Brown recluse spider
Encyclopedia
The brown recluse spider or violin spider, Loxosceles reclusa, is a member of the family Sicariidae
(formerly placed in a family "Loxoscelidae"). The spider has a venomous
bite.
Brown recluse spiders are usually between 6–20 mm ( in and in), but may grow larger. While typically light to medium brown, they range in color from cream-colored to dark brown or blackish gray. The cephalothorax
and abdomen may not necessarily be the same color. These spiders usually have markings on the dorsal
side of their cephalothorax, with a black line coming from it that looks like a violin
with the neck of the violin pointing to the rear of the spider, resulting in the nicknames fiddleback spider, brown fiddler or violin spider.
s), for more assurance in identification it is imperative to examine the eyes. Most spiders have eight eyes; recluse spiders have six eyes arranged in pairs (dyad
s) with one median
pair and two lateral pairs. Only a few other spiders have three pairs of eyes arranged in this way (e.g., scytodids). Recluses have no obvious coloration patterns on the abdomen or legs, and the legs lack spines. The abdomen is covered with fine short hairs that (viewed without magnification) give it the appearance of soft fur. The leg joints may appear to be a slightly lighter color.
ranging from central Texas
to west-central South Carolina
, Southern/Western Virginia, and the domestic variety lives in the lower reaches of the Midwest, and has been introduced to eastern Georgia
through the piedmont of western South Carolina
. They frequently build their webs in woodpiles and sheds, closets, garages, plenum
, cellars and other places that are dry and generally undisturbed. When dwelling in human residences they seem to favor cardboard, possibly because it mimics the rotting tree bark which they inhabit naturally. They have also been encountered in shoes, inside dressers, in bed sheets of infrequently used beds, in clothes stacked or piled or left lying on the floor, inside work gloves, behind baseboards and pictures, in toilets, and near sources of warmth when ambient temperatures are lower than usual. Human-recluse contact often occurs when such isolated spaces are disturbed and the spider feels threatened. Unlike most web weavers, they leave these lairs at night to hunt. Males move around more when hunting than do females, which tend to remain nearer to their webs.
through southern Iowa
, Illinois
, and Indiana
to southwestern Ohio
. In the southern states, it is native from central Texas
to west-central South Carolina
and north to Kentucky
.
Despite rumors to the contrary, the brown recluse spider has not established itself in California
or anywhere outside its native range. Occasional spiders have been intercepted in various states where they have no known established populations; these spiders may be transported fairly easily, though the lack of established populations well outside the natural range also indicates that such movement has not led to colonization of new areas.
There are other species of the genus Loxosceles native to the southwestern part of the United States, including California, that may resemble the brown recluse, but these species have never been documented as medically significant. The number of "false positive" reports based on misidentifications is considerable; in a nationwide study where people submitted spiders that they thought were brown recluses, of 581 from California only 1 was a brown recluse—submitted by a family that moved from Missouri and brought it with them (compared to specimens submitted from Missouri, Kansas, and Oklahoma, where between 75% and 90% were recluses). From this study, the most common spider submitted from California as a brown recluse was in the genus Titiotus, whose bite is deemed harmless. A similar study documented that various arachnids were routinely misidentified by physicians, pest control operators, and other non-expert authorities, who told their patients or clients that the spider they had was a brown recluse when in fact it was not. Despite the absence of brown recluses from the Western U.S., physicians in the region commonly diagnose "brown recluse bites", leading to the popular misperception that the spiders occur there.
The initial brown recluse bite frequently is not felt and may not be immediately painful, yet such a bite can be serious. However, the fangs of the brown recluse are so tiny they are unable to penetrate most fabric, including socks.
