A Serpiginous Lesion on the Foot
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Infested animals deposit parasite eggs via their feces to warm and moist soil where the larvae hatch. Larvae can enter the stratum corneum of human hosts via hair follicles, skin fissures or even intact skin. However, they are unable to penetrate the basement membrane to invade the dermis of humans.2 The condition is confined to the outer layers of human skin, as opposed to an animal host where larvae are able to penetrate the dermis and subsequently migrate via the lymphatic and venous systems to the lungs. The larvae then enter the alveoli and trachea, where they are subsequently swallowed and enter into the gastrointestinal system of the animal hosts in which more parasite eggs can be excreted to begin the cycle again once the larvae mature.2,3
Upon penetration, the larvae may lay dormant or begin migrating from a few millimetres to centimetres daily. The tracks are commonly raised, erythematous, serpiginous, and pruritic.4 Lesions are usually found on the distal lower extremities, but may also appear in the anogenital areas, hands and knees. Systemic signs such as elevated immunoglobulin E (IgE) levels, peripheral eosinophilia, and migratory pulmonary infiltrates rarely occur.5
Cutaneous larva migrans is diagnosed based on its clinical characteristics. It is a self-limiting condition because larvae eventually die in humans without being able to infest new hosts. Depending on the species, most lesions resolve within 8 weeks, but the condition may last for as long as 1 year in rare cases.5 Treatment is used to shorten the disease course, control the intense pruritus, and prevent the risk of secondary infection. Topical thiabendazole is the treatment of choice for mild and localized condition. Systemic treatment such as albendazole, mebendazole, and ivermectin are used in widespread cases or cases recalcitrant to topical treatment.6 Significant reduction in pruritus should be apparent within 48 hours of treatment and most lesions should clear within 1 week. Treatment with antibiotics is necessary in patients who suffer from secondary infections.
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