Georgia epidemiology report, Vol. 23, no. 3 (Mar. 2007)

March 2007

volume 23 number 03

Spider Bites: Fact or Fiction?

How dangerous are spiders? Most spiders are absolutely harmless to humans. In fact, of the approximately 3,000 different species of spiders that inhabit the United States (US), only a very limited number are actually capable of biting humans; most have fangs that are either too short or too 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 hobo or aggressive house spider, and the yellow sac spider. Only the brown recluse and black widow spiders have been associated with significant envenomation and very rare reports of human death; these spiders will be discussed in more detail below.
Among physicians and the general public, the perceived threat of spider bites far exceeds the actual risk. In general, people fear spiders and have misperceptions about spider behavior. A spider generally bites a person to defend itself, and usually just once. Few spiders are truly aggressive; most are timid and will retreat if given a chance. Bites occur because someone inadvertently invades the spider's space.

have been found in California as well. The northern black widow is found primarily in the northeastern US and southeastern Canada, though its range overlaps that of L. mactans quite a bit. The western black widow is found in the western half of the US as well as in southwestern Canada and much of Mexico.
The adult female black widow has a shiny, jet black, spherical abdomen with two connected red (occasionally yellow to orange) triangles on the underside that form a characteristic "hourglass" marking. Adult females are about 1/2-inch long, not including the legs (about 1-1/2 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 abdomen usually has red spots along the upper midline and white lines or bars radiating out to the sides. The surface of the black widow egg case is smooth. Newly hatched spiderlings are predominately white or yellowish-white, gradually acquiring more black and varying amounts of red and white with each molt. Juveniles of both sexes resemble the male and are harmless.

Avoiding Spider Bites Spiders generally prefer to live in undisturbed areas. Places where spiders are commonly found include the crawl spaces beneath homes, piles of stored lumber, hollow tile blocks, among stored items on shelves, behind shutters, in the folds of little-used clothing and shoes, within piles of old newspapers, and under objects in dark, littledisturbed areas. Although outdoor-living spiders also prefer quiet areas, web-builders may position their webs near lighted doorways to catch insects attracted to the light. The use of "bug lights" (outdoor electric lights that give off a yellow illumination designed not to attract insects) will prevent web-building behavior.

The female black widow spider has potent neurotoxic venom and is considered the most venomous spider in North America. Although the bite of a widow spider is much feared, the female injects such a small dose of venom that it rarely causes death. Prior to antivenom availability, black widow spiders killed approximately 5% of human bite victims1. Now, reports indicate human mortality rates to be less than 1% from black widow spider bites. Deaths from black widow bites among healthy adults are relatively rare in terms of the number of bites per thousand people. Only 63 deaths were reported in the US between 1950 and 19892. Widow spiders are generally nonaggressive and will retreat when disturbed.

Spider bites may occur when people put their hands into garden or household gloves that have been lying in a disused area, their feet into shoes that have not been worn for awhile, or when someone picks up and dons an article of clothing that has been lying unused on the floor or in a closet. On such occasions, the spider bites as it is about to be crushed. Some recluse and widow bites occur because people unwittingly reach into or bump their webs and stimulate an attack. Unpacking long-stored cardboard boxes is one method of encountering spiders in this manner and therefore it is prudent to use gloves when handling anything that has been stored.
Black Widow Spiders and a "new" invader, the Brown Widow Spider Currently, there are three recognized species of black widow spiders found in North America: the southern black widow (Latrodectus mactans), the northern black widow (L. variolus), and the western black widow (L. hesperus). The southern black widow is primarily found in (and is indigenous to) the southeastern US, ranging from Florida to New York, and west to Texas and Oklahoma. Southern black widows

The following are the most common symptoms of a black widow spider bite: immediate pain, burning, swelling, and redness at the site (double fang marks may be seen); cramping pain and muscle rigidity in the stomach, chest, shoulders, and back; headache; dizziness; rash and itching; restlessness and anxiety; sweating; eyelid swelling; nausea or vomiting; salivation; tearing of the eyes; weakness, tremors, or paralysis, especially in the legs.
People who are bitten are counseled to remain calm and immediately seek medical attention (contact a physician, hospital and/or poison center). An ice pack should be applied directly to the bite area to relieve swelling and pain. The spider should be collected for positive identification by a spider expert. A plastic bag, small jar, or pill vial is useful and no preservative is necessary, but rubbing alcohol can be used in the container to help preserve the spider.
Brown widow spiders, Latrodectus geometricus, are reported frequently in Georgia, but have not been implicated in human bites. Because of their local abundance, these are the widow spiders most often encountered by Georgians. Like black widow spiders, brown widow