The brown recluse bears a potentially deadly hemotoxic
venom. Most bites are minor with no necrosis
. However, a small number of clinically-diagnosed brown recluse bites do produce severe dermonecrotic lesions (i.e., necrosis); an even smaller number of clinically-diagnosed brown recluse bites produce severe cutaneous (skin) or viscerocutaneous (systemic) symptoms. In one study of clinically-diagnosed brown recluse bites, the incidence of skin necrosis was 37% and the incidence of systemic illness was 14%. In these instances the bites produced a range of symptoms common to many members of the Loxosceles genus known as loxoscelism
, which may be cutaneous (skin) and viscerocutaneous (systemic). In very rare cases, bites can even cause hemolysis
(causes red blood cells to burst).
Most brown recluse spiders' bites do not result in necrosis, let alone systemic effects. When both types of loxoscelism do result, systemic effects may occur before necrosis, as the venom spreads throughout the body in minutes. Debilitated patients, the elderly, and children may be more susceptible to systemic loxoscelism. The systemic symptoms that are most commonly experienced as the result of a brown recluse bite include nausea
, vomiting
, fever
, rash
es, and muscle and joint pain. Rarely, such bites can result in hemolysis
, thrombocytopenia
, disseminated intravascular coagulation
, organ damage, and even death. Most fatalities are children under the age of seven or those with a weaker-than-normal immune system.
While it is important to note that the majority of brown recluse spider bites do not result in any symptoms, cutaneous
symptoms occur as a result of such bites more frequently than systemic symptoms. In such instances, the bite forms a necrotizing ulcer that destroys soft tissue
and may take months to heal, leaving deep scar
s. These bites usually become painful and itchy within 2 to 8 hours, pain and other local effects worsen 12 to 36 hours after the bite, and the necrosis develops over the next few days. Over time, the wound may grow to as large as 25 cm (10 inches) in extreme cases. The damaged tissue becomes gangrenous
and eventually sloughs away.
-based test for brown recluse venom that can determine whether a wound is a brown recluse bite, although it is not commercially available and not in routine clinical use; clinical diagnoses often use Occam's razor principle
in diagnosing bites based on what spiders the patient likely encountered and what previous diagnoses are similar.
There are numerous documented infectious and noninfectious conditions (including pyoderma gangrenosum
, bacterial infections by Staphylococcus
and Streptococcus
, herpes, diabetic ulcer, fungal infections, chemical burns, toxicodendron dermatitis
, squamous cell carcinoma
, localized vasculitis
, syphilis
, toxic epidermal necrolysis
, sporotrichosis
, and Lyme disease
) that produce wounds that have been initially misdiagnosed as recluse bites by medical professionals; many of these conditions are far more common and more likely to be the source of mysterious necrotic wounds, even in areas where recluses actually occur. The most important of these is methicillin-resistant Staphylococcus aureus
("MRSA"), a bacterium whose necrotic lesions are very similar to those induced by recluse bites, and which can be lethal if left untreated; misdiagnoses of MRSA as "spider bites" are extremely common (nearly 30% of patients later documented to have MRSA initially reported that they suspected a spider bite), and can have fatal consequences. In addition, published work has shown that tick
-induced Lyme disease
rashes are often misidentified as brown recluse spider bites.
Reported cases of bites occur primarily in Arkansas
, Colorado
, Kansas
, Missouri
, Nebraska
, Oklahoma
South Carolina
,and Texas
. There have been many reports of brown recluse bites in California
(though a few related species may be found there and elsewhere outside the range of the brown recluse, none of these are known to bite humans). To date the reports of bites from areas outside of the spider's native range have been either unverified, or—if verified—the spiders have been moved to those locations by travelers or commerce. Many arachnologists believe that many bites attributed to the brown recluse in the West Coast
are not spider bites at all or possibly the bites of other spider species. For example, the bite of the hobo spider
has been reported to produce similar symptoms, and is found in the northwestern United States
and southern British Columbia
. However, the toxicity of hobo spider venom has been called into question as bites have not been proven to cause necrosis, and this spider is not considered a problem in Europe
.
Numerous other spiders have been associated with necrotic bites in medical literature
. Other recluse species, such as the desert recluse (found in the desert southwestern United States), are reported to have caused necrotic bite wounds, though only rarely. Other spiders that have been reported to cause necrotic bites include the hobo spider
and the yellow sac spider
s. 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 the danger 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. (For a comparison of the toxicity of several kinds of spider bites, see the list of spiders having medically significant venom.)
