Spider bite
Encyclopedia
A spider bite is an injury resulting from the bites of spider
Spider
Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...
s or other closely related arachnid
Arachnid
Arachnids are a class of joint-legged invertebrate animals in the subphylum Chelicerata. All arachnids have eight legs, although in some species the front pair may convert to a sensory function. The term is derived from the Greek words , meaning "spider".Almost all extant arachnids are terrestrial...
s.
Spiders are active hunters and rely heavily on their bites to paralyze and kill their prey before consuming it. They also bite in self defense. While many spiders will never attack animals larger than themselves, some exhibit a rather aggressive behavior and will stand their ground when approached by larger animals, e.g., Atrax robustus. Most spider bites, however, occur when humans unintentionally press up against spiders and receive a defensive bite. On rare occasions, spiders may make prey mistakes and bite a human finger or other body part as though it were a caterpillar or other such insect.
Only spiders of fairly large species possess chelicera long enough to penetrate human skin. There is nothing smaller than members of the Cheiracanthium
Cheiracanthium
Cheiracanthium is a genus of spiders in the Miturgidae family. Certain species are commonly known as the "yellow sac spider".- Description :...
genus (around 6 mm.) that gives a bite that is greatly troublesome to humans. The effect of a bite on humans is dependent on both the toxicity of the venom and the amount of venom. About 98% of the bites inflicted by species that are large enough that their bites are noticed will have no serious medical consequences. Of those bites that humans notice, venoms can include necrotic
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
agents, neurotoxins, and agents such as serotonin. Only some two hundred species in twenty genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
(out of over 40,000 known species) are known to have serious, potentially lethal bites.
In most cases of bites, the chief concern is the spider's venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
, although in some cases medically non-significant spiders can transmit infectious diseases. Spiders regarded as dangerous possess venom that is sufficiently toxic to humans that a single bite can deliver a medically significant dose. Only three spider families are known to be non-venomous, i.e. lacking venom glands. They are Uloboridae, Holarchaeidae
Holarchaeidae
The Holarchaeidae are a spider family with only two described species in one genus.They are only up to 1.5mm in size and shiny black to beige in color...
and Liphistiidae
Liphistiidae
The spider family Liphistiidae comprises 5 genera and 85 species from Southeast Asia, China, and Japan. They are among the most basal living spiders, belonging to the suborder Mesothelae...
. The Liphistiidae, however, are large enough to deliver unpleasant bites. In addition, their fangs can often inflict infections spread through the skin, mostly due to their large size, which in theory could represent more danger than the bite of a non-lethal venomous spider species.
Spider bites may be misdiagnosed by both the general public and medical practitioners. Many other conditions both infectious and non-infectious can be confused with spider bites. Many of these conditions are far more common and more likely to be the source of necrotic wounds.
Signs and symptoms
Pain from non-venomous spider bites typically lasts for 5 to 60 minutes while pain from venomous spider bites frequently lasts for longer than 24 hours. The rate of a bacterial infection due to a spider bite is low (0.9%).Pathophysiology
A primary concern of the bite of a spider is the effect of its venomVenom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
. A spider envenomation occurs whenever a spider injects venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
into the skin. Not all spider bites involve injection of venom into the skin, and the amount of venom injected can vary based on the type of spider and the circumstances of the encounter. With very few exceptions, such as the so-called camel spider
Solifugae
Solifugae are an order of Arachnida, known as camel spiders, wind scorpions and sun spiders or solifuges, comprising more than 1,000 described species in about 153 genera...
(which is not a true spider), the mechanical injury from a spider bite is not a serious concern for humans. Some spider bites do leave a large enough wound that infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
may be a concern, and other species are known to consume prey which is already dead, which also may pose a risk for transmission of infectious bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
from a bite. However, it is generally the toxicity of spider venom that poses the most risk to human beings; several spiders are known to have venom which can be fatal to humans in the amounts that a spider will typically inject when biting.
All spiders are capable of producing venom, with the exception of the hackled orb-weaver
Hackled orb-weaver
Uloboridae, the cribellate orb weavers or hackled orb weavers, is a family of non-venomous spiders. Their lack of poison glands is a secondarily evolved trait. Instead, they kill their prey by crushing with over 140 metres of thread....
s, the Holarchaeidae
Holarchaeidae
The Holarchaeidae are a spider family with only two described species in one genus.They are only up to 1.5mm in size and shiny black to beige in color...
, and the primitive Mesothelae
Mesothelae
The Mesothelae are a suborder of spiders that includes the extinct families Arthrolycosidae and Arthromygalidae and the only extant family Liphistiidae....
. (Other arachnids often confused with spiders, such as the harvestman and sun spiders, also do not produce venom). Nonetheless, only a small percentage of species have bites that pose a danger to people. Many spiders do not have mouthparts capable of penetrating human skin. While venoms are by definition toxic substances, most spiders do not have venom that is sufficiently toxic (in the quantities delivered) to require medical attention and, of those that do, only a few are known to produce fatalities. (For details that substantiate these claims, see the remainder of this article.)
Spider venoms work on one of two fundamental principles; they are either neurotoxic (attacking the nervous system) or necrotic (attacking tissues surrounding the bite, and, in some cases, attacking vital organs and systems).
Neurotoxic venom
The majority of spiders with serious bites possess a neurotoxicNeurotoxin
A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...
venom of some sort, though the specific manner in which the nervous system
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
is attacked varies from spider to spider.
- Widow spiderWidow spiderLatrodectus is a genus of spider, in the family Theridiidae, which contains 31 recognized species. The common name widow spiders is sometimes applied to members of the genus due to the behavior of the female of eating the male after mating, although sometimes the males of some species are not eaten...
venom contains components known as latrotoxinLatrotoxinA latrotoxin is a high-molecular mass neurotoxin found in the venom of spiders of the genus Latrodectus . Latrotoxin are the main active components of the venom and are responsible for the symptoms of latrodectism....
s, which cause the release of the neurotransmitterNeurotransmitterNeurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...
acetylcholineAcetylcholineThe chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...
, stimulating muscle contractions. This can affect the body in several ways, including causing painful abdominal cramps, as well as interfering with respirationRespiratory systemThe respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...
, and causing other systemic effects. - The venom of Australasian funnel-web spiderAustralasian funnel-web spiderAustralian funnel-web spiders are venomous spiders of the family Hexathelidae, represented by 31 described species of Hadronyche, four Bymainiella spp., two Teranodes and monotyptic genera Plesiothera fentoni and Ilawarra whisharti...
s and mouse spiderMouse spiderMouse spiders are spiders of the genus Missulena, in the mygalomorph family Actinopodidae. There are 11 known species in this genus, all but one of which are indigenous to Australia. One species, M. tussulena, is found in Chile...
s works by opening sodium channels, causing excessive neural activity which interferes with normal bodily function. - The venom of Brazilian wandering spiderBrazilian wandering spiderPhoneutria, commonly known as Brazilian wandering spiders, armed spiders , or banana spiders , are a genus of aggressive and highly venomous spiders found in tropical South and Central America...
s is also a potent neurotoxin, which attacks multiple types of ion channelIon channelIon channels are pore-forming proteins that help establish and control the small voltage gradient across the plasma membrane of cells by allowing the flow of ions down their electrochemical gradient. They are present in the membranes that surround all biological cells...
s In addition, the venom contains high levels of serotoninSerotoninSerotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract, platelets, and in the central nervous system of animals including humans...
