Cutaneous Larva Migrans

Intro & Etiology - The Wandering Worms

• Definition: Cutaneous Larva Migrans (CLM) is a parasitic skin infection caused by animal hookworm larvae migrating within the epidermis.
• Common Name: Creeping eruption.
• Causative Organisms:
  • Most common: Ancylostoma braziliense (cats, dogs).
  • Others: Ancylostoma caninum (dogs).
  • 📌 Mnemonic: "Animals Bring Creeping Larva" (A. braziliense, A. caninum)
• Transmission:
  • Direct skin penetration by infective filariform larvae.
  • Source: Soil/sand contaminated with feces from infected animals (dogs, cats).
• Lifecycle Basics:
  • Animal reservoir (definitive hosts: dogs, cats).
  • Eggs in animal feces → larvae hatch & mature in soil.
  • Humans are accidental, dead-end hosts; larvae cannot complete development.

⭐ CLM is a clinical diagnosis primarily seen in travelers to tropical/subtropical regions or those with soil/sand exposure (e.g., beaches, sandboxes).

Clinical Features - Itchy Tracks Tale

• Incubation Period: Typically a few days to 1 week post-exposure; can extend to 1 month.
• Hallmark Symptom: Intense, localized pruritus (itching); characteristically worse at night or with heat.

  ⭐ The intense itching is disproportionate to the visible skin signs and frequently precedes the appearance of tracks.

• Characteristic Lesion ("Creeping Eruption"):
  • Erythematous, slightly elevated, serpiginous (snake-like), linear, or tortuous tracts or burrows.
  • Width: 2-5 mm.
  • Larval migration rate: 1-2 cm/day (can be up to 5 cm/day); larva is 1-2 cm ahead of the visible advancing track.
  • Lesion advances from one end; older part may become dry, crusted, or vesicular.
• Common Sites (areas of skin exposed to contaminated soil/sand):
  • Feet (most common: soles, interdigital spaces), buttocks, hands, thighs, anogenital region.
• Associated Findings:
  • Vesicles or bullae along tracks.
  • Excoriations due to intense scratching.
  • Secondary bacterial infection (e.g., impetigo, cellulitis) is common.
  • Peripheral eosinophilia may be present.

Diagnosis & DDx - Spotting the Squiggles

• Clinical Diagnosis: Key!
  • History: Exposure to soil/sand contaminated with animal feces (beaches, sandboxes).
  • Lesions: Intensely pruritic, erythematous, serpiginous, or linear raised tracks that advance a few mm to cm daily.
• Dermoscopy: Can show brownish dots (larva) or empty tunnels.
• Biopsy: Rarely indicated; often fails to find larva. Shows eosinophilic infiltrate.

⭐ Biopsy is usually not performed as larvae are often missed; diagnosis is overwhelmingly clinical.

Key Differential Diagnoses (DDx):

Management & Prevention - Halting the Hikers

• Natural Course: Often self-limiting; spontaneous resolution typically occurs in weeks to months.
• Topical Therapy:
  • Thiabendazole 10-15% solution/ointment applied 2-3 times daily for 5-7 days.
• Systemic Therapy (DOC):
  • Ivermectin: 200 µg/kg single oral dose.
  • Albendazole: 400 mg orally daily for 3-7 days.
• Symptomatic Relief:
  • Oral antihistamines for severe pruritus.
  • Topical corticosteroids for inflammation and itching.
• Secondary Infections: Treat with appropriate antibiotics if present.
• Prevention:
  • Wear footwear on beaches, especially in known endemic areas.
  • Use protective barriers (e.g., towels) when sitting/lying on sand.
  • Regular deworming of dogs and cats (reservoir hosts).

⭐ Ivermectin is the drug of choice for systemic therapy due to its high efficacy and excellent tolerability.

High‑Yield Points - ⚡ Biggest Takeaways

• Caused by hookworm larvae (esp. Ancylostoma braziliense) from fecal-contaminated soil.
• Characterized by intensely pruritic, serpiginous, erythematous tracts ("creeping eruption").
• Most common on feet, buttocks, hands from direct skin contact with contaminated surfaces.
• Larva migrates 1-2 cm daily, visibly extending the track.
• Diagnosis is primarily clinical, based on the characteristic migratory lesions.
• Treatment: Oral albendazole or ivermectin are first-line; topical thiabendazole is an alternative.
• Often self-limiting; treatment alleviates severe itching & reduces secondary infection risk from scratching.