Millipede Envenomation

Background

Millipedes are elongated cylindrical segmented arthropods that bear two pairs of legs per body segment. They are found in a wide variety of habitats. They are generally very slow-moving creatures and are relatively innocuous. Falling into the class Diplopoda and the phylum Arthropoda, millipedes comprise some 7000 species.^{[1, 2, 3, 4, 5, 6, 7]}

See the images below.

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The desert millipede, Orthoporus ornatus. Photo by Robert Norris, MD.

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Millipede contact injury on day 3 following exposure.

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Pathophysiology

Millipedes do not have biting mouthparts or fangs. Their medical importance comes from their ability to secrete an irritating defensive liquid from pores along their sides. Such secretions contain benzoquinones, aldehydes, hydrocyanic acid, phenols, terpenoids, nitroethylbenzenes, and other substances.^{[8, 9, 10, 11, 12]}

Some species are capable of squirting these liquids to distances of up to 80 cm.^[13] Most envenomations occur from direct contact of the millipede with the skin.

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Prognosis

Millipede envenomations are self-limited. No deaths have been documented from millipede exposures, and it is unlikely that such an exposure could be fatal, even to a small child.^[14]  

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History

The history may indicate that a patient was handling a millipede. On occasion, the history of a patient (eg, a sleeping victim, small child) may be obscure.^{[15, 16, 17, 18, 19]}

• Skin irritation
• Pain
• Brown staining at the site of contact
• Slight blistering
• Eye irritation and pain

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Physical Examination

Physical examination findings include the following:

• Local erythema
• Mild edema
• Vesicles
• Occasionally, cracked skin that may slough and then heal
• Conjunctivitis, which may lead to ulceration of the conjunctiva and cornea

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Complications

Cutaneous exposures generally heal without complications.

Conjunctivitis or corneal ulcerations can complicate eye exposures.

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Laboratory Studies

No laboratory studies are required.

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Approach Considerations

Any millepede secretions on the patient's skin should be washed away with soap and water.

Eye exposure should be treated similarly to corneal burns, with prompt immediate instillation of local anesthetic drops, followed by copious irrigation with saline solution or water.^{[13, 21]}  In consultation with ophthalmology, topical antimicrobials and topical steroids can be considered.^[13]

Adequate tetanus immunization status should be ensured.

Topical steroid creams may be beneficial for local skin irritation.

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Prevention

Beyond avoidance of handling millipedes, little deterrence is required.

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Long-Term Monitoring

Follow-up care is generally unnecessary for millipede envenomation unless local complications ensue or the eyes are involved.

In ocular cases, the patient should be examined daily until the eye is healed.

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Medication Summary

Significant conjunctivitis or dermatitis caused by toxic millipede secretions can be treated with topical steroids.

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Prednisolone, ophthalmic (Pred Forte)

• Dosing, Interactions, etc.

Clinical Context:  Prednisolone ophthalmic decreases inflammation by suppressing the migration of polymorphonuclear leukocytes and reversing increased capillary permeability.

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Prednisolone/sulfacetamide ophthalmic

• Dosing, Interactions, etc.

Clinical Context:  Prednisolone/sulfacetamide ophthalmic treats steroid-responsive inflammatory ocular conditions that have a risk of infection.

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Class Summary

These agents prevent further ulcerations of the cornea and should be given in consultation with an ophthalmologist.

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Triamcinolone topical

• Dosing, Interactions, etc.

Clinical Context:  Triamcinolone topical treats inflammatory dermatitis that is responsive to steroids. It decreases inflammation by suppressing the migration of polymorphonuclear leukocytes and reversing capillary permeability.

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Hydrocortisone topical

• Dosing, Interactions, etc.

Clinical Context:  Hydrocortisone topical treats inflammatory dermatitis responsive to steroids. It decreases inflammation by suppressing the migration of polymorphonuclear leukocytes and reversing capillary permeability.

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Class Summary

These agents are used to treat erythema and skin irritation that result from chemical insults. They help prevent further ulcerations of the skin.

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