Jay S. Keytsone

Description

Next to fever and diarrheal illness, skin problems are the third most frequent medical problem in returned travelers reported to travel and tropical medicine clinics. The largest case series of dermatologic problems in returned travelers from the GeoSentinel surveillance network showed that cutaneous larva migrans, insect bites, and bacterial infections were the most frequent skin problems in returned travelers, making up 30% of the 4,742 diagnoses (Table 4-2). In another recent review of 165 travelers who returned to France with skin problems, cellulitis, scabies, and pyoderma led the list of skin conditions. These data carry an inherent bias in that they do not include skin problems that were diagnosed and, in many cases, easily managed overseas or that were self-limited.

Skin problems generally fall into one of the following two categories: those associated with fever, usually a rash or secondary bacterial infection (cellulitis, lymphangitis, bacteremia, toxin-mediated), and those not associated with fever. Most skin problems are minor and are not accompanied by fever.

The approach to the diagnosis of skin problems in returned travelers is based on the following:

• Pattern recognition of the lesions (e.g., maculopapular, linear, nodular)
• The location of the lesions (e.g., exposed or unexposed skin surfaces)
• Exposure history (e.g., freshwater, insects, animals, or human contact)
• Associated symptoms (e.g., fever, pain, pruritus)

Papular Lesions

Insect bites, the most common cause of papular lesions, are frequently associated with secondary infection, or hypersensitivity reactions. Bed bugs and fleas can produce papules in groups of three (“breakfast, lunch, and dinner”). Scabies is a mite that frequently presents with a generalized pruritic, papular rash. Very pruritic, excoriated papules may present in a short linear fashion on the skin.

Onchocerciasis, also known as river blindness, is caused by the filarial nematode Onchocerca volvulus (see the Onchocerciasis section in Chapter 5). Skin lesions can present with generalized pruritus, often associated with a papular rash. The filariae are transmitted by day-biting black fly bites. The main risk occurs in long-stay travelers living in rural sub-Saharan Africa, and rarely, Latin America.

Nodular/Subcutaneous Lesions, Including Bacterial Skin Infections

Bacterial skin infections may occur more frequently following bites and other wounds in the tropics, particularly when good hygiene cannot be maintained. Organisms responsible are commonly Staphylococcus aureus or Streptococcus pyogenes. The presentations can include abscess formation, cellulitis, lymphangitis, or ulceration. Furunculosis, or recurrent pyoderma, is the result of colonization of the skin and nasal mucosa with Staphylococcus aureus. Boils may continue to occur weeks or months after a traveler returns.

In addition to pyodermas, cellulitis or erysipelas may complicate excoriated insect bites or any trauma to the skin. Cellulitis and erysipelas manifest as areas of skin erythema, edema, and warmth in the absence of an underlying suppurative focus; unlike cellulitis, erysipelas lesions are raised, there is a clear line of demarcation at the edge of the lesion, and the lesions are more likely to be associated with fever. Cellulitis, on the other hand, is more likely to be associated with lymphangitis. Cellulitis and erysipelas are usually caused by beta-hemolytic steptococci; Staphylococcus aureus (including methicillin-resistant staphylococcus, MRSA) and gram-negative aerobic bacteria may also cause cellulitis.

Emerging antibiotic resistance among staphylococci and Streptococcus pyogenes (erythromycin resistance) is problematic because antimicrobial treatment may be more difficult. After return from travel, antibiotic choice will be determined by the presentation and extent of illness. If such a skin problem occurs during travel, the antibiotic choice may depend on whether medical care and follow up are available, as well as which medications are available. Some travelers may benefit from carrying an antibiotic for self-treatment in these circumstances. Choices are difficult, but include trimethoprim/sulfamethoxazole and extended penicillin, a cephalosporin, or a broad-spectrum quinolone. None of these is ideal.

Another common bacterial skin infection in the tropics, due to S. aureus and/or Str. pyogenes, is impetigo, especially in children. Impetigo is a highly contagious superficial skin infection that generally appears on the arms, legs, or face as “honey-colored” scabs formed from dried serum. The treatment of choice is a topical antibiotic such as mupirocin.

Myiaisis presents as a painful, boil-like lesion. It is caused by an infection with the larval stage of the Tumbu (Cordylobia anthropophaga) or bot fly (Dermatobium hominis). The larvae are frequently acquired in Africa and Latin America. The lesions reveal the presence of a small, central punctum that allows the larvae to breathe. There are several described techniques for removal of the larvae.

