Spider bites are skin injuries caused by the jaws and fangs of spiders. Despite the general perception that spiders are aggressive and dangerous, bites to humans are relatively uncommon<\/b> when compared to bites and stings by insects [R<\/a>, R<\/a>].<\/p>\n The majority of spider species are clinically irrelevant<\/b>, as they have the following traits: [R<\/a>]:<\/p>\n However, a few groups of species produce venom toxic to humans, the main ones being [R<\/a>, R<\/a>]:<\/p>\n Before treating a spider bite, the following procedure must be followed [R<\/a>]:<\/p>\n A meta-analysis of 134 medical spider bite case studies identified 32 different symptoms resulting from a bite. The most common symptoms out of all the species were [R<\/a>]:<\/p>\n The spiders most toxic to humans cause more specific syndromes from bites.<\/p>\n There are over 40 recognized widow spider (Latrodectus<\/i> spp<\/i>.) species distributed throughout Africa, the Americas, Southeast Asia, and Australasia [R<\/a>].<\/p>\n Widow spiders are small (3 to 10 mm body length) and dark grey or black, with a red or orange geometric pattern on the back that can resemble an hourglass. The female is darker, larger (up to 13 mm body length), and more venomous than the male [R<\/a>].<\/p>\n Red-back spider (<\/b>Latrodectus<\/i><\/b> hasselti<\/i><\/b>)<\/b><\/p>\n The venom of these species contains a toxin called \u03b1-latrotoxin<\/b>. This protein binds to receptors on the brain cells and causes a massive release of messenger molecules such as [R<\/a>, R<\/a>]:<\/p>\n The envenoming from widow spider bites is called latrodectism. <\/b>The main symptoms may vary depending on the species, but include [R<\/a>]:<\/p>\n In a study on 68 people bitten by this spider, 1\/3 developed non-specific, systemic symptoms including [R<\/a>]:<\/p>\n The average duration of the effects was 48 hours, with all cases resolved within a week [R<\/a>].<\/p>\n No deaths caused by widow spider bites have been reported since the 1950s. In some cases, the pain persisted after several days or weeks regardless of treatment with antivenom [R<\/a>, R<\/a>, R<\/a>].<\/p>\n In very rare cases, envenoming by widow spiders has caused rhabdomyolysis<\/b>, a condition in which damaged muscles break down rapidly [R<\/a>].<\/p>\n Comb-footed spiders (Steatoda<\/i> spp<\/i>.) belong to the same family as widow spiders (Theridiidae<\/i>). They are distributed throughout Australia, South Africa, the Americas, and Europe [R<\/a>].<\/p>\n Comb-footed spiders have a similar shape to widow spiders (and are sometimes mistaken for them), but their color is uniformly dark brown to black.<\/p>\n The male (4 to 10 mm body length) is almost as big as the female (6 to 10 mm body length) and equally capable of biting humans. Female bites are, however, more common [R<\/a>, R<\/a>].<\/p>\n False black widow (<\/b>Steatoda<\/i><\/b> grossa<\/i><\/b>)<\/b><\/p>\n The clinical syndrome caused by comb-footed spider venom is called steatodism<\/b>. A study of 23 bite cases demonstrated that its symptoms are similar to those of latrodectism, but milder and without local sweating. They included [R<\/a>, R<\/a>]:<\/p>\n The effects normally disappeared within 6 hours [R<\/a>].<\/p>\n Five bite cases by spiders from the genus Achaearanea<\/i><\/b> (also belonging to the Theridiidae <\/i>family) caused similar symptoms to those of the widow and comb-footed spiders. This suggests that the venoms of these three groups contain similar toxins [R<\/a>].<\/p>\n Most species of recluse spiders (Loxosceles<\/i> spp<\/i>.) are found in South America. Additionally, these spiders are in Europe, southern Africa, parts of Asia, the south of Australia, and the US (especially in the central South) [R<\/a>, R<\/a>, R<\/a>].