In a fictional consultation, a 31-year-old man returns from ten days on a Caribbean beach with a thin, wavy red line on the sole of his foot. He says the itch wakes him at night and that the line seems to "move" a little each day. That same afternoon, the clinic sees a student who has returned from volunteering in East Africa with a dark, painful spot beside her big toenail, and a biologist who spent a month in the Amazon with a nodule on his arm that "moves" and releases a clear liquid.

The three cases are examples of parasitic skin diseases that travelers bring home: cutaneous larva migrans, tungiasis and myiasis. This text gathers what traveler surveillance studies, cohorts in endemic communities, treatment trials and systematic reviews show about how to recognize, treat and prevent each one. In each part, the text reports the design and size of the studies and separates what was measured from what is our inference.

Key points

• In a travel clinic in France, 201 of 1,025 patients had skin diseases, and parasitic ones accounted for 36 of those cases (Blaizot et al., 2020).
• Cutaneous larva migrans forms a wavy track that advances 2 to 3 millimeters per day, with itching that disturbs sleep (Boggild et al., 2025).
• In tungiasis, the systematic review found enough evidence in favor of occlusive agents, especially dimethicone-based products (Tardin Martins et al., 2021).
• In the review of myiasis in Sub-Saharan Africa, most patients were travelers returning from the region (Jallow et al., 2024).
• All three diseases weigh on quality of life, with itching, pain, loss of sleep and shame (Schuster et al., 2011; Wiese et al., 2018).

• Why the traveler's skin deserves attention
• Cutaneous larva migrans: the itchy trail
• Tungiasis: the flea that enters the foot
• Myiasis: the larva that forms a boil
• Prevention: what to advise before the trip
• Studies at a glance
• How NEXO helps train this reasoning
• Frequently asked questions
• Take-home messages
• Milestone inventory

Why the traveler's skin deserves attention

The skin is one of the most common complaints after a trip, and the diagnosis depends on combining the appearance of the lesion with the destination, the activity and the time since return. The Bordeaux study, based on the GeoSentinel surveillance network, followed 1,025 travelers seen between August 2015 and March 2018, of whom 201 had skin diseases (Blaizot et al., 2020).

Who returns with skin problems

Patients with skin diseases were more likely to be over 60 years old (OR 1.88; 95 percent CI 1.22 to 2.89), to travel as tourists (OR 3.04; 95 percent CI 2.03 to 4.55) and to have gone to South America (OR 2.18; 95 percent CI 1.29 to 3.67) (Blaizot et al., 2020). They were also less likely to have received advice before the trip (OR 0.53; 95 percent CI 0.31 to 0.91) (Blaizot et al., 2020).

Bacterial skin infections were the most common, at 19.4 percent of cases, followed by Zika infection, at 18.4 percent (Blaizot et al., 2020). Among the 36 parasitic skin diseases, serpiginous eruption was the most frequent, with 19 patients, 15 of them with hookworm-related larva migrans; myiasis appeared in five, two by Dermatobia hominis and three by Cordylobia anthropophaga (Blaizot et al., 2020).

Five questions that guide the reasoning

As our synthesis from the sources, five questions help separate the conditions in this text from other skin lesions brought back from travel:

• Where the person walked or lay without protection, such as beach sand, bare earth or soil with animal feces (Reichert et al., 2016).
• Whether the lesion moves, like the track of larva migrans, or stays fixed, like the nodule of tungiasis and the boil of myiasis (Boggild et al., 2025).
• Whether there is a central opening, present in tungiasis and in furuncular myiasis (Feldmeier et al., 2014; Jallow et al., 2024).
• When the symptoms began relative to the return, since the itch of larva migrans can last for weeks (Boggild et al., 2025).
• Whether there was advice before the trip, which was less frequent among those who returned with a skin disease (Blaizot et al., 2020).

The list is our own script and has not been tested as a diagnostic tool. Fever, diffuse spots or ulcers call for a different line of reasoning, such as fever in the traveler and skin lesions from mpox.

Cutaneous larva migrans: the track that itches

Cutaneous larva migrans is a zoonosis caused, most of the time, by larvae of hookworms of dogs and cats, such as Ancylostoma caninum and Ancylostoma braziliense (Boggild et al., 2025). The eggs leave in the animals' feces, hatch within a day in the sand or soil and, within a week, become larvae able to cross intact skin (Boggild et al., 2025). Humans are an accidental host, and the larva stays trapped in the epidermis.

