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Biological Hazard – Invasive species/migrant arachnids (Brown recluse spider): Genesee County, Michigan

2017/05/06

BROWN RECLUSE SPIDER – USA: (MICHIGAN) NONSTANDARD LOCATION
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Published Date: 2017-04-28 15:57:57
Subject: PRO/EDR> Brown recluse spider – USA: (MI) nonstandard location
Archive Number: 20170428.5001551

[1] Date: Thu 27 Apr 2017 6:02 PM
Source: CBS News [edited]

A family in Michigan is scratching their heads after discovering unusual tenants inside their garage last week [week of 16 April 2017]. On the floor of their unheated, detached garage in Davison, they spotted 2 long-legged spiders, which turned out to be brown recluse spiders — a dangerous type of spider with a powerful bite. Most bites are minor, but occasionally, skin around a brown recluse bite will become necrotic, turning a dark color and becoming a deep, open sore.

The family has no idea where the spiders with up to 3-inch-long legs came from or how they made their way into their garage. Howard Russell, an entomologist at Michigan State University Diagnostic Services, confirmed the spiders were, in fact, brown recluses. “I’ve been doing this for 30 years,” Russell told CBS News. “I’ve had 8 brown recluse out of thousands of spiders submitted, so they’re rare.”
Russell explained that brown recluse spiders are usually found in more southern states with warmer climates, such as Tennessee, Arkansas, Missouri or Kentucky.

So it was surprising to stumble across the dangerous brown recluse in such a cool climate. “The spiders had survived the winter in that unheated garage,” Russell added. “There was no recent history of travel, in some other cases there were.”

In 2011, there were 3 isolated populations of the brown recluse reported in Lansing, Hillsdale and Flint. Since then, 3 additional populations of the brown recluse have been confirmed in Michigan. These new finds were located in Tecumseh in 2015, Ann Arbor in 2016 and now Davison in 2017.

“The Tecumseh population was sharing a home with a human family of 5 including 3 young children and 2 dogs. The homeowner believes the spiders arrived with new kitchen cabinets the previous owner had installed before the family purchased it,” according to a recent Michigan State University Extension report. “The Ann Arbor specimen came from a building on the University of Michigan campus.”
Now Russell is trying to figure out where these creatures came from.

“The interesting question research-wise here: Do these represent sort of a transported population or does this represent the leading edge of a spread of these things to the Midwest?” he asked.

While it may be a frightening finding, Russell wants to assure residents there are deadlier species. “We have Northern Widows up here, too, which are probably as dangerous as or more dangerous than recluse spiders,” Russell said. “A lot more people get sick by bee or wasp stings.”

If you spot a spider that resembles the brown recluse, call an expert, Russell advises. “Have it confirmed by somebody who actually knows spiders — and possibly confirmed by somebody who doesn’t have business interest in the result of that determination,” he adds.

[Byline: Jennifer Earl]

Communicated by:
ProMED-mail
<promed@promedmail.org>
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[2] Date: Fri 21 Apr 2017
Source: Michigan State University Extension [edited]

Update on brown recluse spiders in Michigan

The brown recluse spider, _Loxosceles reclusa_ (_Sicariidae_), is a medically important arachnid whose bite can cause severe necrosis in a small number of cases. However, most recluse bites are minor with no necrosis.

In 2011, I reported the discovery of 3 isolated populations of brown recluse spiders in Michigan’s Genesee, Hillsdale and Ingham counties. These populations were noteworthy because they are considerably north of the generally accepted native range of the brown recluse (shown below in red with the word “reclusa” [the map of distribution can be seen on the original URL. – Mod.LL]). In each case, specimens of the spiders were collected and submitted to Michigan State University Diagnostic Services where they were confirmed to be brown recluse spiders.

Since the 2011 article was published on the MSU Extension website, 3 additional populations of brown recluse spiders have been confirmed in Michigan. These new finds are located in Tecumseh in Lenawee County (2015), Ann Arbor in Washtenaw County (2016) and Davison in Genesee County (2017). The Tecumseh population was sharing a home with a human family of 5 including 3 young children and 2 dogs. The homeowner believes the spiders arrived with new kitchen cabinets the previous owner had installed before the family purchased it. The Ann Arbor specimen came from a building on the University of Michigan campus.

The latest find in Davison is noteworthy because the spiders were found this past week [week of 16 April 2017] in an unheated detached garage. There was no history of anything being stored in the garage that originated from areas located within the native range of the brown recluse. Cold winter temperatures are thought to be a limiting factor in brown recluse spider populations. In the case in Davison, it appears brown recluse spiders survived the winter of 2016-17 in an unheated garage.

[Byline: Howard Russell]

Communicated by:
ProMED-mail
<promed@promedmail.org>

[Overall, this was a milder winter in Michigan which may explain the wintering over. Finding recluse spiders in Michigan is quite rare and as noted, some of the arachnids may have been imported into the state.

A picture of the brown recluse showing the violin shaped marking on its dorsal surface can be found at:
http://entnemdept.ufl.edu/creatures/urban/spiders/brown_recluse03.jpg.

Photographs of bite wounds from the brown recluse can be found at:
https://www.brownreclusespider.org/brown-recluse-spider-bite-picture.htm.

A map of the counties of the state of Michigan can be found at:
http://www.worldatlas.com/webimage/countrys/namerica/usstates/counties/minames.gif. All 5 of the counties noted are located in the southeastern quadrant of the lower peninsula of Michigan. – Mod.LL

A HealthMap/ProMED-mail map can be accessed at: http://healthmap.org/promed/p/225.]

See Also

Toxic spider Bite – Australia: funnel web spider 20170225.4864792
2016
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Toxic spider bite – UK: false widow 20161005.4539443
2007
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Loxosceles spider bite, fatal – Peru 20070430.1398
………………………………………….ll/ec/dk

Source:
A ProMED-mail post
ProMED-mail is a program of the International Society for Infectious Diseases


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