Cutaneous larva migrans

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Animal hookworm eggs passed in dog or cat faeces develop in warm, moist soil or sand. Infective filariform larvae penetrate human epidermis, often through bare feet or skin in direct contact with beaches. Humans are an accidental host, so the larvae cannot mature in the intestine. They migrate within superficial skin before dying, producing a delayed inflammatory track that may continue for weeks or months without treatment.

The history should define country, beach or soil exposure, barefoot walking, sleeping on sand, animal contact, onset, daily rate and direction of movement, number of lesions, systemic symptoms and previous treatments. A dated photograph or pen mark at the leading edge can document true migration and distinguish it from a fixed dermatitis.

Oral ivermectin or albendazole shortens symptoms and usually clears migration rapidly. Choice is influenced by availability, pregnancy, age or weight, liver function, drug interactions and whether Strongyloides is plausible. Persistent movement after a correctly absorbed regimen warrants diagnostic review before automatic redosing.

Key points

Cutaneous larva migrans is usually caused by dog or cat hookworm larvae, especially Ancylostoma braziliense or A. caninum, penetrating exposed skin contaminated by animal faeces.
The key feature is an intensely itchy, raised, winding track that advances slowly, commonly about one to two centimetres each day.
Feet, toes, buttocks, thighs and hands are typical sites after barefoot walking, lying or sitting on warm moist sand or soil.
Diagnosis is first-line clinical from morphology, migration and exposure; routine biopsy, serology and stool microscopy add little in a typical case.
First-line oral treatment options are ivermectin 200 micrograms/kg as a single dose or albendazole 400 mg once daily for three days.
Treat excoriation and bacterial superinfection separately; an antibiotic is not needed for the sterile larval track itself.
Larva currens moves much faster and signals Strongyloides infection, which has different systemic consequences and must not be relabelled as ordinary beach-acquired disease.
There is no person-to-person transmission and no routine notification requirement; footwear, barriers on sand and pet faeces control reduce exposure.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Animal hookworms

Dog and cat hookworms, particularly Ancylostoma braziliense and A. caninum, account for most cases in tropical and subtropical settings.

Contaminated sand

Eggs in animal faeces hatch and develop into infective larvae in warm moist sand or soil before penetrating exposed human skin.

Accidental human host

Humans interrupt the parasite lifecycle because animal-hookworm larvae cannot normally cross the basement membrane and mature in the human intestine.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Epidermal penetration
Filariform larvae use enzymes and mechanical movement to enter intact skin, frequently through soles or other surfaces pressed against contaminated ground.
2
Superficial migration
The larva tunnels within epidermal layers, leaving a curved inflammatory track whose visible edge follows behind the organism.
3
Eosinophilic inflammation
Parasite antigens provoke local eosinophilic and hypersensitivity responses, producing papules, vesicles, erythema and often intense pruritus.
4
Spontaneous attrition
Unable to mature in humans, larvae eventually die, but untreated symptoms may continue for weeks or months and invite excoriation.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Serpiginous advancing track

A narrow erythematous, raised and tortuous line appears days after exposure and develops a visibly new leading edge while the older segment fades.

Intense pruritus

Itch is often severe, worse at night and may disrupt sleep; scratching produces crusting, excoriation and an entry point for bacterial infection.

Exposure distribution

Lesions favour soles, interdigital skin, ankles, buttocks, thighs, hands or elbows corresponding to contact with contaminated sand or soil.

Multiple or bullous lesions

Several tracks, papules, vesicles or bullae can occur after heavy exposure and should not by themselves imply systemic invasion.

Secondary infectionRed flag

Increasing warmth, tenderness, diffuse erythema, pus, fever or lymphangitis extends beyond the expected itchy track and needs separate clinical assessment.

