March 2007 volume 23 number 03
Spider Bites: Fact or Fiction?
How dangerous are spiders? have been found in California as well. The northern black widow
Most spiders are absolutely harmless to humans. In fact, of the is found primarily in the northeastern US and southeastern Canada,
approximately 3,000 different species of spiders that inhabit the though its range overlaps that of L. mactans quite a bit. The western
United States (US), only a very limited number are actually capable black widow is found in the western half of the US as well as in
of biting humans; most have fangs that are either too short or too southwestern Canada and much of Mexico.
fragile to break human skin. Within this small group, only 4 spiders are
thought to be dangerous to humans: the brown recluse, widow spiders, The adult female black widow has a shiny, jet black, spherical abdomen
the hobo or aggressive house spider, and the yellow sac spider. Only with two connected red (occasionally yellow to orange) triangles on
the brown recluse and black widow spiders have been associated with the underside that form a characteristic “hourglass” marking. Adult
signiﬁcant envenomation and very rare reports of human death; these females are about 1/2-inch long, not including the legs (about 1-1/2
spiders will be discussed in more detail below. inches when legs are spread). Adult males are harmless, and are about
half the female’s size, with smaller bodies and longer legs. The male’s
Among physicians and the general public, the perceived threat of abdomen usually has red spots along the upper midline and white
spider bites far exceeds the actual risk. In general, people fear spiders lines or bars radiating out to the sides. The surface of the black widow
and have misperceptions about spider behavior. A spider generally egg case is smooth. Newly hatched spiderlings are predominately
bites a person to defend itself, and usually just once. Few spiders are white or yellowish-white, gradually acquiring more black and varying
truly aggressive; most are timid and will retreat if given a chance. Bites amounts of red and white with each molt. Juveniles of both sexes
occur because someone inadvertently invades the spider’s space. resemble the male and are harmless.
Avoiding Spider Bites The female black widow spider has potent neurotoxic venom and is
Spiders generally prefer to live in undisturbed areas. Places where considered the most venomous spider in North America. Although
spiders are commonly found include the crawl spaces beneath homes, the bite of a widow spider is much feared, the female injects such a
piles of stored lumber, hollow tile blocks, among stored items on small dose of venom that it rarely causes death. Prior to antivenom
shelves, behind shutters, in the folds of little-used clothing and shoes, availability, black widow spiders killed approximately 5% of human
within piles of old newspapers, and under objects in dark, little- bite victims1. Now, reports indicate human mortality rates to be less
disturbed areas. Although outdoor-living spiders also prefer quiet than 1% from black widow spider bites. Deaths from black widow
areas, web-builders may position their webs near lighted doorways to bites among healthy adults are relatively rare in terms of the number
catch insects attracted to the light. The use of “bug lights” (outdoor of bites per thousand people. Only 63 deaths were reported in the US
electric lights that give off a yellow illumination designed not to attract between 1950 and 19892. Widow spiders are generally nonaggressive
insects) will prevent web-building behavior. and will retreat when disturbed.
The following are the most common symptoms of a black widow
Spider bites may occur when people put their hands into garden or
spider bite: immediate pain, burning, swelling, and redness at the site
household gloves that have been lying in a disused area, their feet into
(double fang marks may be seen); cramping pain and muscle rigidity
shoes that have not been worn for awhile, or when someone picks
in the stomach, chest, shoulders, and back; headache; dizziness; rash
up and dons an article of clothing that has been lying unused on the
and itching; restlessness and anxiety; sweating; eyelid swelling; nausea
ﬂoor or in a closet. On such occasions, the spider bites as it is about
or vomiting; salivation; tearing of the eyes; weakness, tremors, or
to be crushed. Some recluse and widow bites occur because people
paralysis, especially in the legs.
unwittingly reach into or bump their webs and stimulate an attack.
