The condition is caused by the larvae of hookworms that infect dogs, cats and other animals.
The infection of a human host usually occurs as a result of lying, sitting or walking barefoot on ground contaminated with animal faeces. The condition remains confined to the outer layers of the skin as the larvae are unable to penetrate the basement membrane to invade the deeper layers.
Warm and humid conditions are conducive to hatching infective larvae. The condition is more common in tropical or subtropical regions such as the northern parts of Australia and tropical Asian countries.
Individuals who come into contact with warm, moist, sandy soil infested with animal faeces are most at risk of developing this condition. This includes barefoot beachgoers and sunbathers, tourists and children who play in sandboxes. Occupations at risk include carpenters, electricians, plumbers, farmers, gardeners and pest exterminators.
Affected individuals may have intense localised itch that begins shortly after the hookworm penetrates the skin. Red, swollen lumps, fluid-filled lumps and/or one or more snake-like tracts appear as the condition progresses. Hundreds of such lesions may be found on a single person.
Non-specific dermatitis, blistering lesions and superimposed bacterial infection may make larva migrans more difficult to diagnose.
The condition most frequently affects the lower extremities, abdomen or buttocks but any exposed site may be affected.
The condition is self-limiting which means that it resolves spontaneously without treatment. The time taken to resolve varies considerably depending on the species of larvae involved. In most cases, lesions will resolve without treatment within 4 to 8 weeks but some may persist for many months.