The Georgia Epidemiology Report Via E-Mail To better serve our readers, we would like to know if you would prefer to receive the GER by e-mail as a readable PDF file.
If yes, please send your name and e-mail address to Gaepinfo@dhr.state.ga.us. | Please visit, http://health.state.ga.us/epi/manuals/ger.asp for all current and past pdf issues of the GER.

spiders also have an "hour glass" marking on the ventral side of the abdomen, and the brown widow is often mistaken for a black widow spider. However, the base coloration of this spider is a dark brown or mahogany and the top surface of the abdomen has a distinct pattern of markings. The brown widow egg case is textured and rough in appearance, due to the tufts of silk that are incorporated during the formation of the case. These egg cases can easily be spotted within the web, most often within the tunnel section where the female spider lives. Like all Latrodectus species, the female brown widow spider has a bite which is potentially venomous. However, very little venom is injected during a brown widow bite, so we do not see the serious, protracted symptoms characteristic of black widow spider bites.

rare because it requires a witness to the biting, recovery of and identification of the spider, and exclusion of other causes. In May 2002, the American College of Emergency Physicians published an article about a method for detecting brown recluse spider venom3 in skin biopsies of bite victims. A study done at the University of Michigan by a team of emergency medicine investigators found evidence that invasive biopsies are not necessary and, in fact, the Loxosceles (brown recluse) ELISA assay can detect brown recluse venom in hair samples. Since the vast majority of spider bites, specifically brown recluse spider bites, are difficult to diagnose if the spider is not brought in, this could be a beneficial test to ascertain the etiology of the skin lesion.

Recluse Spiders in Georgia The brown recluse or violin spider, Loxosceles reclusa, is the spider most often associated with reports of spider bites. It is about 1 inch long and has a violin shaped mark on its upper back. It is often found in warm, dry climates and prefers to stay in undisturbed areas such as basements, closets, and attics. It is not an aggressive spider, but will attack if trapped or held against the skin. Despite widespread fear of brown recluse spider bites, they are less deadly than black widow spider bites; almost all brown recluse bites heal without medical intervention, and very few result in serious outcomes such as skin grafting or death. Bites from brown recluse spiders can be unremarkable (requiring no care), localized (requiring some care but usually healing without intervention), dermonecrotic (a slow-healing, necrotic ulcerated skin lesion needing supportive care) or systemic (causing vascular and renal damage, sometimes life-threatening).
The following are the most common symptoms of a bite from a brown recluse spider: burning, pain, itching, or redness at the site which is usually delayed and may develop within several hours or days of the bite; a deep blue or purple area around the bite, surrounded by a whitish ring and large red outer ring similar to a "bulls eye"; an ulcer or blister that turns black; headache; body aches; rash; fever; and nausea or vomiting.
Diagnosing Spider Bites Most people with a spider bite will not recall being bitten. It is important to ask if the patient actually saw the spider that bit them, and whether they still have the spider. This is the best way to document a spider bite and determine which spider was involved. Any spider bite may result in itching or pain, rarely with small puncture wounds at the site. Typical symptoms, if any, include redness, itching and/or swelling that lasts a couple of days. Ninety percent of spider bites are selfhealing. Because spiders usually bite only once, a patient with multiple bite lesions is more likely to have been bitten by other arthropods such as fleas, bed bugs, ticks, mites or biting flies. Because spiders do not bite humans frequently or systematically, bites affecting multiple people in the same locale (such as a house, prison, dorm, etc.) are not spider bites.
Spider bites cannot be diagnosed just by looking at a skin lesion. However, diagnosis is based on physical signs. Confirmation is

Misdiagnosis of Spider Bites For decades, physicians have consistently used spider bites as a default diagnosis for idiopathic dermal necrosis, but the diagnosis of spider bite should not be used if the patient did not see the spider. Although brown recluse spider bites are often suspected, they are almost certainly over-diagnosed. In one study of 600 suspected "spider bite cases" in southern California, 80% were caused by other arthropods, mostly ticks and reduviid bugs4. During the 2001 anthrax attacks in the US, a famously misdiagnosed skin lesion in a 7-month old infant in New York was thought be a brown recluse spider bite; the actual diagnosis was cutaneous anthrax.