Unpacking long-stored cardboard boxes is one method of encountering People who are bitten are counseled to remain calm and immediately
spiders in this manner and therefore it is prudent to use gloves when seek medical attention (contact a physician, hospital and/or poison
handling anything that has been stored. center). An ice pack should be applied directly to the bite area to
relieve swelling and pain. The spider should be collected for positive
Black Widow Spiders and a “new” invader, the Brown Widow identiﬁcation by a spider expert. A plastic bag, small jar, or pill vial is
Spider useful and no preservative is necessary, but rubbing alcohol can be
Currently, there are three recognized species of black widow spiders used in the container to help preserve the spider.
found in North America: the southern black widow (Latrodectus
mactans), the northern black widow (L. variolus), and the western black Brown widow spiders, Latrodectus geometricus, are reported frequently
widow (L. hesperus). The southern black widow is primarily found in in Georgia, but have not been implicated in human bites. Because
(and is indigenous to) the southeastern US, ranging from Florida to of their local abundance, these are the widow spiders most often
New York, and west to Texas and Oklahoma. Southern black widows encountered by Georgians. Like black widow spiders, brown widow
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spiders also have an “hour glass” marking on the ventral side of the rare because it requires a witness to the biting, recovery of and
abdomen, and the brown widow is often mistaken for a black widow identiﬁcation of the spider, and exclusion of other causes. In May
spider. However, the base coloration of this spider is a dark brown or 2002, the American College of Emergency Physicians published an
mahogany and the top surface of the abdomen has a distinct pattern article about a method for detecting brown recluse spider venom3
of markings. The brown widow egg case is textured and rough in in skin biopsies of bite victims. A study done at the University of
appearance, due to the tufts of silk that are incorporated during the Michigan by a team of emergency medicine investigators found
formation of the case. These egg cases can easily be spotted within evidence that invasive biopsies are not necessary and, in fact, the
the web, most often within the tunnel section where the female spider Loxosceles (brown recluse) ELISA assay can detect brown recluse
lives. Like all Latrodectus species, the female brown widow spider has venom in hair samples. Since the vast majority of spider bites,
a bite which is potentially venomous. However, very little venom is speciﬁcally brown recluse spider bites, are difﬁcult to diagnose if the
injected during a brown widow bite, so we do not see the serious, spider is not brought in, this could be a beneﬁcial test to ascertain the
protracted symptoms characteristic of black widow spider bites. etiology of the skin lesion.
Recluse Spiders in Georgia Misdiagnosis of Spider Bites
The brown recluse or violin spider, Loxosceles reclusa, is the spider For decades, physicians have consistently used spider bites as a default
most often associated with reports of spider bites. It is about 1 inch diagnosis for idiopathic dermal necrosis, but the diagnosis of spider
long and has a violin shaped mark on its upper back. It is often found bite should not be used if the patient did not see the spider. Although
in warm, dry climates and prefers to stay in undisturbed areas such brown recluse spider bites are often suspected, they are almost
as basements, closets, and attics. It is not an aggressive spider, but certainly over-diagnosed. In one study of 600 suspected “spider bite
will attack if trapped or held against the skin. Despite widespread cases” in southern California, 80% were caused by other arthropods,
fear of brown recluse spider bites, they are less deadly than black mostly ticks and reduviid bugs4. During the 2001 anthrax attacks in
widow spider bites; almost all brown recluse bites heal without the US, a famously misdiagnosed skin lesion in a 7-month old infant
medical intervention, and very few result in serious outcomes such in New York was thought be a brown recluse spider bite; the actual
as skin grafting or death. Bites from brown recluse spiders can be diagnosis was cutaneous anthrax.
unremarkable (requiring no care), localized (requiring some care but
usually healing without intervention), dermonecrotic (a slow-healing, The misdiagnosis of “spider bites” can be applied to a wide spectrum
necrotic ulcerated skin lesion needing supportive care) or systemic of dermatologic conditions, some of which are far more dangerous
(causing vascular and renal damage, sometimes life-threatening). than a spider bite (Table 1). A number of these conditions require
therapy and should not be overlooked. Of particular note is
The following are the most common symptoms of a bite from a methicillin-resistant Staphylococcus aureus or MRSA, which has become
brown recluse spider: burning, pain, itching, or redness at the site
Table 1. Some conditions which can cause necrotic skin wounds
which is usually delayed and may develop within several hours or days and have been misdiagnosed as or could be confused with “brown
of the bite; a deep blue or purple area around the bite, surrounded recluse spider bites” (Vetter – various sources)
by a whitish ring and large red outer ring similar to a “bulls eye”; an Bite of the pajahuello Periarteritis nodosa
ulcer or blister that turns black; headache; body aches; rash; fever; (Ornithodoros coriaceus, an Argasid tick)
and nausea or vomiting. Chemical burn Poison ivy/oak infection
Chronic herpes simplex Pressure ulcers/bed sores
Diagnosing Spider Bites
Cutaneous anthrax Purpura fulminans
Most people with a spider bite will not recall being bitten. It is important
Diabetic ulcer Pyoderma gangrenosum
to ask if the patient actually saw the spider that bit them, and whether
Erythema chronicum migrans
they still have the spider. This is the best way to document a spider (Lyme disease)
bite and determine which spider was involved. Any spider bite may
Erythema multiforma Rocky Mountain spotted fever
result in itching or pain, rarely with small puncture wounds at the site.
