Cutaneous Larva Migrans - Transmission, Symptoms and Treatment
Cutaneous larva migrans, is an infection caused by larvae of parasites that live in the intestines of dogs and cats, such as the helminths Ancylostoma braziliense or Ancylostoma caninum.
The life cycle of the parasites that cause the cutaneous larva migrans begins when animals infected by helminths eliminate eggs from the parasite in the feces. Contaminated faeces when in contact with warm, moist and sandy soil become an optimum medium for the evolution of eggs, which hatch, releasing the larvae.
In the soil, newborn larvae feed on bacteria, and over 5 to 10 days, they go through two evolutionary stages until they become capable of infecting humans or other animals. Larvae in the 3rd evolutionary stage (infectious phase) can survive in the environment for up to 4 weeks if favorable conditions are found.
The contamination of the man occurs when there is a contact of the skin with the soil contaminated by larvae, usually, when we walk barefoot on sandy ground. Beaches, especially those where there are feces of dogs and cats in the sand, are places favorable to contain larvae of helminths.
The regions of the sand where there is shade, but there is no contact with the sea water, are the best points for the development of the larvae. Another common site of contamination are the outdoor sandboxes where children play. Cats often look for places with dirt or sand to bury their faeces, and can easily contaminate these areas.
About 3/4 of the cases of larval contamination with larvae of larva migrans occur in the lower limbs, especially in the feet. Infections in the trunk or upper limbs occur in less than 10% of cases. In children who play in sandboxes or on the beach, buttocks and thighs are usually affected.
The larvae in the 3rd evolutionary phase can penetrate the most superficial layer of human skin, but can not cross the underlying layers. Without being able to invade more deeply, the worms happen to move at random under the skin, forming a small tunnel that gives rise to drawings in the skin, looking like a map.
The moment of penetration of the larvae may go unnoticed, but in some patients it is possible to notice the presence of a reddish and pruritic papule (a relief point about 1 cm in diameter). If the soil is heavily contaminated by larvae, several papules may appear on the skin, indicating various invasion sites.
Within two to three days after the invasion, small tunnels arise due to the migration of the worm under the skin. Each invasion creates a tunnel. These lesions are slightly elevated, serpiginous, reddish-brown, and itchy. The tunnels advance about 2 to 5 cm per day and can form capricious designs.
As the days pass, the older part of the path tends to deflate, leaving in its place only a darker strip, which will disappear later.
The duration of the process is very variable and can heal spontaneously after 2 weeks or last for months. The larva migrans when it disappears spontaneously, without treatment, can reappear weeks or months later.
The most uncomfortable symptom is itching, and may even prevent the patient from sleeping. If the patient overcoaches the area, it can cause wounds and facilitate the contamination of the skin by bacteria, leading to cellulitis or erysipelas.
The treatment of larva migrans is done with antiparasitic drugs that have action against helminths, such as Thiabendazole, Albendazole or Ivermectin.
Ivermectin is used at a dose of 200 mcg/kg per day for one to two days. Albendazole is usually prescribed at a dose of 400 mg per day for three days. Thiabendazole can be used as an ointment in the initial cases, mild or with few lesions.
Topical treatment lasts for 5 to 7 days, but lesions and itching usually show improvement within the first 48 hours of treatment.
