Attack of the arthropods
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Global travel helps spread of infestations, vector-borne infections

Every dermatologist sees bug bites. While many will be little more than an annoyance to the patient, others can have serious, even deadly, consequences. Some are difficult to identify; others are easy to diagnose but stubbornly resist treatment, or recur after successful treatment. “Dermatologists are interested in arthropods for three reasons,” said Dirk M. Elston, MD, managing director of the Ackerman Academy of Dermatopathology in New York City and deputy editor of the Journal of the American Academy of Dermatology, who takes office as president of the AAD this month. “One is the growing incidence of scabies and lice,” and their impact on patients. “Two, when we treat bites and stings, we may see the first indication of a serious underlying illness. A bizarre, extreme reaction to a mosquito bite, for example, can be a presenting sign of chronic lymphocytic leukemia. And finally, arthropods can be the vector for diseases. Some of those have skin manifestations, and dermatologists are the ones to diagnose them.” Arthropods include insects, arachnids, crustaceans, and millipedes. 

International (and domestic) travel has reinvigorated infestations once thought to be on the wane. Bedbugs (Cimex lecturlarius), for example, were declining in the Americas after the introduction of DDT and pyrethrum insecticides in the 1940s, according to a Journal of the American Academy of Dermatology article on tropical dermatology (2012;67(3):331.e1-331.e14). A resurgence in the U.S. in recent years, robust enough to warrant national news coverage, is attributed to international travel, as well as resistance to current insecticides, abandonment of the most potent insecticides, and the ability of bedbugs to survive up to a year without food. [pagebreak]

“The infestations we see coming from other countries are mainly bedbugs, scabies, and lice,” said Jose Dario Martinez, MD, professor of internal medicine and dermatology at University Autonomous of Nuevo Leon Monterrey, Mexico. “Certainly you had these in the U.S. before international travel was common, but it is so easy to bring back bedbugs when you travel. Scabies is in crowded countries with poor hygiene, and bedbugs are all over the world. Head lice, too, are common all over the world. There are other things you can catch from international travel, but these are the three principal infestations.”

The uninvited guest

Bedbugs emerge from hiding at night to feast on human blood. Being notorious hitchhikers (they can’t fly), they also crawl into luggage and clothing that’s left on the floor and accompany the traveler to the next destination. International travelers are bringing new types of bedbugs to the U.S. to interbreed with their American cousins, Dr. Elston said. “But you don’t have to go to exotic places — you can go to New York or Orlando and bring them home in your suitcase.” Dr. Martinez recalled that bedbugs bit him several times on the leg in a New York City hotel room while he was attending a summer meeting of the AAD (he saved a photo of the bites as a souvenir of his trip). The JAAD article notes that while the presence of bedbugs has traditionally been associated with low standards of sanitation, bedbugs are “now reported in upscale’ homes and hotels” and tend to be found in overcrowded areas of towns and cities. While bedbug infestations have been reported throughout the U.S., Philadelphia now ranks as the nation’s most bedbug-infested city, according to pest control company Terminix (reported on’s NewsFeed). [pagebreak]

Bedbugs tend to bite exposed areas of the body such as an arm hanging out of the covers, Dr. Elston said. “You can also get them on the trunk, where they often appear three in a row — that’s sometimes referred to as breakfast, lunch, and dinner.’” Dermatologists are likely to recognize bedbug bites on the trunk, he noted, but they may not realize that a patient with hundreds of bites on the arm who has picked them is also a victim of bedbugs. “These cases can look like prurigo nodularis on the arm when in fact they represent bedbug bites,” he said. “The key to the diagnosis is doing a biopsy and seeing eosinophil, a wedge-shaped infiltrate, and endothelial swelling typical of a bite.”

Repellents are relatively ineffective against bedbugs, Dr. Elston said, so “choose your hotel wisely. An acidic smell in the room can indicate bedbugs. The mattress seams may be stained brown, which represents bloody feces. Eggs may appear as white specks, and the bugs themselves are reddish-brown and about the size of a small tick.” Bedbugs also lurk in offices and movie theaters, he added, so “when you put your purse on the floor, they can crawl in and come home with you.” While bedbugs are highly resistant to traditional insecticides (which, the JAAD authors note, are generally more harmful to humans than bedbug bites), Dr. Martinez said that some new insecticides are proving to be effective, including those in the pyrrole, neonicotinoid, and phenylbrazole groups. Four volunteers at Eastern Virginia Medical School are trying a different method — poisoning the food supply. The New York Times reports that, under the supervision of an emergency room physician, the researchers are taking oral ivermectin and inviting bedbugs to bite. Ivermectin is a common deworming drug sometimes deployed against treatment-resistant head lice (see sidebar) and scabies; while it is not curative, the researchers have found that after they took one dose of it, 60 percent of the bedbugs that bit them died. [pagebreak]