How to recognize it

The typical sign is a raised, serpiginous track that advances on average 2 to 3 millimeters per day, almost always on the foot or the buttocks, the areas that touch the sand (Boggild et al., 2025). The itching is intense, disturbs sleep and concentration and can last as long as the larva lives, on average five to six weeks, with reports of a year or more (Boggild et al., 2025).

In a poor community in Manaus, a cross-sectional study with 806 residents found larva migrans in 8.2 percent (95 percent CI 6.3 to 10.1) of the population, with a peak of 18.2 percent among children aged 10 to 14 years (Reichert et al., 2016). Most of the tracks were on the feet, 62.4 percent, and 10.6 percent were infected by bacteria (Reichert et al., 2016).

The factors linked to the disease were age under 15 years, male sex, animal feces in the yard, walking barefoot on sandy ground and poverty (Reichert et al., 2016). The authors conclude that reducing the burden of the disease requires improving living conditions, and this view of animal, environment and person is the same as that of One Health.

The Caribbean traveler

The Canadian surveillance network CanTravNet, with eight centers, saw 17,644 travelers between 2009 and 2018, and 328 of them, 1.9 percent, returned from the Caribbean with larva migrans (Boggild et al., 2025). The median age was 34 years, women were 58 percent and 95 percent traveled for tourism (Boggild et al., 2025).

Jamaica was the most common origin, with 216 patients, 67 percent, followed by Barbados, with 8 percent, and the Dominican Republic, with 7 percent (Boggild et al., 2025). The share of imported larva migrans coming from the Caribbean rose from 9 percent in 2016 to 24.5 percent in 2018 (Boggild et al., 2025). The authors call for more attention from doctors and travelers and easier access to treatment.

Also outside the tropics

Larva migrans is not restricted to the tropics. A 40-year-old Dutch traveler became infected after two weeks camping on the beaches of Brittany, in France, and was first treated as cellulitis, with an antibiotic, before receiving ivermectin, which stopped the itching and the advance of the lesion (Tamminga et al., 2009). The authors cite similar reports in Germany, England, Scotland and southern France.

A systematic review on occupational risk, which started from a dog breeder in southern Italy, included 12 articles and points to breeders, farmers and gardeners as groups exposed to contaminated soil (Stufano et al., 2022). As our hypothesis, the question about travel is not enough, and the history of work and of contact with animals also guides the diagnosis.

Treating and what to expect

Albendazole and ivermectin are the two most recognized treatments, and ivermectin was treated as first line in the Canadian surveillance (Boggild et al., 2025). The authors report that, in earlier cohorts in Canada, the median duration of symptoms before care or effective treatment usually exceeded one month (Boggild et al., 2025).

The impact of treatment was measured in Manaus with a dermatology quality of life index in 91 patients (Schuster et al., 2011). At diagnosis, 91.5 percent had a considerable reduction in quality of life, and itching, loss of sleep and embarrassment were reported by 93.4, 73.6 and 64.8 percent, respectively (Schuster et al., 2011). Four weeks after ivermectin, 73.3 percent considered their quality of life back to normal (Schuster et al., 2011).

The study had no control group, and part of the improvement may reflect the natural course of the disease. The itchy track can also be confused with other parasitic diseases that cause migratory lesions and eosinophilia, reviewed in eosinophilia in the traveler and in strongyloidiasis.

Tungiasis: the flea that burrows into the foot

Tungiasis is caused by the female flea Tunga penetrans, which penetrates the skin and stays there until it dies, four to six weeks later (Feldmeier et al., 2014). Through the last abdominal segments, the flea keeps an opening of 250 to 500 micrometers to breathe, defecate and expel eggs, which serves as a gateway for bacteria (Feldmeier et al., 2014).

Where it lives and who gets sick

The flea cycle involves people, domestic animals and wild animals, and in houses with dirt floors, common in poor areas of South America and sub-Saharan Africa, it can be completed indoors (Feldmeier et al., 2014). The authors say there are no reliable data on occurrence at national or regional level, and that the poorest strata are the most affected (Feldmeier et al., 2014).

Aerobic and anaerobic bacteria, including clostridia, have already been isolated from embedded fleas (Feldmeier et al., 2014). The authors also raise the hypothesis that home removal with non-sterile pins, needles or thorns, shared among neighbors, may transmit blood-borne viruses such as hepatitis B and C; this link is a hypothesis of the authors, without direct measurement (Feldmeier et al., 2014).