<\/p>\n The main clinically relevant species are L<\/i>. laeta <\/i>(distributed throughout most of the South American continent), L<\/i>. intermedia <\/i>(found in Brazil and Argentina), and L<\/i>. gaucho <\/i>(restricted to Brazil) [R<\/a>].<\/p>\n These spiders are small (6 to 12 mm body length) and brown, with long legs (20 to 30 mm in length). Females are larger and more venomous than males [R<\/a>, R<\/a>].<\/p>\n Recluse spiders are nocturnal and prefer dry, dark places under rocks, wood, or tree barks. They often invade houses, where their flat body helps them hide in clothes, bed sheets, and cupboards [R<\/a>].<\/p>\n Brown recluse spider (<\/b>Loxosceles<\/i><\/b> reclusa<\/i><\/b>)<\/b><\/p>\n Their venom contains phospholipase-D <\/b>proteins and hyaluronidase <\/b>as key components, triggering the following reactions that lead to skin necrosis<\/b> [R<\/a>]:<\/p>\n After a painless bite, the symptoms of loxoscelism <\/b>take 12 to 24 hours to start developing and include [R<\/a>, R<\/a>]:<\/p>\n Progression of skin necrosis caused by a recluse spider bite. Pictures were taken at days: 1 (A), 9 (B), 16 (C), and 25 (D)<\/b> [R<\/a>].<\/p>\n In about 50% of the cases, systemic symptoms also occur within the first 48 hours. The most common ones are [R<\/a>]:<\/p>\n On rare occasions, normally involving L<\/i>. laeta<\/i>, the envenoming leads to more severe conditions like [R<\/a>, R<\/a>, R<\/a>, R<\/a>]:<\/p>\n Australian funnel-web spiders (Atrax<\/i> and Hadronyche spp<\/i>.) are the most venomous spiders in the world<\/b>. They are distributed throughout the east of Australia, with the most venomous species living between southern New Wales and southern Queensland [R<\/a>, R<\/a>].<\/p>\n Australian funnel-web spiders are medium to large (10 to 50 mm body length) spiders with prominent jaws and parallel fangs that live in logs, rocks, and leaf litter. They are nocturnal and very aggressive [R<\/a>].<\/p>\n Sydney funnel-web spider (<\/b>Atrax<\/i><\/b> robustus<\/i><\/b>)<\/b><\/p>\n Their venom contains \u03b4-atracotoxins<\/b>. These toxins target sodium channels on the surface of nerve cells and cause the excessive release and ultimate exhaustion of messenger molecules (such as hormones and neurotransmitters) [R<\/a>].<\/p>\n Severe envenoming (sometimes referred to as atraxism<\/b>) is rare, with only 5 to 10 cases per year (representing 10 to 75% of confirmed bites). It is considered an important medical condition because its effects are rapid and life-threatening. An effective antivenom is available [R<\/a>].<\/p>\n When envenoming does not occur, there are still prevalent effects from the bite, including: [R<\/a>]:<\/p>\n In some cases, the envenoming is only mild and causes the following systemic symptoms [R<\/a>]:<\/p>\n The most frequent symptoms of severe envenoming found in a study of 8 different cases were [R<\/a>]:<\/p>\n Severe envenoming is especially critical to children, who may die within 1 to 2 hours if left untreated [R<\/a>].<\/p>\n In untreated adults, severe envenoming may result in a progressive, irreversible decrease of blood pressure, profound coma, continuous muscle spasm, and eventual death [R<\/a>].<\/p>\n Mouse spiders (Missulena<\/i> spp<\/i>.) are distributed throughout mainland Australia and often mistaken for funnel-web spiders due to their similar appearance [R<\/a>].<\/p>\n Eastern mouse spider (<\/b>Missulena<\/i><\/b> bradleyi<\/i><\/b>)<\/b><\/p>\n Their venom is similar to that of funnel web spiders and is treated with the same antivenom. Despite the similarities in venom, these spiders are significantly less dangerous to humans [R<\/a>].<\/p>\n In a systematic review of 40 different confirmed bite cases, the effects were generally minor and included [R<\/a>]:<\/p>\n Severe envenoming similar to that caused by funnel-web spiders occurred in only one case. This affected a 19-month-old child who developed high blood pressure, muscle spasm, arched back, and unconsciousness. The child responded well to funnel-web spider antivenom [R<\/a>].