, making an envenomation by this species particularly painful.
Necrotic venom
Spiders known to have necrotic venom are found in the family SicariidaeSicariidae
Sicariidae is a family of six-eyed venomous spiders known for their necrotic bites. The members of this family are haplogyne by definition . The family consists of two genera, Loxosceles and Sicarius, and contains about 120 species...
, a family which includes both the recluse spider
Recluse spider
The recluse spiders or brown spiders , also known as fiddle-back, violin spiders or reapers, are a venomous genus of spiders known for their necrotic bite, which sometimes produces a characteristic set of symptoms known as Loxoscelism...
s and the six-eyed sand spider
Six-eyed sand spider
The six-eyed sand spider is a medium-sized spider with body measuring 8 to 15 mm and legs spanning up to 50 mm, found in deserts and other sandy places in southern Africa. It is a member of the Sicariidae family; close relatives may be found in both Africa and in South America, and its...
s. Spiders in this family possess a known dermonecrotic agent sphingomyelinase D, which is otherwise found only in a few pathogenic bacteria. Some species in this family are more venomous than others; according to one study, the venom of the chilean recluse
Chilean recluse
The Chilean recluse spider is a venomous spider, Loxosceles laeta, of the family Sicariidae . In Spanish, it is known as , or "corner spider"; in Portuguese, as or "brown spider"...
and several species of six-eyed sand spider indigenous to southern Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, contains an order of magnitude more of this substance than do other sicariid spiders such as the brown recluse. Bites by spiders in this family can produce symptoms ranging from minor localized effects, to severe dermonecrotic lesions, up to and including severe systemic reactions including renal failure
Renal failure
Renal failure or kidney failure describes a medical condition in which the kidneys fail to adequately filter toxins and waste products from the blood...
, and in some cases, death. Even in the absence of systemic effects, serious bites from sicariid spiders may form a necrotising ulcer that destroys soft tissue and may take months and very rarely years to heal, leaving deep scar
Scar
Scars are areas of fibrous tissue that replace normal skin after injury. A scar results from the biological process of wound repair in the skin and other tissues of the body. Thus, scarring is a natural part of the healing process. With the exception of very minor lesions, every wound results in...
s. The damaged tissue may become gangrenous
Gangrene
Gangrene is a serious and potentially life-threatening condition that arises when a considerable mass of body tissue dies . This may occur after an injury or infection, or in people suffering from any chronic health problem affecting blood circulation. The primary cause of gangrene is reduced blood...
and eventually slough away. Initially there may be no pain from a bite, but over time the wound may grow to 10 inches (25 cm) in extreme cases. Bites usually become painful and itchy within two to eight hours, pain and other local effects worsen 12 to 36 hours after the bite, and then necrosis will develop over the next few days.
Serious systemic effects may occur before this time, because the venom spreads throughout the body in minutes. Mild symptoms include nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
, vomiting
Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
, fever
Fever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
, rash
Rash
A rash is a change of the skin which affects its color, appearance or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, cracked or blistered, swell and may be painful. The causes, and...
es, and muscle and joint pain. Rarely more severe symptoms occur including hemolysis
Hemolysis
Hemolysis —from the Greek meaning "blood" and meaning a "loosing", "setting free" or "releasing"—is the rupturing of erythrocytes and the release of their contents into surrounding fluid...
, thrombocytopenia
Thrombocytopenia
Thrombocytopenia is a relative decrease of platelets in blood.A normal human platelet count ranges from 150,000 to 450,000 platelets per microliter of blood. These limits are determined by the 2.5th lower and upper percentile, so values outside this range do not necessarily indicate disease...
, and disseminated intravascular coagulation
Disseminated intravascular coagulation
Disseminated intravascular coagulation , also known as disseminated intravascular coagulopathy or consumptive coagulopathy, is a pathological activation of coagulation mechanisms that happens in response to a variety of diseases. DIC leads to the formation of small blood clots inside the blood...
. Debilitated patients, the elderly, and children may be more susceptible to systemic loxoscelism
Loxoscelism
thumb|Scars left over from a healed recluse biteLoxoscelism is a condition produced by the bite of the recluse spiders . It is the only proven cause of arachnogenic necrosis in humans. While there is no known therapy effective for loxoscelism, there has been research on potential antivenoms and...
. Deaths have been reported for both the brown recluse and the related South American species Loxosceles laeta and Loxosceles intermedia.
Numerous other spiders have been associated with necrotic bites in the medical literature. Examples include the Hobo spider
Hobo spider
The hobo spider is a member of the genus of spiders known colloquially as funnel web spiders, but not to be confused with the Australian funnel-web spider. It is one of a small number of spiders in North America whose bites are generally considered to be medically significant...
and the Yellow Sac spider
Cheiracanthium
Cheiracanthium is a genus of spiders in the Miturgidae family. Certain species are commonly known as the "yellow sac spider".- Description :...
. However, the bites from these spiders are not known to produce the severe symptoms that often follow from a recluse spider bite, and the level of danger posed by each has been called into question. So far, no known necrotoxins have been isolated from the venom of any of these spiders, and some arachnologists have disputed the accuracy of many spider identifications carried out by bite victims, family members, medical responders, and other non-experts in arachnology. There have been several studies questioning whether danger is posed by some of these spiders. In these studies, scientists examined case studies of bites in which the spider in question was positively identified by an expert, and found that the incidence of necrotic injury diminished significantly when "questionable" identifications were excluded from the sample set.
Comparative analysis
It is often asked which type of spider is the most "dangerous" in the world. There isn't a simple answer to this question, as there are many things which must be taken into accountwhen considering the amount of danger posed by spider bites:
- Firstly, it is often the case that a spider bite is "dry" – the skin may be pierced, but little or no venom is injected into the victim. In such an instance, little or none of the spider's dangerous potential for harm is manifested.
- Secondly, there have been reports of spider bites (by spiders considered otherwise harmless) causing allergic reactions in some individuals, up to and including anaphylactic shockAnaphylaxisAnaphylaxis is defined as "a serious allergic reaction that is rapid in onset and may cause death". It typically results in a number of symptoms including throat swelling, an itchy rash, and low blood pressure...
, a life-threatening condition (much the same as a sting from an antAntAnts are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
, beeBeeBees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila...
, or waspWaspThe term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...
may produce a harmful effect apart from the toxic quality of its venom). - Thirdly, many spiders listed as dangerous are seldom encountered, or have dispositions that make them unlikely to bite despite the high toxicity of their venom.
- Finally, little is known about the toxicity of many spiders, due to their infrequent encounters with humans; the list of venomous spiders is limited to those that are linked to medical events in humans or who otherwise have been extensively studied.
It should also be noted that, for healthy adults, a bite by even the most toxic spiders on the list may require hours before death ensues; if timely appropriate emergency medical treatment is administered, victims may be expected to recover. The scenario given in movies such as Arachnophobia
Arachnophobia (film)
Arachnophobia is a 1990 American comedy horror film directed by Frank Marshall and starring Jeff Daniels and John Goodman. It was the first film released by Hollywood Pictures....
, where bite victims die within minutes, does not occur. One exception to this picture occurs in the case of very small children because the amount of venom dispersed throughout the body is many times the concentration in an adult. There is at least one recorded case of a small child dying within 15 minutes of a bite from a Sydney funnel-web spider
Sydney funnel-web spider
The Sydney funnel-web spider, Atrax robustus, is an Australian funnel-web spider usually found within a radius of Sydney, New South Wales, Australia.-Description:...
