Reports of Presumptive Brown Recluse Spider Bites Reinforce

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Reports of Presumptive Brown Recluse
Spider Bites Reinforce Improbable Diagnosis
in Regions of North America Where the Spider
Is Not Endemic
Richard S. Vetter1 and Sean P. Bush2
 Department of Entomology, University of California, Riverside, and 2Department of Emergency Medicine, Loma Linda University School of Medicine,
Loma Linda, California

Envenomations by the brown recluse spider have been reported throughout North America, despite the fact that the spider’s

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range is limited to the South and central Midwest of the United States. Several of these medical reports have originated from
regions of nonendemicity where the spider has never or rarely been documented and brown recluse spider populations are
unknown. In most of these reports, no spider is positively identified in association with the dermonecrotic wound, and
diagnosis has been based on clinical examination findings. Considering the extreme rarity of brown recluse spiders in areas
of nonendemicity, the diagnosis of a presumptive bite is a misdiagnosis that reinforces the assumption that brown recluse
spiders are common local etiologic agents of necrosis. There are many medical conditions of diverse origin that have been
misdiagnosed as brown recluse spider bites, some of which can be fatal or debilitating. Physicians’ awareness of these conditions
will increase diagnostic accuracy in areas of North America where bites from brown recluse spiders are improbable.

Recently, Clinical Infectious Diseases pub-                   of the severity of the ensuing necrosis, and     cluse spider [D. Currie, personal com-
lished a Photo Quiz describing a patient                      because the spider was hiding in a work          munication], in the taxonomic revision
with a necrotic lesion that was attributed                    glove, the bite was presumed to be caused        [2]). Second, no spider was definitively as-
to a brown recluse spider bite [1]. A la-                     by a brown recluse spider” [1, p. 636]. All      sociated with the event, merely “a patch
borer felt a sudden sensation of warmth                       the authors are from Winnipeg, Canada,           of black fur” that was not further iden-
under a work glove, which he removed,                         and we assume that the patient was also          tified (at least, not in the report) yet was
and “a patch of black fur (diameter, 1 cm)                    from this area, because he left work to          presumed to have been a medically im-
fell from the…glove” [1, p. 595], after                       be evaluated at the authors’ emergency           portant, nonendemic spider. Third, after
which he continued working. A necrotic                        department.                                      the initial “bite,” the laborer continued to
wound ensued on his index finger. On the                          It is highly unlikely that a brown recluse    work, which complicated the situation, in
basis of clinical examination findings, the                    spider (Loxosceles reclusa) was the cause of     that any dermal puncture was then subject
authors concluded that the “culprit species                   the wound. First, there are no brown re-         to secondary bacterial infection. Although
in this case remains uncertain, but because                   cluse spiders in Canada. Only 3 verified          it might be posited that the bite was that
                                                              specimens of Loxosceles spiders have ever        of a hobo spider (Tegenaria agrestis), a re-
   Received 26 November 2001; revised 27 February 2002;       been found in Canada, and all were Loxo-         cently completed study shows no evidence
electronically published 24 July 2002.                        sceles laeta, a South American recluse spi-      of this spider in Canada east of British
  Reprints or correspondence: R. S. Vetter, Dept. of Ento-
mology, University of California, Riverside, Riverside, CA
                                                              der. One was found in Vancouver, British         Columbia (R. S. Vetter, A. H. Roe, R. G.
92521 (                                Columbia [2], and 2 were found in the            Bennett, C. R. Baird, L. A. Royce, W. T.
Clinical Infectious Diseases 2002; 35:442–5                   basement of the Royal Ontario Museum             Lanier, A. L. Antonelli, and P. E. Cushing,
    2002 by the Infectious Diseases Society of America. All
rights reserved.
                                                              (1 of these latter 2 was originally mis-         unpublished data).
1058-4838/2002/3504-0015$15.00                                identified as a North American brown re-             Many medical reports of brown recluse

442 • CID 2002:35 (15 August) • Vetter and Bush
spider envenomation originate from areas       the United States where the spider is not       identify harmless spiders as brown re-
of North America where the spiders are         endemic [7, 13–17] is tens to hundreds of       cluses. Therefore, reliance on a patient’s
not endemic, are extremely rare, or have       times greater than the historically verified     identification of a spider in a bite scenario
never been found and, hence, are highly        number of brown recluse spiders ever            is another avenue that leads to incorrect
unlikely to be the etiologic agent of the      found in that region [2, 7, 17]. In contrast,   diagnoses of recluse spider bites in areas
wounds. Unsubstantiated reports re-            in areas of endemicity in the Western hem-      of nonendemicity. Furthermore, although
inforce the erroneous notion that the          isphere, dozens to thousands of brown re-       physicians in such areas have allegedly
brown recluse spider is a common, wide-        cluse spiders can be found annually in in-      identified brown recluse spiders associated
spread cause of necrosis. These reports can    dividual homes (whose inhabitants sustain       with envenomations [10, 13, 14], many
lead to aggressive, incorrect treatment be-    no envenomations), and each home shel-          harmless spiders have dark cephalic pat-
cause of the recluse spider’s well-known       ters more recluse spiders than have ever        terns that are routinely mistaken for the
but overstated potential for causing der-      been collected from individual American         recluse spider’s “violin” pattern [26]. Phy-
monecrotic damage; this erroneous notion       states where the spider is not endemic [18;     sicians have misidentified as brown recluse
can also increase medicolegal risk [3],        R.S.V., unpublished data]. This para-           spiders several virtually harmless non-
heighten patient anxiety [4, 5], perpetuate    dox—many recluse spiders but no bites in        recluse spiders associated with verified
misinformation in the medical literature,      areas of endemicity—demonstrates the            bites or dermonecrotic lesions ([4]; R.S.V.,
and cause incorrect manifestations to be       improbability of recluse spider bites oc-       unpublished data), which reinforces the
attributed to the venom’s toxicity.            curring in areas where there are few or no      tendency toward incorrect diagnoses in
   The range of the brown recluse spider,      recluse spiders.                                their area.
L. reclusa, extends from southeastern Ne-         However, physicians from American
                                                                                                   One of the consequences of erroneous
braska to southernmost Ohio and south          states or Canadian provinces that lack ver-