<\/p>\n This group includes 5 different species (Phoneutria<\/i> spp<\/i>.) distributed throughout South America and Costa Rica [R<\/a>, R<\/a>].<\/p>\n Armed spiders are large (30 to 50 mm body length), solitary, nocturnal spiders that construct no web and catch their prey by active hunting during long wanders. They are sometimes transported in banana boxes (and thus commonly referred to as \u2018banana spiders\u2019), and occasionally enter houses [R<\/a>].<\/p>\n Their characteristic defensive behavior consists of raising 4 front legs, showing the fangs, bristling their leg spines, and rotating to continuously face the threat [R<\/a>].<\/p>\n Brazilian wandering spider (<\/b>Phoneutria<\/i><\/b> nigriventer<\/i><\/b>) in a defensive position<\/b><\/p>\n Armed spiders, especially Phoneutria nigriventer<\/i>, cause thousands of bites in Brazil every year, mainly during their mating season (March and April) [R<\/a>].<\/p>\n Their venom contains a mixture of proteins called phoneutriatoxins <\/b>that block ion channels on nerve cells, thus preventing both the transmission of nerve signals and the release of messenger molecules [R<\/a>].<\/p>\n In an observational study on 422 people bitten by armed spiders, 90% had mild envenoming. The most common symptoms were [R<\/a>]:<\/p>\n Systemic, less common effects included [R<\/a>]:<\/p>\n Severe envenoming occurs in less than 1% of cases and mostly affects children. It causes frequent vomiting and can lead to complications like [R<\/a>, R<\/a>]:<\/p>\n The target organisms of spiders are almost universally invertebrates. Human bites generally occur by accidental contact or when the spider is disturbed [R<\/a>].<\/p>\n Most widow spider bites<\/b> occur in and around dark, dry areas of the house when people put on clothing attire where a spider was hidden. The accidental compression of the spider between the fingers and external objects is another frequent cause of bite. In rural areas, widow spider bites are an occupational hazard of farm workers [R<\/a>, R<\/a>].<\/p>\n Recluse spiders <\/b>are not aggressive and bites are rare, even in heavily infested houses. They generally occur by accident when the female spider is trapped between human flesh and an object [R<\/a>, R<\/a>].<\/p>\n Most bites by Australian funnel-web spiders<\/b> occur when the highly venomous males (6-fold more than females) leave their burrows in search of females, which often brings them into houses [R<\/a>].<\/p>\n South American armed spiders<\/b> mostly bite when they feel threatened after being found in shoes, piles of sticks or rubbish, and construction material [R<\/a>].<\/p>\n Children are more prone to severe envenoming<\/b> by widow spiders and must be treated with antivenom up to 90 hours after the bite occurs [R<\/a>].<\/p>\n In pregnant women, the symptoms can include [R<\/a>]:<\/p>\n\n
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Symptoms of Spider Bites<\/b><\/span><\/h2>\n
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1) Widow Spiders<\/b><\/span><\/h3>\n
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2) Comb-Footed Spiders<\/b><\/span><\/h3>\n
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3) Recluse Spiders<\/b><\/span><\/h3>\n
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4) Australian Funnel-Web Spiders<\/b><\/span><\/h3>\n
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5) Mouse Spiders<\/b><\/span><\/h3>\n
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6) South American Armed Spiders<\/b><\/span><\/h3>\n
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Causes of Spider Bites<\/b><\/span><\/h2>\n
Risk Factors for Spider Bites<\/b><\/span><\/h2>\n
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