Tropical travelers’ top dermatologic infestations
This story appears courtesy of MDedge News
REPORTING FROM THE SDEF HAWAII DERMATOLOGY SEMINAR
WAIKOLOA, HAWAII – The Caribbean islands and Central and South America are among the most popular travel destinations for Americans. And some of these visitors will come home harboring unwelcome guests: Infestations that will eventually bring them to a dermatologist’s attention.
Dr. Natasha A. Mesinkovska, University of California, Irvine
Bruce Jancin/MDedge News
“I always tell the residents that if a patient’s country of travel starts with a B – Barbados, Belize, Bolivia, Brazil – it’s going to be something fun,” Natasha A. Mesinkovska, MD, PhD, said at the Hawaii Dermatology Seminar provided by Global Academy for Medical Education/Skin Disease Education Foundation.
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According to surveillance conducted by the Centers for Disease Control and Prevention and the International Society for Travel Medicine, the four most common tropical skin infestations brought back by U.S. travelers within the Americas are cutaneous larva migrans, myiasis, tungiasis, and leishmaniasis.
Cutaneous larva migrans is the easiest to diagnosis because it’s a creeping eruption that often migrates at a rate of 1-2 cm per day. Patients with the other disorders often present with a complaint of a common skin condition – described as a pimple, a wart, a patch of sunburn – that just doesn’t go away, according to Dr. Mesinkovska, director of clinical research in the department of dermatology at the University of California, Irvine.
Tungiasis is caused by the female sand flea, Tunga penetrans, which burrows into the skin, where it lays hundreds of eggs within a matter of a few days. The sand flea is harbored by dogs, cats, pigs, cows, and rats. It’s rare to encounter tungiasis in travelers who’ve spent their time in fancy resorts, ecolodges, or yoga retreats, even if they’ve been parading around with lots of exposed skin. This is a disease of impoverished neighborhoods; hence, affected Americans often have been doing mission work abroad. In tropical areas, tungiasis is a debilitating, mutilating disorder marked by repeated infections, persistent inflammation, fissures, and ulcers.
Treatment involves a topical antiparasitic agent such as ivermectin, metrifonate, or thiabendazole and removal of the flea with sterile forceps or needles. But there is a promising new treatment concept: topical dimethicone, or polydimethylsiloxane. Studies have shown that following application of dimethicone, roughly 80%-90% of sand fleas are dead within 7 days.
“It’s nontoxic and has a purely physical mechanism of action, so resistance is unlikely ... I think it’s going to change the way this condition gets controlled,” Dr. Mesinkovska said.
The differential diagnosis of myiasis includes impetigo, a furuncle, an infected cyst, or a retained foreign body. Myiasis is a cutaneous infestation of the larva of certain flies, among the most notorious of which are the botfly, blowfly, and screwfly. The female fly lays her eggs in hot, humid, shady areas in soil contaminated by feces or urine. The larva can invade unbroken skin instantaneously and painlessly. Then it begins burrowing in. An air hole is always present in the skin so the organism can breathe. Ophthalmomyiasis is common, as are nasal and aural infections, the latter often accompanied by complaints of a crawling sensation inside the ear along with a buzzing noise. To avoid infection, in endemic areas it’s important not to go barefoot or to dry clothes on bushes or on the ground. Treatment entails elimination of the larva. Covering the air hole with petroleum jelly will force it to the surface. There is just one larva per furuncle, so no need for further extensive exploration once that critter has been extracted.
The vector for this protozoan infection is the sandfly, which feeds from dusk to dawn noiselessly and painlessly. Because cutaneous and mucocutaneous leishmaniasis are understudied orphan diseases for which current treatments are less than satisfactory, prevention is the watchword. In endemic areas it’s important to close the windows and make use of air conditioning and ceiling fans when available. When in doubt, it’s advisable to sleep using a bed net treated with permethrin.
Cutaneous larva migrans
This skin eruption is caused by parasitic hookworms, the most common of which in the Americas is Ancylostoma braziliense. The eggs are transmitted through dog and cat feces deposited on soil or sand.
“Avoid laying or sitting on dry sand, even on a towel. And wear shoes,” Dr. Mesinkovska advised.
Among the CDC’s treatment recommendations for cutaneous larva migrans are several agents with poor efficacy and/or considerable side effects. But there is one standout therapy.
“Really, I would say nowadays the easiest thing is one 12-mg oral dose of ivermectin. It’s almost 100% effective,” she said.
Dr. Mesinkovska reported having no financial interests relevant to her talk.
SDEF/Global Academy for Medical Education and MDedge are owned by the same parent company.