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Tuesday, August 9, 2011

Brown recluse spider might be migrating to Michigan

Brown recluse spiders are not supposed to live in Flint, according to Howard Russell, an entomologist at Michigan State University.
And yet a woman captured three of the notorious spiders in her house and took them into the MSU Extension Office in Genesee County in June.
"It's the first time I've seen live ones," said Ruth Simon, a master gardener volunteer and diagnostic technician who sent them to Russell. "It's exciting to get something like this in.... It's not a common occurrence."
Although it is unclear how brown recluse spiders ended up at the house, an online peer-reviewed study published this year has projected that the brown recluse, whose venom can leave necrotic lesions as skin dies around the bite area, could be calling the Wolverine State home in coming years as global climate change shifts its range to Michigan, Pennsylvania and Wisconsin.
Most experts say brown recluse spiders in Michigan likely hitched a ride from areas including parts of Illinois, southern Indiana and far southwestern Ohio. The spiders primarily live in places such as Texas, Oklahoma and Kansas.
"Here in Kansas, you do tend to see them fairly frequently," said Erin Saupe, a PhD candidate at the University of Kansas in Lawrence.
Saupe coauthored an online peer-reviewed report published in March on PLoS (Public Library of Science) ONE that raises the possibility that the spider's range could move into southern Michigan by 2020 and most of the state by 2080 because of climate change, which is projected to increase temperatures.
Although that prospect would likely give the willies to any arachnophobes in Michigan -- especially because the spider's venom can destroy skin tissue or, in extremely rare cases, could be deadly -- the study also suggests that the spider could fail to adapt in time and become extinct in parts of its current range.
When Russell received a jar containing the spiders found at Simon's house, he put them in alcohol, preserving them for future study but also easing the minds of his co-workers.
The mystery of how they got there prompted Russell to acknowledge that small groups of brown recluse live in the state.
Although brown recluse venom is dangerous, Rick Vetter, a researcher at the University of California, Riverside, said there is no consistent reaction to being bitten. The Internet has plenty of images of gruesome, flesh-deforming wounds attributed to the spiders, which populate states from approximately Iowa south to Texas and east to Georgia, but Vetter, considered one of the world's pre-eminent brown recluse experts, said the majority of the spiders' bites heal without lasting consequence. Hysteria, however, tends to develop over the minority of cases where necrotic lesions develop. Vetter compared it with a car crash -- we only hear about the horrific crashes, never about the fender-benders that are much more common.
He estimated that there might be one death for every five years from a brown recluse bite, although much has been written about the lack of confirmed deaths from the spider's bite. Considering that millions of the spiders live close to humans -- Vetter referenced a case in Kansas where more than 2,000 were collected in a house and it took 11 years for a resident to actually get bitten -- the danger is low. The spiders, as their name implies, are reclusive. They hide -- in boxes, basements, clothing left on the floor. Most bites occur accidentally, when someone puts on a sock or shirt where a brown recluse is hiding or when someone rolls over on them in bed.
Those factors also make the them difficult to control.
"Be aware that it is almost impossible to eliminate recluse spiders from a building once they get established. The best you can hope for is a significant reduction in the numbers of spiders and take steps to reduce the chances of being bitten," according to information posted on the University of California, Riverside's Web site.
Vetter and others say brown recluse bites are wildly overdiagnosed. People often wrongly assume they've been bitten by a brown recluse even when they live outside the spider's range and an unexplained wound is more likely the result of Lyme disease, flesh-eating bacteria or some other condition, experts say. Lyme disease, which is carried by infected ticks, can cause a wide range of adverse health effects.
Russell said "99.99% of people who live in Michigan will live their whole life without seeing a brown recluse spider."

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