, the application of aloe vera
to soothe and help control the pain, and prompt medical care. If it can be easily captured, the spider should be brought with the patient in a clear, tightly closed container so it may be identified.
Routine treatment should 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
, antihistamines (e.g., cyproheptadine
), antibiotics, dextran
, glucocorticoids, vasodilators, heparin
, nitroglycerin, electric shock
, curettage
, surgical excision
, and antivenom. None of these treatments have been subjected to randomized controlled trial
s to conclusively show benefit. In almost all cases, bites are self-limited and typically heal without any medical intervention.
Cases of brown recluse venom traveling along a limb through a vein or artery are rare, but the resulting tissue mortification can affect an area as large as several inches and in extreme cases require excising of the wound.
is often used effectively for the treatment of necrosis, but controlled clinical trials do not demonstrate similar effectiveness; however, dapsone may be effective at treating many "spider bites" because many such cases are actually misdiagnosed microbial infections. There have been conflicting reports about its efficacy and some have suggested it should no longer be used routinely, if at all.A home remedy is cutting a potato in half and taping to the wound for a few hours.
Wound infection is rare. Antibiotics are not recommended unless there is a credible diagnosis of infection.
Studies have shown surgical intervention is ineffective and may worsen outcome. Excision may delay wound healing, cause abscesses, and lead to objectionable scarring.
Anecdotal evidence
suggests benefit can be gained with the application of nitroglycerin patches. Brown recluse venom is a vasoconstrictor, and nitroglycerin causes vasodilation
that allows the venom to be diluted into the bloodstream and fresh blood to flow to the wound. Theoretically this prevents necrosis, as vasoconstriction may contribute to necrosis. However, one scientific animal study found no benefit in preventing necrosis, with the study's results showing it increased inflammation and caused symptoms of systemic envenoming. The authors concluded the results of the study did not support the use of topical nitroglycerin in brown recluse envenoming.
Antivenom, available in South America for the venom of other species of recluse spiders, appears to be the most promising therapy. However, antivenoms are most effective if given early. Because of the often painless bite patients do not often present symptoms until 24 or more hours after the event of a brown recluse bite, possibly limiting the effect of this intervention.
for several seasons with no food or water and to survive after losing limbs. Additionally, the spiders survive significantly longer in a relatively cool, thermally stable environment.
The increased abilities of the spiders to survive during times of starvation, thirst, and regulated room temperatures makes extermination of this species particularly challenging. Many chemicals which have proven effective have now been made illegal or restricted in the U.S., making the use of chemicals to eradicate the spiders impractical. Chemicals that do not kill the spider may cause disruption to its nervous system or other systems, inducing undesirable aggressive behavior.
Sicariidae
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...
(formerly placed in a family "Loxoscelidae"). The spider has a venomous
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...
bite.
Brown recluse spiders are usually between 6–20 mm ( in and in), but may grow larger. While typically light to medium brown, they range in color from cream-colored to dark brown or blackish gray. The cephalothorax
Cephalothorax
The cephalothorax is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. The word cephalothorax is derived from the Greek words for head and thorax...
and abdomen may not necessarily be the same color. These spiders usually have markings on the dorsal
Dorsum (biology)
In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...
side of their cephalothorax, with a black line coming from it that looks like a violin
Violin
The violin is a string instrument, usually with four strings tuned in perfect fifths. It is the smallest, highest-pitched member of the violin family of string instruments, which includes the viola and cello....
with the neck of the violin pointing to the rear of the spider, resulting in the nicknames fiddleback spider, brown fiddler or violin spider.