The seven-year itch

The tiny mite Sarcoptes scabiei doesn’t bite, but provokes intense pruritis by burrowing into the epidermis and depositing eggs, which mature in 21 days. “Scabies exists in epidemic proportions. Every dermatologist sees it, and we see it a lot,” Dr. Elston said. “It used to come in cycles of about seven years, but starting about 30 years ago, it stopped cycling and just stayed.” Travel is likely one factor underlying the spread of scabies, which shows no sign of abatement, Dr. Elston said.

Scabies spreads through skin-to-skin contact and via fomites like bedding and clothing, and is particularly common among children, Dr. Martinez said. “In children, scabies affects the head, palms, soles, and genital area. In adults, it’s mainly the umbilicus, hands, and genitals. The lesions look like papules with scales, but the identifying feature is the burrow made by the female.” Scabies do not pose a health threat to patients with healthy immune systems, but “some people are very allergic to these mites, and instead of 12 to 14 lesions, they develop eczema and itch like crazy.” Bacteria harbored under the nails can cause secondary infections when patients scratch scabies lesions, Dr. Martinez added.

First-line treatment for scabies is permethrin, Dr. Elston said, but off-label alternatives are available in cases of treatment failure. In addition to oral ivermectin, these include 10 percent sulfur in white petroleum jelly, “which is how much of the world still treats scabies. A recent study indicated that aloe jelly performs about as well as benzyl benzoate, another standard treatment used in many parts of the world.” While dermatologists are observing some resistance to permethrin, failure to use the medication properly may contribute to lack of efficacy. “Failure to treat areas like under the nails, where the mites are living, can result in treatment failure,” Dr. Elston said. “People scratch and mites and ova end up under the nails, and if you don’t clean out under the nails and apply the medication there, the infestation may recur. They also have to treat between the fingers and toes, in the belly button, and on the genitalia. They’re often nervous about putting the medication on their genitals, so you have to tell them that it’s an important place to treat.” [pagebreak]

Vector-borne disease

If global travel plays only a supporting role in the spread of scabies and bedbugs, it’s solely responsible for bringing to the U.S. Chikungunya, a mosquito-borne viral infection, and certain forms of cutaneous leishmaniasis, spread by sand flies. “Chikungunya was an isolated African fever that made its way to islands in the Indian Ocean that served as vacation destinations for Europeans and Americans,” Dr. Elston said. “In the U.S., we have the vectors that can carry it [Asian tiger mosquitoes], so if someone comes back sick from a vacation, the disease can spread. It now has a wide distribution.”

Patients with Chikungunya present with fever, severe muscle and joint pain, headache, and a rash that tends to occur in acral sites such as the ear, Dr. Elston said. Because several diseases can cause headache, fever, and rash, he suggested that dermatologists consider the location of a patient who presents with these symptoms. “In the Eastern U.S., especially the Carolinas, you should think first of Rocky Mountain spotted fever. Away from the East coast, it might be Ehrlichia. And then if they have rash on the ear and don’t have exposure to tick bites but do have mosquito bites, in Texas you think of dengue and in the southeast of the country you now think of things like Chikungunya.” According to a report from Cornell University, published on Cornell Chronicle Online, the Asian tiger mosquito is now established up the East coast through New Jersey, and its numbers are rising in New York City. A new Cornell computer model predicts that outbreaks of Chikungunya could occur in 2013 in New York City during August and September, in Atlanta June through September, and year-round in Miami. [pagebreak]

Cutaneous leishmaniasis (CL), the most common form of leishmaniasis, can be caused by about 20 different species of Leishmania (a protozoan parasite spread by sand flies), according to the Centers for Disease Control and Prevention. “Leishmaniasis naturally occurs in places like Texas, where it’s usually the mexicana variety,” Dr. Elston explained. “That will often heal on its own. But there are more aggressive types that are picked up in places like southwest Asia and South America. While soldiers returning from Iraq and Afghanistan can show up with leishmaniasis, the more severe types, especially from certain portions of South America, can come back years later and cause very destructive lesions in the central face. If you picked it up in areas with mucocutaneous disease, you often need treatment with systemic medication to prevent that kind of highly destructive manifestation.” The CDC states that the geographic distribution of CL in the U.S. reflects travel and immigration patterns, and that more than 75 percent of the cases diagnosed in U.S. civilians have been acquired in Latin America, including Costa Rica.

