Cutaneous larva migrans

A creeping eruption worries a young man recently back from a Thai holiday.

A 35-year-old man presents with a three-week history of a raised, serpiginous (snake-like) and pruritic eruption over the back of the heel since returning from a beach vacation in Thailand.

He is otherwise well and does not recall any injury or illness while away. He is convinced the rash is “alive and expanding”. He feels certain he has an elongating worm tunnelling under his skin. What is the diagnosis and is he correct?

PROVISIONAL DIAGNOSIS

Cutaneous larva migrans (CLM) – or creeping eruption – is a parasitic skin infection caused by animal hookworm larvae. The larvae are present in infected animal droppings in soil and sand, including tropical beaches. Less commonly, infestations can occur within Australia.

Worldwide, Ancylostoma braziliense is the most common hookworm responsible for CLM.

Non-human hosts such as cats and dogs are true hosts required by the larva to complete its life cycle.

Humans are accidental or dead-end hosts where the larva is unable to penetrate the full thickness of the skin to complete its life cycle. In humans, the condition is therefore self-limiting and the larva eventually dies, still trapped within the skin.

Cutaneous larva migrans has a serpiginous appearance.

Strictly speaking, the serpiginous appearance of CLM is the result of the microscopic larva leaving a trail of inflamed and irritated skin, rather than the adult hookworm burrowing underneath the skin. The larva only reaches adult hookworm stage in animal hosts.

Early, active cases can be effectively treated with anthelmintics (anti-worm medication) and topical thiabendazole or albendazole are preferred for localised and limited disease.

For older infections, where there does not appear to be further advancement of the rash, no active intervention may be warranted as the larva may no longer be active (alive). Liquid nitrogen is not consistently reliable as it is not always easy to accurately target the larva, which is usually 1-2 cm ahead of the advancing end of the rash, on normal looking skin.

MANAGEMENT

Reassure the patient that the eruption is benign and is self-limiting. Follow the treatment recommendations above.

Treat any secondary infection.

This patient was prescribed oral ivermectin 12 mg (stat), as he preferred a single dose of oral medication rather than creams. After treatment, the itch subsided within 1-2 days and the rash cleared up within one week.

The patient was educated about the use of adequate footwear and towels to prevent repeat episodes through unnecessary contact with bare sand or soil.

Key facts: Cutaneous larva migrans

• Typically occur in tropics
• Children > adults
• No sex or racial predilection
• Portal of entry through the skin
• Commonly on buttocks and lower limbs
• Pruritic, serpiginous rash
• Migrates or ‘creeps’ up to 1 cm a day
• Self-limiting (1-2 months)
• Not infectious to others
• Can be treated with de-worming creams or tablets
• Treatment hastens clinical resolution
• Secondary infection may develop.

Treatment options

• Non-intervention
• Topical or oral thiabendazole
• Oral ivermectin
• Liquid nitrogen.

Dr Adrian Lim is a Fellow of the Australasian College of Dermatologists. Dr Stephen Shumack is Honorary Secretary of the Australasian College of Dermatologists