer of fat may protect it against snake venom, most venoms pass easily through vascular fat layers, making this unlikely to contribute to its ability to resist venoms. The garden dormouse
The garden dormouse (''Eliomys quercinus'') is a rodent in the dormouse family.
Characteristics
The garden dormouse is gray or brown, with a whitish underside. It has black eye markings and large ears. Its hair is short, and its tail has a whi ...
(''Eliomys quercinus'') has recently been added to the list of animals refractory to viper venom. Some populations of California ground squirrel
The California ground squirrel (''Otospermophilus beecheyi''), also known as the Beechey ground squirrel, is a common and easily observed ground squirrel of the western United States and the Baja California Peninsula; it is common in Oregon and ...
(''Otospermophilus beecheyi'') are at least partially immune to rattlesnake venom as adults.
Among humans
The acquisition of human immunity against snake venom is ancient (from around 60 CE, Psylli The Psylli (Seli) were a native Berber tribe inhabiting Ancient Libya.
Historical accounts
Pliny the Elder (Hist. Nat., vii 14) places the Psylli on the Syrtic coast above the Garamantes, and gives Psyllikos Kolpos as an early name of the Syrtic G ...
tribe). Research into development of vaccines that will lead to immunity is ongoing. Bill Haast
Bill Haast (December 30, 1910 – June 15, 2011) was the owner and operator, from 1947 until 1984, of the Miami Serpentarium, a tourist attraction south of Miami, Florida, where he extracted venom from snakes in front of paying customers. Afte ...
, owner and director of the Miami Serpentarium, injected himself with snake venom during most of his adult life, in an effort to build up an immunity to a broad array of venomous snakes, in a practice known as mithridatism
Mithridatism is the practice of protecting oneself against a poison by gradually self-administering non-lethal amounts. The word is derived from Mithridates VI, the King of Pontus, who so feared being poisoned that he regularly ingested small dose ...
. Haast lived to age 100, and survived a reported 172 snake bites. He donated his blood to be used in treating snake-bite patients when a suitable antivenom was not available. More than 20 so-treated individuals recovered. Amateur researcher Tim Friede also lets venomous snakes bite him in the hopes of a vaccine against snake venom being developed, and has survived over 160 bites from different species as of January 2016.
Traditional treatments
The World Health Organization
The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of h ...
estimates that 80% of the world's population depends on traditional medicine for their primary health-care needs. Methods of traditional treatments of snakebites, although of questionable efficacy and perhaps even harmful, are nonetheless relevant.
Plants used to treat snakebites in Trinidad and Tobago are made into tinctures with alcohol or olive oil and kept in rum flasks called snake bottles, which contain several different plants and/or insects. The plants used include the vine called monkey ladder ('' Bauhinia cumanensis'' or '' Bauhinia excisa'', Fabaceae), which is pounded and put on the bite. Alternatively, a tincture is made with a piece of the vine and kept in a snake bottle. Other plants used include mat root ('' Aristolochia rugosa''), cat's claw ('' Pithecellobim unguis-cati''), tobacco (''Nicotiana tabacum
''Nicotiana tabacum'', or cultivated tobacco, is an annually grown herbaceous plant of the ''Nicotiana'' genus. The plant is tropical in origin, is commonly grown throughout the world, and is often found in cultivation. It grows to heights bet ...
''), snake bush ('' Barleria lupulina''), obie seed (''Cola nitida
''Cola nitida'' is a species of plant belonging to the family Malvaceae.
It is a tree native to the rainforests of tropical West Africa. Common names include kola nut, cola, kola and bitter kola. The seeds contain caffeine and are chewed as a s ...
''), and wild gri gri root (''Acrocomia aculeata
''Acrocomia aculeata'' is a species of palm native to the Neotropics, from southern Mexico and the Caribbean south to Paraguay and northern Argentina. Common names include grugru palm, gloo gloo, macaúba palm, coyol palm, and macaw palm; synonym ...
''). Some snake bottles also contain the caterpillars (''Battus polydamas
''Battus polydamas'', also known as the gold rim swallowtail, the Polydamas swallowtail or the tailless swallowtail, is a species of butterfly in the family Papilionidae. The species was first described by Carl Linnaeus in his 10th edition of ' ...
'', Papilionidae) that eat tree leaves ('' Aristolochia trilobata''). Emergency snake medicines are obtained by chewing a three-inch piece of the root of bois canôt (''Cecropia peltata
''Cecropia peltata'' is a fast-growing tree in the genus ''Cecropia''. Common names include trumpet tree, trumpet-bush, bacano and snakewood. It is listed as one of the world's 100 worst invasive alien species.
Description
''Cecropia peltata'' ...
'') and administering this chewed-root solution to the bitten subject (usually a hunting dog). This is a common native plant of Latin America and the Caribbean, which makes it appropriate as an emergency remedy. Another native plant used is mardi gras (''Renealmia alpinia
''Renealmia alpinia'' is a flowering plant species native to the Americas, where it grows from southern Mexico through much of South America, though not in the Southern Cone. It can also be found on several Caribbean islands.
In Quechua it is ...