; that event occurred before the development of an antivenom. Since the antivenom was developed there have been no fatalities due to this species.
The spider-bites documented as the most dangerous to humans are those of the Sydney funnel-web spider
Sydney funnel-web spider
The Sydney funnel-web spider, Atrax robustus, is an Australian funnel-web spider usually found within a radius of Sydney, New South Wales, Australia.-Description:...
and the Brazilian wandering spider
Brazilian wandering spider
Phoneutria, commonly known as Brazilian wandering spiders, armed spiders , or banana spiders , are a genus of aggressive and highly venomous spiders found in tropical South and Central America...
. These spiders are potentially more dangerous than widow spider
Widow spider
Latrodectus is a genus of spider, in the family Theridiidae, which contains 31 recognized species. The common name widow spiders is sometimes applied to members of the genus due to the behavior of the female of eating the male after mating, although sometimes the males of some species are not eaten...
s because they have longer fangs and can inject greater quantities of venom to greater depths. Phoneutria nigriventer has approximately 2 mg of venom, but frequently gives dry bites or at least does not deliver all of its available venom. Atrax robustus has approximately 1.7 mg of venom. Bites of Six-eyed sand spider
Six-eyed sand spider
The six-eyed sand spider is a medium-sized spider with body measuring 8 to 15 mm and legs spanning up to 50 mm, found in deserts and other sandy places in southern Africa. It is a member of the Sicariidae family; close relatives may be found in both Africa and in South America, and its...
s have been described as dangerous to humans, but there is a lack of proof for this, though Sicarius venom has been shown to be fatal to rabbits.
The genus Latrodectus (of which the black widow spider is the most notorious) have been credited with killing more people per year, worldwide, than any other spider. Because they are not very large, they are much harder to detect than a large Brazilian wandering spider or a tarantula. Their venom is extremely potent. Compared to many other species of spiders, their chelicerae are not very large. In the case of a mature female, the hollow, needle shaped part of each chelicera, the part that penetrates the skin, is approximately 1 mm (0.04 in) long, sufficiently long to inject the venom to a dangerous depth. The males, being much smaller, can inject far less venom and inject it far less deeply. The actual amount injected, even by a mature female, is very small in physical volume (.02–.03 mg). When this small amount of venom is diffused throughout the body of a healthy, mature human, it usually does not amount to a fatal dose. Deaths in healthy adults from Latrodectus bites are rare in terms of the number of bites per thousand people. Only sixty-three deaths were reported in the United States between 1950 and 1989 (Miller, 1992). On the other hand, the geographical range of the widow spiders is very great. As a result, far more people are exposed, worldwide, to widow bites than are exposed to bites of more dangerous spiders, so the highest number of deaths worldwide are caused by members of the genus Latrodectus. Widow spiders have more potent venom than most spiders, and prior to the development of antivenom, 5% of bites resulted in fatalities, although comparable figures are not available for the other species.
Measurements
The LD-50 (Median lethal dose) figures have limited utility since the effects of venoms differ widely from species to species. Before an antivenom was developed, deaths from Atrax and Hadronyche did occur, but the frequency of non-lethal bites is unknown. Some deaths from Phoneutria bites are reported, but much of their range is in the AmazonAmazon Rainforest
The Amazon Rainforest , also known in English as Amazonia or the Amazon Jungle, is a moist broadleaf forest that covers most of the Amazon Basin of South America...
so reporting of bites may not be very complete.
Most LD-50 figures are based on experiments with laboratory mice. There are great differences in the sensitivities of various kinds of organisms to various kinds of venom. The relative sensitivities of mice to various venoms may not allow prediction of the exact degree of human sensitivity. So most of these figures can only give a rough approximation of the medical consequences of various spider bites to humans. A case in point are the Sicarius spp. The venom of these spiders is extremely active in laboratory animals, but there are few if any documented reports of Sicarius bites in humans, so data on which to base valid conclusions is lacking.
| Genus | Species | Common name | Body length | Venom amount | LD-50 | Alternate LD-50 | Deaths reported |
|---|---|---|---|---|---|---|---|
| Atrax | A. robustus | Sydney funnel-web spider Sydney funnel-web spider The Sydney funnel-web spider, Atrax robustus, is an Australian funnel-web spider usually found within a radius of Sydney, New South Wales, Australia.-Description:... |
24–32 mm. | 0.25 mg (F) and 0.81 mg (M) 2 mg | .16 mg/kg | unknown | 1927–1980 13 deaths |
| Hadronyche Hadronyche Hadronyche is a genus of venomous spiders found in Australasia. Some species are termed Australian funnel-web spider, being highly venomous members of the Hexathelidae family... |
H. formidabilis | Northern tree funnel-web spider | 23–45 mm. | ||||
| Latrodectus | L. mactans | Black widow Black widow spider Latrodectus mactans, the Southern black widow, is a highly venomous species of spider in the genus Latrodectus. They are well known for the distinctive black and red coloring of the female of the species and for the fact that she will occasionally eat her mate after reproduction. The species is... |
8–15 mm | 0.02–.03 mg. | 0.002 mg/kg * | 0.9 mg/kg | 5% of reported bites prior to antivenom availability |
| Latrodectus | L. tredecimguttatus | Malmignatte Latrodectus tredecimguttatus Latrodectus tredecimguttatus, commonly known as the Mediterranean black widow or steppe spider, is a species of widow spiders in the genus Latrodectus. It is commonly found throughout the Mediterranean region, ranging from Spain to southwest and central Asia, hence the name... |
(approx. same) | (approx. same) | 0.68 μg/kg | 16.25 μg/kg | |
| Loxosceles | L. reclusa | Brown recluse | 1.2 cm (0.75 in) 6–10 mm | .13–.27 mg. | (rare) | ||
| Loxosceles | L. intermedia | 0.48 mg/kg | unknown | ||||
| Loxosceles | L. laeta | Chilean recluse Chilean recluse The Chilean recluse spider is a venomous spider, Loxosceles laeta, of the family Sicariidae . In Spanish, it is known as , or "corner spider"; in Portuguese, as or "brown spider"... |
1.45 mg/kg | ||||
| Loxosceles | L. gaucho | 0.74 mg/kg | |||||
| Phoneutria | P. bahiensis | Brazilian wandering spider Brazilian wandering spider Phoneutria, commonly known as Brazilian wandering spiders, armed spiders , or banana spiders , are a genus of aggressive and highly venomous spiders found in tropical South and Central America... |
30 mm | 1.079 mg | .00061–.00157 mg/kg | ||
| Phoneutria | P. boliviensis | Brazilian wandering spider Brazilian wandering spider Phoneutria, commonly known as Brazilian wandering spiders, armed spiders , or banana spiders , are a genus of aggressive and highly venomous spiders found in tropical South and Central America... |
30 mm | 1.079 mg. | .00061–.00157 mg/kg | ||
| Phoneutria | P. fera | Brazilian wandering spider Brazilian wandering spider Phoneutria, commonly known as Brazilian wandering spiders, armed spiders , or banana spiders , are a genus of aggressive and highly venomous spiders found in tropical South and Central America... |
30 mm | 1.079 mg | .00061–.00157 mg/kg | occasional deaths even after antivenin treatment | |
| Phoneutria | P. nigriventer | Brazilian wandering spider Brazilian wandering spider Phoneutria, commonly known as Brazilian wandering spiders, armed spiders , or banana spiders , are a genus of aggressive and highly venomous spiders found in tropical South and Central America... |
3–5 cm (1.25–2 in) | 2.15 mg 1.079 mg. | 15.20 ng/mg. 00061–.00157 mg/kg | 200 µg/kg (0.2 ng/mg) | |
| Phoneutria | P. reidyi | Brazilian wandering spider Brazilian wandering spider Phoneutria, commonly known as Brazilian wandering spiders, armed spiders , or banana spiders , are a genus of aggressive and highly venomous spiders found in tropical South and Central America... |