The first lesion (which may be single or multiple) in localized CL is a papule which appears at the site of the sand fly bite, said Yahya Dowlati, MD, PhD, director of the Center for Research and Training in Skin Diseases and Leprosy at the Tehran University of Medical Sciences and president of the Iranian Society of Dermatology. “This lesion grows and converts into an ulcer which is covered by dry exudates, or the papules may turn into nodules instead.” The history of traveling to endemic areas is an important factor in the diagnosis of leishmaniasis in countries where the disease is not endemic, he said, adding that “a direct smear from the periphery of an active lesion is the most commonly performed method of diagnosis; when the Giemsa stain is used, the non-flagellated amastigote forms will be seen.” [pagebreak]

The treatment of CL is challenging, Dr. Dowlati noted, particularly for the diffuse and mucocutaneous forms of the disease. “Despite the existence of a large number of randomized controlled trials, the bottom line is that there is no high-level evidence available for the treatment of Old World [endemic in Afghanstan, Iran, Saudi Arabia, Iraq, Tunisia, Algeria and Syria] or New World [e.g., Brazil, Bolivia, Peru] CL.” Dr. Martinez said he is currently reviewing the use of oral miltefosine, and had success in treating one of his own leishmaniasis patients with multiple lesions. Dr. Elston said that once a dermatologist has determined where CL was acquired, “the CDC can be very helpful in providing guidelines for how a given site should be treated, and also putting a physician in touch with an expert to help.”

Dr. Martinez emphasizes the importance of asking patients about recent travel, “especially when they have a lesion that’s unusual for their area, because these infestations are a common cause of morbidity among international travelers.” For patients who come in before an international trip and inquire about vaccines, dermatologists should counsel prevention “because for these things, there are no vaccines — only use of appropriate clothes and repellents, and avoiding places where the bugs can bite you.” [pagebreak]

Treatment resistance in head lice

Head lice have been found on ancient Egyptian mummies, and it’s likely that humanity’s struggle to rid itself of Pediculus humanus capitis predates recorded history. The latest chapter in the ongoing saga involves the worldwide overuse of the topical insecticides permethrin and malathion, widely recommended as first-line treatment, with the result that lice in many areas are demonstrating resistance to these agents. Permethrin has an immobilizing effect on the louse, called “knockdown;” DNA sequencing has shown that “knockdown resistance” (kdr) to permethrin results from a genetic mutation, according to an editorial published in the New England Journal of Medicine about the use of topical ivermectin as an alternative treatment (2012;367(18):1750-2). The authors cite the frequency of “resistant kdr-like louse alleles” as ranging from zero in Thailand to 100 percent in California, Florida, and Texas.

A group of French researchers conducted a large-scale observational study to evaluate the occurrence of head lice resistance to pyrethroids (a group that includes permethrin) and malathion in the elementary schools of Paris. They collected live and uninjured lice and performed a series of ex vivo bioassays to test for sensitivity to malathion and to a formulation of permethrin and piperonyl butoxide. In addition, the researchers conducted molecular analysis on a portion of the lice to look for kdr mutations. Among the findings, published in JAAD (2012;67(6):1143-50): 98.7 percent of the tested lice had homozygous kdr mutations; 100 percent of the lice were dead after one hour of contact with malathion; and 85.7 percent of the lice exposed to the permethrin formulation were dead after one hour. The researchers concluded that formulations containing malathion can still be recommended as pediculicides for schoolchildren of Paris, and that in clinical practice, longer exposure times “could result in relatively good efficacy, even on resistant’ head lice.”

Dirk Elston, MD, maintained that although permethrin still works in some patients, the effect of kdr is that “it takes longer and longer exposures for it to work. And the longer the exposure, the more concerned you become about the use of the medication.” Citing epidemiological data suggesting a link between insecticide use and childhood leukemia, he noted that “it’s a statistical link, but it’s concerning, and many parents and physicians prefer to find alternatives that are safer.” These may include Ulesfia, which contains benzyl alcohol, and spinosad, a naturally derived insecticide “that can be a little irritating but also seems to be fairly effective. If it were my child, I would use Ulefsia because it’s completely free of any insecticides, and I personally don’t like the idea of using insecticides on children.”

Help your patients

When patients visit with questions about infestations, you can feel confident referring them online to learn more. Dermatology A-Z, located at, includes sections on bedbugs, lice, and scabies. Each section offers information about signs and symptoms; causes; diagnosis, treatment, and outcome; and prevention and management tips.



Treatment resistance in head lice
Help your patients