AUTHOR AND EDITOR INFORMATION

Section 1 of 8  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Treatment
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 8  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Treatment
• Follow-up
• Miscellaneous
• References

Background

Bites of spiders belonging to the genera Latrodectus, Phoneutria, and Loxosceles can cause severe, even fatal, systemic poisoning in humans. The most numerous of the venomous spiders are of the genus Latrodectus.

Pathophysiology

The venom of spiders in the genus Latrodectus (which includes the American black widow spider) and in members of the genus Phoneutria is a nonhemolytic, noncytotoxic neurotoxin that produces diffuse central and peripheral nervous excitement, autonomic activity, muscle spasm, hypertension, and vasoconstriction in humans. Other symptoms may include abdominal rigidity, intense pain, paresthesia, headache, sweating, nausea, and facial blood vessel congestion.

The venom of spiders of the Loxosceles genus (which includes the brown recluse spider) is a mixture of hemolysin and cytotoxin that causes ischemic necrosis at the site of the bite. The bite is often relatively painless, and the lesion is initially surrounded by a bluish-white halo of vasoconstriction that may later develop extensive gangrene. Tarantulas, or wolf spiders, of various genera, including Lycosa and Phidippus, also may cause necrosis and ulceration in humans.

The ocular effects of these spiders' venom include edema, gangrene, necrosis, ptosis, and purpura of the lid; conjunctivitis; subconjunctival hemorrhages; pupil constriction; retinal cyanosis; and visual disturbances.

Frequency

United States

Infrequent

Mortality/Morbidity

The genera Latrodectus, Phoneutria, and Loxosceles can cause severe, even fatal, systemic poisoning in humans.

Sex

Spider bites are more frequent in males than in females.

Age

Spider bites are most frequent among persons aged 10-30 years.

CLINICAL

Section 3 of 8  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Treatment
• Follow-up
• Miscellaneous
• References

History

Patients may report a history of an insect bite while moving wood or working in dark areas.

Physical

Usually, a white area appears around the lesion. The genera Latrodectus, Phoneutria, or Loxosceles may cause systemic reactions.

Causes

See Pathophysiology.

DIFFERENTIALS

Section 4 of 8  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Treatment
• Follow-up
• Miscellaneous
• References

TREATMENT

Section 5 of 8  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Treatment
• Follow-up
• Miscellaneous
• References

Medical Care

For mild lesions, broad-spectrum antibiotics and antihistamines are used.

It is important for the patient to capture and bring in the spider, if possible, to help determine the necessary treatment.

Poisoning by spiders of the Latrodectus genus may require intravenous calcium gluconate alternating with methocarbamol to relieve muscle cramps. These drugs are usually a part of the management by the emergentologist.

• Victims of poisoning by members of the genus Loxosceles may require hospitalization if sequelae develop. Hydroxyzine 100 mg may be given by the emergentologist to alter the necrotic lesion.
• If hemolysis develops, renal dialysis should be started within the initial 48-72 hours. Surgery may be required for large necrotic bites that extend into the fat.
• Antivenin is available for bites by spiders of the Loxosceles and Latrodectus genera and is very effective if given soon after the bite.
• Because of the excellent blood supply to the eyelids, the lid margin may be spared of gangrenous processes, and a propensity exists for self-repair.
• Complete blood count and observation of potential problem cases should be recognized early.

Consultations

Internist or family practitioner

FOLLOW-UP

Section 6 of 8  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Treatment
• Follow-up
• Miscellaneous
• References

Deterrence/Prevention

• Be aware of the potential for spider bites.

Complications

• Complications include hemolysis requiring renal dialysis.

Prognosis

• The prognosis is generally favorable.

Patient Education

• Educating the public on the importance of capturing the spider and bringing it to the physician's office can help determine the necessary treatment.
• For excellent patient education resources, visit eMedicine's Bites and Stings Center. Also, see eMedicine's patient education articles Black Widow Spider Bite and Brown Recluse Spider Bite.

MISCELLANEOUS

Section 7 of 8  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Treatment
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Prompt diagnosis and early treatment help reduce untoward sequelae.

REFERENCES

Section 8 of 8

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Treatment
• Follow-up
• Miscellaneous
• References

• Cole HP 3rd, Wesley RE, King LE Jr. Brown recluse spider envenomation of the eyelid: an animal model. Ophthal Plast Reconstr Surg. Sep 1995;11(3):153-64. [Medline].
• Edwards JJ, Anderson RL, Wood JR. Loxoscelism of the eyelids. Arch Ophthalmol. Nov 1980;98(11):1997-2000. [Medline].
• Jarvis RM, Neufeld MV, Westfall CT. Brown recluse spider bite to the eyelid. Ophthalmology. Aug 2000;107(8):1492-6. [Medline].
• Kelly TD, deHaro L. The dangers of pet tarantulas: experience of the Marseilles Poison Centre. J Toxicol Clin Toxicol. 1998;36:55-6.
• Portilla Cuenca J, Maresca Quintero M, Hoyos Sanabria B, Garcia Benito JI, Velez Medina J, et al. Spider's bite that develop eyelid necrosis. Arch Soc Esp Oftalmol. Feb 2005;80(2):105-7. [Medline].
• Wilson DC, King LE. Spiders and spider bites. Dermatol Clin. 1990;8:277-286. [Medline].
• Zeligowski AA, Peled IJ, Wexler MR. Eyelid necrosis after spider bite. Am J Ophthalmol. Feb 15 1986;101(2):254-5. [Medline].

Article Last Updated: Aug 20, 2007