The burden for the child

In Kenya, a quality-of-life index adapted to tungiasis was applied to 50 children from poor coastal communities (Wiese et al., 2018). At diagnosis, 78 percent reported a moderate to very large effect on quality of life, and sleep disturbance and difficulty concentrating were the most frequent restrictions, at 86 and 84 percent (Wiese et al., 2018).

The degree of impairment followed the number of live fleas, the severity of inflammation and the intensity of pain, and quality of life improved four weeks after treatment (Wiese et al., 2018). The review article also notes that children with tungiasis are mocked in Kenya and that, in Brazil and Nigeria, patients suffer social stigma (Feldmeier et al., 2014).

As our hypothesis, the traveler usually has few lesions and quick access to care, which differs from the child in an endemic area with repeated infestation. The severity in poor communities may not apply directly to the tourist, and this difference was not measured in the sources.

Treating: extraction, occlusion and dimethicone

The systematic review by Tardin Martins and colleagues started from 3,376 references and included 19 articles, nine of them clinical trials; only two had low risk of bias and three, some risk (Tardin Martins et al., 2021). The two studies with oral drugs, niridazole and ivermectin, had discouraging results (Tardin Martins et al., 2021).

Six trials evaluated topical products, and the two with dimethicone compounds reported reduction of lesions and cure, without important adverse reactions (Tardin Martins et al., 2021). Surgical extraction, the most used method, was only evaluated in observational studies, and the authors conclude that there is enough evidence in favor of occlusive agents, especially dimethicone ones (Tardin Martins et al., 2021).

The proof-of-principle study in Kenya compared dimethicone with potassium permanganate, the routine local treatment, in 47 schoolchildren, each foot receiving one of the products (Thielecke et al., 2014). Seven days later, 78 percent (95 percent CI 67 to 86) of the fleas treated with dimethicone had lost signs of life, versus 39 percent (95 percent CI 28 to 52) with permanganate (Thielecke et al., 2014). One of the authors declared fees from the manufacturer of the product tested, which should weigh on the reading.

A randomized pilot trial in Homa Bay, also in Kenya, compared two-component dimethicone with 5 percent sodium carbonate in 23 children aged 3 to 13, with 126 fleas (Suzuki et al., 2024). On day seven, dead fleas were 87 percent with dimethicone and 64 percent with carbonate, with a p value of 0.01, and there was no difference in inflammation, pain or itching (Suzuki et al., 2024).

The authors note that two-component dimethicone is the only treatment recommended by the WHO, but it was not available in Kenya, and they call for larger studies (Suzuki et al., 2024). For the traveler who returns with one or two lesions, the practical decision is between sterile extraction and occlusion, and tetanus deserves review as with any wound, a topic covered in wounds after floods.

Myiasis: the larva that forms a boil

Myiasis is the infestation of living tissues by fly larvae. The systematic review of Sub-Saharan Africa gathered 75 articles, from 1959 to 2022, with 157 patients (Jallow et al., 2024). Eleven fly species were identified, and Cordylobia anthropophaga, the tumbu fly, was the most common, with 104 patients, 66.2 percent (Jallow et al., 2024).

The traveler returning from Africa

Most patients, 122 of 157, or 77.7 percent, were travelers returning from the region, and cutaneous myiasis was the most common form, with 54.7 percent (Jallow et al., 2024). The review gathers published reports, and so it tends to show more the traveler seen in a wealthy country than the local resident.

The female tumbu fly lays 100 to 300 eggs in soil with urine or feces or on damp clothes, especially those dried in the shade, and the larvae penetrate the parts of the body in contact with that fabric (Jallow et al., 2024). The review therefore advises against lying on the ground and drying clothes on a shaded line or over shrubs, and recommends ironing clothes and bedding after washing (Jallow et al., 2024).

Removal of the larva is the center of treatment, by manual pressure, by a mechanical method or by surgery, and occlusive substances, such as paraffin, are applied to the central opening to suffocate the larva (Jallow et al., 2024). Antibiotics were used in some patients (Jallow et al., 2024). The authors warn that clinicians in the region often miss the diagnosis and cannot identify the larvae.

