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Ancylostoma braziliense, A. caninum (Pathogen – Tissue Nematode)
Cause of Cutaneous Larva Migrans (CLM)

Organism:
Cutaneous larva migrans (CLM), also called creeping eruption, was recognized as a clinical syndrome before the 1800s. Various reports were published during the late 1800s; however, it was not until 1926 that the most common etiologic agent of CLM in the southern United States was found to be Ancylostoma braziliense, a very common hookworm of dogs and cats. A. caninum, the common hookworm of dogs, has been implicated in cases of CLM. Other species are also capable of producing CLM, although they are less common than A. braziliense.

Ancylostoma spp. larval tracks in the skin

Life Cycle:
Infection in humans is acquired through skin penetration by infective larvae from the soil. These larvae can also cause infection when ingested. When the larvae penetrate the skin, they produce pruritic papules, which after several days become linear tracks that are elevated and vesicular. Movement by the larvae in the tunnel may extend the track several millimeters each day. Secondary infections often occur as a result of intense scratching of the tracks.

Acquired:
Infection in humans is acquired through skin penetration by infective larvae from the soil.

Epidemiology:
Most infections are acquired from contact with larvae in moist or sandy soil. Such areas include beaches and sandboxes. Dogs and cats tend to defecate in such areas, providing a perfect situation for accidental infection with the filariform larvae.

Clinical Features:
Within a few hours after larval penetration of the skin, an itching red papule develops.  As the worm begins to migrate from the area of the papule, a serpiginous track appears.  The surrounding tissues are edematous and very inflamed.  The larva continues to migrate several centimeters each day, and the older portion of the track dries and becomes scarred.  This process is associated with severe pruritus, and scratching can lead to secondary infection. Larvae that first enter the skin and cause creeping eruption may later migrate to the deeper tissues (lungs). Deeper‑tissue migration may lead to pneumonitis with larval recovery in the sputum. A peripheral eosinophilia, as well as many eosinophils and Charcot‑Leyden crystals in the sputum, may also be present.

Laboratory Diagnosis:
Diagnosis is usually based on possible exposure history and/or the presence of the linear tracks. Biopsy is not recommended. However, newer PCR methods for the detection and identification of larvae in human tissues may provide improved test results. Usually, the diagnosis is made by the physician, rather than any specific laboratory test result.

Treatment:
Treatment is generally with thiabendazole and can be administered either by mouth or topically. Specific drug dosages are provided in chapter 25. Symptoms can also be treated with antihistamines, antipruritic agents, sedatives, and/or topical anesthetics.
Garcia, L.S. 2007.  Diagnostic Medical Parasitology, 5th ed., ASM Press, Washington, D.C.

Control:
Specific preventive measures include covering all sandboxes when they are not being used, keeping dogs and cats away from beaches, and periodic deworming of domestic dogs and cats.