Brown Recluse Spider Bites

admin — Tue, 23 Sep 2008 13:23:52 +0000

Like other spiders, the brown recluse is not aggressive. It is quite common, in fact, to live in a building that is heavily infested and never be bitten. Most bites occur in response to body pressure, when a spider is inadvertently trapped against bare skin. Some people are bitten when they roll over one in bed. Other bites occur while moving stored items or putting on a piece of clothing that a spider has chosen for its daytime retreat. Brown recluse spiders have remarkably small fangs and cannot bite through clothing.

The initial bite is usually painless. Oftentimes the victim is unaware until 3 to 8 hours later when the bite site may become red, swollen, and tender. The majority of brown recluse spider bites remain localized, healing within 3 weeks without serious complication or medical intervention. In other cases, the victim may develop a necrotic lesion, appearing as a dry, sinking bluish patch with irregular edges, a pale center and peripheral redness. Often there is a central blister. As the venom continues to destroy tissue, the wound may expand up to several inches over a period of days or weeks. The necrotic ulcer can persist for several months, leaving a deep scar. Infrequently, bites in the early stages produce systemic reactions accompanied by fever, chills, dizziness, rash or vomiting. Severe reactions to the venom are more common in children, the elderly, and patients in poor health. Persons bitten by a brown recluse spider should apply ice, elevate the affected area, and seek medical attention immediately.

As indicated by its name, this spider is not aggressive and usually bites only when pressed against the skin, such as when tangled up within clothes, bath towels, or in bedding. In fact, many wounds that are necrotic and diagnosed as brown recluse bites can actually be Methicillin-resistant Staphylococcus aureus(MRSA). Actual brown recluse bites are rare. Brown recluse bites may produce a range of symptoms known as loxoscelism. There are two types of loxoscelism: cutaneous (skin) and systemic (viscerocutaneous).

Most bites are minor with 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 a systemic condition with occasional fatalities. Most fatalities are in children under 7 or those with a weaker than normal immune system. (For a comparison of the toxicity of several kinds of spider bites, see the list of spiders having medically significant venom.)

A minority of brown recluse spider bites form a necrotizing ulcer that destroys soft tissue and may take months to heal, leaving deep scars. The damaged tissue will become gangrenous 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, vomiting, fever, rashes, and muscle and joint pain. Rarely more severe symptoms occur including hemolysis, thrombocytopenia, and disseminated intravascular coagulation. 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. 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.

Numerous other spiders have been associated with necrotic bites in the medical literature. A partial list includes the hobo spider and the yellow sac spiders. 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 has been some information that the brown recluse spider bite is sometimes as dangerous as the fire ant bite. There have been several studies questioning 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.

Brown Recluse Spider Regions

admin — Mon, 22 Sep 2008 20:23:25 +0000

The brown recluse spider is found throughout the south central and midwestern United States. Infestations in these areas are intermittent, becoming more common as one travels westward. Other species of Loxosceles spiders occur in the southwestern U.S. and southern California, but the brown recluse is the most notable and widespread. Recluse spiders are rare outside their native range and are widely over-reported. Occasionally, one or a few spiders may be transported to a non-native area in boxes or furnishings, but infestations seldom become established.

Though variable in size, adult brown recluse spiders with legs extended are about the size of a U.S. quarter. Coloration ranges from tan to dark brown, and the abdomen and legs are uniformly colored with no stripes, bands or mottling. The legs are long and thin and lack conspicuous spines. For laypersons, the most distinguishing feature of a brown recluse is a dark violin-shaped mark on its back, with the neck of the violin pointing toward the rear (abdomen) of the spider. This feature is consistent in adult brown recluses, but sometimes less obvious in younger spiders.

Notice the Fiddleback Design

In nature, brown recluse spiders live outdoors under rocks, logs, woodpiles and debris. The spider is also well adapted to living indoors with humans. They are resilient enough to withstand winters in unheated basements and stifling summer temperatures in attics, persisting many months without food or water. The brown recluse hunts at night seeking insect prey, either alive or dead. It does not employ a web to capture food — webs strung along walls, ceilings, outdoor vegetation, and in other exposed areas are nearly always associated with other types of spiders.

Brown Recluse Spider Guide

Brown Recluse Spider Bites

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Brown Recluse Spider Regions

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