Spider bite - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Spider_bite Spider bite From Wikipedia, the free encyclopedia Spider bite, sometimes called arachnidism in technical literature, is injury resulting from the bites of spiders. It is an unusual class of injury and the effects of most confirmed spider bites are trivial, Venomous spiders even though nearly all species of spider are venomous. For all practical purposes arachnidism is Classification and external resources substantial envenomation by a spider bite, their bites otherwise being medically insignificant. Depending on the species of spider and the victim, arachnidism will have various effects, ranging from going practically unnoticed, through transient pain, to gangrene, or fatal neurotoxicity.[1]:455 Bites from the widow spiders (genus Latrodectus) produce a special class of arachnidism, a neurotoxic condition known as Latrodectism,[2] Similarly, bites from the recluse spiders (genus Loxosceles) cause the condition called Loxoscelism, which has become particularly notorious in recent decades as the predominant cause of "necrotic arachnidism", in which necrosis of the surrounding tissue is the major concern.[3][4] Another medical condition that has historically been claimed to arise from spider bites is Tarantism, but there is no substantial evidence for the existence of this supposed condition. Chelicerae of a black wishbone (nemesiid) spider, a mygalomorph. ICD-10 T14.1 (http://apps.who.int Contents /classifications/icd10/browse /2010/en#/T14.1) · T63.3 1 General considerations (http://apps.who.int/classifications 2 Signs and symptoms /icd10/browse/2010/en#/T63.3) 3 Pathophysiology W57 (nonvenomous) 3.1 Neurotoxic venom X21 (venomous) 3.2 Necrotic venom ICD-9 989.5 (http://www.icd9data.com 3.3 Comparative analysis 3.3.1 Measurements /getICD9Code.ashx?icd9=989.5) · 4 Diagnosis E905.1 (http://www.icd9data.com 5 Management /getICD9Code.ashx?icd9=E905.1) · 5.1 Necrosis E906.4 (http://www.icd9data.com 5.2 Other /getICD9Code.ashx?icd9=E906.4) 6 Epidemiology 1 of 25 4/27/2014 12:03 PM Spider bite - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Spider_bite 6.1 Australia DiseasesDB 12299 6.2 United States (http://www.diseasesdatabase.com 7 Classification /ddb12299.htm) 7.1 Brazilian wandering spiders MedlinePlus 002858 (http://www.nlm.nih.gov 7.2 Australian funnel-web spiders /medlineplus/ency/article 7.3 Tangle-web spiders 7.3.1 Widow spiders /002858.htm) 7.3.2 False black widows eMedicine article/772484 7.4 Sicariidae spiders (http://emedicine.medscape.com 7.4.1 Six-eyed sand spiders /article/772484-overview) 7.4.2 Recluse spiders 7.5 Mouse spiders 7.6 Tarantulas 7.6.1 New-world tarantulas 7.6.2 Old-world tarantulas 7.7 Yellow Sac spiders 7.8 Others 7.8.1 Hobo spiders 7.8.2 Lycosa tarantula 7.8.3 White-tailed spiders 7.8.4 Harvestman 7.8.5 Sun spiders 8 Historical remedies 9 See also 10 References 11 External links General considerations Spiders are predators and most species rely largely on their bites to subdue and kill their prey before consuming it. With the exception of web-building spiders that may feed on almost any creature that their webs can immobilise, spiders do not generally attack animals larger than themselves. However, some species also may bite in self-defense. Some in particular — e.g., Atrax robustus — will stand their ground when approached by larger animals, and will adopt an aggressive stance. Still, nearly all spider bites occur when humans unintentionally press up against spiders and receive a defensive bite. 2 of 25 4/27/2014 12:03 PM Spider bite - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Spider_bite Only two spider families, Uloboridae and Holarchaeidae, are known to be non-venomous, i.e., lacking venom glands, but only spiders of fairly large species possess chelicera long enough to penetrate human skin, and most (though by no means all) spiders that are large enough to bite humans effectively are mature females. Apart from the size and effectiveness of the venom-delivery organs, the toxicity and the quantity of the venom are the main factors determining the harm that the bite is likely to cause. Spiders regarded as dangerous possess venom that is sufficiently toxic to humans that a single bite can deliver a medically significant dose. The vast majority of bites by species large enough for their bites to be noticeable will have no serious medical consequences.[5] In various combinations and concentrations, medically significant spider venoms include necrotic agents, neurotoxins, and pharmacologically active compounds such as serotonin. Out of over 40,000 known species of spider only some two hundred species in twenty genera are known to have medically significant bites, a few of them of them potentially lethal.[6] In most cases of bites, the chief concern is the spider's venom, although in some cases medically non-significant spiders can transmit infectious diseases or serious non-contagious infections. Spider bites commonly are misdiagnosed by both the general public and medical practitioners. Many other conditions, both infectious and non-infectious can be confused with spider bites.[7] Many of these conditions are far more common and more likely to be the source of necrotic wounds.[8] 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.[9] The rate of a bacterial infection due to a spider bite is low (0.9%).[9] Pathophysiology A primary concern of the bite of a spider is the effect of its venom. A spider envenomation occurs whenever a spider injects venom 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. 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 may be a concern However, it is generally the toxicity of spider venom that poses the most risk to human beings; several spiders are known to have venom that can cause injury to humans in the amounts that a spider will typically inject when biting. A Brazilian man 31 hours after having been bitten on his face by a All spiders are capable of producing venom, with the exception of the hackled orb-weavers, the Holarchaeidae, Loxosceles spider. and the primitive Mesothelae. (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 3 of 25 4/27/2014 12:03 PM Spider bite - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Spider_bite 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, fatalities are exceedingly rare. (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 4 months after a brown recluse spider bite with scar remaining The majority of spiders with serious bites possess a neurotoxic venom of some sort, though the specific manner in which the nervous system is attacked varies from spider to spider.[10][11][12] Widow spider venom contains components known as latrotoxins, which cause the release of the neurotransmitter acetylcholine, stimulating muscle contractions. This can affect the body in several ways, including causing painful abdominal cramps, as well as interfering with respiration, and causing other systemic effects.[6] The venom of Australian funnel-web spiders and mouse spiders works by opening sodium channels, causing excessive neural activity which interferes with normal bodily function. The venom of Brazilian wandering spiders is also a potent neurotoxin, which attacks multiple types of ion channels [13] In addition, the venom contains high levels of serotonin, making an envenomation by this species particularly painful. Necrotic venom Spiders known to have necrotic venom occur most notoriously in the family Sicariidae, which includes both the recluse spiders and the six-eyed sand spiders. Spiders in this family possess a known dermonecrotic agent sphingomyelinase D,[14][15] which is otherwise found only in a few pathogenic bacteria.[16][17] Some species in this family are more venomous than others; according to one study, the venom of the Chilean recluse and several species of six-eyed sand spider indigenous to southern Africa, contains an order of magnitude more of this substance than do other sicariid spiders such as the brown recluse.[18] 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, and in some cases, death.[19] 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 scars. The damaged tissue may become gangrenous 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.[20] 4 of 25 4/27/2014 12:03 PM Spider bite - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Spider_bite Systemic effects are unusual but include Mild symptoms such nausea, vomiting, fever, rashes, and muscle and joint pain.