Erythema nodosum Sporotrichosis
Typical symptoms, if any, include redness, itching and/or swelling
that lasts a couple of days. Ninety percent of spider bites are self- Focal vasiculitis Streptococcus infection
healing. Because spiders usually bite only once, a patient with multiple Gonococcal arthritis dermatitis Stevens-Johnson syndrome
bite lesions is more likely to have been bitten by other arthropods Infected herpes simplex Syphilitic chancre
such as ﬂeas, bed bugs, ticks, mites or biting ﬂies. Because spiders do Leishmaniasis Thromboembolic phenomena
not bite humans frequently or systematically, bites affecting multiple Lymphomatoid papulosis Toxic epidermal necrolysis
people in the same locale (such as a house, prison, dorm, etc.) are not (Lyells syndrome)
spider bites. Methicillin-resistant Staphylococcus aureus Varicella zoster (shingles)
Spider bites cannot be diagnosed just by looking at a skin lesion. Other arthropod bites Warfarin poisoning
However, diagnosis is based on physical signs. Conﬁrmation is (ﬂea, mite, biting ﬂy, true bug, bed bug)
Division of Public Health Epidemiology Branch Georgia Epidemiology Report Two Peachtree St., N.W.
http://health.state.ga.us http://health.state.ga.us/epi Editorial Board Atlanta, GA 30303-3186
Carol A. Hoban, M.S., M.P.H. Editor Phone: (404) 657-2588
Kathryn E. Arnold, M.D. Fax: (404) 657-7517
Stuart T. Brown, M.D. Susan Lance, D.V.M., Ph.D.
Cherie Drenzek, D.V.M., M.S.
Director Director Susan Lance, D.V.M., Ph.D.
State Health Ofﬁcer State Epidemiologist Stuart T. Brown, M.D. Georgia Department of Please send comments to:
Angela Alexander - Mailing List Human Resources firstname.lastname@example.org
Division of Public Health
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increasingly common in the community in recent Figure 1. U.S. Geographic Distribution of Veriﬁed Widespread Populations of Six
years. This organism is notorious for causing Native Loxosceles Species. The remaining native and nonnative species of loxosceles either
furuncles and abscesses that require drainage and are very rare or their distribution is highly circumscribed. The presence of recluse spiders is
sometimes antibiotics. A purulent lesion caused by seldom veriﬁed outside the demarcated areas. More information is available at http://spiders.
MRSA should not be mistaken for a necrotic lesion
characteristic of a spider bite. In addition, skin and
soft tissue infections caused by MRSA are sometimes
thought to result from superinfected spider bites.
However, a recent study done in Illinois5 shows no
link between spiders and MRSA infections.
Evidence for over-diagnosis of brown recluse spider
bites includes the fact that bites are rare in places
where brown recluse spiders are common, but bites
are frequently reported where the spiders do not
live. In parts of the country where brown recluse
spiders are endemic (Figure 1), they can occasionally
be found in large numbers. For example, in 2002,
investigators collected 2,055 brown recluse spiders
over a 6-month period from an occupied but historic
19th-century home in Lenexa, Kansas6. At least 400
of these spiders were large enough to cause bites.
Additional collections from more typically infested U.S. Map -Loxosceles spp distribution, Rick Vetter, UCR
homes in Missouri and Oklahoma during 2001 yielded 45 and 30
brown recluse spiders, respectively. Despite these infestations, no
Spiders. Pest Control Technology. Franzak & Foster Co., Cleveland, Ohio. 200
spider bites of the inhabitants of these three homes occurred. With pp.
the lack of reported recluse bites despite high levels of infestation, it Rosenstein ED, Kramer N. Lyme disease misdiagnosed as a brown recluse spider bite.
is implausible that brown recluse spider bites would occur frequently Ann Intern Med 1987; 107:782.
