Cutaneous larva migrans — DTM&H MCQ

Correct answer: E — Ancylostoma braziliense

The correct answer is E, Ancylostoma braziliense. This dog and cat hookworm causes cutaneous larva migrans: filariform larvae penetrate bare skin (classically the foot) after contact with sand or soil contaminated by animal faeces, exactly as described with beach exposure. Humans are a dead-end host, so the larvae lack the collagenase needed to breach the basement membrane and invade deeper tissue; they wander in the epidermis, producing an intensely pruritic, serpiginous, migratory track that advances at roughly 1 to 2 cm per day, matching the stem precisely. This clinical picture (travel history, animal-contaminated sand, slow serpiginous creeping eruption) is pathognomonic and is the classic DTMH exam vignette for Ancylostoma braziliense. Why the other options are wrong: D. Necator americanus: this human hookworm penetrates skin but larvae migrate onward through the venous system to the lungs and gut to mature, they do not produce a prolonged creeping cutaneous eruption. B. Strongyloides stercoralis: causes larva currens, a similar but much faster migrating urticarial track (centimetres per hour, often perianal), and autoinfection persists for years, unlike the day-scale migration here. A. Dracunculus medinensis: acquired by drinking water containing infected copepods, not skin penetration; presents with a painful blister that ruptures to release a visible worm, not a migrating track. C. Tunga penetrans: the female sand flea burrows into the skin (usually feet) causing a static painful, itchy nodule with a central black punctum, it does not migrate. Key point: A serpiginous, intensely itchy track migrating slowly (1 to 2 cm/day) after walking barefoot on sand contaminated by dog or cat faeces is cutaneous larva migrans from Ancylostoma braziliense, treated with oral ivermectin or albendazole.

Reference: Caumes E. Treatment of cutaneous larva migrans. Clinical Infectious Diseases. 2000;30(5):811-814 (aetiology and albendazole/ivermectin dosing for Ancylostoma braziliense cutaneous larva migrans); dosing consistent with BNF entries for albendazole and ivermectin, bnf.nice.org.uk