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Skin problems in returning travellers

Skin diseases are common among returned travellers ­

they comprise the third most common reason for referral

to the hospital for tropical diseases after febrile illness and diarrhoea. The diagnosis is usually straightforward.

Many people who travel to the tropics become hot and sweaty and bacteria such as streptococci and staphylococci thrive in hot, sweaty places.

Minor trauma to the skin occurs very commonly while travelling and abrasions and insect bites can easily become infected.

A small proportion of individuals may become colonised by staphylococci, particularly in the nasal mucosae.

These individuals will present with recurrent crops of boils that multiple courses of antibiotics fail to eradicate.

The secret is to use a combination of rifampicin 600mg od for two days, Naseptin nasal cream and a cleansing solution to clear the nasal passages of the infection.

Remember to rule out diabetes as well.

Cutaneous leishmaniasis

Boils are usually precisely that ­ boils. A course of flucloxacillin will do the trick. Occasionally, however, they can be something else. The primary chancre of trypanosomiasis looks just like a boil though there may be more regional lymphadenitis than might be expected. And boils that fail to respond to conventional antibiotics may in fact be cutaneous leishmaniasis classically slowly growing with a raised edge and a sloughy centre.

Leishmaniasis is most commonly acquired either around the Mediterranean or in the Near East for 'Old World' disease, or anywhere from Mexico to Bolivia for 'New World'. The parasite is transmitted by sandflies. The diagnosis can be difficult to confirm. If you suspect it, it is best to refer either to the local dermatology or infectious disease unit, where diagnosis is usually based on finding the parasite in affected tissue.

Generalised rashes

Ringworm and other fungal infections such as pityriasis versicolor are common among travellers and are relatively easy to diagnose either with skin scrapings or examining the skin under Wood's ultraviolet light.

They are easy to treat with either topical or systemic antifungal agents. The rash of dengue fever, classically acquired in south-east Asia but also widespread throughout the Caribbean and much of South America, varies from a mild morbilliform rash to a more severe eruption. Other symptoms of this acute febrile viral infection include headache, arthralgia and myalgia. Diagnosis is by serology and treatment is supportive.

Various viral illnesses such as measles and rubella are perhaps more common among an adult immigrant population who have not been vaccinated against them.

And always inquire about sex ­ HIV seroconversion illness and secondary syphilis can both mimic virtually anything.

Cutaneous larva migrans

Worm-like tracks under the skin are precisely that. Larvae of either dog or cat hook worms can penetrate human skin, but then realise their mistake! In a dog or cat the worms would be able to complete their lifecycle and migrate to the intestine. In a human, they can't and wander around causing an itchy lesion until they ultimately die of old age (which can take weeks or even months). These cutaneous larva migrans are most common on the feet and are commonly acquired when travellers walk barefoot on beaches, but can occur anywhere. They respond well either to albendazole 400mg daily for three days or to Ivermectin as a single dose.

Eschar

Another characteristic lesion is the eschar of African tick typhus, almost invariably seen among holidaymakers in southern or east Africa who have been on safari. These lesions are virtually pathognomonic and a course of doxycycline 100mg daily for three days will produce a very satisfactory result.

A minority of infected individuals will develop a more generalised rash as well as the eschar but the response to doxycycline is just as good.

Tumbu flies

Suppurating boils are bad enough. Wriggling boils are even worse. 'Tumbu flies' and 'bot flies' are in fact maggots. The flies are attracted to the moisture on either washing or swimming costumes hung up to dry. The flies lay their eggs while drinking the moisture and the eggs then hatch and burrow into the skin the next time that item of clothing is worn. A few days later the egg has grown to become a maggot that resembles a boil, but it moves. Treatment is very easy ­ cover the opening with an occlusive dressing and the maggot dies of asphyxiation.

Further reading

Caumes E et al. Dermatoses associated with travel to tropical countries:

a prospective study of the diagnosis and management of 269 patients presenting to a tropical disease unit.

Clin. Infect. Dis. 1995;20:542-8

Pollard A and Murdoch DR. Fast facts: Travel medicine. Oxford:

Health Press, 2001

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