Red flags requiring action

Rapidly advancing erythema, severe pain, fever, lymphangitis or purulent discharge suggests secondary bacterial cellulitis rather than uncomplicated larval migration.
A track moving centimetres per hour, especially around the buttocks or trunk, raises concern for Strongyloides larva currens and requires systemic-risk assessment.
Intermittent deep migratory swellings, visceral symptoms or neurological features after raw fish or freshwater exposure suggest gnathostomiasis rather than epidermal hookworm.
Wheeze, breathlessness, fever and pulmonary infiltrates with eosinophilia can represent a rare pulmonary hypersensitivity syndrome or an alternative helminth infection.
Pregnancy, breastfeeding, very young age, low body weight or significant liver disease requires medicine-specific specialist review before ivermectin or albendazole.
Immunosuppression does not make the classic animal-hookworm larvae complete their lifecycle, but it lowers the threshold to investigate Strongyloides and atypical infection.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
First-line clinical diagnosisFirst stepFirst line
Why
Combine the slowly advancing serpiginous lesion with direct skin exposure in a compatible environment.
Interpretation and limitations
A classic migrating track is sufficient for treatment. Photograph and measure its edge when the history is uncertain; migration over the next day strengthens the diagnosis.
02
Full blood count
Why
Look for eosinophilia when lesions are numerous, pulmonary symptoms occur or an alternative invasive helminth is considered.
Interpretation and limitations
Mild eosinophilia may occur but is neither required nor diagnostic. Marked or persistent eosinophilia should trigger broader travel and helminth assessment.
03
Skin sampling
Why
Evaluate an atypical fixed lesion or exclude fungal, bacterial, inflammatory or neoplastic disease.
Interpretation and limitations
Biopsy frequently misses the larva because it lies ahead of the visible track. Histology may show eosinophilic spongiosis but is not a gold-standard test.
04
Bacterial swab or culture
Why
Identify a pathogen when excoriations become purulent or cellulitis fails standard treatment.
Interpretation and limitations
Sample exudate rather than an intact sterile track. Treat according to clinical severity and culture; colonising growth alone does not prove infection.
05
Strongyloides assessment
Why
Exclude systemic strongyloidiasis when migration is extremely fast, gastrointestinal or pulmonary symptoms occur, or immunosuppression is planned.
Interpretation and limitations
Request serology and appropriately repeated or specialist stool testing according to exposure; a single routine stool examination has limited sensitivity.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Larva currens

Strongyloides autoinfection produces a rapidly moving, transient urticarial track, often on buttocks or trunk, with potential gastrointestinal and systemic disease.

Scabies

Short fixed burrows, interdigital or genital involvement, generalised nocturnal itch and affected contacts favour scabies over a solitary advancing track.

Tinea corporis

An enlarging annular scaly plaque with central clearing may appear serpiginous but expands evenly rather than developing a migrating raised tunnel.

Contact dermatitis

Geometric or exposure-shaped erythema, vesiculation and itch remain fixed at contact sites and lack progressive directional movement.

Gnathostomiasis

Intermittent deep painful migratory swellings after raw freshwater fish exposure, sometimes with neurological disease, require systemic tropical-medicine assessment.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01RECOGNISEConfirm the clinical patternFirst stepAn itchy linear or serpiginous eruption develops after beach, soil or animal-associated exposure.

1Record exposure location, date and direct skin contact, then examine the entire skin surface for tracks, papules, burrows, interdigital lesions and bacterial complications.
2Mark or photograph the leading edge and estimate migration speed; ordinary cutaneous larva migrans advances slowly over days rather than racing within hours.
3Ask about gastrointestinal, respiratory, neurological and constitutional symptoms, raw food exposure, immunosuppression and pregnancy before choosing treatment.
4Treat a classic presentation clinically; reserve biopsy, cultures and broader parasite testing for an atypical morphology, systemic features or failure.

02FIRST-LINEEradicate epidermal larvaeFirst lineThe exposure and slowly migrating pruritic track are typical and no red flag suggests a different invasive process.

1Offer ivermectin 200 micrograms/kg orally as a single dose, using actual weight and checking pregnancy, breastfeeding, age, weight and interacting or neurological concerns.
2Alternatively give albendazole 400 mg orally once daily for three days, particularly where ivermectin is unsuitable or unavailable, after reviewing pregnancy and liver status.
3Use emollient, a non-sedating antihistamine or a short course of appropriate topical corticosteroid for residual itch; these measures do not kill the larva.
4Advise that itching can persist briefly after migration stops, but a genuinely advancing track after several days needs reassessment and sometimes a specialist-directed repeat course.

03COMPLICATIONManage excoriation or bacterial infectionScratching has produced broken skin, weeping, crusting, spreading tenderness or systemic signs.

1Clean and cover excoriations, reduce scratching and assess the extent of impetigo, cellulitis, abscess or lymphangitis.
2Do not prescribe an antibacterial solely because the hookworm track is inflamed; use an antibiotic only when clinical bacterial infection is present.
3Follow the local skin-infection pathway and obtain culture when purulent, severe, recurrent or treatment resistant, accounting for travel-associated resistant organisms.
4EscalationEscalate fever, rapid progression, severe pain, immune compromise or systemic toxicity for urgent face-to-face review and possible intravenous treatment.

04REASSESSInvestigate atypical or persistent migrationLesions move unusually quickly, are deep or nodular, recur, or remain active after a correctly taken regimen.

1Recheck the original diagnosis, dose calculation and absorption and compare serial photographs rather than treating residual itch as live migration.
2Test for Strongyloides when larva currens, immunosuppression or visceral symptoms are plausible; seek infection or tropical-medicine advice before steroids.
3Consider gnathostomiasis, loiasis, migratory myiasis, scabies and inflammatory dermatoses using geography, food exposure, morphology and systemic findings.
4Refer to dermatology for uncertain morphology or biopsy and to infection or tropical medicine for eosinophilia, systemic disease or complex antiparasitic prescribing.