Russell FE. A confusion of spiders. Emerg Med 1986; 18:8-13.
in non-endemic areas. It has been estimated that 60% of alleged
Russell FE, Gertsch WJ. Letter to the editor. Toxicon 1982; 21:337-339.
brown recluse bites occur in areas where no recluse spiders are Russell FE, Waldron WG. Letter to editor. Calif Med 1967; 106:248-249
known to exist! David L. Swanson, M.D., and Richard S. Vetter, M.S. 2005. Bites of Brown Recluse
Spiders and Suspected Necrotic Arachnidism. N Engl J Med 352:700-7.
Richard S. Vetter. 2005. Arachnids Submitted as Suspected Brown Recluse Spiders
In Georgia, brown recluse spiders have rarely been documented
(Araneae: Sicariidae): Loxosceles Spiders Are Virtually Restricted to their Known
in the northern and central parts of the state. This means that Distributions but Are Perceived to Exist Throughout the United States. J. Med.
brown recluse bites should be considered rare in Georgia, and other Entomol. 42(4): 512-521.
etiologies entertained ﬁrst. Richard S. Vetter, Paula E. Cushingc, Rodney L. Crawford, Lynn A. Royce. 2003.
Diagnoses of brown recluse spider bites (loxoscelism) greatly outnumber actual
veriﬁcations of the spider in four western American states. Toxicon 42: 413–418.
This article was written by Rosmarie Kelly, Ph.D., M.P.H. Young VL, Pin P. The brown recluse spider bite. Ann Plast Surg 1988; 20:447-452.
Zetola, N., J. S. Francis, E. L. Nuermberger, and W. R. Bishai. 2005. Community-
REFERENCES acquired methicillin-resistant. Staphylococcus aureus: an emerging threat. Lancet
1. Bettini S. Epidemiology of latrodectism. Toxicon 1964; 2:93-101. Infect. Dis. 5: 275-286.
2. Miller, T. 1992. Latrodectism: bite of the black widow spider. Am. Fam.
Phys. 45:181 WEB SITES
3. HF Gomez, DM Krywko, WV Stoecker. May 2002. New Methods http://www.calpoison.org/public/spiders.html
for Detecting Brown Recluse Spider Venom. American College of http://www.entomology.cornell.edu/SpiderOutreach/Resources/Spider_
Emergency Physicians. pp 469-474. Identiﬁcation.shtml
4. Richard S. Vetter and P. Kirk Visscher. 1998. Bites and Stings of University of Maryland Medical Center, First Aid – Spider Bites. http://www.umm.
Medically Important Venomous Arthropods. International Journal of edu/non_trauma/spider.htm
Dermatology 37: 481-496. http://spiders.ucr.edu/dermatol.html eMedicineHealth: Brown Recluse Spider Bite
5. Catherine Baxtrom, Tara Mongkolpradit, John N. Kasimos, Laima M. http://www.emedicinehealth.com/spider_bite_brown_recluse_spider_bite/article_
Braune, Ronald D. Wise, Petra Sierwald, and Kyle H. Ramsey. 2006.
Brown recluse spider info: http://spiders.ucr.edu
Common House Spiders Are Not Likely Vectors of Community- Hobo spider ID guide: http://www.puyallup.wsu.edu/plantclinic/resources/pdf/
Acquired Methicillin-Resistant Staphylococcus aureus Infections. J. Med. pls116hobospider.pdf
Entomol. 43(5): 962-965 The Illinois-Iowa Brown Recluse Project: http://department.monm.edu/biology/
6. Richard S. Vetter and Diane K. Barger. 2002. An Infestation of 2,055 recluse-project/index.htm
Brown Recluse Spiders (Araneae: Sicariidae) and No Envenomations Spider Myths Web Site: http://www.washington.edu/burkemuseum/spidermyth/
in a Kansas Home: Implications for Bite Diagnoses in Nonendemic index.html
Areas. J. Med. Entomol. 39(6): 948-951. USA Spider Chart. www.termite.com
Questions About MRSA and Answers From the Experts
ADDITIONAL RESOURCES Answers to many practical, clinical questions about MRSA, ranging from the best
Gertsch, W.J., Ennik, F., 1983. The spider genus Loxosceles in North America, Central
way to identify patients with MRSA to what clinicians should do if they have
America, and the West Indies (Araneae, Loxoscelidae). Bull. Am. Mus. Nat. Hist.
personally had an infection. Medscape Nurses 8(2) 2006.