The traveler returning from the Americas

In Ecuador, a review of clinical reports and Ministry of Health data identified four flies in 39 patients, 29 described in the literature and 10 seen by the authors themselves (Calvopina et al., 2020). Dermatobia hominis, the human botfly, caused boil-like lesions in 17 patients, 43.5 percent, on the Pacific coast and in the Amazon (Calvopina et al., 2020).

Cochliomyia hominivorax, the screwworm fly, caused 15 infestations, 38 percent, in wounds and cavities such as the orbit, nose, ear and vagina, including one wound acquired in hospital (Calvopina et al., 2020). Eight patients, 21 percent, were tourists, and ivermectin, when it became available, was used successfully in boil-like lesions, wounds and cavities (Calvopina et al., 2020).

Official data from 2013 to 2015 recorded 2,187 notifications, with the highest annual incidence in the Amazon, of 23 per 100,000 inhabitants (Calvopina et al., 2020). In Mexico, a report of three patients with Dermatobia hominis, two with local infestation in the south of the country and one with infestation brought from Costa Rica, shows that myiasis also appears outside endemic areas because of travel (Toussaint-Caire et al., 2018).

A boil that does not improve

The boil of myiasis is usually treated as a bacterial infection until someone notices the opening and the movement of the larva. As our hypothesis, a boil that does not improve with antibiotics in a traveler who returned from Africa or Latin America should raise the suspicion, just as the larva migrans from Brittany was first treated as cellulitis (Tamminga et al., 2009).

Wound myiasis, such as the one caused by the screwworm, has a different profile and is linked to open wounds, cavities and people with poor care (Calvopina et al., 2020). Wounds that worsen quickly after contact with warm seawater call for another line of reasoning, discussed in Vibrio and wounds.

Prevention: what to advise before the trip

Advice before the trip was less frequent among travelers who returned with a dermatosis (Blaizot et al., 2020). The sources of this text describe risk factors and habits linked to each parasite, and we have gathered, as our own synthesis, five recommendations that rely on them:

• Wear footwear on sand and on bare ground, since walking barefoot on sandy ground was a risk factor for larva migrans (Reichert et al., 2016).
• Avoid lying directly on the sand of beaches frequented by dogs and cats, because the larvae come from the feces of these animals (Boggild et al., 2025).
• Examine the feet every day in areas of tungiasis, especially around the nails, and seek care for sterile removal (Feldmeier et al., 2014).
• Dry clothes in the sun, away from bushes, and iron them in sub-Saharan Africa (Jallow et al., 2024).
• Seek evaluation on return if an itchy track, a nodule with a hole or a boil that does not improve appears (Calvopina et al., 2020).

The cited studies did not test these recommendations as an intervention in travelers, and the strength of each one comes from studies of risk factors and of the life cycle. The consultation before the trip is also the moment to review vaccines and other risks, as shown by the pregnant traveler and the text on neglected diseases.

Studies in summary

Study	Design, sample and unit	Main finding
Blaizot 2020	Prospective GeoSentinel cohort, Bordeaux, 1,025 travelers; unit traveler	201 with dermatoses, 36 parasitic
Boggild 2025	CanTravNet surveillance, 17,644 travelers; unit traveler	328 with larva migrans from the Caribbean
Reichert 2016	Cross-sectional study, Manaus, 806 residents; unit person	Prevalence of 8.2 percent, higher in children
Schuster 2011	Uncontrolled cohort, Manaus, 91 patients; unit patient	Normal quality of life in 73.3 percent after ivermectin
Tamminga 2009	Single patient report, Brittany; unit patient	Larva migrans acquired in Europe
Stufano 2022	Systematic review, 12 articles; unit article	Occupational risk in those who work with soil and animals
Feldmeier 2014	Expert review; unit not applicable	Indoor cycle, stigma and lack of data
Wiese 2018	Cohort, Kenya, 50 children; unit child	Moderate to very large effect in 78 percent
Tardin Martins 2021	Systematic review, 19 articles; unit study	Evidence in favor of occlusives with dimethicone
Thielecke 2014	Proof-of-principle trial, Kenya, 47 schoolchildren; unit flea	Dimethicone 78 versus 39 percent
Suzuki 2024	Randomized pilot trial, Kenya, 23 children; unit flea	Dimethicone 87 versus 64 percent
Jallow 2024	Systematic review, 75 articles, 157 patients; unit patient	Tumbu fly in 66.2 percent, mostly travelers
Calvopina 2020	Review of reports and notifications, Ecuador; unit patient	Tumbu fly and screwworm; 21 percent in tourists
Toussaint-Caire 2018	Series of three patients, Mexico; unit patient	Local and imported tumbu fly

