Cutaneous Larva Migrans

Cutaneous larva migrans is a skin eruption caused by the larvae of animal hookworms [Not the human hookworms which affect the alimentary system but rarely can cause this condition too].

The term literally means “wandering larvae in the skin”.  It is the most common tropically acquired dermatosis.

Ancylostoma braziliense is the most frequently found species.

Larval migration through the skin is marked by an intensely pruritic, linear, or serpiginous track which is also called as creeping eruption. [ Creeping eruptions occur in many other human skin diseases.]

Hookworm folliculitis is an uncommon form of cutaneous larva migrans, marked by pustular folliculitis of the buttocks.

Cutaneous larva migrans usually heals spontaneously within weeks or months but the larvae have been known to migrate for up to 1 year.

Complications include impetigo and local or general allergic reactions.

Cutaneous larva migrans is most commonly found in tropical and subtropical geographic areas [ Caribbean, Central America, South America, Southeast Asia, and Africa] but the spread has occur to other parts because of frequent travel. Prevalence is high in regions of warm climate.

Common causative agents are ancylostoma braziliense, Ancylostoma caninum, Uncinaria stenocephalaand Bunostomum phlebotomum are commonly involved types of hoo worm.

Other species including ancylostoma duodenale and nectar americanas [human hookworms are rare].

Who is at Risk to Get Cutaneous larva Migrans?

• Hobbies and occupations that involve contact with warm, moist, sandy soil
• Traveling to tropical/subtropical climate
• Barefoot beachgoers
• Sunbathers lying on sand or twoel [instead of mattress]
• Children in sandboxes
• Professions involving frequent soil contact
  • Carpente
  • Plumber
  • Farmer
  • Gardener
  • Pest exterminator

Pathophysiology

The eggs of hook worm are passed from animal feces into warm, moist, sandy soil, where the larvae hatch. They molt twice before the infective third stage. By using their proteases, larvae penetrate through follicles, fissures, or intact skin of the new host.

After penetrating the stratum corneum, the larvae shed their natural cuticle and begin migration.

In their natural animal hosts, the larvae are able to penetrate into the dermis and are transported via the lymphatic and venous systems to the lungs. They break through into the alveoli and migrate to the trachea, where they are swallowed.

In the intestine they mature sexually, and the cycle begins again as their eggs are excreted.

But humans are accidental hosts, and the larvae lack the enzymes needed to penetrate the basement membrane and invade the dermis. Therefore, cutaneous larva migrans remains limited to the skin.

The itch or pruritis occur secondary to an immune response to both the larvae and their products.

Clinical Presentation

The patient complains of intense pruritus and rythematous, often linear lesions that advance.

There is a history of tingling/prickling at the site of exposure within 30 minutes of penetration of larvae though the event of the exposure is not always noticed and remembered.

Often there is a associated history of sunbathing, walking barefoot on the beach, or similar activity in a tropical location but again, it may not be available.

On examination there would be pruritic, erythematous, edematous papules and/or vesicles and erpiginous , slightly elevated, erythematous tunnels that are 2- to 3-mm wide and track 3-4 cm from the penetration site.

Nonspecific dermatitis or secondary impetiginization may occur. Repeated examination may reveal tract advancement of 1-2 cm/day.

Lesions are typically distributed on the distal lower extremities but can also occur in the anogenital region, the buttocks, the hands, and the knees. Scalp lesions have been reported.

Systemic signs are usually absent.

However, lab studies may show peripheral eosinophilia and increased immunoglobulin E (IgE) levels. X-rays may show increased infiltrates.

Differential Diagnoses

Also consider the following:

• Erythema migrans of Lyme borreliosis
• Migratory myiasis [infection by fly larva]
• Allergic dermatitis
• Larva currens [ Strongyloides stercoralis]
• Contact Dermatitis
• Impetigo
• Scabies
• Tinea Infections

Laboratory Studies

Some patients may show peripheral eosinophilia on a CBC and increased immunoglobulin E (IgE) levels.

A skin biopsy is not necessary for diagnosis but if it needs to be done, it must be taken 1-2 cm ahead of the leading edge of a tract. It is where larva is present. Otherwise the larva may be missed.

Biopsy may confirm the presence of tunneling larvae just above the dermoepidermal junction or in the superficial epidermis. The surrounding epidermis reveals spongiosis, intraepidermal vesiculation, with a mixed inflammatory infiltrate and eosinophils.

Use of polarized dermoscopy can reveal an oval structure with a yellow periphery and brown center, representing the body of the larvae.

Treatment of Cutaneous Larva Migrans

Cutaneous larva migrans is self-limited but the intense pruritus and risk for infection mandate treatment.

Oral thiabendazole, albendazole, oral ivermectin, or topical ivermectin are the main drugs used in this condition.

Albendazole at 400 mg/day for 3 days is recommended.

As an alternative, Ivermectin can be administered as a 12-mg dose and repeated the next day.

Thiabendazole is poorly effective when given as a single dose and is  is less well tolerated than either albendazole or ivermectin.

Ivermectin, an avermectin B derivative and its mechanism of action is poorly understood.

Topical ivermectin or topical thiabendazole [10-15%] are also used as treatment. Topical therapies take upto a week to resolve the condition.

Prevention

It is best to wear shoes when walking in sandy areas. A mattress may be used for sun bathing. For professionals, non-penetranable gloves could help.

Complications

• Secondary bacterial infection may lead to cellulitis.
• Allergic reactions may occur.
• Loeffler syndrome [rarely]

References

• Jones WB 2nd. Cutaneous larva migrans. South Med J. 1993 Nov. 86(11):1311-3.
• Veraldi S, Persico MC, Francia C, Schianchi R. Chronic hookworm-related cutaneous larva migrans. Int J Infect Dis. 2013 Apr. 17 (4):e277-9.
• Bowman DD, Montgomery SP, Zajac AM, Eberhard ML, Kazacos KR. Hookworms of dogs and cats as agents of cutaneous larva migrans. Trends Parasitol. 2010 Apr. 26(4):162-7
• Leung AK, Barankin B, Hon KL. Cutaneous larva migrans. Recent Pat Inflamm Allergy Drug Discov. 2017 Jan 10.
• Kincaid L, Klowak M, Klowak S, Boggild AK. Management of imported cutaneous larva migrans: A case series and mini-review. Travel Med Infect Dis. 2015 Sep-Oct. 13 (5):382-7.