Researcher: Brown Spiders Not Deadly After All

ByLee Dye

Dec. 12, 2002 -- Diane Barger's family had been living in their Kansas home for more than five years when her 13-year-old daughter noticed that there was something distinctive about the spiders she had seen so often in the 150-year-old house.

Many of the spiders had the violin pattern on their backs that is characteristic of the dreaded brown recluse spider, widely believed to be so poisonous that a single bite can cause death. Barger quickly collected a few of the spiders and headed down to the University of Kansas, where her son had just enrolled as an entomology major.

Indeed, the daughter had been right. The spiders were brown recluses. That finding sent Barger and her husband and two children off on a mission that should lead to a re-evaluation of the threat of brown recluses, and a new image for one of the most feared members of the world of arachnids.

Spider Hunt

Here's the bottom line. The brown recluse is undeserving of its horrid reputation, and thousands of reports each year of serious injuries from brown recluse bites are clearly wrong. The brown recluse can cause a nasty wound, but there is not a single confirmed death in the United States from a brown recluse spider, according to Richard S. Vetter, the leading expert in the field who found in Barger the collaborator he had been looking for.

Vetter is a researcher in the department of entomology at the University of California, Riverside, and brown recluses have become his passion. Not just the spiders, but how they are perceived. Vetter believes that thousands of doctors each year routinely misdiagnose potentially deadly skin lesions as brown recluse bites, so the victims receive the wrong treatment.

He bases that on the fact that many reports come from areas where there simply are no significant numbers of brown recluses, like California. And Barger helped him demonstrate something else. It takes a lot of brown recluses to pose a significant threat.

Vetter asked Barger to capture as many spiders as she could and send them to him, dead or alive. So for six months Barger and her husband and children crawled around the attic and basement of their old limestone house, catching as many spiders as they could.

"It was our quality time," Barger later told Vetter.

They published their findings in the November issue of the Journal of Medical Entomology, and the numbers are nothing less than astounding.

Not a Bite

The family collected 2,055 brown recluse spiders during that six-month period, including some they found crawling on them as they slept, or stuffed clothes into the washing machine, or picked up the newspaper. The spiders were found in every room of the house, including "high human use areas such as bedrooms, kitchen, and bathroom," according to the study.

Yet here's the most astonishing part. During the six years that the family has lived in the house no one has received a single bite. Not even one.

Even Vetter was surprised by the numbers.

"You would think that's an incredible infestation, and people are going to die," he says. Nobody got bitten, he says, because it isn't in a spide's interest to go looking for trouble. A spider typically bites out of self defense, and the brown recluse is no exception.

"They don't bite, unless you roll over on one while sleeping," he says.

Vetter repeated the experiment with the help of two other home owners, one in Missouri and one in Oklahoma. Although the numbers were nowhere near as large, both homes had dozens of brown recluses, and no one had ever been bitten in either of those houses either.

What it all shows, Vetter argues, is that it takes a bunch of brown recluses to pose much of a problem. And therein lies a peculiar fact concerning the spider's reputation. Many reports of brown recluse bites come from areas far beyond the spider's range, which is limited to the south-central Midwest from southeastern Nebraska down through Texas and along the southernmost edge of Ohio to parts of Georgia.

There are related species in the Southwest and elsewhere, but these are even more reclusive and pose much less of a problem for humans because they shy away from populated areas, Vetter says.

The occasional brown recluse that hitches a ride to somewhere outside its habitat poses no real threat, he adds, but all it takes is one citing to add to its legend.

Over the years Vetter has collected statistics showing that the reported number of bites is way out of proportion to the confirmed number of brown recluses found in areas outside its range. Some 478 brown recluse bites were reported in South Carolina in 1990 by physicians who answered his questionnaire, and 95 in Florida in 2000, and 120 in California in the past three years. Yet none of these areas have significant numbers of brown recluse spiders. Vetter confirmed fewer than 10 brown recluse specimens in California during the same period when 120 bites were reported.

"Without a doubt, virtually every single brown recluse bite diagnosis from a non-endemic recluse area is incorrect," he says.

It can be a tough call, he admits, because the wound left by a brown recluse can range from mild redness "to a rotting flesh wound." But a wrong diagnosis leads to the wrong treatment, and such deadly illnesses as lyme disease can look very similar to a recluse bite, he adds.

Vetter says 90 percent of all brown recluse bites heal by themselves without treatment, and only 3 percent require skin grafts.

"And there is not one proven brown recluse death yet in the United States," he insists. "There have been reported deaths, but none proven."

Bite Complaints Widespread

Still, the spider's legend continues to grow, and sometimes Vetter feels like he's shouting into the wind.

"If you have enough people saying the world is flat, people will believe it," he says. So the unsubstantiated reports keep coming into his office of brown recluses found in Canada and even Alaska, and it's impossible to prove that these warm-weather spiders aren't in either of those places.

"Can you prove there are no elephants running around in Alaska?" he asks. "If you go around and don't find any, is that because you are inept and don't know where to look? Did you look at night? Maybe they come out at night. So no matter what you do, you can't prove there are no elephants there."

Of course, Vetter admits he can?t rule out the possibility that a lone brown recluse might hitch a ride in someone?s luggage and end up biting someone thousands of miles away. He puts it this way:

"Yeah, like I'm male so I can have sex with a Playboy bunny. It's a possibility, but is it a likelihood? No."

Lee Dye’s column appears weekly on A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.

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