Cutaneous larva migrans is a skin infestation caused by nematode larvae that penetrate the skin and migrate leaving a characteristic erythematous, serpiginous burrow underneath the skin.
SYNONYM Creeping eruption.
AGE Children > adults.
GENDER M = F.
INCIDENCE Uncommon; mostly in tropical climates (see Geography).
ETIOLOGY Hookworm larvae of cats/dogs (Ancylostoma braziliense, Uncinaria stenocephala, Ancylostoma caninum), cattle (Bunostomum phlebotomum), or other nematodes.
GEOGRAPHY Common in warm, humid, sandy, coastal areas, central United States, southern United States, central America, South America, and the Caribbean.
In animal hosts (dogs, cats), the hookworm penetrates the skin and spreads through the lymphatic and venous systems to the lungs, breaks through into the alveoli, migrates to the trachea, and is swallowed. The hookworm then matures in the intestine and produces eggs that are excreted by the animal host. Once the animal defecates infested feces, the hookworm ova in the sand or soil hatch into larvae. The larvae penetrates the skin of accidental hosts (humans) when they are stepped on with bare feet or come into contact with other bare skin, but cannot cross the basement membrane and are confined to the epidermis. Thus the larvae wander serpiginously through the epidermis creating visible track patterns, giving the nickname “creeping eruption.”
Larvae tend to penetrate the skin and begin to migrate at a rate of 1 to 2 cm/d for 4 weeks to 6 months and may cause pruritus. After aimless wandering, the larvae typically die and the cutaneous tracts self-resolve. Systemic symptoms are absent.
TYPE Tracks/burrows (Fig. 24-1). Vesicles or bullae can develop in individuals previously sensitized to the invading species.
COLOR Flesh colored to pink.
SIZE Width 2 to 3 mm, extending at 1 to 2 cm/d.
NUMBER One, several, or many tracks.
DISTRIBUTION Exposed sites: feet, lower legs, buttocks >> hands, thighs.
Can be associated with peripheral blood eosinophilia and generalized pruritus. Very rare cases of hematogenous dissemination and resultant pulmonary infiltrates have been reported.
The differential diagnosis of cutaneous larvae migrans includes phytophotodermatitis, tinea pedis, erythema chronicum migrans, jellyfish sting, contact dermatitis, larva currens, and granuloma annulare.
DERMATOPATHOLOGY PAS may show larva in a suprabasalar burrow, spongiosis, intraepidermal vesicles, necrotic keratinocytes, and chronic inflammatory infiltrate with many eosinophils.
Cutaneous larva migrans is typically self-limited because the human skin is an accidental “dead-end” host. Most larvae die after 2 to 4 weeks of aimless wandering underneath the skin, and the skin rash resolves in approximately 4 to 6 weeks.
Ultimately, the larval eruption will self-resolve in 4 to 6 weeks. Symptomatic relief with topical steroids until the pruritus self-resolves is a safe treatment of choice. Antihistamines may also offer relief from pruritus.
Severe cases with intense pruritus may be treated with systemic albendazole or ivermectin; side effects include dizziness, nausea, cramps, and vomiting. Systemic albendazole for 3 to 5 days or a single dose of oral ivermectin can achieve rapid cure rates of >90% within 1 week. Topical 10% thiabendazole cream may be better tolerated but must be used thrice daily for 10 days. Historically, attempts at larval destruction modalities including TCA, cryotherapy, or electrocautery aimed at progressing skin burrow were not very effective.
Cercarial dermatitis is an acute allergic pruritic eruption sparing the bathing suit areas of the body that develops following skin infiltration by water-borne Schistosoma cercariae.
SYNONYMS Swimmers’ itch, collector’s itch, schistosome dermatitis, duck itch, duckworms, clam-diggers itch, rice paddy itch.
AGE Children > adults.
GENDER M = F.
INCIDENCE Common. Often in local episodic outbreaks.
GEOGRAPHY Worldwide; most common in freshwater lakes in north and central United States.
ETIOLOGY Parasitic cercariae of the Schistosoma genus have birds, ducks, and cattle as their usual hosts, with snails as the intermediate host. Humans may become an accidental host by contacting either the freshwater or marine form of the parasite.
SWIMMER’S ITCH Trichobilharzia ocellata and T. physellae, common in swamps.
COLLECTOR’S ITCH T. stagnicolae, common in shallow waters.
ONSET Initial exposure causes no symptoms. Subsequent exposures incite an allergic response to a protein residue deposited by the invading parasite. At the time of cercarial penetration, an itching sensation (lasting 1 hour) associated with 1- to 2-mm macules at the sites of penetration may be noted. Cercariae die after penetration into human skin. Initial macules persist a few hours and are followed by a more severe pruritic eruption 10 to 15 hours later. The eruption may progress to a more severe state, peaking in 2 or 3 days and resolving within 7 days. Systemic symptoms are rare.
TYPE Macules, papules, edema, vesicles, and urticarial wheals.
COLOR Pink to red.
SIZE 3 to 5 mm.
DISTRIBUTION On exposed skin. Spares area covered by clothing (Fig. 24-2).
Severe cases may have associated fever, nausea, and malaise.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