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                                                                                               case histories is that a wide variety of med-
into Georgia and most of Texas [2, 6, 7].      ified populations of brown recluse spiders
                                                                                               ical conditions are reported in the medical
The spider is rarely found outside this        have reported brown recluse spider en-
                                                                                               literature under the umbrella diagnosis of
range and is not widespread throughout         venomations, despite having no evidence
                                                                                               “brown recluse spider bite,” and the cu-
North America. Because it occurs in high       of spider involvement [10–12, 14, 19–25].
                                                                                               mulative spectrum of manifestations is re-
concentrations in close proximity to hu-       Although several reports admit that brown
                                                                                               iterated by later researchers. For example,
mans, the brown recluse spider is the most     recluse spider involvement has been as-
                                                                                               in a report of a case from Colorado that
medically important recluse spider species     sumed, such medical articles then typically
                                                                                               relied on the patient’s identification of
in North America. There are additional         review the characteristics of the brown re-
                                                                                               the spider, the authors concluded that
native and nonnative recluse spider species    cluse spider life history, the manifestations
                                                                                               “wounds from the venom of a brown re-
in the United States, and, although their      of the venom’s toxicity, and the treatment
                                                                                               cluse spider do not often take the pro-
venom is equally toxic, they are of less       for necrotic arachnidism. Some of these
                                                                                               tracted, complex clinical path described in
concern, because they inhabit southwest-       publications have relied upon the patient’s
                                                                                               this case” [25, p. 143]. Published reports
ern deserts with sparse human population       identification of a spider or other circum-
                                                                                               of unsubstantiated recluse spider bites
or live where interaction with humans is       stantial evidence as proof of brown recluse
highly improbable. In justifying diagnoses     spider involvement: for example, a Mon-         such as this one muddle the clinical pic-
of recluse spider bites, reviews of necrotic   tana family member [10] and a Chicago           ture and decrease the probability that
arachnidism [8, 9] and case histories of       patient [14] identified the spider as a          proper diagnoses will be made by later in-
unsubstantiated “recluse spider bite” from     brown recluse from memory after being           vestigators [27]. Similar unsubstantiated
areas where the spider is not endemic          shown pictures of recluse spiders; a Col-       reports exaggerated the importance of or
[10–12] claim that brown recluse spiders       orado patient’s wife saw what she “be-          erroneously identified the white-tailed spi-
are readily transported around North           lieved to be a brown recluse spider” [25,       der in Australia [28] and a wolf spider in
America. This logical but uncorroborated       p. 137]; and a Chicago patient did not feel     Brazil [29] as causes of necrotic arach-
supposition is resoundingly contradicted       a nocturnal bite but saw a dark brown           nidism. With regard to the Brazilian wolf
by biological evidence, yet it has led to      spider the next morning [14]. From the          spider, initial conclusions about its ne-
overreliance on the idea that the recluse      hundreds of suspected “recluse spiders”         crotic capability were based on undocu-
spider is a common cause of necrotic le-       submitted to one of us (R.S.V.) by the          mented clinical observations and necrosis
sions [7]. There are several examples of       general public in the continental United        in rabbit ears that resulted from injection
reports in which the annual number of          States, it is evident that, even after ex-      with high doses of venom [27]. Wolf spi-
reported or presumed brown recluse spi-        amining photographs of brown recluse            der antivenin was used for decades after
der bites in a particular state or area in     spiders, many nonarachnologists still mis-      it was developed, yet not 1 of 515 verified

                                                                    Presumptive Brown Recluse Spider Bites • CID 2002:35 (15 August) • 443
wolf spider envenomations in humans re-        ness, it is hoped that the diagnosis of               13. Mara JE, Myers BS. Brown spider bite. Rocky
                                                                                                         Mountain Med J 1977; 74:257–8.
sulted in necrosis [27, 29].                   brown recluse spider bite would be limited
                                                                                                     14. Erickson T, Hryhorczuk DO, Lipscomb J,
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among cases in which the identity of an        ified populations of the spider. When the                  bites in an urban wilderness. J Wilderness Med
                                               diagnosis of brown recluse spider bite is                 1990; 1:258–64.
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                                                                                                     15. Schuman SH, Caldwell ST. 1990 South Car-
of manifestations for that species is narrow   made outside the spider’s range, it should                olina physician survey of tick, spider and fire
and consistent in presentation. However,       be reserved for cases in which the bite is                ant morbidity. J S C Med Assoc 1991; 87:
recluse spider venom manifestations do         witnessed and the spider is reliably iden-                429–32.
                                               tified. Secondarily, this increased aware-             16. Vest DK, Keene WE, Kaufman S. Necrotic
vary from mild erythema to extensive ne-
                                                                                                         arachnidism—Pacific Northwest, 1988–1996.
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                                                                                                         osceles spp. (Araneae; Sicariidae), in Florida.
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                                                                         Presumptive Brown Recluse Spider Bites • CID 2002:35 (15 August) • 445

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