Description
Since the violin pattern is not diagnostic, and other spiders may have similar markings (such as cellar spiders and pirate spiderPirate spider
The family Mimetidae, commonly called pirate spiders, are spiders which typically feed on other spiders.The family Mimetidae contains roughly 200 species divided among 12 genera, of which Mimetus and Ero are the most common. Mimetids are usually yellow and brown and are usually 3 to 7 mm long...
s), for more assurance in identification it is imperative to examine the eyes. Most spiders have eight eyes; recluse spiders have six eyes arranged in pairs (dyad
Dyad
Dyad may refer to:*Dyad , a pair of sister chromatids occurring in prophase I of meiosis; may also be used to describe protein morphology*Dyad , Greek philosophers' principle of "twoness" or "otherness"...
s) with one median
Median
In probability theory and statistics, a median is described as the numerical value separating the higher half of a sample, a population, or a probability distribution, from the lower half. The median of a finite list of numbers can be found by arranging all the observations from lowest value to...
pair and two lateral pairs. Only a few other spiders have three pairs of eyes arranged in this way (e.g., scytodids). Recluses have no obvious coloration patterns on the abdomen or legs, and the legs lack spines. The abdomen is covered with fine short hairs that (viewed without magnification) give it the appearance of soft fur. The leg joints may appear to be a slightly lighter color.
Life-cycle
Adult brown recluse spiders often live about one to two years. Each female produces several egg sacs over a period of two to three months, from May to July, with approximately 50 eggs in each sac. The eggs hatch in about one month. The spiderlings take about one year to grow to adulthood. The brown recluse spider is resilient, and can tolerate up to 6 months of extreme drought and scarcity or absence of food, most notably observed on one occasion to survive in controlled captivity for over five seasons without food.Behavior
A brown recluse's stance on a flat surface is usually with all legs radially extended. When alarmed it may lower its body, withdraw the forward two legs straight rearward into a defensive position, withdraw the rearmost pair of legs into a position for lunging forward, and stand motionless with pedipalps raised. The pedipalps in mature specimens are dark, quite prominent, and are normally held horizontally forward. When threatened it usually flees, seemingly to avoid a conflict, and if detained may further avoid contact with quick horizontal rotating movements. The spider does not usually jump unless touched brusquely, and even then its avoidance movement is more of a horizontal lunge rather than a vaulting of itself entirely off the surface. When running the brown recluse does not appear to leave a silk line behind, which at any rate might make it more easily tracked when it is being pursued. Movement at virtually any speed is an evenly paced gait with legs extended. When missing a leg or two it appears to favor this same gait, although (presumably when a leg has been injured) it may move and stand at rest with one leg slightly withdrawn. During travel it stops naturally and periodically when renewing its internal hydraulic blood pressure that, like most spiders, it requires to renew strength in the legs.Habitat
Recluse spiders build irregular webs that frequently include a shelter consisting of disorderly threads. The wild variety lives in the Southern United StatesSouthern United States
The Southern United States—commonly referred to as the American South, Dixie, or simply the South—constitutes a large distinctive area in the southeastern and south-central United States...
ranging from central Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
to west-central South Carolina
South Carolina
South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...
, Southern/Western Virginia, and the domestic variety lives in the lower reaches of the Midwest, and has been introduced to eastern Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...
through the piedmont of western South Carolina
South Carolina
South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...
. They frequently build their webs in woodpiles and sheds, closets, garages, plenum
Plenum
Plenum may refer to:* Plenum chamber, a chamber intended to contain air, gas, or liquid at positive pressure* Plenism, or Horror vacui...
, cellars and other places that are dry and generally undisturbed. When dwelling in human residences they seem to favor cardboard, possibly because it mimics the rotting tree bark which they inhabit naturally. They have also been encountered in shoes, inside dressers, in bed sheets of infrequently used beds, in clothes stacked or piled or left lying on the floor, inside work gloves, behind baseboards and pictures, in toilets, and near sources of warmth when ambient temperatures are lower than usual. Human-recluse contact often occurs when such isolated spaces are disturbed and the spider feels threatened. Unlike most web weavers, they leave these lairs at night to hunt. Males move around more when hunting than do females, which tend to remain nearer to their webs.
