Practice Tip: Cutaneous larva migrans

Miguel Imperial MD FRCPC (biography, no disclosures)

What I did before

Cutaneous larva migrans (CLM) is a zoonotic worm infection that presents in travelers as an intensely pruritic, serpiginous skin eruption that is caused by the migration of these animal-origin (i.e. dog and cat) hookworm larva in the subcutaneous skin. Travelers to tropical and sub-tropical climates most often acquire this parasitic infection through direct contact with larvae-contaminated sand or soil. Although self-limited, the symptoms can cause considerable discomfort and distress.

The most frequent care gaps that I have noticed are (a) not correctly identifying the skin eruption as a treatable parasitic infection and (b) using the incorrect therapy, as access to the appropriate anti-helminthic drugs has been a challenge in Canada.

• Diagnosis

The travel history and the characteristic eruption are the two most important factors in correctly identifying this infection.  Travel to a tropical or sub-tropical climate and direct skin exposure to hookworm larvae (e.g. laying directly on the sand without a mat, walking barefoot on the sand or being buried in the sand) is the usual history. Areas of the beach that are shaded (i.e. under trees) and away from the water are much more likely to be able to harbor viable and infective hookworm larvae.

As for the skin eruption, it may start as little as a day after exposure but occasionally presentation may be delayed by more than a month as some larvae can remain dormant in the skin for some time. The rash may start as itchy papules but then quickly, the characteristic serpiginous subcutaneous tracts appear as a local tissue reaction to the larvae migrating in the skin. Biopsy is not helpful for diagnosis, nor is there is ever any indication for trying to surgically excise migrating larvae.

• Treatment

In the past, I would consider treating patients for (1) the itch and skin inflammation, with either topical or systemic steroids and an antihistamine and (2) definitively with a topical antihelminthic: topical thiabendazole 15% in petroleum jelly, applied 2-3 times a day to the affected area for 1-2 weeks. Unfortunately, only select compounding pharmacies had timely access to thiabendazole. Furthermore, while topical therapy was usually effective, it was a challenge to use when the infection was severe and widespread. One of my patients who returned from Jamaica where his nieces and nephews had buried him up to the neck in contaminated sand, had lesions virtually over his entire body.

Unfortunately, the two other antihelminthic drugs that could be used for systemic treatment (albendazole and ivermectin) were not available for human use in Canada. They required Special Access application through Health Canada, a hurdle that often resulted in a treatment delay while authorization was sought.

Other patients I had seen in referral had already been given a course of the antihelminthic mebendazole (trade name: Vermox) which was unlikely to resolve their infection. Mebendazole is an oral drug that is effective for intestinal roundworms and hookworm infection, but it has poor systemic absorption, making it relatively ineffective for systemic and tissue stages of worm infections.

What changed my practice

As of September 2018, Health Canada finally approved the human use of Ivermectin, meaning it can be accessed through any community pharmacy.

Ivermectin is an effective oral treatment for CLM with few side effects.

What I do now

Once I diagnose a patient with CLM based on a compatible travel history and characteristic serpiginous rash, I continue to treat the itch and inflammatory symptoms symptomatically if indicated, but I am able to much more readily offer systemic therapy with ivermectin since it no longer requires a Health Canada Special Access application.  Ivermectin is given as a weight based dose of 200 mcg/kg po once daily for 1-2 days. For an average 70kg person, that works out to ivermectin 15mg once a day for 1-2 days. (note that it comes in 3mg tablets)

For localized infections (i.e. to one foot), I still offer the option of topical therapy with thiabendazole 15% in petroleum jelly tid x 7-14 days.

Images from Centers for Disease Control and Prevention www.cdc.gov/parasites:

1. https://wwwnc.cdc.gov/eid/images/09-0261-F1.jpg
2. https://www.cdc.gov/parasites/images/zoonotichookworm/cutaneous-larva-migrans-clm-patient_1.jpg
3. https://www.cdc.gov/parasites/images/zoonotichookworm/clm_1.jpg

References

1. Blackwell V, Vega-Lopez F. Cutaneous larva migrans: clinical features and management of 44 cases presenting in the returning traveller. Br J Dermatol 2001; 145:434. (Request from CPSBC or with UBC http://tinyurl.com/yy23d7s3)
2. Feldmeier H, Schuster A. Mini review: Hookworm-related cutaneous larva migrans. Eur J Clin Microbiol Infect Dis 2012; 31:915. (View with CPSBC or with UBC http://tinyurl.com/y3ktdzmg)
3. 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 (View with CPSBC or with UBC http://tinyurl.com/y5outv7r)

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Practice Tip: Cutaneous larva migrans

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