30 mm | .00061–.00157 mg/kg | 0.3 mg/kg | ||
| Sicarius | spp. | Six-eyed sand spider Six-eyed sand spider The six-eyed sand spider is a medium-sized spider with body measuring 8 to 15 mm and legs spanning up to 50 mm, found in deserts and other sandy places in southern Africa. It is a member of the Sicariidae family; close relatives may be found in both Africa and in South America, and its... |
17 mm | ||||
| Haplopelma Haplopelma Haplopelma is a genus of old-world tarantula found in Southeast Asia. The range of this genus includes Myanmar, southeastern China, Cambodia, Thailand, Vietnam, Malaysia, Singapore, and Borneo.- Description :... |
H. huwenum (previously Selenocosmia huwena) | Chinese bird spider Chinese bird spider Chinese bird spider is an English name given to several species of old-world tarantulas which are found in the People's Republic of China and Vietnam. The spider, also known in English as the earth tiger, is currently classified in the genus Haplopelma... |
0.70 mg/kg | ||||
| Poecilotheria | P. ornata | Fringed ornamental tarantula | Instances of coma reported. | ||||
| Poecilotheria | P. fasciata |
Sri Lankan ornamental tarantula | Instances of cardiac failure reported | ||||
| Cheiracanthium | spp. | Yellow Sac spider Yellow sac spider Cheiracanthium inclusum, alternately known as the black-footed yellow sac spider or the American yellow sac spider , was formerly classified as a true sac spider , but now belongs to the long-legged sac spiders... |
6–10 mm | (No severe consequences) | |||
| Cheiracanthium | C. japonicum | Japanese sac spider | 6–10 mm | ||||
| Macrothele | M. holsti, M. gigas, M. taiwanensis | Primitive burrowing spiders | No deaths reported in Taiwan. | ||||
| Steatoda Steatoda The spider genus Steatoda, in the family Theridiidae, includes over 120 recognized species, distributed around the world .... |
S. grossa | Cupboard spider Steatoda grossa Steatoda grossa, commonly known as the cupboard spider, the dark comb-footed spider, the brown house spider , or the false black widow , is a common species of spider in the genus Steatoda... |
Mild widow-like symptoms reported, no severe consequences |
Diagnosis
Assumption that a reported injury was caused by a spider is the most common source of false reports, which in some cases have led to misdiagnosis and mistreatment, with potentially life-threatening consequences. Many spider bites, including those by some dangerous species, are relatively painless at first and may go unnoticed if not directly observed. These bites may only be noticed later if serious symptoms appear.Occasionally, infections of methicillin-resistant Staphylococcus aureus
Methicillin-resistant Staphylococcus aureus
Methicillin-resistant Staphylococcus aureus is a bacterium responsible for several difficult-to-treat infections in humans. It is also called multidrug-resistant Staphylococcus aureus and oxacillin-resistant Staphylococcus aureus...
(MRSA) are misdiagnosed as necrotic spider bites; this can have severe consequences as a MRSA infection is frequently a medical emergency.
Management
Most spider bites are harmless, and require no specific treatment. Treatment of bites may depend on the type of spider; thus, capture of the spider—either alive, or in a well-preserved condition, is useful.In the case of bites by widow spider
Widow spider
Latrodectus is a genus of spider, in the family Theridiidae, which contains 31 recognized species. The common name widow spiders is sometimes applied to members of the genus due to the behavior of the female of eating the male after mating, although sometimes the males of some species are not eaten...
s, Australian venomous funnel-web spiders, or Brazilian wandering spider
Brazilian wandering spider
Phoneutria, commonly known as Brazilian wandering spiders, armed spiders , or banana spiders , are a genus of aggressive and highly venomous spiders found in tropical South and Central America...
s, prompt medical attention should be sought as in some cases the bites of these spiders may develop into a medical emergency
Medical emergency
A medical emergency is an injury or illness that is acute and poses an immediate risk to a person's life or long term health. These emergencies may require assistance from another person, who should ideally be suitably qualified to do so, although some of these emergencies can be dealt with by the...
.
Treatment for non-poisonous spider bites include washing the bite with soap and water and ice to reduce inflammation. Analgesics and antihistamines may be used, however antibiotics are not recommended unless there is also a bacterial infection present.
Necrosis
There is no established treatment for necrosisNecrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
. Recommendations include elevation and immobilization of the affected limb, application of ice, local wound care, and tetanus prophylaxis. Many other therapies have been used with varying degrees of success including hyperbaric oxygen, dapsone
Dapsone
Dapsone is a medication most commonly used in combination with rifampicin and clofazimine as multidrug therapy for the treatment of Mycobacterium leprae infections . It is also second-line treatment for prophylaxis against Pneumocystis pneumonia caused by Pneumocystis jiroveci Dapsone...
, antihistamines (e.g., cyproheptadine
Cyproheptadine
Cyproheptadine , sold under the brand name Periactin, is a first-generation antihistamine with additional anticholinergic, antiserotonergic, and local anesthetic properties.- Indications :...
), antibiotics, dextran
Dextran
Dextran is a complex, branched glucan composed of chains of varying lengths...
, glucocorticoids, vasodilators, heparin
Heparin
Heparin , also known as unfractionated heparin, a highly sulfated glycosaminoglycan, is widely used as an injectable anticoagulant, and has the highest negative charge density of any known biological molecule...
, nitroglycerin, electric shock
Electric shock
Electric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....
, curettage
Curettage
Curettage, in medical procedures, is the use of a curette to remove tissue by scraping or scooping.Curettages are also a declining method of abortion. It has been replaced by vacuum aspiration over the last decade....
, surgical excision
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
, and antivenom. None of these treatments have been subjected to controlled, randomized trials to conclusively show benefit. In almost all cases, bites are self-limited and typically heal without any medical intervention.
Dapsone
Dapsone
Dapsone is a medication most commonly used in combination with rifampicin and clofazimine as multidrug therapy for the treatment of Mycobacterium leprae infections . It is also second-line treatment for prophylaxis against Pneumocystis pneumonia caused by Pneumocystis jiroveci Dapsone...
is commonly used in the USA and Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
for the treatment of necrosis. There have been conflicting reports about its efficacy and some have suggested it should no longer be used routinely, if at all.
Other
- Studies have shown surgical intervention is ineffective and may worsen outcome. Excision may delay wound healing, cause abscesses, and lead to objectional scarring.
- Use of antivenom for severe spider bites may be indicated, especially in the case of neurotoxic venoms. Effective antivenoms exist for Latrodectus, Atrax, and Phoneutria venom. Recluse bites are treatable by antivenom; an antivenom for Loxosceles bites is available in South America, and it appears antivenom may be the most promising therapy. However, the recluse antivenom is most effective if given early, and because of the relatively painless bite delivered by recluses, patients do not often present until 24 or more hours after the event, possibly limiting the effect of this intervention. Due to the risk of serum sicknessSerum sicknessSerum sickness in humans is a reaction to proteins in antiserum derived from an non-human animal source. It is a type of hypersensitivity, specifically immune complex hypersensitivity . The term serum sickness–like reaction is occasionally used to refer to similar illnesses that arise from the...