The misdiagnosis of "spider bites" can be applied to a wide spectrum of dermatologic conditions, some of which are far more dangerous than a spider bite (Table 1). A number of these conditions require therapy and should not be overlooked. Of particular note is methicillin-resistant Staphylococcus aureus or MRSA, which has become

Table 1. Some conditions which can cause necrotic skin wounds and have been misdiagnosed as or could be confused with "brown

recluse spider bites" (Vetter various sources)

Bite of the pajahuello (Ornithodoros coriaceus, an Argasid tick)

Periarteritis nodosa

Chemical burn

Poison ivy/oak infection

Chronic herpes simplex

Pressure ulcers/bed sores

Cutaneous anthrax

Purpura fulminans

Diabetic ulcer

Pyoderma gangrenosum

Erythema chronicum migrans (Lyme disease)

Erythema multiforma

Rocky Mountain spotted fever

Erythema nodosum

Sporotrichosis

Focal vasiculitis

Streptococcus infection

Gonococcal arthritis dermatitis

Stevens-Johnson syndrome

Infected herpes simplex

Syphilitic chancre

Leishmaniasis

Thromboembolic phenomena

Lymphomatoid papulosis

Toxic epidermal necrolysis (Lyells syndrome)

Methicillin-resistant Staphylococcus aureus Varicella zoster (shingles) (MRSA)

Other arthropod bites

Warfarin poisoning

(flea, mite, biting fly, true bug, bed bug)

Division of Public Health http://health.state.ga.us
Stuart T. Brown, M.D. Director
State Health Officer

Epidemiology Branch http://health.state.ga.us/epi
Susan Lance, D.V.M., Ph.D. Director
State Epidemiologist

Georgia Epidemiology Report
Editorial Board Carol A. Hoban, M.S., M.P.H. Editor
Kathryn E. Arnold, M.D. Cherie Drenzek, D.V.M., M.S. Susan Lance, D.V.M., Ph.D.
Stuart T. Brown, M.D. Angela Alexander - Mailing List
Jimmy C-l2ant-on, Jr. - Graphic Designer

Two Peachtree St., N.W. Atlanta, GA 30303-3186 Phone: (404) 657-2588
Fax: (404) 657-7517

Georgia Department of Human Resources
Division of Public Health

Please send comments to: gaepinfo@dhr.state.ga.us

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 ucr.edu/index.html. 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 homes in Missouri and Oklahoma during 2001 yielded 45 and 30 brown recluse spiders, respectively. Despite these infestations, no spider bites of the inhabitants of these three homes occurred. With the lack of reported recluse bites despite high levels of infestation, it is implausible that brown recluse spider bites would occur frequently in non-endemic areas. It has been estimated that 60% of alleged brown recluse bites occur in areas where no recluse spiders are known to exist!
In Georgia, brown recluse spiders have rarely been documented in the northern and central parts of the state. This means that brown recluse bites should be considered rare in Georgia, and other etiologies entertained first.
This article was written by Rosmarie Kelly, Ph.D., M.P.H.
REFERENCES 1. Bettini S. Epidemiology of latrodectism. Toxicon 1964; 2:93-101. 2. Miller, T. 1992. Latrodectism: bite of the black widow spider. Am. Fam.
Phys. 45:181 3. HF Gomez, DM Krywko, WV Stoecker. May 2002. New Methods
for Detecting Brown Recluse Spider Venom. American College of Emergency Physicians. pp 469-474. 4. Richard S. Vetter and P. Kirk Visscher. 1998. Bites and Stings of Medically Important Venomous Arthropods. International Journal of Dermatology 37: 481-496. http://spiders.ucr.edu/dermatol.html 5. Catherine Baxtrom, Tara Mongkolpradit, John N. Kasimos, Laima M. Braune, Ronald D. Wise, Petra Sierwald, and Kyle H. Ramsey. 2006. Common House Spiders Are Not Likely Vectors of CommunityAcquired Methicillin-Resistant Staphylococcus aureus Infections. J. Med. Entomol. 43(5): 962-965 6. Richard S. Vetter and Diane K. Barger. 2002. An Infestation of 2,055 Brown Recluse Spiders (Araneae: Sicariidae) and No Envenomations in a Kansas Home: Implications for Bite Diagnoses in Nonendemic Areas. J. Med. Entomol. 39(6): 948-951.