Distribution
The brown recluse spider is native to the United States from the southern Midwest south to the Gulf of Mexico. The native range lies roughly south of a line from southeastern NebraskaNebraska
Nebraska is a state on the Great Plains of the Midwestern United States. The state's capital is Lincoln and its largest city is Omaha, on the Missouri River....
through southern Iowa
Iowa
Iowa is a state located in the Midwestern United States, an area often referred to as the "American Heartland". It derives its name from the Ioway people, one of the many American Indian tribes that occupied the state at the time of European exploration. Iowa was a part of the French colony of New...
, Illinois
Illinois
Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...
, and Indiana
Indiana
Indiana is a US state, admitted to the United States as the 19th on December 11, 1816. It is located in the Midwestern United States and Great Lakes Region. With 6,483,802 residents, the state is ranked 15th in population and 16th in population density. Indiana is ranked 38th in land area and is...
to southwestern Ohio
Ohio
Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...
. In the southern states, it is native from central Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
to west-central South Carolina
South Carolina
South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...
and north to Kentucky
Kentucky
The Commonwealth of Kentucky is a state located in the East Central United States of America. As classified by the United States Census Bureau, Kentucky is a Southern state, more specifically in the East South Central region. Kentucky is one of four U.S. states constituted as a commonwealth...
.
Despite rumors to the contrary, the brown recluse spider has not established itself in 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...
or anywhere outside its native range. Occasional spiders have been intercepted in various states where they have no known established populations; these spiders may be transported fairly easily, though the lack of established populations well outside the natural range also indicates that such movement has not led to colonization of new areas.
There are other species of the genus Loxosceles native to the southwestern part of the United States, including California, that may resemble the brown recluse, but these species have never been documented as medically significant. The number of "false positive" reports based on misidentifications is considerable; in a nationwide study where people submitted spiders that they thought were brown recluses, of 581 from California only 1 was a brown recluse—submitted by a family that moved from Missouri and brought it with them (compared to specimens submitted from Missouri, Kansas, and Oklahoma, where between 75% and 90% were recluses). From this study, the most common spider submitted from California as a brown recluse was in the genus Titiotus, whose bite is deemed harmless. A similar study documented that various arachnids were routinely misidentified by physicians, pest control operators, and other non-expert authorities, who told their patients or clients that the spider they had was a brown recluse when in fact it was not. Despite the absence of brown recluses from the Western U.S., physicians in the region commonly diagnose "brown recluse bites", leading to the popular misperception that the spiders occur there.
Bite
As suggested by its specific epithet reclusa ("recluse"), the brown recluse spider is rarely aggressive, and actual bites from the species are uncommon. In 2001, more than 2,000 brown recluse spiders were removed from a heavily infested home in Kansas, yet the four residents who had lived there for years were never harmed by the spiders, despite many encounters with them. The spider usually bites only when pressed against the skin, such as when tangled up within clothes, towels, bedding, inside work gloves, etc. Many human victims of brown recluse bites report having been bitten after putting on clothes that had not recently been worn or had been left for many days undisturbed on the floor.The initial brown recluse bite frequently is not felt and may not be immediately painful, yet such a bite can be serious. However, the fangs of the brown recluse are so tiny they are unable to penetrate most fabric, including socks.
The brown recluse bears a potentially deadly hemotoxic
Hemotoxin
Hemotoxins, haemotoxins or hematotoxins are toxins that destroy red blood cells , disrupt blood clotting, and/or cause organ degeneration and generalized tissue damage. The term hemotoxin is to some degree a misnomer since toxins that damage the blood also damage other tissues...
venom. Most bites are minor with 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 clinically-diagnosed brown recluse bites do produce severe dermonecrotic lesions (i.e., necrosis); an even smaller number of clinically-diagnosed brown recluse bites produce severe cutaneous (skin) or viscerocutaneous (systemic) symptoms. In one study of clinically-diagnosed brown recluse bites, the incidence of skin necrosis was 37% and the incidence of systemic illness was 14%. In these instances the bites produced a range of symptoms common to many members of the Loxosceles genus known as 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...
, which may be cutaneous (skin) and viscerocutaneous (systemic). In very rare cases, bites can even cause 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...
