Cutaneous Larva Migrans

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Susan Montgomery

Infection is caused by the larval stages of dog and cat hookworms (Ancylostoma spp.). Although other worms, such as Strongyloides and Gnathostoma spp., can migrate through the skin, this section will describe infections with Ancylostoma spp.

Infection occurs by contact of skin with contaminated soil or beach sand. Eggs shed in the feces of infected hosts hatch in the soil and develop into third-stage larvae, which penetrate the skin and migrate through the epidermis. In humans, larvae are generally confined to the dermis and only rarely penetrate deeper. Deeper penetration is thought to be species specific (such as A. caninum).

Dog hookworms are found worldwide and are the species most commonly associated with cutaneous larva migrans (CLM). Cat hookworms are less commonly implicated. Infection is more likely to occur in tropical and semitropical countries where skin exposure is common and environmental conditions are conducive to larval development in the soil. For tourists, beach environments are the most likely source of infection due to walking and sitting in the sand with bare skin. Most cases are reported in travelers to the Caribbean, Africa, Asia, and South America. Patients without travel history may have acquired the infection in the United States. CLM can occur during summer months in northern areas when warmth and moisture are adequate for development of infective larvae in soil.

CLM is typically characterized by a serpiginous, erythematous track that appears in the skin, associated with intense itchiness, redness, and mild swelling. The larvae causing the tracks can migrate a few millimeters to several centimeters per day, depending on parasite species. Typical locations are the bottom or top of the foot or the buttocks.

Itching can occur as the larvae penetrate the skin. Creeping eruption usually appears 1–5 days later, but the incubation period may be up to a month or longer. Infection usually heals spontaneously within weeks to months but has been reported to persist for years in rare cases. Bacterial secondary infection can occur.

CLM is diagnosed clinically on the basis of characteristic skin lesions. Eosinophilia may not be present, and total IgE is usually normal. Serologic tests are not helpful in CLM except to rule out other causes of larva migrans syndromes such as toxocariasis or strongyloidiasis. Biopsy is not recommended since the track does not usually correlate with larva location.

Albendazole, 400 mg orally, daily for 3 days, is considered the treatment of choice. Ivermectin (200 µg/kg orally, daily for 1–2 days) is effective but not approved by the Food and Drug Administration for this indication. Additional information can be found on the CDC website (www.cdc.gov/parasites/hookworm).

Infective larvae take about 7 days to develop from eggs passed in dog feces and can survive for weeks in warm, moist soil. Preventive measures include reducing contact with contaminated soil by wearing shoes and protective clothing and using barriers when seated on the ground.

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