Tungiasis is a sand flea (Tunga penetrans). The female burrows into the skin, usually the foot, and produces a nodular, subcutaneous lesion with a central dark spot. The lesion expands as the female produces eggs in her uterus. The flea must be extracted surgically.

Loa Loa filariasis can rarely occur in long-stay travelers living in rural sub-Saharan Africa. It is transmitted by day-biting deer flies. The traveler may present with transient, migratory, subcutaneous, painful, or pruritic swelling produced by the adult nematode migration. Rarely, the worm can be visualized crossing the conjunctiva of the eye or eyelid. Eosinophilia is common. It can be diagnosed by finding the larval stages (microfilaria) in blood collected during the day. Serologic tests are also available, but usually not in commercial laboratories. Infection can be prevented by taking 200 mg of diethylcarbmazine once a week while at risk.

Gnathostomiasis is a nematode infection found primarily in Southeast Asia and less commonly in Africa and Latin America. Infection results from eating undercooked or raw freshwater fish. The traveler experiences transient, migratory, subcutaneous, pruritic, or painful swellings that may occur weeks or even years after exposure. The symptoms are due to a single worm migrating throughout the body, including the central nervous system. Eosinophilia is common, and the diagnosis can be made by serology.

Macular Lesions

By far the most frequent macular lesions seen in returned travelers living in warm climates are superficial mycoses such as tinea versicolor and tinea corporis.

Tinea versiclor, which is due to Malassezia furfura (previously Pityrosporum ovale), is characterized by asymptomatic hypo- or hyperpigmented oval, slightly scaley patches measuring 1–3 cm, found on the upper chest, neck, and back. Diagnosis is by Wood’s lamp or by placing a drop of methylene blue on a slide onto which clear cellulose acetate tape is placed sticky side down, after it has been touched briefly to the skin lesions to pick up superficial scales. Hyphae (“spaghetti”) and spores (“meatballs”) are readily visible. Treatment with topical or systemic azoles (ketoconazole, fluconazole), or terbenifine is recommended.

Tinea corporis (ringworm) is caused by a number of different superficial fungi. The lesion is often a single lesion, with an expanding red, raised ring, with a central area of clearing in the middle. Treatment is several weeks’ application of a topical antifungal agent.

Lyme disease, a tick-borne infection with Borrelia burgdorferi, is common in North America, Europe, and Russia (see theLyme Disease section in Chapter 5). The traveler presents with one or more large erythematous patches, with or without central clearing, surrounding a prior tickbite. The patient may not have noted the tick bite.

Linear Lesions

Cutaneous larva migrans is the result of infection of the skin with a larva from a dog or cat hookworm (Ancylostoma brasiliensis) (see the Cutaneous Larva Migrans section in Chapter 5). Dogs and cats that defecate on beaches appear to be one of the main risks for travelers. Lesions appear on the feet or buttocks most commonly. The traveler presents with an extremely pruritic, serpiginous, linear lesion that migrates within the skin at the rate of 2–4 cm per day. Treatment is with oral albendazole or ivermectin, but a topical cream of 10% thiabendazole is also effective.

Phytophotodermatitis results from spilling lime juice onto the skin in a sunny climate. The result is exaggerated sunburn that gives rise to a linear, asymptomatic lesion that later develops hyperpigmentation. The hyperpigmentation may take weeks or months to resolve.

Lymphocuticular spread of infection occurs when organisms spread along superficial cutaneous lymphatics, producing a raised, linear cord-like lesion along which nodules or ulcers may be found. Examples are sporotrichosis, Mycobacterium marinum (associated with exposure to water), bartonellosis (cat-scratch disease), tularemia, and blastomycosis.

Skin Ulcers

Ulcerated skin lesions may result from Staphyloccus infections or may be the direct result of an unseen spider bite. Often the etiology of such an ulcer is not clear. Of particular concern is the ulcer caused by cutaneous leishmaniasis, which results from the bite of a sand fly. The main areas of risk are Latin America, the Mediterranean, Middle East, and Asia. The lesion is a chronic, usually painless ulcer with heaped-up margins on exposed skin surfaces. Special diagnostic techniques are necessary to confirm the diagnosis, and treatment is problematic. If cutaneous leishmaniasis is suspected, contact the CDC for further advice (see the Leishmaniasis, Cutaneous section in Chapter 5 for contact information).

