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UCR Spider Expert: Brown Recluse Spiders Are Scapegoats

UCR Spider Expert: Brown Recluse Spiders Are Scapegoats

(November 6, 2000)

In the November issue of the Western Journal of Medicine, a University of California, Riverside spider expert warns physicians not to fall into the trap of blaming the brown recluse spider for mysterious flesh wounds, especially in California.

"There are no populations of brown recluses in California," Richard S. Vetter, a staff research associate in the UCR Department of Entomology, wrote in the article released this week. "However, there have been several hundred California diagnoses of 'brown recluse bites' reported to me in the last decade," he said. "Undoubtedly, this is only a small fraction of the total number of 'brown recluse bites' that have been diagnosed."

The article, titled "Medical myth: idiopathic wounds are often due to brown recluse or other spider bites throughout the United States," goes on to describe the spider's appearance, habitat and the effect of the bite. He also lists possible medical conditions that could create wounds that look similar to a spider bite.

Vetter suggests that physicians consider a wider range of causes for necrotic wounds, (i.e. rotting flesh wounds). Chemical burns, skin cancer, diabetic ulcers and infections from bacteria and fungus can all look like recluse spider bites, he said.
Although a native spider called a "desert recluse," (a relative of the brown recluse) lives in the southeastern deserts of California, virtually all the diagnosed bites originate from coastal and northern California, areas that have never had any recluse populations, Vetter noted.

Ticks, fleas, bedbugs and assassin bugs feed on blood, and can leave a wound that looks similar to a spider bite, Vetter said. Lyme disease leaves a bull's eye wound similar to a recluse bite. "Because Lyme disease can lead to irreversible neural and cardiac complications, its misdiagnosis as a brown recluse bite could have serious clinical consequences," Vetter said.

Vetter has made a thorough review of medical and arachnological literature, corresponded with arachnologists, county entomologists, vector control personnel, and with the California Department of Food and Agriculture, which handles all exotic pest identifications in the state. He has found fewer than 10 verified sightings of brown recluse spiders in the entire state, and most of those can be traced to facilities that receive goods imported from other places.

California is just one of several areas where doctors are over-diagnosing brown recluse bites, Vetter said. Other areas where brown recluse spiders are either extremely rare, or non-existent, yet recluse bites are still diagnosed, include Vermont, New York, Pennsylvania, Florida, Chicago, South Dakota, Colorado and northern Nevada.

Vetter operates a Website about the brown recluse spider at that issues a challenge to people who believe brown recluse spiders are found in California.

"Send it to me, and I'll identify it," said Vetter. "After 10 years of receiving spiders from Californians, I still have not had a single one sent to me that was in reality a brown recluse. They turn out to be immature black widows, wolf spiders, male false black widows and cellar spiders. You've got to know a lot about spiders to identify them properly," he said.

Editors and writers, further information is available from:
Rick Vetter, (909) 787-3550


The full article from the Western Journal of Medicine is posted online at

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