05PREVENTReduce repeat exposureThe patient or household will return to an endemic beach or warm-soil environment.

1Wear footwear and avoid direct bare-skin contact with damp sand or soil in areas contaminated by dogs or cats.
2Use a clean towel, mat or raised chair rather than lying directly on beach sand, especially where stray animals roam.
3Support responsible pet deworming and prompt faeces disposal; environmental control is more effective than attempting to disinfect a whole beach.
4Explain that affected people do not pass animal hookworm larvae directly to family members and do not require isolation.

Key medicines and prescribing safety3 treatments · regimens, roles and cautions

First-line systemic therapy with high cure rates and a convenient one-dose regimen.

Ivermectin

Give 200 micrograms/kg orally as a single dose for uncomplicated cutaneous larva migrans; use a specialist-directed repeat dose only for persistent proven migration.

Obtain specialist advice in pregnancy, breastfeeding, children under 15 kg, significant neurological disease or possible Loa loa exposure; weigh accurately and distinguish residual itch from failure.

Effective first-line alternative when ivermectin is unavailable, contraindicated or less suitable.

Albendazole

Give 400 mg orally once daily for three days for uncomplicated cutaneous larva migrans, extending only on specialist advice for extensive or refractory disease.

Avoid unsupervised use in pregnancy, especially the first trimester; review liver disease and interactions, and monitor liver tests if a longer course is prescribed.

Reduces itch, sleep disruption and scratching while antiparasitic treatment stops migration.

Symptomatic antipruritic treatment

Use a standard non-sedating oral antihistamine at its licensed adult dose and, where needed, a short thin application of an appropriate topical corticosteroid.

Neither option eradicates larvae; avoid potent steroid on infected or ulcerated skin, and reassess drowsiness, pregnancy and occupational driving risk for antihistamines.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Bacterial superinfection

Scratching disrupts the skin barrier and can lead to impetigo, cellulitis, abscess or lymphangitis requiring antibacterial management.

Sleep disturbance

Severe nocturnal pruritus causes insomnia, impaired concentration and reduced quality of life despite the infection usually remaining superficial.

Bullous reaction

An intense hypersensitivity response may produce vesicles or larger bullae along the track, complicating morphology and increasing skin-barrier damage.

Pulmonary hypersensitivity

Rarely, eosinophilia, cough, wheeze and transient infiltrates occur; prominent respiratory illness should also prompt assessment for alternative helminths.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Ask the patient to photograph the lesion with a scale before treatment and again over the next three to seven days; cessation of forward movement is the clearest response.
Review sooner if erythema spreads diffusely, pain replaces itch, pus, fever or lymphangitis appears, because bacterial infection needs a separate pathway.
Persistent itch without extension may represent post-inflammatory irritation; avoid repeated antiparasitic courses unless objective migration continues.
Recheck eosinophil count and broaden parasite testing when marked eosinophilia, respiratory or gastrointestinal symptoms persist.
After an atypical or failed course, verify weight-based dosing, vomiting, adherence and the possibility of Strongyloides or another migratory parasite.
Document pregnancy or immunosuppression plans so that unresolved Strongyloides risk is addressed before systemic corticosteroids are given.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

The larva is ahead

The organism usually lies beyond the visible advancing edge, explaining why a punch biopsy taken from the obvious track often fails to capture it.

Speed separates mimics

Cutaneous larva migrans advances roughly millimetres to centimetres per day; larva currens may travel several centimetres within an hour.

Humans are accidental hosts

Animal hookworm larvae remain confined to superficial skin and do not usually mature into adult intestinal worms, so stool ova testing is unhelpful.

Inflammation can outlast infection

Pruritus and erythema may persist after the larva dies; serial position rather than itch intensity is the better marker of active disease.

Topical therapy is limited

Topical thiabendazole has historical use but variable availability and practicality; oral ivermectin or albendazole provides more reliable treatment for multiple tracks.

11Common pitfallsFrequent interpretation and management errors.

01
Do not diagnose scabies solely because itching is nocturnal; look for household spread, burrows and a fixed symmetrical distribution rather than a single migrating track.
02
Do not order stool ova and parasite microscopy as the definitive test for animal-hookworm cutaneous larva migrans because the larvae do not become egg-producing adults in humans.
03
Do not prescribe antibiotics for the inflamed serpiginous lesion unless there is evidence of secondary bacterial infection.
04
Do not repeat ivermectin for residual itch without confirming continued migration; post-inflammatory symptoms are common.
05
Do not miss larva currens before giving systemic steroids or other immunosuppression, as Strongyloides hyperinfection is a distinct life-threatening risk.
06
Do not assume every beach-associated eruption is parasitic; jellyfish injury, contact dermatitis, tinea and phototoxic reactions have different patterns.