Toxic Spider Species Gets A Bad Rap, Expert Says

Emily Sohn
for National Geographic News
February 13, 2003
Despite their negative reputation, brown recluse spiders get blamed for
crimes they did not commit, says an arachnologist who is doing his best
to set the record straight.

"People are very wrong to believe really bad things about them," said Rick Vetter, of the University of California, Riverside. Doctors misdiagnose hundreds of brown recluse bites around the country every year, Vetter said, often in places where the creepy-crawlers don't even live. Meanwhile the spiders have lived with people for years, apparently without biting them.

In extreme cases, the poisonous venom of a brown recluse bite produces nasty effects. First, the flesh around a bite starts to rot within 12 to 24 hours. The wound turns into a multi-color lesion that can last for up to three weeks. Theoretically, people can die from the venom. But fatal bites are considered highly unlikely, and more than 90 percent of recluse bites heal without complications, though bites can leave permanent scars.

But in the vast majority of cases, spider bite victims develop a negligible wound or show no symptoms whatsoever.

One reason the spiders have earned their bad reputation is that no one knows how many people are bitten by brown recluses each year. And doctors commonly mistake other maladies for brown recluse spider bites.

Epidemic of Fear

Vetter hopes his research will help doctors better treat their patients. Spider bite misdiagnoses can mask serious health problems, like flesh-eating bacteria or cancer, which require specific and immediate care.

Brown recluse spiders caught Vetter's attention in 1992, when a woman in California, who lost her arms, legs, and part of her nose to amputation, said she remembered being bitten by a spider. The media ran with it. Since then, doctors have routinely blamed mysterious splotches of rotting human flesh on bites by brown recluse spiders, regardless of whether the victim ever saw a spider, and often without knowing whether those spiders even live in the area.

"It's like a bunch of people telling you the world is flat," Vetter said. "The myth of the brown recluse is kept alive by a medical community who diagnoses brown recluse bites and the general public who believes the diagnosis."

At least 30 other medical conditions can cause those same symptoms, Vetter said, including bacterial infections, blood disorders, drug reactions, Lyme disease, and poison ivy. In one famous case in New York in October, 2001, a 7-month-old boy who was initially diagnosed with a brown recluse bite turned out to be infected with anthrax.

In fact, fewer than a hundred recluse spider bites have ever been documented, and there have been no confirmed deaths, said Sean Bush, an emergency room doctor at California's Loma Linda University Medical Center. Bush specializes in venomous bites and stings.

"Suspicion of spider bites is exceedingly common," he said. "I call it a pandemic. All over the world, people come in with wounds and think they've been bitten by a spider. This is one of the most controversial areas of medicine," Bush said.

Show Me the Spider

Brown recluse spiders, as their name suggest, are shy and secretive creatures. Like 12 other species of recluse spiders, the brown recluse spider has six eyes arranged in pairs. (Most spiders found in the United States have eight eyes.) The spiders average about half an inch (1.3 centimeters) in length and their brown, silky bodies lack any discernible pattern. Fine hairs cover their legs. The nocturnal arachnid uses venom to subdue their prey.

Many diagnoses of brown recluse spider bites come from areas apparently outside of the brown recluse's habitat. Brown recluse spiders are found mostly in the central and southern U.S., an area that includes Texas, Arkansas, Missouri, Kentucky, Tennessee, parts of Illinois, Indiana, and Georgia. Brown recluse spiders also inhabit the states bordering the Gulf of Mexico.

Yet Vetter has fielded reports of brown recluse bites from Wisconsin, New York, even Alaska and Canada. In virtually every case, systematic searches in those places have turned up no brown recluse spiders.

In one analysis, Vetter counted 188 reports of brown recluse bites in three years in California, Oregon, Washington, and Colorado. But only 15 brown recluse spiders have ever been found in those four states. "These bite diagnoses are everywhere, and yet no one can find the spider," Vetter said. "Show me the spider."

Even where brown recluses do live, people overestimate their risk, Vetter said. In one recent case in Kansas, a family of four collected more than 2,000 brown recluse spiders in their house during a six-month period. The family found spiders on the paper towel rack, crawling up the stairs, and lurking in piles of laundry. "There were four people living in that house for six years," said Vetter, who wrote about the case in the November issue of the Journal of Medical Entomology. "Guess how many bites? None."

Vetter and colleagues have recently embarked on a project to census brown recluse spiders in northern Illinois and southern Iowa. Similar studies elsewhere should provide doctors and the public a better understanding of brown recluse spiders.

"These spiders are dangerous and they can cause nasty wounds," Vetter said, "but the perception of the brown recluse as a serious health threat is overstated."

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