You are in: eMedicine Specialties > Dermatology > ENVIRONMENTAL Black Widow Spider BiteArticle Last Updated: Jan 27, 2006AUTHOR AND EDITOR INFORMATIONSection 1 of 11
  Author: Adam S Stibich, MD, Staff Physician, Department of Dermatology, University of Medicine and Dentistry of New Jersey Adam S Stibich is a member of the following medical societies: American Academy of Dermatology and American Medical Association Coauthor(s): Robert A Schwartz, MD, MPH, Professor and Head of Dermatology, Professor of Medicine, Professor of Pediatrics, Professor of Pathology, Professor of Preventive Medicine and Community Health, UMDNJ-New Jersey Medical School Editors: James J Nordlund, MD, Professor Emeritus, Department of Dermatology, University of Cincinnati College of Medicine; David F Butler, MD, Professor of Dermatology, Texas A&M University College of Medicine; Director, Division of Dermatology, Scott and White Clinic; Director Dermatology Residency Training Program, Scott and White Clinic; Jeffrey J Miller, MD, Associate Professor, Department of Dermatology, Penn State University, Milton S Hershey Medical Center; Glen H Crawford, MD, Assistant Clinical Professor, Department of Dermatology, University of Pennsylvania School of Medicine; Chief, Division of Dermatology, The Pennsylvania Hospital; William D James, MD, Paul R Gross Professor of Dermatology, University of Pennsylvania School of Medicine; Vice-Chair, Program Director, Department of Dermatology, University of Pennsylvania Health System Author and Editor Disclosure Synonyms and related keywords: Latrodectus mactans bite, L mactans bite, hourglass spider bite, neurotoxin, latrotoxin, salivation, lacrimation, diaphoresis INTRODUCTIONSection 2 of 11
  BackgroundThe black widow, or hourglass, spider is the most dangerous species in the United States because of its potent venom. Spiders of the genus Latrodectus are worldwide in distribution. In the United States, they are found in every state except Alaska. They are predominantly observed in southern and western states. Five species of widow spiders are extant in the United States. Spiders of the Latrodectus genus are not aggressive, biting only when disturbed. Black widow spiders spin webs and await their prey. They can usually be found in their webs, which are often located near protected places, such as the undersides of stones and logs; in the angles of doors, windows, and shutters; and in littered areas such as city dumps, garages, barns, outhouses, and sheds. Often, these webs are found around outdoor toilet seats, resulting in bites on or near the genitalia. Adult females are mostly jet-black and often have striking red markings on their abdomens. On the ventral surface of the globular abdomen is a characteristic marking that consists of 2 equilateral triangles arranged apex to apex in an hourglass configuration. PathophysiologyThe venom of the black widow is a neurotoxin. It primarily causes systemic symptoms with little local damage at the bite site and no local necrosis. The venom mediates its effects through an initial release of massive amounts of acetylcholine at neuromuscular junctions. Latrotoxin is specific to nerve terminals; no direct release of transmitters from the adrenal medulla has been shown. As depolarization of the membrane occurs, a Ca++-dependent release of neurotransmitters down the concentration gradient ensues. Reuptake of the neurotransmitters appears to be blocked as well. FrequencyUnited StatesThe incidence of envenomation from black widow spiders is unknown. In Texas, 760 black widow spider bites were documented from 1998-2002, with an increased prevalence in western Texas. Mortality/MorbidityMore than 13,000 spider bites were reported to the American Association of Poison Control Centers in 1997, with no deaths; more than 1,300 of the bites were described as moderate or severe. The reported death rate from documented bites occurs in less than 1% of reported cases. Young children appear to be at highest risk for a lethal bite. AgeEnvenomation can occur in people of any age. The very young, the very old, and persons with cardiovascular disease are at increased risk for complications. CLINICALSection 3 of 11
