Cutaneous Larva Migrans
Cutaneous larva migrans (also known as creeping eruption) is a skin reaction to infestation by the nematodes (hookworms or roundworms) that usually infect dogs and cats. This parasitic infection most often affects people who come in contact with infected soil or sand, such as children and farmers.
Eruptions associated with cutaneous larva migrans clear completely with treatment.
Ancylostoma braziliense, the larvae of dog and cat hookworms, is responsible for cutaneous larva migrans. The other dog hookworms, A.caninum and Uncinaria stenocephala, as well as the human parasites Strongyloides stercoralis and Necator americanus, also may produce the disease.
Under favorable conditions - warmth, moisture, and sandy soil - hookworm or roundworm ova are present in the feces of affected animals and hatch into larvae, which can then burrow into human skin on contact. After penetrating its host, the larva becomes trapped under the skin, unable to reach the intestines to complete its normal life cycle. It then begins to move around, producing peculiar, tunnel-like, alternately meandering and linear lesions that reflect the nematode's persistent and unsuccessful attempts to escape its host.
Signs and Symptoms
At the site of penetration a non-specific eruption occurs. There may be a tingling or prickling sensation within 30 minutes of the larvae penetrating. The larvae can then either lie dormant for weeks or months or immediately begin creeping activity that create 2-3mm wide, snakelike tracks stretching 3-4cm from the penetration site. These are slightly raised, flesh-coloured or pink and cause intense itching. Tracks advance a few millimetres to a few centimetres daily and if many larvae are involved a disorganised series of loops and tortuous tracks may form.
Sites most commonly affected are the feet, spaces between the toes, hands, knees and buttocks.
The condition is usually diagnosed clinically by a physician. Microscopic inspection can be utilized to reveal the hookworm eggs or larvae in the feces or stools. Biopsies, with or without cryo surgery of the lesions, are not necessary - they do not visualize the migrating parasite and might even result in further development of the local inflammation.
Cutaneous larva migrans infections may require administration of thiabendazole given orally for 2 or 3 days. Alternatively, a 10% aqueous suspension may be applied topically to avoid systemic toxicity. Oral albendazole for 3 days is effective as an alternative, as is Imervectin in a single dose. Treatment may also include antihistamines to alleviate itching.
Public sanitation has decreased the incidence of hookworm infestation in the United States. De-worming of cats and dogs can reduce the incidence among these animals. Wearing shoes in endemic areas (areas where hookworm infections are known to occur frequently) will prevent penetration of the larvae through the feet (a common site).
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