(causes red blood cells to burst).
Most brown recluse spiders' bites do not result in necrosis, let alone systemic effects. When both types of loxoscelism do result, systemic effects may occur before necrosis, as the venom spreads throughout the body in minutes. Debilitated patients, the elderly, and children may be more susceptible to systemic loxoscelism. The systemic symptoms that are most commonly experienced as the result of a brown recluse bite 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, such bites can result in 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...
, 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...
, organ damage, and even death. Most fatalities are children under the age of seven or those with a weaker-than-normal immune system.
While it is important to note that the majority of brown recluse spider bites do not result in any symptoms, cutaneous
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
symptoms occur as a result of such bites more frequently than systemic symptoms. In such instances, the bite forms a necrotizing ulcer that destroys soft tissue
Soft tissue
In anatomy, the term soft tissue refers to tissues that connect, support, or surround other structures and organs of the body, not being bone. Soft tissue includes tendons, ligaments, fascia, skin, fibrous tissues, fat, and synovial membranes , and muscles, nerves and blood vessels .It is sometimes...
and may take months 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. These bites usually become painful and itchy within 2 to 8 hours, pain and other local effects worsen 12 to 36 hours after the bite, and the necrosis develops over the next few days. Over time, the wound may grow to as large as 25 cm (10 inches) in extreme cases. The damaged tissue becomes 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 sloughs away.
Validity of necrosis claims
It is estimated that 80% of reported brown recluse bites may be misdiagnosed. The misdiagnosis of a wound as a brown recluse bite could delay proper treatment of serious diseases. There is now an ELISAELISA
Enzyme-linked immunosorbent assay , is a popular format of a "wet-lab" type analytic biochemistry assay that uses one sub-type of heterogeneous, solid-phase enzyme immunoassay to detect the presence of a substance in a liquid sample."Wet lab" analytic biochemistry assays involves detection of an...
-based test for brown recluse venom that can determine whether a wound is a brown recluse bite, although it is not commercially available and not in routine clinical use; clinical diagnoses often use Occam's razor principle
Occam's razor
Occam's razor, also known as Ockham's razor, and sometimes expressed in Latin as lex parsimoniae , is a principle that generally recommends from among competing hypotheses selecting the one that makes the fewest new assumptions.-Overview:The principle is often summarized as "simpler explanations...
in diagnosing bites based on what spiders the patient likely encountered and what previous diagnoses are similar.
There are numerous documented infectious and noninfectious conditions (including pyoderma gangrenosum
Pyoderma gangrenosum
Pyoderma gangrenosum is a disease that causes tissue to become necrotic, causing deep ulcers that usually occur on the legs. When they occur, they can lead to chronic wounds. Ulcers usually initially look like small bug bites or papules, and they progress to larger ulcers. Though the wounds...
, bacterial infections by Staphylococcus
Staphylococcus
Staphylococcus is a genus of Gram-positive bacteria. Under the microscope they appear round , and form in grape-like clusters....
and Streptococcus
Streptococcus
Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...
, herpes, diabetic ulcer, fungal infections, chemical burns, toxicodendron dermatitis
Urushiol-induced contact dermatitis
Urushiol-induced contact dermatitis is the medical name given to allergic rashes produced by the oil urushiol, which is contained in various plants, including the plants of the genus Toxicodendron , other plants in the family Anacardiaceae Urushiol-induced contact dermatitis (also called...
, squamous cell carcinoma
Squamous cell carcinoma
Squamous cell carcinoma , occasionally rendered as "squamous-cell carcinoma", is a histologically distinct form of cancer. It arises from the uncontrolled multiplication of malignant cells deriving from epithelium, or showing particular cytological or tissue architectural characteristics of...
, localized vasculitis
Vasculitis
Vasculitis refers to a heterogeneous group of disorders that are characterized by inflammatory destruction of blood vessels. Both arteries and veins are affected. Lymphangitis is sometimes considered a type of vasculitis...
, syphilis
Syphilis
Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...