, use of antivenom is generally not indicated unless serious symptoms are present, and/or a person fails to respond to other forms of treatment.
Australia
A study of 750 definite spider bites in Australia indicated that 6% of spider bites cause significant effects, the vast majority of these being redback spider bites causing significant pain lasting more than 24 hours.United States
The jumping spiderJumping spider
The jumping spider family contains more than 500 described genera and about 5,000 described species, making it the largest family of spiders with about 13% of all species. Jumping spiders have some of the best vision among invertebrates and use it in courtship, hunting and navigation...
is probably the most common biting spider in the United States, the main species being Phidippus audax
Phidippus audax
Phidippus audax is a common jumping spider of North America. It is commonly referred to as the daring jumping spider, or bold jumping spider. The average size of adults ranges from roughly 13 to 20 mm in length....
. Bites from a jumping spider are usually painful, itchy and cause redness and significant swelling.
The spiders of most concern in the United States, however, are brown recluse spider
Brown recluse spider
The brown recluse spider or violin spider, Loxosceles reclusa, is a member of the family Sicariidae . The spider has a venomous bite....
s and black widow spider
Black widow spider
Latrodectus mactans, the Southern black widow, is a highly venomous species of spider in the genus Latrodectus. They are well known for the distinctive black and red coloring of the female of the species and for the fact that she will occasionally eat her mate after reproduction. The species is...
s. Most recluse spider bites are minor with little or no necrosis. However, a small number of bites produce severe dermonecrotic lesions, and, sometimes, severe systemic symptoms, including organ damage. Rarely the bite may also produce the systemic condition with occasional fatalities.
Black widow spider bites may cause muscle cramps, but no one in the United States has died from a black widow spider bite in over 10 years.
Classification
A spider is classified as "venomous" if it is able to cause significant harm to humans. Spiders having medically significant venom exist in all but the coldest parts of the world. There is general agreement on which spiders give bites that may produce lasting damage or death, but not such general agreement on how one might sort spiders identified by genus and species in order of their threat to humans.The following types of spider are known to have medically significant bites, with symptoms ranging from localized pain all the way to severe tissue
Biological tissue
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
destruction and potential death
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....
. Spiders whose bites have caused fatalities which are well documented in the scientific literature are so indicated in the section headers. Only four genera (Phoneutria, Atrax, Latrodectus, and Loxosceles) are known to have killed humans; three other genera (Hadronyche
Hadronyche
Hadronyche is a genus of venomous spiders found in Australasia. Some species are termed Australian funnel-web spider, being highly venomous members of the Hexathelidae family...
, Missulena, and Sicarius) possess venom which toxicology studies have shown have lethal potential (being similar to Atrax and Loxosceles venom in composition). There are suspected but unconfirmed deaths reported in the literature from species in Tegenaria
Tegenaria
House spiders of the genus Tegenaria are fast-running brownish funnel-web weavers that occupy much of the Northern Hemisphere except for Japan, Indonesia, Australia and New Zealand. Of all Agelenids, Tegenaria possesses the largest species of funnel weavers: the dust spider , the Cardinal spider ...
and Haplopelma
Haplopelma
Haplopelma is a genus of old-world tarantula found in Southeast Asia. The range of this genus includes Myanmar, southeastern China, Cambodia, Thailand, Vietnam, Malaysia, Singapore, and Borneo.- Description :...
.
Brazilian wandering spiders
Brazilian wandering spider
Phoneutria, commonly known as Brazilian wandering spiders, armed spiders , or banana spiders , are a genus of aggressive and highly venomous spiders found in tropical South and Central America...
(a ctenid spider) is a large brown spider similar to North American wolf spider
Wolf spider
Wolf spiders are members of the family Lycosidae, from the Ancient Greek word "" meaning "wolf". They are robust and agile hunters with good eyesight. They live mostly solitary lives and hunt alone. Some are opportunistic hunters pouncing upon prey as they find it or even chasing it over short...
s in appearance, although somewhat larger. It has a highly toxic venom (the most neurologically active of all spiders), and is regarded (along with the Australian funnel-web spiders, whose bites deliver slightly less venom, but are faster-acting) as among the most dangerous spiders in the world.
Brazilian wandering spiders, like their name says, are active hunters and travel a lot. They tend to crawl into cozy, comfortable places for the night, and thus can easily be found in fruits and flowers that humans consume and cultivate. If the spider has a reason to be alarmed, it will bite in order to protect itself, but unless startled or enraged, most bites will be delivered dry (i.e. without venom). Venom bites will occur if the spider is pressed against something (such as fingers) and hurt. In this case, the high levels of serotonin
Serotonin
Serotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract, platelets, and in the central nervous system of animals including humans...
contained in the venom, plus at minimum strong chelicera, will contribute to deliver a very painful bite that can result in muscle shock.
Children are more sensitive to the bites of wandering spiders, as the spiders often make threat gestures (such as raising up their legs, or hopping sideways on the ground), which might amuse a child to the point of reaching towards the spider. Children have weaker immune systems, and even if antivenom is quickly administered, death can occur within minutes after the bite. In male humans, bites of this spider may also result in priapism
Priapism
Priapism is a potentially harmful and painful medical condition in which the erect penis or clitoris does not return to its flaccid state, despite the absence of both physical and psychological stimulation, within four hours. There are two types of priapism: low-flow and high-flow. Low-flow...
. Scientists are attempting to create an erectile dysfunction treatment that can be combined with other medicines out of the peptide that causes this reaction.
Australian funnel-web spiders
Sydney funnel-web spider
The Sydney funnel-web spider, Atrax robustus, is an Australian funnel-web spider usually found within a radius of Sydney, New South Wales, Australia.-Description:...
Atrax robustus (a mygalomorph only distantly related to the araneomorph funnel-web spiders) are regarded as among the most dangerous in the world. They react vigorously to threats and, reputedly, will more often attempt to bite than run away. A. robustus, a large black spider, is found within a radius of about 100 km from Sydney
Sydney
Sydney is the most populous city in Australia and the state capital of New South Wales. Sydney is located on Australia's south-east coast of the Tasman Sea. As of June 2010, the greater metropolitan area had an approximate population of 4.6 million people...
. Its venom contains a compound known as atracotoxin which is highly toxic to primates. Unlike the Brazilian wandering spider, which is alleged to occasionally deliver dry bites, these spiders typically deliver a full envenomation when they bite.
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
and Tasmania
Tasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...
. The males in this case have somewhat more potent venom than females and they also wander, making them more likely to be encountered in summer. Bites by males of two large species, the Sydney funnel-web and northern tree funnel-web, have resulted in death.
One other genus in the Hexathelidae
Hexathelidae
The spider family Hexathelidae, the only family in the super-family Hexatheloidea, is one of two families of spiders known as funnel-webs...
family has been reported to cause severe symptoms in humans. Severe bites have been attributed to members of the genus Macrothele
Macrothele
Macrothele is a genus of mygalomorph spiders.Most species occur in Asia from India to Japan and Java, with four found in Africa, and two in Europe.-Description:...
in Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
, but no fatalities.