Sources: Blaizot et al., 2020; Boggild et al., 2025; Reichert et al., 2016; Schuster et al., 2011; Tamminga et al., 2009; Stufano et al., 2022; Feldmeier et al., 2014; Wiese et al., 2018; Tardin Martins et al., 2021; Thielecke et al., 2014; Suzuki et al., 2024; Jallow et al., 2024; Calvopina et al., 2020; Toussaint-Caire et al., 2018.

How NEXO helps train this reasoning

In NEXO, the case of the day is fictional, with a real clinical presentation and up to six progressive clues, and you propose the diagnosis by looking for the ICD-10 code. One clue might say "28-year-old tourist, returned from a tropical beach, intense itching on the foot"; another, "thin, winding track that advances a few millimeters per day". The five-level proximity feedback helps separate larva migrans, tungiasis, myiasis, scabies and bacterial skin infection, without turning the practice into a protocol.

Frequently asked questions

Is larva migrans transmitted from person to person?

The sources describe the infection as occurring through the entry of larvae present in soil or sand contaminated by dog and cat feces, with humans as accidental hosts (Boggild et al., 2025).

How long does the itching of larva migrans last without treatment?

On average five to six weeks, the lifespan of the larva, but there are reports of a year or more (Boggild et al., 2025).

Does oral ivermectin treat tungiasis?

The two studies with oral drugs, one of them with ivermectin, had discouraging results in the systematic review, and the evidence favors occlusives with dimethicone (Tardin Martins et al., 2021).

How does the tumbu fly reach the skin?

The female lays eggs in contaminated soil or on wet clothes drying in the shade, and the larvae penetrate the skin that touches this fabric (Jallow et al., 2024).

Does larva migrans only occur in the tropics?

There are reports of infection acquired in Europe, such as the one in Brittany, and of occupational risk in southern Italy (Tamminga et al., 2009; Stufano et al., 2022).

Take-home messages

• Dermatoses are common in travelers, and parasitic ones accounted for 36 of 201 at a French clinic (Blaizot et al., 2020).
• The serpiginous track that advances and itches suggests larva migrans, with ivermectin and albendazole as the most recognized treatments (Boggild et al., 2025).
• In tungiasis, the evidence favors occlusives with dimethicone, with small trials in Kenya (Tardin Martins et al., 2021; Suzuki et al., 2024).
• A furuncle with a hole in someone returning from Africa or the Americas suggests myiasis, treated by removing the larva (Jallow et al., 2024).
• Footwear, care with sand and ironed clothes are recommendations supported by risk studies, not by trials (Reichert et al., 2016).

Milestone inventory

• 2009: a report of larva migrans acquired in Brittany reinforces that the disease also appears in Europe (Tamminga et al., 2009).
• 2011: a study in Manaus measures quality of life in larva migrans and the improvement after ivermectin (Schuster et al., 2011).
• 2014: a proof-of-principle study in Kenya tests dimethicone in tungiasis (Thielecke et al., 2014).
• 2021: a systematic review concludes in favor of occlusives with dimethicone in tungiasis (Tardin Martins et al., 2021).
• 2024: a randomized pilot trial compares dimethicone and sodium carbonate in Kenyan children (Suzuki et al., 2024).

References

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10. Thielecke M, Nordin P, Ngomi N, et al. Treatment of Tungiasis with dimeticone: a proof-of-principle study in rural Kenya. PLoS Negl Trop Dis. 2014;8(7):e3058. PMID: 25079375. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4117482/
11. Suzuki K, Kamiya Y, Smith C, et al. A pilot study of dimeticone oils versus sodium carbonate treatment for tungiasis: A randomized cohort trial in Homa Bay County, Kenya. PLoS Negl Trop Dis. 2024;18(7):e0012341. PMID: 39042700. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11296639/
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14. Toussaint-Caire S, Woroszylski-Yoselevitz A, Vega-Memije ME, et al. Imported and Autochthonous Cases of Myiasis Caused by Dermatobia hominis: Taxonomic Identification Using the Internal Transcribed Spacer Region. Am J Trop Med Hyg. 2018;99(4):940-944. PMID: 30062994. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6159586/