, toxic epidermal necrolysis
Toxic epidermal necrolysis
Toxic epidermal necrolysis is a rare, life-threatening dermatological condition that is usually induced by a reaction to medications...
, sporotrichosis
Sporotrichosis
Sporotrichosis is a disease caused by the infection of the fungus Sporothrix schenckii. This fungal disease usually affects the skin, although other rare forms can affect the lungs, joints, bones, and even the brain...
, and Lyme disease
Lyme disease
Lyme disease, or Lyme borreliosis, is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia. Borrelia burgdorferi sensu stricto is the main cause of Lyme disease in the United States, whereas Borrelia afzelii and Borrelia garinii cause most...
) that produce wounds that have been initially misdiagnosed as recluse bites by medical professionals; many of these conditions are far more common and more likely to be the source of mysterious necrotic wounds, even in areas where recluses actually occur. The most important of these is 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"), a bacterium whose necrotic lesions are very similar to those induced by recluse bites, and which can be lethal if left untreated; misdiagnoses of MRSA as "spider bites" are extremely common (nearly 30% of patients later documented to have MRSA initially reported that they suspected a spider bite), and can have fatal consequences. In addition, published work has shown that tick
Tick
Ticks are small arachnids in the order Ixodida, along with mites, constitute the subclass Acarina. Ticks are ectoparasites , living by hematophagy on the blood of mammals, birds, and sometimes reptiles and amphibians...
-induced Lyme disease
Lyme disease
Lyme disease, or Lyme borreliosis, is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia. Borrelia burgdorferi sensu stricto is the main cause of Lyme disease in the United States, whereas Borrelia afzelii and Borrelia garinii cause most...
rashes are often misidentified as brown recluse spider bites.
Reported cases of bites occur primarily in Arkansas
Arkansas
Arkansas is a state located in the southern region of the United States. Its name is an Algonquian name of the Quapaw Indians. Arkansas shares borders with six states , and its eastern border is largely defined by the Mississippi River...
, Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
, Kansas
Kansas
Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...
, Missouri
Missouri
Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...
, Nebraska
Nebraska
Nebraska is a state on the Great Plains of the Midwestern United States. The state's capital is Lincoln and its largest city is Omaha, on the Missouri River....
, Oklahoma
Oklahoma
Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...
South Carolina
South Carolina
South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...
,and Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
. There have been many reports of brown recluse bites in 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...
(though a few related species may be found there and elsewhere outside the range of the brown recluse, none of these are known to bite humans). To date the reports of bites from areas outside of the spider's native range have been either unverified, or—if verified—the spiders have been moved to those locations by travelers or commerce. Many arachnologists believe that many bites attributed to the brown recluse in the West Coast
West Coast of the United States
West Coast or Pacific Coast are terms for the westernmost coastal states of the United States. The term most often refers to the states of California, Oregon, and Washington. Although not part of the contiguous United States, Alaska and Hawaii do border the Pacific Ocean but can't be included in...
are not spider bites at all or possibly the bites of other spider species. For example, the bite of 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...
has been reported to produce similar symptoms, and is found in the northwestern United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and southern British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
. However, the toxicity of hobo spider venom has been called into question as bites have not been proven to cause necrosis, and this spider is not considered a problem in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
.
Numerous other spiders have been associated with necrotic bites in medical literature
Medical literature
Medical literature refers to articles in journals and texts in books devoted to the field of medicine.Contemporary and historic views regarding diagnosis, prognosis and treatment of medical conditions have been documented for thousands of years. The Edwin Smith papyrus is the first known medical...
. Other recluse species, such as the desert recluse (found in the desert southwestern United States), are reported to have caused necrotic bite wounds, though only rarely. Other spiders that have been reported to cause necrotic bites 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
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...
s. 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
Arachnology
Arachnology is the scientific study of spiders and related animals such as scorpions, pseudoscorpions, harvestmen, collectively called arachnids. However, the study of ticks and mites is sometimes not included in arachnology, but is called Acarology...