Tangle-web spiders
Two genera of the tangle web spiderTangle web spider
Theridiidae is a large family of spiders, also known as the tangle-web spiders, cobweb spiders and comb-footed spiders. The diverse family includes over 2200 species in over 100 genera) of three-dimensional space-web-builders found throughout the world...
s have venom which is known to be medically significant. One genus, the widow spider
Widow spider
Latrodectus is a genus of spider, in the family Theridiidae, which contains 31 recognized species. The common name widow spiders is sometimes applied to members of the genus due to the behavior of the female of eating the male after mating, although sometimes the males of some species are not eaten...
s of genus Latrodectus, has caused more human fatalities than any other. The other genus, the false widow spiders of Steatoda, has a far less serious bite.
Widow spiders
Black widow spider
Latrodectus mactans, the Southern black widow, is a highly venomous species of spider in the genus Latrodectus. They are well known for the distinctive black and red coloring of the female of the species and for the fact that she will occasionally eat her mate after reproduction. The species is...
, redback spider, and katipo
Katipo
Latrodectus katipo, the katipo, is an endangered species of spider native to New Zealand. A member of the genus Latrodectus, it is related to the Australian redback spider, and the North American black widow spiders. The species is venomous to humans, capable of delivering a comparatively dangerous...
are spiders that carry a neurotoxic venom which can cause a set of symptoms known as Latrodectism
Latrodectism
Latrodectism is the clinical syndrome caused by the neurotoxic venom , that can be injected by the bite of any spider that is a member of the spider genus Latrodectus, in the family Theridiidae....
.
Like many spiders, widows have very poor vision, and they move with difficulty when not on their web. Widow spiders are large, strong-looking house spiders (but still have relatively spindly legs and deep, globular abdomens). The abdomen is dark and shiny, and has one or several red spots, either above or below. The spots may take the form of an hourglass, or two triangles, point-to-point. Male widows, like most spider species, are much smaller than the females and may have a variety of streaks and spots on a browner, less globular abdomen. The males are generally less dangerous than the females of the same species. Widows tend to be non-aggressive, but will bite if the web is disturbed and the spider feels threatened.
The venom, while seldom life-threatening, produces very painful effects including muscle spasms, 'tetanus-like' contractions and, in some cases, spinal or cerebral paralysis (which is generally temporary, but might leave permanent damage to central nervous system). A serious bite will often require a short hospital stay. Children, elderly, and ill individuals are at most risk of serious effects.
False black widows
.jpg)
Widow spider
Latrodectus is a genus of spider, in the family Theridiidae, which contains 31 recognized species. The common name widow spiders is sometimes applied to members of the genus due to the behavior of the female of eating the male after mating, although sometimes the males of some species are not eaten...
s in size and physical form, due to being members of the same family. While the bite of Steatoda spiders is nowhere near as serious as that of true widow spiders, several of these spiders do have medically significant bites. The bite of Steatoda grossa
Steatoda grossa
Steatoda grossa, commonly known as the cupboard spider, the dark comb-footed spider, the brown house spider , or the false black widow , is a common species of spider in the genus Steatoda...
, commonly known as the cupboard spider, is known to cause symptoms which have been described as a very minor widow bite; the medical community now refers to the symptoms of Steatoda bites as steatodism. Other spiders in this genus known to be problem biters include two chiefly European varieties, S. paykulliana and S. nobilis
Steatoda nobilis
Steatoda nobilis, commonly known in England as the biting spider or the false widow , is a common species of spider in the genus Steatoda...
, and a species found mainly in New Zealand and South Africa, S. capensis
Steatoda capensis
Steatoda capensis is a spider originating from South Africa. Its common names include the black cobweb spider, brown house spider, cupboard spider and due to its similarities to the katipo spider it is commonly known as the false katipo in New Zealand...
Use of widow spider antivenom has been shown effective in treating steatodism. The genera Steatoda and Latrodectus are biologically close cousins; both belong to the family Theridiidae
Theridiidae
Theridiidae is a large family of spiders, also known as the tangle-web spiders, cobweb spiders and comb-footed spiders. The diverse family includes over 2200 species in over 100 genera) of three-dimensional space-web-builders found throughout the world...
. There are over 100 species in this genus, but only several species have been associated with medically significant bites.
Members of this genus are characterized by the "D" shape of the cephalothorax, and the way the relatively straight line thus formed is mirrored by the blunt forward surface of the abdomen. Other genera in this family generally have cephalothoraxes that are more oval in shape or even rather round, and that give the appearance of two body parts that are joined by a small connector.
Sicariidae spiders
The family SicariidaeSicariidae
Sicariidae is a family of six-eyed venomous spiders known for their necrotic bites. The members of this family are haplogyne by definition . The family consists of two genera, Loxosceles and Sicarius, and contains about 120 species...
includes two genera which inflict necrotoxic bites. One genus, Loxosceles, comprises the recluse spiders (below). The other genus, Sicarius is found only in the southern hemisphere, an example being the Six-eyed sand spider, Sicarius hahni
Six-eyed sand spiders
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
and others of the genus Sicarius inject a cytotoxic
Cytotoxicity
Cytotoxicity is the quality of being toxic to cells. Examples of toxic agents are a chemical substance, an immune cell or some types of venom .-Cell physiology:...
venom, believed to contain sphingomyelinase D, for which there is currently no antivenom. Fortunately, this specimen rarely interacts with humans, and is seldom known to bite. This spider buries itself in sand in order to ambush prey that wanders nearby. Sand particles adhere to cuticles on its abdomen, thus acting as a natural camouflage if uncovered. If disturbed, it will run a short distance and bury itself again.
Recluse spiders
Brown recluse spider
The brown recluse spider or violin spider, Loxosceles reclusa, is a member of the family Sicariidae . The spider has a venomous bite....
, also known as "violin spiders," "fiddlers," or "fiddlebacks," from the dark violin-shaped marking on the cephalothorax, are slow-moving, retiring spiders which wander about in dim areas and under things, and so are more easily trapped against one's skin by clothing, bed sheets, etc. The spiders will often creep along at a very slow pace and then make a sudden dart for a couple of inches, then return to the previous languid pace. Recluses are extremely venomous. Most encounters with this spider occur from moving boxes or rooting about in closets or under beds. The range of the brown recluse, L. reclusa in the US is approximately the southern two-thirds by the eastern three-quarters of the country. A number of related recluse spiders (some non-native introductions) are found in southern California and nearby areas.
Most recluse spider bites are minor with little or no necrosis
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
. However, a small number of bites produce severe dermonecrotic lesions, and, sometimes, severe systemic symptoms, including organ damage. Rarely the bite may also produce the systemic condition with occasional fatalities.
A minority of bites form a necrotizing ulcer that destroys soft tissue and may take months and, on very rare occasions, years to heal, leaving deep scar
Scar
Scars are areas of fibrous tissue that replace normal skin after injury. A scar results from the biological process of wound repair in the skin and other tissues of the body. Thus, scarring is a natural part of the healing process. With the exception of very minor lesions, every wound results in...
s similar to MRSA. The damaged tissue will become gangrenous
Gangrene
Gangrene is a serious and potentially life-threatening condition that arises when a considerable mass of body tissue dies . This may occur after an injury or infection, or in people suffering from any chronic health problem affecting blood circulation. The primary cause of gangrene is reduced blood...
and eventually slough away. The initial bite frequently cannot be felt and there may be no pain, but over time the wound may grow to as large as 10 inches (25 cm) in extreme cases. Bites usually become painful and itchy within 2 to 8 hours, pain and other local effects worsen 12 to 36 hours after the bite with the necrosis developing over the next few days.
