Larva migrans

Introduction The life cycle of most nematodes parasitising humans include migration through various tissues and organs of the body. Sometimes the larvae appear to lose their way and wander around aimlessly. This condition is called larvae migrans.

This is generally seen when human infections occurs with non human species of nematodes. The worm is unable to undergo normal development and complete its life cycle. Larva migrans can be classified into cutaneous larva migrans visceral larva migrans

Cutaneous larva migrans This condition is called the creeping eruption It is caused by nematode larvae that infect the skin by penetration most commonly by non human species of hookworms Ancylostoma braziliense and Acylostoma caninum. Infection with these hookworms of dogs and cats is acquired from soil contaminated with excreta of these animals.

The larvae produce itching papules which develop in the epidermis. With the movement of larva in the skin, the lesion also shifts, hence the name creeping eruption.

A rapidly moving lesion is produced by Strongyloides stercoralis particularly in immune persons. This is known as larva currens.

Visceral larva migrans This condition is caused by migration of larvae of non human species of nematodes that infect by oral route. The most common cause is the dog ascarid Toxocara canis and less often the cat ascarid T. cati.

When the infective eggs present in the soil are ingested the larvae hatch in the intestine, penetrate the gut wall and migrate to the liver. They may remain there or migrate to other organs such as lung, brain or eyes. In humans they do not develop into adults, but induce granulomatous lesion which cause local damage.

Clinical manifestations depend on the sites affected and the degree and duration of infection. As children are more likely to swallow dirt, this condition occurs much more frequently in them. Fever, hepatomegaly, pneumonitis, are common findings Patients may develop neurological disturbances – neural larva migrans and endophthalmitis- ophthalmic larva migrans.

Lab diagnosis Marked leucocytosis occurs with high eosinophilia is seen in the case of visceral larva migrans. TREATMENT Thiabendazole may be useful in treatment When few, freezing the advancing part of the eruption with ethyl chloride is effective in the case of cutaneous larva migrans.

Prevention Deworming of household pets helps in prevention by limiting the contamination of soil.