'') (berries), which are crushed together with the juice of wild cane (''Costus scaber
''Costus'' is a group of herbaceous perennial plants in the family Costaceae, described by Linnaeus as a genus in 1753. It was formerly known as ''Hellenia'' after the Finnish botanist Carl Niclas von Hellens. It is widespread through tropica ...
'') and given to the bitten. Quick fixes have included applying chewed tobacco from cigarettes, cigars, or pipes. Making cuts around the puncture or sucking out the venom had been thought helpful in the past, but this course of treatment is now strongly discouraged, due to the risk of self-envenomation through knife cuts or cuts in the mouth (suction cups from snake bite kits can be used, but suctioning seldom provides any measurable benefit).
Serotherapy
Serotherapy using 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 a common current treatment and has been described back in 1913. Both adaptive immunity and serotherapy are specific to the type of snake; venom with identical physiological action do not cross-neutralize. Boulenger 1913 describes the following cases:
A European in Australia who had become immune to the venom of the deadly Australian tiger snake (''Notechis scutatus''), manipulating these snakes with impunity, and was under the impression that his immunity extended also to other species, when bitten by a lowland copperhead
The lowland copperhead or lowlands copperhead (''Austrelaps superbus'') is a venomous snake species in the family Elapidae, found in southeastern Australia and Tasmania. It is commonly referred to as the copperhead, but is not closely related to ...
(''Austrelaps superbus''), an allied elapine, died the following day.
In India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
, the serum prepared with the venom of monocled cobra
The monocled cobra (''Naja kaouthia''), also called monocellate cobra and Indian spitting cobra, is a venomous cobra species widespread across South and Southeast Asia and listed as Least Concern on the IUCN Red List.
Taxonomy
The scientific n ...
''Naja kaouthia'' has been found to be without effect on the venom of two species of kraits
''Bungarus'' is a genus of venomous elapid snakes, the kraits ("krait" is pronounced , rhyming with "kite"), found in South and Southeast Asia. The genus ''Bungarus'' has 16 species.
Distribution
Kraits are found in tropical Asia, from near Ir ...
(''Bungarus''), Russell's viper (''Daboia russelli''), saw-scaled viper (''Echis carinatus''), and Pope's pit viper (''Trimeresurus popeiorum''). Russell's viper serum is without effect on colubrine venoms, or those of ''Echis
''Echis'' (common names: saw-scaled vipers, carpet vipersSpawls S, Branch B. 1995. ''The Dangerous Snakes of Africa''. Dubai: Ralph Curtis Books. Oriental Press. 192 pp. .) is a genus of vipers found in the dry regions of Africa, the Middle East ...
'' and ''Trimeresurus
''Trimeresurus'' is a genus of venomous pit vipers found in Asia from the Indian Subcontinent throughout Southeast Asia, China, and the Pacific Islands. Currently 44 species are recognized. Common names include Asian palm pit vipers,Mehrtens JM ( ...
''.
In Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
, serum prepared with the venom of lanceheads (''Bothrops'' spp.) is without action on rattlesnake (''Crotalus'' spp.) venom.
Antivenom snakebite treatment must be matched as the type of envenomation that has occurred. In the Americas, polyvalent antivenoms are available that are effective against the bites of most pit vipers. Crofab
Crotalidae polyvalent immune fab, sold under the brandname CroFab, is a snake antivenin, indicated for minimal or moderate North American Crotalid ( Rattlesnake, Copperhead and Cottonmouth/Water moccasin) snake envenomation.
CroFab is composed o ...
is the antivenom developed to treat the bite of North American pit vipers.[http://www.savagelabs.com/Products/CroFab/Home/crofab_frame.htm Link to PDF for full prescribing information, retrieved 11/12/12] These are not effective against coral snake
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' ...
envenomation, which requires a specific antivenom to their neurotoxic venom. The situation is even more complex in countries such as India, with its rich mix of vipers (Viperidae) and highly neurotoxic cobras and kraits of the Elapidae.
Notes
See also
*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 ...
*Venomoid A venomoid is a venomous snake that has undergone a surgical procedure to remove or inhibit its production of snake venom, venom. This procedure has been used for venomous snakes kept as pets or used in public demonstrations in order to remove the r ...
*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 ...
*Toxicofera
Toxicofera (Greek for "those who bear toxins") is a proposed clade of scaled reptiles (squamates) that includes the Serpentes (snakes), Anguimorpha (monitor lizards, gila monster, and alligator lizards) and Iguania (iguanas, agamas, and chamel ...
References
Further reading
*
*
External links
An overview of the diversity and evolution of snake fangs.
- Calculated orientations of snake venom phospholipases A2 and myotoxins in the lipid bilayer.
Australian Venom Research Unit
- a general source of information for venomous creatures in Australia.
biomedcentral.com
- Medicinal and ethnoveterinary remedies of hunters in Trinidad
Trinidad is the larger and more populous of the two major islands of Trinidad and Tobago. The island lies off the northeastern coast of Venezuela and sits on the continental shelf of South America. It is often referred to as the southernmos ...
.
reptilis.net
- How venom works.
snakevenom.net
- Drying and storage of snake venom.
{{DEFAULTSORT:Snake Venom
*
Vertebrate toxins
Wilderness medical emergencies