U.S. Map -Loxosceles spp distribution, Rick Vetter, UCR
Spiders. Pest Control Technology. Franzak & Foster Co., Cleveland, Ohio. 200 pp. Rosenstein ED, Kramer N. Lyme disease misdiagnosed as a brown recluse spider bite. Ann Intern Med 1987; 107:782. Russell FE. A confusion of spiders. Emerg Med 1986; 18:8-13. Russell FE, Gertsch WJ. Letter to the editor. Toxicon 1982; 21:337-339. Russell FE, Waldron WG. Letter to editor. Calif Med 1967; 106:248-249 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 (Araneae: Sicariidae): Loxosceles Spiders Are Virtually Restricted to their Known Distributions but Are Perceived to Exist Throughout the United States. J. Med. Entomol. 42(4): 512-521. 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: 413418. 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. Communityacquired methicillin-resistant. Staphylococcus aureus: an emerging threat. Lancet Infect. Dis. 5: 275-286.
WEB SITES http://www.webmd.com/hw/skin_wounds/hw95886.asp http://www.calpoison.org/public/spiders.html h t t p : / / w w w. e n t o m o l o g y. c o r n e l l . e d u / S p i d e r O u t r e a ch / Re s o u r c e s / S p i d e r _
Identification.shtml University of Maryland Medical Center, First Aid Spider Bites. http://www.umm.
edu/non_trauma/spider.htm eMedicineHealth: Brown Recluse Spider Bite http://www.emedicinehealth.com/spider_bite_brown_recluse_spider_bite/article_
em.htm Brown recluse spider info: http://spiders.ucr.edu Hobo spider ID guide: http://www.puyallup.wsu.edu/plantclinic/resources/pdf/
pls116hobospider.pdf The Illinois-Iowa Brown Recluse Project: http://department.monm.edu/biology/
recluse-project/index.htm Spider Myths Web Site: http://www.washington.edu/burkemuseum/spidermyth/
index.html USA Spider Chart. www.termite.com

ADDITIONAL RESOURCES Gertsch, W.J., Ennik, F., 1983. The spider genus Loxosceles in North America, Central
America, and the West Indies (Araneae, Loxoscelidae). Bull. Am. Mus. Nat. Hist. 175,264360. Stoy A Hedges and Mark S Lacey. 2001. Field Guide for the Management of Urban

Questions About MRSA and Answers From the Experts Answers to many practical, clinical questions about MRSA, ranging from the best way to identify patients with MRSA to what clinicians should do if they have personally had an infection. Medscape Nurses 8(2) 2006.

-3 -

The Georgia Epidemiology Report Epidemiology Branch Two Peachtree St., NW Atlanta, GA 30303-3186

PRESORTED STANDARD U.S. POSTAGE
PAID ATLANTA, GA PERMIT NO. 4528

March 2007

Volume 23 Number 03

Reported Cases of Selected Notifiable Diseases in Georgia, Profile* for December 2006

Selected Notifiable Diseases
Campylobacteriosis Chlamydia trachomatis Cryptosporidiosis E. coli O157:H7 Giardiasis Gonorrhea Haemophilus influenzae (invasive) Hepatitis A (acute) Hepatitis B (acute) Legionellosis Lyme Disease Meningococcal Disease (invasive) Mumps Pertussis Rubella Salmonellosis Shigellosis Syphilis - Primary Syphilis - Secondary Syphilis - Early Latent Syphilis - Other** Syphilis - Congenital Tuberculosis

Total Reported for December 2006
2006 22 3027 11 0 36 1338 14 3 9 3 0 4 0 2 0 115 126 1 14 8 21 0 40

Previous 3 Months Total

Ending in December

2004

2005 2006

130

110

126

8067

8180

9177

39

46

80

8

7

6

238

209

158

4040

3974

4533

26

26

33

43

20

9

114

43

34

7

14

13

0

1

1

3

4

6

1

1

0

10

7

7

0

0

0

458

550

471

170

258

587

27

35

14

111

137

67

71

108

38

221

221

130

2

1

2

151

135

124

Previous 12 Months Total

Ending in December

2004 2005

2006

592

591

572

34473

33277

38012

181

155

285

23

31

44

916

757

652

16067

15707

19030

117

113

121

317

126

50

448

201

183

43

39

37

12

6

8

15

18

19

2

2

4

29

48

30

1

0

0

1945

1935

1885

659

673

1379

119

137

105

481

538

407

397

408

311

868

969

870

6

2

9

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 Period
Latest 12 Months**:
2/06-1/07
Five Years Ago:
2/02-1/03

Disease

Total Cases Reported*

Classification <13yrs

>=13yrs Total

HIV, non-AIDS

19

3,094

3,113

AIDS

10

2,204

2,214

HIV, non-AIDS

-

-

-

AIDS

1

1,560

1,561

Percent Risk Group Distribution

Female MSM

IDU

30

31

8

2

28

32

8

3

-

-

-

-

25

39

9

3

Race Distribution

HS

Unknown Perinatal White Black

Hispanic Other

15

43

0.5

20

75

4

1

12

45

0.5

21

73

6

<1

-

-

-

-

-

-

-

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

- 4 -