Miscellaneous Skin Infections

Skin Infections Associated with Water

Soft tissue infections can occur after both freshwater and saltwater exposure, particularly if there is associated trauma. Puncture wounds due to fishhooks and fish spines, lacerations due to inanimate objects during wading and swimming, and bites from fish or other sea creatures may be the source of the trauma leading to waterborne infections. The most common soft tissue infections associated with exposure to water or water-related animals include Mycobacterium marinum, Aeromonas species, Edwardsiella tarda, Erysipelothrix rhusiopathiae, and Vibrio vulnificus. A variety of skin and soft tissue manifestations may occur in association with these infections, including cellulitis, abscess formation, ecthyma gangrenosum, and necrotizing fasciitis. The majority of Vibrio infections occur in men; Vibrio vunificus may be especially severe in those with underlying liver disease. M. marinum lesions usually appear as solitary nodules or papules on an extremity, especially on the dorsum of feet and hands that subsequently progress to shallow ulceration and scar formation. Occasionally “sporotrichoid” spread may occur as the lesions spread proximally along superficial lymphatics.

“Hot tub folliculitis” due to Pseudomonas aeruginosa may result from the use of spa pools or whirlpools, or exposure to inadequately chlorinated swimming pools and hot tubs. Folliculitis typically develops 8–48 hours after exposure in contaminated water and consists of tender, pruritic papules, papulopustules, or nodules. Most patients have malaise and some have low grade fever. The condition is self-limited in 2–12 days; no antibiotic therapy is typically required.

Skin Infections Associated with Bites

Wound infections following dog and cat bites are caused by a variety of microorganisms. Staphylococcus aureus, alpha-, beta-, and gamma-hemolytic streptococci, several genera of gram-negative organisms, and a number of anaerobic microorganisms have all been isolated. The prevalence of Pasteurella multocida isolates from dog bite wounds is 20%–50% and is the major pathogen in cat bite wound infections. Management of dog and cat bites includes consideration of rabies prophylaxis, tetanus immunization, and antibiotic prophylaxis. Primary closure of puncture wounds and dog bites to the hand should be avoided. Antibiotic prophylaxis for dog bites is controversial, but because Pasteurella multocida is a common accompaniment of cat bites, prophylaxis with amoxicillin–clavulanate or a fluoroquinolone for 3–5 days should be considered.

Fever and Rash

Fever and rash in returned travelers are most often due to a viral infection, with dengue being the most frequent and perhaps most easily recognizable example.

Dengue fever is caused by one of four strains of dengue viruses (see the Dengue Fever section in Chapter 5). The disease is transmitted by a day-biting Aedes mosquito often found in urban areas. The disease is characterized by the abrupt onset of high fever, frontal headache (often accompanied by retro-orbital pain), myalgia, and a faint macular rash that becomes evident on the second to fourth day of illness. The rash may become visible only after one presses on the skin, and an area of blanching persists for several seconds.

Chikungunya fever, a virus transmitted by a day-biting Aedes mosquito, has recently caused major outbreaks of illness in Southeast Africa and South Asia (see the Chikungunya Fever section in Chapter 5). Chikungunya fever is similar to dengue clinically, including the rash. The major distinguishing feature is that arthritis is common with chikungunya fever and may persist for months. Treatment of the arthritis is with nonsteroidal anti-inflammatory drugs (NSAIDS). Aspirin should be avoided in dengue fever. Serologic tests are available for the diagnosis of both chikungunya and dengue, but often require a convalescent-phase serum to confirm.

South African tick typhus, or African tick bite fever (Rickettsia africae) is the most frequent cause of fever and rash in Southern Africa. Transmitted by ticks, the disease is characterized by fever and a papular or vesicular rash associated with localized lymphadenopathy and the presence of an eschar, a mildly painful 1–2-cm black necrotic lesion with an erythematous margin. Diagnosis can be suspected clinically and confirmed by serology. Treatment is with doxycycline.

The category of fever with rash is large, and travel medicine physicians should also consider the following diagnoses: enteroviruses, such as echovirus and coxsackie virus, hepatitis B virus, measles, Epstein–Barr virus, cytomegalovirus, typhus, leptospirosis, and HIV.

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