Cutaneous larva migrans (creeping eruption) — SAQ

Stem

A 27-year-old woman returns from a 10-day beach holiday in Barbados. Four days after returning, she develops an intensely itchy, slowly advancing (2–3 mm per day), serpiginous, erythematous tract on the lateral border of her right foot, which has now reached the medial border over the past 4 days. She walked barefoot on the beach and lay directly on the sand on most days. There is no abdominal pain, no cough, no fever, and no past medical history of note. On examination, the tract is raised, erythematous, and 6 cm long; the leading edge shows a small vesicle. There is no eosinophilia on full blood count. The rest of the skin examination is unremarkable.

Tasks

a) What is the most likely diagnosis? Justify your answer with the clinical features that support it. (2 marks)

b) List two clinical conditions that can mimic this presentation and describe the single most useful bedside or laboratory feature that distinguishes each from your diagnosis. (3 marks)

^[4]c) Outline your first-line and second-line treatment for this patient, including drug name, dose, duration, mechanism of action, and one key contraindication or precaution for each. (3 marks)

d) What advice would you give the patient about prevention of recurrence and about warning features that should prompt an earlier return to clinic? (2 marks)

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Suggested answer outline (marking guide)

^[3]a) Diagnosis (2 marks)

• Cutaneous larva migrans (creeping eruption / hookworm-related cutaneous larva migrans) — a common tropically acquired dermatosis in returned travellers.
• Supporting features: (1) recent tropical beach exposure with barefoot walking and direct sand contact; (2) intensely pruritic, slowly advancing (millimetres per day) serpiginous erythematous tract on a contact site (lateral foot); (3) short incubation of a few days; (4) leading-edge vesicle marking the larva's position; (5) absence of systemic features, normal eosinophil count.
• Causative organism: animal hookworm larvae. Humans are an aberrant host.

^[3]b) Two mimics and distinguishing features (3 marks)

• Larva currens (Strongyloides stercoralis) — recurrent urticarial wheal that migrates centimetres per HOUR (not millimetres per day); typically perianal/buttock; associated with eosinophilia, abdominal pain, and diarrhoea. Distinguishing test: Strongyloides serology (IgG ELISA) and stool O&P/agar plate.
• Cutaneous gnathostomiasis (Gnathostoma spinigerum) — intermittent migratory subcutaneous swellings (not a thin tract), marked eosinophilia, history of raw freshwater fish in Southeast Asia or Mexico. Distinguishing test: Gnathostoma serology; management differs (albendazole 400 mg BD for 21 days).
• (Accept also: cutaneous myiasis — visible maggot; tinea corporis — annular scaly plaque with central clearing; erythema chronicum migrans of Lyme disease — single annular expanding erythema with tick-bite history; scabies — burrows in webs of fingers with multiple family contacts.)

^[2]c) Treatment (3 marks)

• First-line: oral ivermectin 200 µg/kg as a SINGLE dose (cure rate >95%). Mechanism: binds glutamate-gated chloride channels in nematode neurons → paralysis and death of the larva. Key contraindication/precaution: avoid in pregnancy, in children under 15 kg body weight, and in patients from West/Central Africa with possible Loa loa co-infection (risk of ivermectin-induced encephalopathy in heavily microfilaraemic patients) — screen for microfilariae if exposure fits.
• Second-line: oral albendazole 400 mg orally once daily for 3–7 days (cure rate ~80–90%). Mechanism: binds β-tubulin and impairs microtubule assembly in the larva. Key contraindication/precaution: first-trimester pregnancy (teratogenicity in animal studies); mild hepatotoxicity — caution in pre-existing liver disease.
• (Optional 1 mark for adjuncts: oral antihistamines for pruritus; oral anti-staphylococcal antibiotic if impetiginised; tetanus status check.)

^[1]d) Prevention and warning features (2 marks)

• Avoid barefoot walking on tropical beaches and sand; use beach mats or towels when sitting or lying on sand; wear protective footwear (sandals, water shoes) in endemic areas; deworm domestic pets and keep dogs and cats off beaches and sandboxes.
• Warning features for early return: new lesions; secondary bacterial infection (increasing pain, redness, swelling, pus, fever); spreading cellulitis; new systemic symptoms (cough, wheeze, abdominal pain, diarrhoea) suggesting Strongyloides or Löffler-like pulmonary eosinophilia; marked peripheral eosinophilia on follow-up bloods; lack of improvement within 1–2 weeks of ivermectin (consider second dose or alternative diagnosis).

References4ShowHide

1. [1]Caumes E, et al. A randomized trial of ivermectin versus albendazole for the treatment of cutaneous larva migrans Am J Trop Med Hyg, 1993.PMID 8250105
2. [2]Kincaid L, et al. Management of imported cutaneous larva migrans: A case series and mini-review Travel Med Infect Dis, 2015.PMID 26243366
3. [3]Heukelbach J, et al. Epidemiological and clinical characteristics of hookworm-related cutaneous larva migrans Lancet Infect Dis, 2008.PMID 18471775
4. [4]Davies HD, Sakuls P, Keystone JS. Creeping eruption. A review of clinical presentation and management of 60 cases presenting to a tropical disease unit Arch Dermatol, 1993.PMID 8481019