Serious systemic effects may occur before this time, as the venom spreads throughout the body in minutes. Mild symptoms include nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
, vomiting
Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
, fever
Fever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
, rash
Rash
A rash is a change of the skin which affects its color, appearance or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, cracked or blistered, swell and may be painful. The causes, and...
es, and muscle and joint pain. Rarely more severe symptoms occur including hemolysis
Hemolysis
Hemolysis —from the Greek meaning "blood" and meaning a "loosing", "setting free" or "releasing"—is the rupturing of erythrocytes and the release of their contents into surrounding fluid...
, thrombocytopenia
Thrombocytopenia
Thrombocytopenia is a relative decrease of platelets in blood.A normal human platelet count ranges from 150,000 to 450,000 platelets per microliter of blood. These limits are determined by the 2.5th lower and upper percentile, so values outside this range do not necessarily indicate disease...
, and disseminated intravascular coagulation
Disseminated intravascular coagulation
Disseminated intravascular coagulation , also known as disseminated intravascular coagulopathy or consumptive coagulopathy, is a pathological activation of coagulation mechanisms that happens in response to a variety of diseases. DIC leads to the formation of small blood clots inside the blood...
. Debilitated patients, the elderly, and children may be more susceptible to systemic loxoscelism. Deaths have been reported for both the brown recluse and the related South American species L. laeta and L. intermedia.
Even more dangerous is the Chilean recluse
Chilean recluse
The Chilean recluse spider is a venomous spider, Loxosceles laeta, of the family Sicariidae . In Spanish, it is known as , or "corner spider"; in Portuguese, as or "brown spider"...
, a species native to South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
and found in many parts of the world, including in southern California and other southwestern states. Bites of this spider have been known to cause systemic reactions in 15% of reported cases, and fatalities in 3-4% of cases.
Mouse spiders
Tarantulas
The tarantulas of the family Theraphosidae are fearsome-looking spiders with (sometimes justified) reputations for inflicting harm. As large spiders, they have very powerful fangs and are capable of delivering a sizable quantity of venom. However, many tarantula species are known to be relatively harmless to humans.New-world tarantulas
Urticating hair
Urticating hairs, i.e. stinging hairs, are one of the primary defense mechanisms used by numerous plants, some New World tarantulas, and various lepidopteran caterpillars. Urtica is Latin for "nettle", and hairs that urticate are characteristic of this type of plant, and many other plants in...
s, which can cause irritant symptoms in humans.
Old-world tarantulas
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
, lack urticating hair
Urticating hair
Urticating hairs, i.e. stinging hairs, are one of the primary defense mechanisms used by numerous plants, some New World tarantulas, and various lepidopteran caterpillars. Urtica is Latin for "nettle", and hairs that urticate are characteristic of this type of plant, and many other plants in...
s and use biting as a defensive mechanism as well for subduing prey. They are far less docile than new-world tarantulas, and are more likely to bite when provoked. Incomplete studies of old-world tarantula venoms, as well as anecdotal evidence, suggests that they are more potent than those of new-world counterparts.
There have been reports of significant bites by Poecilotheria
Poecilotheria
Poecilotheria is a genus of the family Theraphosidae containing various species of arboreal tarantula. This genus is known for vivid color patterns, fast movement, and potent venom compared to other tarantulas. The genus is native to Sri Lanka and India. The name Poecilotheria is derived from...
species, occasionally resulting in hospitalization. Symptoms include localized pain and swelling, exhaustion, moderate to severe muscle cramping, labored breathing and fever, sometimes delayed days after the initial bite.
One tarantula whose venom has been studied extensively is the Chinese bird spider
Chinese bird spider
Chinese bird spider is an English name given to several species of old-world tarantulas which are found in the People's Republic of China and Vietnam. The spider, also known in English as the earth tiger, is currently classified in the genus Haplopelma...
, a tarantula of the subfamily Ornithoctoninae
Ornithoctoninae
Ornithoctoninae, also known as earth tigers, are a subfamily of old-world tarantulas, which were first erected in 1895 by Reginald Innes Pocock on basis of the genotype Ornithoctonus andersoni described in 1892 from former Burma, now Myanmar....
. The venom has been found to contain numerous novel toxins, is effective at killing mice
MICE
-Fiction:*Mice , alien species in The Hitchhiker's Guide to the Galaxy*The Mice -Acronyms:* "Meetings, Incentives, Conferencing, Exhibitions", facilities terminology for events...
, and has been blamed for at least one fatality in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
. However, there is little documented clinical evidence of the effects of this spiders' bite in humans, so firm conclusions about the level of danger posed by this spider cannot be drawn.
Yellow Sac spiders
The Yellow Sac spiders, Cheiracanthium sp., take shelter in silk tubes during the daytime and generally come out to hunt at night. These pale yellow or whitish spiders are often found in houses at the top of walls, or wandering across ceilings. They are also commonly found outdoors on foliage. The draglines they leave while hunting are one of the most common "spiderwebs" that are removed with broom and vacuum cleaner. People may unintentionally make contact with them in the dark and so be bitten if the spider is irritated or provoked. However, many people will live their entire lives in close proximity to them and never suffer a bite. Nevertheless, the spider's bite is considered toxic.
Others
There are several species of spider (and a few other arachnidArachnid
Arachnids are a class of joint-legged invertebrate animals in the subphylum Chelicerata. All arachnids have eight legs, although in some species the front pair may convert to a sensory function. The term is derived from the Greek words , meaning "spider".Almost all extant arachnids are terrestrial...
s which are not spiders, but are frequently confused with them), who have had unsupported reputations for being harmful to humans. In some cases, that the species is now considered harmless is a settled matter for arachnologists and other professionals; in other cases (such as the hobo spider
Hobo spider
The hobo spider is a member of the genus of spiders known colloquially as funnel web spiders, but not to be confused with the Australian funnel-web spider. It is one of a small number of spiders in North America whose bites are generally considered to be medically significant...
), prior scientific belief that a spider is harmful to humans is now being questioned.
Hobo spiders
The hobo spider, Tegenaria agrestis, may wander away from its web, especially in the fall, and thus come into contact with people and potentially bite. This spider is found in the northwestern United States, western Canada and throughout much of Europe. Studies performed by arachnologist Darwin Vest
Darwin Vest
Darwin Kenneth Vest was a biologist who worked on hobo spiders and other venomous spiders and snakes. He went missing in Idaho Falls, U.S. on June 3, 1999, and his whereabouts are still unknown ; police suspect foul play.-External links:**...
reported that this spider's venom caused significant necrotic effects in laboratory animals, and medical authorities in the Pacific Northwest who were aware of Vest's research subsequently blamed this spider for at least one fatality. Many agricultural authorities have published the advice that this species is potentially harmful, and medical personnel in the western United States and Canada have been advised to consider hobo spider bites when patients present with necrotic wounds. Many brown recluse bites have been reported in the U.S. west coast states (Washington, Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
, and northern California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
) where populations of brown recluse spider
Brown recluse spider
The brown recluse spider or violin spider, Loxosceles reclusa, is a member of the family Sicariidae . The spider has a venomous bite....
s have not been found; some of these alleged bites have been attributed to hobo spiders instead.