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 the danger 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. (For a comparison of the toxicity of several kinds of spider bites, see the list of spiders having medically significant venom.)
Bite treatment
First aid involves the application of an ice pack to control inflammationInflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
, the application of aloe vera
Aloe vera
Aloe vera, pronounced , also known as the true aloe or medicinal aloe, is a species of succulent plant in the genus Aloe that is believed to have originated in the Sudan. Aloe vera grows in arid climates and is widely distributed in Africa, India, Nepal and other arid areas.The species is...
to soothe and help control the pain, and prompt medical care. If it can be easily captured, the spider should be brought with the patient in a clear, tightly closed container so it may be identified.
Routine treatment should 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 randomized controlled trial
Randomized controlled trial
A randomized controlled trial is a type of scientific experiment - a form of clinical trial - most commonly used in testing the safety and efficacy or effectiveness of healthcare services or health technologies A randomized controlled trial (RCT) is a type of scientific experiment - a form of...
s to conclusively show benefit. In almost all cases, bites are self-limited and typically heal without any medical intervention.
Cases of brown recluse venom traveling along a limb through a vein or artery are rare, but the resulting tissue mortification can affect an area as large as several inches and in extreme cases require excising of the wound.
Specific treatments
In presumed cases of recluse bites, dapsoneDapsone
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 often used effectively for the treatment of necrosis, but controlled clinical trials do not demonstrate similar effectiveness; however, dapsone may be effective at treating many "spider bites" because many such cases are actually misdiagnosed microbial infections. There have been conflicting reports about its efficacy and some have suggested it should no longer be used routinely, if at all.A home remedy is cutting a potato in half and taping to the wound for a few hours.
Wound infection is rare. Antibiotics are not recommended unless there is a credible diagnosis of infection.
Studies have shown surgical intervention is ineffective and may worsen outcome. Excision may delay wound healing, cause abscesses, and lead to objectionable scarring.
Anecdotal evidence
Anecdotal evidence
The expression anecdotal evidence refers to evidence from anecdotes. Because of the small sample, there is a larger chance that it may be true but unreliable due to cherry-picked or otherwise unrepresentative of typical cases....
suggests benefit can be gained with the application of nitroglycerin patches. Brown recluse venom is a vasoconstrictor, and nitroglycerin causes vasodilation
Vasodilation
Vasodilation refers to the widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large arteries, smaller arterioles and large veins. The process is essentially the opposite of vasoconstriction, or the narrowing of blood vessels. When...
that allows the venom to be diluted into the bloodstream and fresh blood to flow to the wound. Theoretically this prevents necrosis, as vasoconstriction may contribute to necrosis. However, one scientific animal study found no benefit in preventing necrosis, with the study's results showing it increased inflammation and caused symptoms of systemic envenoming. The authors concluded the results of the study did not support the use of topical nitroglycerin in brown recluse envenoming.
Antivenom, available in South America for the venom of other species of recluse spiders, appears to be the most promising therapy. However, antivenoms are most effective if given early. Because of the often painless bite patients do not often present symptoms until 24 or more hours after the event of a brown recluse bite, possibly limiting the effect of this intervention.
Domestic variety as a pest
Due to the emphasized fear of these spiders ever since the increase of public awareness in recent years, extermination of domestic brown recluses is performed frequently in the lower Midwest. Brown recluse spiders possess a variety of adaptations, including the abilities to maintain homeostasisHomeostasis
Homeostasis is the property of a system that regulates its internal environment and tends to maintain a stable, constant condition of properties like temperature or pH...
for several seasons with no food or water and to survive after losing limbs. Additionally, the spiders survive significantly longer in a relatively cool, thermally stable environment.
The increased abilities of the spiders to survive during times of starvation, thirst, and regulated room temperatures makes extermination of this species particularly challenging. Many chemicals which have proven effective have now been made illegal or restricted in the U.S., making the use of chemicals to eradicate the spiders impractical. Chemicals that do not kill the spider may cause disruption to its nervous system or other systems, inducing undesirable aggressive behavior.