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Spider Envenomation, Widow
Updated: Jul 24, 2008
Introduction
Background
Widow spiders belong to the genus Latrodectus and include the black widow spider (Latrodectus mactans mactans) in the United States. The term widow spider is used because not all species in the genus Latrodectus are black. Other widow spiders in North America include the brown widow (Latrodectus geometricus), the red-legged widow (Latrodectus bishopi), Latrodectus variolus, and Latrodectus hesperus. The redback spider (Latrodectus hasselti) is endemic to Australia. Latrodectus mactans tredecimguttatus and Latrodectus pallidus are found in Europe and South America, and the button spider (Latrodectus indistinctus) is found in South Africa.
The adult female black widow spider is approximately 2 cm in length and shiny black with a red-orange hourglass or spot on the ventral abdomen. The male is much smaller, brown, and incapable of envenomating humans. Juvenile females are also brown but have the general body morphology of the adult. Males and juveniles have a pale hourglass shape, similar to adult females. The female sometimes eats the male during or after copulation. Webs are irregular, low-lying, and commonly seen in garages, barns, outhouses, and foliage. Other widow spiders are generally black but may have red spots, such as Latrodectus mactans tredecimguttatus, or a dorsal red stripe, such as the redback spider. Latrodectus geometricus is brown with red and yellow markings.
Black widow spider (Latrodectus mactans) with egg sac. Photo by Sean Bush, MD.
Black widow spider (Latrodectus mactans) and offspring. Photo by Sean Bush, MD.
Pathophysiology
Alpha-latrotoxin causes the toxic effects observed in humans by opening cation channels (including calcium channels) presynaptically, causing increased release of multiple neurotransmitters. This results in excess stimulation of motor endplates with resultant clinical manifestations. Clinically, the predominant effects are neurological and autonomic, in contrast to the dermonecrotic local effects associated with spiders causing necrotic arachnidism (eg, brown spiders [Loxosceles species]).
Frequency
United States
Approximately 2500 widow spider bites were reported to the American Association of Poison Control Centers (AAPCC) in 2006, although this figure is probably conservative because of underreporting.
Mortality/Morbidity
In the United States, an average of 4 deaths per year are reported to occur as a result of spider bites. However, no deaths caused by widow spider envenomation have been reported to the AAPCC since its first annual report in 1983. Deaths after black widow spider bites were reported in 2001 and 2003 in Spain and Greece, respectively.
Clinical
History
- Initial pain at the bite site is generally trivial and may go unnoticed. It commonly is described as a pinch or pinprick; however, infants may present with unexplained crying.
- Within about 1 hour, systemic symptoms begin and may last for a few days.
- Muscle cramping
- Cramping may occur locally, around the area bitten.
- It may extend into large muscle groups, such as the abdomen, back, chest, and thighs.
- Case reports suggest involvement of smooth muscles, such as bronchial or endometrial.
- Nausea and vomiting
- Headache
- Anxiety
Physical
- Abnormal vital signs
- Hypertension
- Tachycardia
- Diaphoresis
- Locally, around the area bitten
- Remote from site of envenomation
- Tiny fang marks may be visible.
- Local effects are usually limited to a small circle of redness and/or induration around the immediate bite site. A central reddened fang puncture site surrounded by an area of blanching and an outer halo of redness is described as a having a target appearance.
- Abdominal rigidity may mimic an acute abdomen.
- Neurologic effects, including mild weakness, fasciculations, and ptosis, have been described.
- Latrodectus facies, characterized by spasm of facial muscles, edematous eyelids, and lacrimation may occur. This can be mistaken for an allergic reaction.
- Bronchorrhea and pulmonary edema have been described in Europe and South Africa.
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References
Allen RC, Norris RL. Delayed use of widow spider antivenin. Ann Emerg Med. Sep 1995;26(3):393-4. [Medline].
Boyer Hassen LV, McNally JT, Binford GJ. Spider bites. In: Auerbach PS, ed. Wilderness Medicine. 4th ed. St. Louis: Mosby-Year Book; 2001:807-838.
Bush SP, Thomas TL, Chin ES. Envenomations in children. Pediatr Emerg Med Rep. 1997;2:1-12.
Bush SP, Naftel J. Injection of a whole black widow spider. Ann Emerg Med. Apr 1996;27(4):532-3. [Medline].
Bush SP. Black widow spider envenomation mimicking cholecystitis. Am J Emerg Med. May 1999;17(3):315. [Medline].
Clark RF, Wethern-Kestner S, Vance MV, Gerkin R. Clinical presentation and treatment of black widow spider envenomation: a review of 163 cases. Ann Emerg Med. Jul 1992;21(7):782-7. [Medline].
Cohen J, Bush S. Case report: compartment syndrome after a suspected black widow spider bite. Ann Emerg Med. Apr 2005;45(4):414-6. [Medline].
Gonzalez Valverde FM, Gomez Ramos MJ, Menarguez Pina F, Vazquez Rojas JL. [Fatal latrodectism in an elderly man]. Med Clin (Barc). Sep 22 2001;117(8):319. [Medline].
Langley RL, Morrow WE. Deaths resulting from animal attacks in the United States. Wild Environ Med. 1997;8:8-16.
Pneumatikos IA, Galiatsou E, Goe D, Kitsakos A, Nakos G, Vougiouklakis TG. Acute fatal toxic myocarditis after black widow spider envenomation. Ann Emerg Med. Jan 2003;41(1):158. [Medline].
Watson WA, Litovitz TL, Klein-Schwartz W, Rodgers GC Jr, Youniss J, Reid N, et al. 2003 annual report of the American Association of Poison Control Centers Toxic Exposure Surveillance System. Am J Emerg Med. Sep 2004;22(5):335-404. [Medline].
Woestman R, Perkin R, Van Stralen D. The black widow: is she deadly to children?. Pediatr Emerg Care. Oct 1996;12(5):360-4. [Medline].
Bronstein AC, Spyker DA, Cantilena LR Jr, Green J, Rumack BH, Heard SE. 2006 Annual Report of the American Association of Poison Control Centers' National Poison Data System (NPDS). Clin Toxicol (Phila). Dec 2007;45(8):815-917. [Medline].
Hoxha R. Two Albanians die from black widow spider bites. BMJ. Aug 5 2006;333(7562):278. [Medline].
Further Reading
Keywords
black widow spider, spider bite, black widow spider bite, spider envenomation, Latrodectus, Latrodectus mactans mactans, brown widow, Latrodectus geometricus, red-legged widow, Latrodectus bishopi, redback spider, Latrodectus hasselti, button spider, Latrodectus indistinctus, Latrodectus variolus, Latrodectus hesperus, Latrodectus mactans tredecimguttatus, Latrodectus pallidus