However, in Europe, where the spider originates, the species is considered a harmless outdoor relative of the common house spider (Tegenaria domestica), and no other spider in the genus Tegenaria
Tegenaria
House spiders of the genus Tegenaria are fast-running brownish funnel-web weavers that occupy much of the Northern Hemisphere except for Japan, Indonesia, Australia and New Zealand. Of all Agelenids, Tegenaria possesses the largest species of funnel weavers: the dust spider , the Cardinal spider ...
is considered to be harmful to people. Attempts to replicate Vest's study that reported necrotic effects of the venom have failed, thus casting the "dangerous" status of this spider into doubt. In addition, Vest's methodologies have been questioned; he has been accused of incorrectly attributing symptoms to hobo spider bites when no positive identification of the spider was made. The one fatality attributed to the spider by medical authorities has also been questioned, and there are no documented cases where an otherwise-healthy person has developed a necrotic lesion from a positively-identified hobo spider bite. Many scientists now question whether or not the spider is harmful at all.
Lycosa tarantula
Lycosa tarantula
The tarantula wolf spider or just tarantula is a wolf spider found in southern Europe, especially in Italy and near the city of Taranto...
, a species of wolf spider
Wolf spider
Wolf spiders are members of the family Lycosidae, from the Ancient Greek word "" meaning "wolf". They are robust and agile hunters with good eyesight. They live mostly solitary lives and hunt alone. Some are opportunistic hunters pouncing upon prey as they find it or even chasing it over short...
which is found near Taranto
Taranto
Taranto is a coastal city in Apulia, Southern Italy. It is the capital of the Province of Taranto and is an important commercial port as well as the main Italian naval base....
, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
, Serbia
Serbia
Serbia , officially the Republic of Serbia , is a landlocked country located at the crossroads of Central and Southeast Europe, covering the southern part of the Carpathian basin and the central part of the Balkans...
, Montenegro
Montenegro
Montenegro Montenegrin: Crna Gora Црна Гора , meaning "Black Mountain") is a country located in Southeastern Europe. It has a coast on the Adriatic Sea to the south-west and is bordered by Croatia to the west, Bosnia and Herzegovina to the northwest, Serbia to the northeast and Albania to the...
(and the origin of the name tarantula
Tarantula
Tarantulas comprise a group of often hairy and often very large arachnids belonging to the family Theraphosidae, of which approximately 900 species have been identified. Some members of the same Suborder may also be called "tarantulas" in the common parlance. This article will restrict itself to...
, which today refers to a completely different kind of spider), was once blamed for a condition known as tarantism
Tarantism
Tarantism is an alleged, possibly deadly envenomation, popularly believed to result from the bite of a kind of wolf spider called a "tarantula"...
. Workers in the fields would suffer bites, and observe large, conspicuous, hairy spiders in the area. That spider, L. tarantula, was blamed for the pain and suffering (and occasional death) associated with tarantism. It is known that the bite of L. tarantula, while sometimes painful, has no serious medical consequences for humans. It is also suspected that the real culprit was another spider, Latrodectus tredecimguttatus
Latrodectus tredecimguttatus
Latrodectus tredecimguttatus, commonly known as the Mediterranean black widow or steppe spider, is a species of widow spiders in the genus Latrodectus. It is commonly found throughout the Mediterranean region, ranging from Spain to southwest and central Asia, hence the name...
, a type of widow spider
Widow spider
Latrodectus is a genus of spider, in the family Theridiidae, which contains 31 recognized species. The common name widow spiders is sometimes applied to members of the genus due to the behavior of the female of eating the male after mating, although sometimes the males of some species are not eaten...
, and one which is now known to be very dangerous to people.
White-tailed spiders
White-tailed spiderWhite-tailed spider
White-tailed spiders are medium-sized spiders native to southern and eastern Australia, and so named because of the whitish tips at the end of their abdomens. Common species are Lampona cylindrata and Lampona murina. Both these species have been introduced to New Zealand.White-tailed spiders are...
s (Lampona
Lampona
Lampona is a genus of spiders in the family Lamponidae and native to Australia and New Guinea. At least two species have a whitish tip to the abdomen and are known as white-tailed spiders. Both have been introduced to New Zealand...
spp.), indigenous to Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and present as an invasive pest in New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, have been blamed for a necrotic bite, producing symptoms similar to a brown recluse. However, a scientific study published in 2003 showed that their bites produce pain equivalent to a bee sting, a red mark, local swelling and itchiness; very occasionally nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
, vomiting
Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
, malaise
Malaise
Malaise is a feeling of general discomfort or uneasiness, of being "out of sorts", often the first indication of an infection or other disease. Malaise is often defined in medicinal research as a "general feeling of being unwell"...
or headache
Headache
A headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...
may occur. The study of 130 white-tailed spider bites found no necrotic ulcers or confirmed infections.
Harvestman
Opiliones
Opiliones are an order of arachnids commonly known as harvestmen. , over 6,400 species of harvestmen have been discovered worldwide, although the real number of extant species may exceed 10,000. The order Opiliones can be divided into four suborders: Cyphophthalmi, Eupnoi, Dyspnoi and Laniatores...
(also known as "harvestmen" or "daddy-long-legs"), are a species often handled by humans. They are the subject of an urban legend
Urban legend
An urban legend, urban myth, urban tale, or contemporary legend, is a form of modern folklore consisting of stories that may or may not have been believed by their tellers to be true...
which not only claims that Harvestmen are venomous, but are in fact more venomous than any of the spiders but are incapable of biting humans due to their lack of penetration. This is untrue on several counts. None of the known species have venom glands or fangs, instead having chelicerae
Chelicerae
The chelicerae are mouthparts of the Chelicerata, an arthropod subphylum that includes arachnids, Merostomata , and Pycnogonida . Chelicerae are pointed appendages which are used to grasp food, and are found in place of the chewing mandibles most other arthropods have...
. In addition, incidents of opiliones biting people are rare, and no reported bites by these species have had any lasting effects.
The term "daddy-long-legs" also can refer to the similar-looking cellar spider. This species (a true spider) can bite humans, but its venom is not known to have any effects beyond mild discomfort at the site of the bite.
Sun spiders
The arachnids of the order SolifugaeSolifugae
Solifugae are an order of Arachnida, known as camel spiders, wind scorpions and sun spiders or solifuges, comprising more than 1,000 described species in about 153 genera...
, also known as wind scorpions or sun spiders, are neither spiders nor scorpion
Scorpion
Scorpions are predatory arthropod animals of the order Scorpiones within the class Arachnida. They have eight legs and are easily recognized by the pair of grasping claws and the narrow, segmented tail, often carried in a characteristic forward curve over the back, ending with a venomous stinger...
s. In the Middle East
Middle East
The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...
, it is common belief among some American soldiers stationed there that Solifugae will feed on living human flesh. The story goes that the creature will inject some anesthetizing venom into the exposed skin of its sleeping victim, then feed voraciously, leaving the victim to awaken with a gaping wound. Solifugae, however, do not produce such an anesthetic, and do not attack prey larger than themselves unless threatened.
Further, Solifugae are known to not possess any venom (other than one species in India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, which may possess venom according to one study ). However, due to the large size of their jaws, bites by Solifugae can cause significant wounds, which should be treated accordingly to avoid infection.
External links
- Brazilian article reporting medical research
- Medical Journal of Australia article gives statistics on the most frequent biters and the most serious bites.
- Pictures and descriptions of spider bites from around the world.
- Richard S. Vetter and P. Kirk Visscher of the University of California at Riverside
- Spider bites are an overrated menace