What is cutaneous larva migrans?
Cutaneous larva migrans (creeping eruption) is a very characteristic skin condition caused by parasites that dig tunnels through the skin. They are the larvae of small worms (nematodes) that actually parasitise other animals such as dogs or cows. The species that causes the most infections is Ancylostoma braziliense, which normally lives as a parasite in the intestines of the dog. The condition is caught mainly in tropical and subtropical regions; tourists from northern Europe not infrequently bring back a creeping eruption from their holiday as an unexpected souvenir.
How does it develop?
The eggs of the worm (which in the case of A. braziliense lives in the dog’s intestine) reach the ground via the dog’s faeces. When conditions are favourable (warm, sandy soil, shade), small larvae emerge from the eggs in the ground. These larvae — although they are really dog parasites — can, if given the chance, penetrate the human body through the skin. The larva then creeps parallel to the skin surface through the victim’s skin, which causes an intense itch.
What does it look like?
With cutaneous larva migrans, red tunnels (tracks) are seen on the skin, which become a little longer each day. They are seen on those parts of the skin that have been in contact with the ground — in many cases the feet, the buttocks or the back (from lying under the palm tree on that beautiful (sub)tropical beach).
How is it treated?
In principle cutaneous larva migrans passes by itself, because for the parasite the human is the wrong host: it gets no further than the skin and eventually dies, which takes on average 4–10 weeks. Few people want to wait for this. In the past it was sometimes treated by dabbing with liquid nitrogen or with thiabendazole. Nowadays a single treatment with ivermectin tablets is usually preferred. Until the remnants of the dead larva have completely disappeared from the skin, the itch can persist, which can sometimes take a few weeks.
When to see a doctor
See your GP or a dermatologist if you develop an itchy, winding red track on the skin after a trip to a warm country or contact with sandy soil, as a short course of treatment quickly relieves the itch. Also seek advice if the area becomes infected with spreading redness, pus or crusting.