HistoryEnvenomation can occur in people of any age. Initially, a severe pain in local muscle groups occurs, which then spreads to regional muscle groups. Severe cramps and contraction of musculature may extend throughout the body. The abdominal pains are frequently most severe, mimicking appendicitis, colic, or food poisoning. Other symptoms include headache, restlessness, anxiety, fatigue, and insomnia. PhysicalSigns of latrodectism include salivation, lacrimation, diaphoresis, tremors, tachycardia, bradycardia, hypertension, shock, and coma. Slight erythema, piloerection locally, mild edema or urtication, local perspiration, and lymphangiitis are the primary local features that may be present. DIFFERENTIALSSection 4 of 11
Brown Recluse Spider Bite Insect Bites
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| Drug Name | Calcium gluconate (Kalcinate) |
|---|---|
| Description | Mechanism of action remains uncertain. Moderates nerve and muscle performance and facilitates normal cardiac function. Can be administered IV initially, and calcium levels maintained with high-calcium diet. |
| Adult Dose | 1-2 mL/kg of 10% solution as slow IV; not to exceed 10 mL/dose |
| Pediatric Dose | Administer as in adults |
| Contraindications | Renal calculi; hypercalcemia; hypophosphatemia; renal or cardiac disease; digitalis toxicity |
| Interactions | May decrease effects of tetracyclines, atenolol, salicylates, iron salts, and fluoroquinolones; antagonizes effects of verapamil; large intakes of dietary fiber may decrease calcium absorption and levels |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | Extravasation necrosis; caution in digitalized patients, respiratory failure, acidosis, or severe hyperphosphatemia |
Relieve moderate to severe pain and decrease smooth muscle spasm.
| Drug Name | Meperidine (Demerol) |
|---|---|
| Description | Analgesic with multiple actions similar to those of morphine; may produce less constipation, smooth muscle spasm, and depression of cough reflex than similar analgesic doses of morphine. |
| Adult Dose | 50-150 mg PO/IV q3-4h prn; adjust dose according to severity of pain and response of patient |
| Pediatric Dose | 0.5-0.8 mg/lb up to adult dose q3-4h prn |
| Contraindications | Documented hypersensitivity; administration of MAOIs; upper airway obstruction or significant respiratory depression; administration during labor when delivery of premature infant is anticipated |
| Interactions | Monitor for increased respiratory and CNS depression with coadministration of cimetidine; hydantoins may decrease effects of meperidine; avoid with protease inhibitors |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | Caution in patients with head injuries because meperidine may increase respiratory depression and CSF pressure (use only if absolutely necessary); caution when using postoperatively and with history of pulmonary disease (suppresses cough reflex); substantially increased dose levels, because of tolerance, may aggravate or cause seizures, even if no prior history of convulsive disorders; monitor closely for morphine-induced seizure activity if prior seizure history |
Used to treat patients with symptoms due to bite by the black widow spider, L mactans.
| Drug Name | Latrodectus antivenin |
|---|---|
| Description | Neutralizes toxin, reducing morbidity and complications. |
| Adult Dose | 2.5 mL IM in anterolateral thigh; 2.5 mL of antivenin can be diluted in 10-50 mL of saline and administered IV over a 15-min period in severe cases or when patient is <12 y or in shock |
| Pediatric Dose | Administer as in adults |
| Contraindications | Documented hypersensitivity (may administer in severe envenomation despite hypersensitivity) |
| Interactions | None reported |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | Because of the presence of horse serum, agents for emergency treatment of anaphylaxis should be available |
| Media file 1: Black widow spider. Reprinted with permission from Cutis 1995; 56: 257. | |
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| Media file 2: Black widow spider (Latrodectus mactans) with egg sac. Photo by Sean Bush, MD. | |
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| Media file 3: Black widow spider (Latrodectus mactans) and offspring. Photo by Sean Bush, MD. | |
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Black Widow Spider Bite excerpt
Article Last Updated: Jan 27, 2006