Stoy A Hedges and Mark S Lacey. 2001. Field Guide for the Management of Urban
The Georgia Epidemiology Report STANDARD
Two Peachtree St., NW
Atlanta, GA 30303-3186
PERMIT NO. 4528
March 2007 Volume 23 Number 03
Reported Cases of Selected Notiﬁable Diseases in Georgia, Proﬁle* for December 2006
Selected Notiﬁable Total Reported Previous 3 Months Total Previous 12 Months Total
Diseases for December 2006 Ending in December Ending in December
2006 2004 2005 2006 2004 2005 2006
Campylobacteriosis 22 130 110 126 592 591 572
Chlamydia trachomatis 3027 8067 8180 9177 34473 33277 38012
Cryptosporidiosis 11 39 46 80 181 155 285
E. coli O157:H7 0 8 7 6 23 31 44
Giardiasis 36 238 209 158 916 757 652
Gonorrhea 1338 4040 3974 4533 16067 15707 19030
Haemophilus inﬂuenzae (invasive) 14 26 26 33 117 113 121
Hepatitis A (acute) 3 43 20 9 317 126 50
Hepatitis B (acute) 9 114 43 34 448 201 183
Legionellosis 3 7 14 13 43 39 37
Lyme Disease 0 0 1 1 12 6 8
Meningococcal Disease (invasive) 4 3 4 6 15 18 19
Mumps 0 1 1 0 2 2 4
Pertussis 2 10 7 7 29 48 30
Rubella 0 0 0 0 1 0 0
Salmonellosis 115 458 550 471 1945 1935 1885
Shigellosis 126 170 258 587 659 673 1379
Syphilis - Primary 1 27 35 14 119 137 105
Syphilis - Secondary 14 111 137 67 481 538 407
Syphilis - Early Latent 8 71 108 38 397 408 311
Syphilis - Other** 21 221 221 130 868 969 870
Syphilis - Congenital 0 2 1 2 6 2 9
Tuberculosis 40 151 135 124 536 502 504
* The cumulative numbers in the above table reﬂect the date the disease was ﬁrst diagnosed rather than the date the report was received at the state ofﬁce, and therefore
are subject to change over time due to late reporting. The 3 month delay in the disease proﬁle for a given month is designed to minimize any changes that may occur.
This method of summarizing data is expected to provide a better overall measure of disease trends and patterns in Georgia.
** Other syphilis includes latent (unknown duration), late latent, late with symptomatic manifestations, and neurosyphilis.
AIDS Proﬁle Update
Report Disease Total Cases Reported* Percent Risk Group Distribution Race Distribution
Period Classiﬁcation <13yrs >=13yrs Total Female MSM IDU HS Unknown Perinatal White Black Hispanic Other
Latest 12 HIV,
19 3,094 3,113 30 31 8 2 15 43 0.5 20 75 4 1
2/06-1/07 AIDS 10 2,204 2,214 28 32 8 3 12 45 0.5 21 73 6 <1
Five Years HIV,
- - - - - - - - - - - - - -
2/02-1/03 AIDS 1 1,560 1,561 25 39 9 3 16 32 - 20 74 5 1
Cumulative: HIV, non-AIDS 243 9,997 10,240 34 30 8 3 12 47 1.5 22 74 3 1
07/81-1/07 AIDS 273 36,236 36,509 20 44 15 5 14 21 0.6 31 66 3 <1
Yrs - Age at diagnosis in years MSM - Men having sex with men IDU - Injection drug users HS - Heterosexual
* Case totals are accumulated by date of report to the Epidemiology Section ** Due to a change in the surveillance system, case counts may be artiﬁcially low during this time period
***HIV, non-AIDS was not collected until 12/31/2003