Friday, February 20, 2009

Brown Recluse Spider isn’t Typically a Southerner

Many Georgia doctors have likely diagnosed a patient’s suspect wound as a brown recluse spider bite. There’s just one problem with this: The spider really doesn’t call the Deep South home, says a University of Georgia spider expert.

Over the past six years, only 19 brown recluse spiders have been identified in a study conducted in Georgia for the spider. And most were found in the northwest corner of the state, said Nancy Hinkle, an entomologist with the UGA College of Agricultural and Environmental Sciences. Brown recluse spiders have only been collected 58 times in Georgia.

“Hundreds of entomologists, extension agents from across the state, thousands of pest control inspectors and millions of citizens have been able to find brown recluse spiders in only 31 Georgia counties,” she said.

From 2002 to May of 2008, Hinkle tracked verified brown recluse reports in Georgia. The findings were published in the January issue of the Journal of Medical Entomology.

The spider is brown but has a darker, violin-shaped design where its legs attach. With its legs extended, it's about the size of a quarter. If the brown recluse spiders in the state caused all the reported wounds, she said, they’d be very busy spiders.

Hinkle received thousands of samples from across the state. Rick Vetter from the University of California at Riverside identified the samples. He is the world's expert on the brown recluse spider.

Brown recluse spider bites are very rare in Georgia. Hinkle said there is only one confirmed account of anyone being bitten by one in Georgia. However, 963 reports of bites in 103 counties have been filed at Georgia poison centers in the last five years.

Over-diagnosis is a problem nationwide. Hinkle said South Carolina physicians diagnosed 738 bites in 2004, but only 44 brown recluse spiders have been found in the state’s recorded history. Similarly, Floridians claimed 95 brown recluse bites in 2000, but Florida has recorded brown recluse spiders at only 11 places in more than 100 years.

The study was prompted by Hinkle's arrival from California. "When I first came to Georgia, I heard several people say they knew someone who'd seen or been seriously wounded by a recluse," she said. "I found that odd since the recluse is a Midwesterner, not a Southerner."

The spider’s native range does include North Georgia, but its distribution is limited there.

Hinkle hopes the study will educate Georgia's medical community and reduce the number of erroneous recluse bite cases. A mark on the skin that looks like a spider bite could be something more serious.

She believes many assumed brown recluse bites could be methicillin-resistant Staphylococcus aureus.

MRSA is a type of staph infection resistant to antibiotics like penicillin, amoxicillin and oxacillin. MRSA causes mild skin infections that result in pimples or boils, but it can also cause more serious skin lesions or infect surgical wounds.

Incorrectly diagnosing MRSA as a spider bite, and vice versa, can result in a patient getting the wrong therapy, Hinkle said.

“MRSA infections require a specific set of antibiotics,” she said. “Brown recluse spider bites, on the other hand, cause tissue damage by salivary secretions in their venom and antibiotics have no effect on salivary secretions.”

Other misdiagnosed wounds could be infections, insect bites, diabetes, bed sores, Lyme disease, anthrax or necrotizing bacteria, some of which can be fatal if not treated fast, she said.

Almost all brown recluse bites heal without medical intervention, Hinkle said. And in spite of all the horror stories, only 1 percent requires medical attention.

By April Sorrow
University of Georgia

April Sorrow is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.

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