Cutaneous Larva Migrans
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Direct answer
Cutaneous larva migrans is a pruritic, serpiginous skin eruption caused by hookworm larvae of animal origin, most often Ancylostoma braziliense, that wander through the epidermis of a dead-end human host. It is acquired by skin contact with sand or soil contaminated by the faeces of infected dogs and cats, classically on beaches. Albendazole or single-dose ivermectin is the usual treatment, and the infestation resolves once the larvae are killed.
What you must remember
- Causative agents: larvae of animal hookworms, chiefly Ancylostoma braziliense from dogs and cats, with A. caninum also implicated.
- Route of entry: penetration of intact or abraded skin on the feet, buttocks, hands or knees after contact with contaminated sand or soil.
- Classic lesion: an intensely itchy, raised, erythematous, serpiginous track that advances by a few millimetres to a centimetre a day.
- Dead-end host: the larvae cannot mature in humans, so the eruption is self-limiting and not spread from person to person.
- Drug of choice: albendazole, commonly 400 mg daily for three days; single-dose oral ivermectin 200 micrograms/kg is equally effective and often preferred.
- Adjuncts: topical thiabendazole and cryotherapy are options for lesions that resist oral therapy, and antihistamines control the itch.
- Key mimic: larva currens of Strongyloides stercoralis, which advances far faster and raises the possibility of an underlying gastrointestinal infection.
From a beach walk to a cured track
A 24-year-old returns from a beach holiday with an itchy, raised red track on the sole that extends a few millimetres each day. The management is clinical first, then therapeutic, and finally preventive, with each step tied to the pattern of the eruption.
- Take the exposure history: Ask about barefoot walks on sand, lying on beaches, gardening and pets at home. Symptoms usually appear within days to weeks of exposure, which supports the diagnosis.
- Examine the track: Look for a slightly raised, serpiginous, erythematous track whose leading edge is the active part of the lesion. Tracing the margin helps distinguish it from other creeping lesions.
- Exclude the mimics: Consider larva currens when the track advances over hours rather than days, since this points to Strongyloides. Stool examination and a complete blood count with eosinophil count help when the spread is unusually rapid.
- Treat with an anthelmintic: Oral albendazole, commonly 400 mg daily for three days, is a standard course, and single-dose ivermectin 200 micrograms/kg is an equally effective alternative. Treatment is directed at the larvae because antibiotics have no effect on them.
- Relieve symptoms and review: Antihistamines reduce itch, and topical thiabendazole or cryotherapy can be added for stubborn tracks. The patient is reviewed after a few weeks to confirm that the track has stopped advancing.
- Advise prevention: Covering the feet on sand, avoiding bare-skin contact with contaminated soil and deworming pets interrupt reinfection.
Where the exam tries to catch you
Cutaneous larva migrans items test the parasite's dead-end biology and the difference from its rapidly spreading mimic.
- Trap: treating the track with antibiotics as for an ordinary bacterial infection. Correct: the lesion is parasitic, so an anthelmintic such as albendazole is the definitive treatment.
- Trap: believing the infection spreads from one patient to another. Correct: humans are dead-end hosts, so the disease is acquired from animal-contaminated sand or soil.
- Trap: mistaking larva currens for cutaneous larva migrans. Correct: the faster advance and the possibility of immunosuppression or gut infection point to Strongyloides, which needs stool and serological evaluation.
- Trap: overlooking that ivermectin is an alternative and not a second line of the same class. Correct: albendazole and ivermectin act through different mechanisms, so either may be used when the first is unavailable.
Frequently asked questions
Which hookworm species most commonly causes cutaneous larva migrans?
Ancylostoma braziliense is the species most commonly implicated in cutaneous larva migrans, its larvae reaching humans from the faeces of infected dogs and cats. A. caninum is also reported in the same clinical syndrome.
Why is cutaneous larva migrans not transmitted from person to person?
Humans are dead-end hosts for animal hookworm larvae, which wander in the skin without maturing into adult worms. Because the larvae cannot complete their life cycle in people, cutaneous larva migrans is acquired only from contaminated sand or soil.
What is the drug of choice for cutaneous larva migrans?
Albendazole is the usual exam answer for cutaneous larva migrans, commonly given as 400 mg daily for three days. Single-dose oral ivermectin 200 micrograms/kg is an equally effective alternative, and topical thiabendazole or cryotherapy may be added for resistant lesions.
How does larva currens differ from cutaneous larva migrans?
Larva currens is a rapidly advancing serpiginous eruption caused by Strongyloides stercoralis, moving over hours, whereas cutaneous larva migrans advances over days. The rapid spread of larva currens suggests an underlying gastrointestinal infection, which needs evaluation in immunosuppressed patients.