Cutaneous Larva Migrans: Diagnosis and Treatment
Diagnosis
This is cutaneous larva migrans (CLM), a hookworm larval infection acquired from contaminated soil or sand, presenting as a characteristic serpiginous, intensely pruritic rash that migrates 1-2 cm per day. 1
Clinical Features
- Characteristic serpiginous (snake-like), raised, erythematous track that advances 1-2 cm daily, distinguishing it from other dermatoses 1
- Intense pruritus that may prevent sleep, often leading to bacterial superinfection from scratching 2
- Most commonly affects the feet (39% of cases), followed by buttocks (18%) and abdomen (16%) after barefoot contact with contaminated beaches or soil 3
- Caused by dog and cat hookworm larvae (Ancylostoma braziliense and A. caninum) that penetrate human skin but cannot complete their life cycle 4, 2
Diagnostic Approach
- Diagnosis is purely clinical based on the characteristic migratory rash and exposure history 1
- Laboratory tests (eosinophil count, serology) are typically normal and not required 3
- Eosinophilia may occasionally be present but is not a reliable diagnostic feature 1
Treatment Recommendations
Treat with oral ivermectin 200 μg/kg as a single dose OR albendazole 400 mg once daily for 3 days. 1
First-Line Oral Therapy
- Ivermectin 200 μg/kg as a single dose achieves 81-100% cure rates and is the preferred option 1, 5
- Albendazole 400 mg once daily for 3 days is an equally effective alternative, with cure rates of 77-100% 1, 3
- Both agents are superior to topical therapy for multiple lesions or extensive disease 5
When to Consider Topical Therapy
- Topical thiabendazole 10-15% cream applied 3 times daily for 10-15 days may be used for single, localized lesions but has limited efficacy (80% cure rate) 5, 3
- Topical therapy requires prolonged application and is impractical for multiple lesions 5
Agents to Avoid
- Do NOT use oral thiabendazole due to poor efficacy (68-84% cure rate with single dose) and poor tolerability compared to albendazole or ivermectin 5, 3
- Cryotherapy (freezing the leading edge) rarely works and is not recommended 5
Treatment Monitoring and Follow-Up
Expected Response
- Most patients (64%) are cured with a single treatment course, though 25% require a second course and 2% may need three courses 3
- Median symptom duration before treatment is 8 weeks (range 1-104 weeks), but treatment accelerates resolution 3
- The infection is self-limited; larvae eventually die within months even without treatment, but treatment is mandatory due to intense pruritus and risk of bacterial superinfection 4, 2
When to Retreat
- If the rash continues to advance 7-10 days after treatment, repeat the same regimen 5, 3
- Persistent itching without track advancement may represent healing inflammation rather than treatment failure 2
Prevention Counseling
Individual Protection
- Avoid direct skin contact with potentially contaminated sand or soil, particularly on beaches in tropical regions 2
- Wear protective footwear in endemic areas to prevent larval penetration 2, 6
Epidemiological Context
- Most infections are acquired in Africa (32%), the Caribbean (30%), and Southeast Asia (25%) 3
- 95% of patients have a history of beach exposure, making this the primary risk setting 3
- Children playing barefoot are at particular risk in areas where dog and cat hookworms are endemic 6
Common Pitfalls to Avoid
- Do not confuse CLM with "larva currens" (Strongyloides infection), which moves much faster (several millimeters per second vs. 1-2 cm per day) and typically affects the trunk, upper legs, and buttocks 1
- Do not misdiagnose as tinea pedis or other fungal infections, which lack the characteristic advancing serpiginous track 7, 8
- Do not order unnecessary laboratory tests; the diagnosis is clinical and eosinophilia is typically absent 3
- Do not use inadequate treatment durations with albendazole; a full 3-day course is required for optimal efficacy 1