Author(s): Mary Kamb, Sharon Roy, Paul Cantey

Infectious Agent

Leishmaniasis is caused by obligate intracellular protozoan parasites; >20 Leishmania species cause cutaneous leishmaniasis (CL). Leishmaniasis has different forms, including visceral leishmaniasis (the most severe form), but CL is the most common form. An aggressive form of CL, mucosal leishmaniasis (ML), affects mucosal areas.

Transmission

Leishmania parasites that cause CL are transmitted through the bites of infected female phlebotomine sand flies. CL also can occur after accidental occupational (laboratory) exposures to Leishmania parasites. Transmission risk is greatest from dusk to dawn because sand flies typically feed (bite) at night and during twilight hours. Although sand flies are less active during the hottest part of the day, they can bite if they are disturbed, for instance when people brush against tree trunks or other sites where sand flies are resting. Vector activity might easily be overlooked because sand flies are small and silent, and their bites can go unnoticed. Travelers with potentially increased risk for CL include adventure travelers, bird watchers, construction workers, ecotourists, military personnel, missionaries, Peace Corps volunteers, and people doing research or humanitarian work outdoors at night or twilight. Even short-term travelers in leishmaniasis-endemic areas have developed CL, however. Immigrants and refugees from endemic areas also might present with CL.

Epidemiology

As of 2017, CL was reported to be endemic in 87 countries on 6 continents, with an estimated annual prevalence of 4.13 million, including 700,000 new cases globally. The ecologic settings for leishmaniasis transmission range from rainforests to arid regions.

In the Eastern Hemisphere, CL is found in Africa, particularly the tropical region and North Africa; Asia, particularly central and southwest Asia; southern Europe, including southern France, Greece, Italy, Portugal, Spain, and the Mediterranean islands; and some countries of the Middle East. In the Western Hemisphere, CL is found in parts of Mexico, all countries of Central America, and most of South America. Endemic transmission in the United States has been identified in Texas, especially among people living in areas bordering northeastern Mexico, and in neighboring Oklahoma. CL is not found in Canada, Chile, or Uruguay.

GeoSentinel Surveillance from 1997–2017 indicated that among patients examined at specialized travel or tropical medicine clinics on 6 continents, including North America, and who had laboratory-confirmed diagnoses, common source countries for travel-associated CL were Bolivia; countries in the Amazon Basin, including Brazil, Colombia, Ecuador, and Peru; Costa Rica; El Salvador; and Israel. Among immigrants, common source countries were Afghanistan and Syria. Cases of CL in US service personnel have reflected military activities (e.g., in Afghanistan and Iraq). CL is usually more common in rural than urban areas but is found in some peri-urban and urban areas (e.g., in Kabul, Afghanistan).

Clinical Presentation

CL can present with a broad variety of dermatologic manifestations ranging from small and localized skin lesions to large nodules or plaques covering multiple body surfaces; ≈10% of infections are asymptomatic. The clinical spectrum can mimic other skin conditions (e.g., leprosy, squamous cell cancer, fungal or other skin infections).

CL is characterized by skin lesions, which can be closed or open sores, that typically develop on exposed areas of the skin within several weeks or months after infection. In some people, however, the sores first appear months or years later, often in the context of trauma (e.g., skin wounds, surgery). The sores can change in appearance and size over time. Sores typically progress from small, erythematous papules or nodular plaques to open sores with a raised border and central crater (ulcer), which can be covered with crust or scales. Lesions usually are painless but can be painful if superinfected with bacteria. Satellite lesions, regional lymphadenopathy, and nodular lymphangitis can occur. Even without treatment, most sores eventually heal; they can last for months or years, however, and typically result in scarring.

Mucosal Leishmaniasis

Some Leishmania species in Central and South America are a potential concern because parasites might spread from the skin to the mucosal surfaces of the nose or mouth and cause sores in these areas. ML might not be apparent until years after the original skin sores appear to have healed. Although ML is uncommon, it has occurred in travelers and expatriates, including in people whose cases of CL were not treated or were treated inadequately. The initial clinical manifestations typically involve the nose, with bleeding, chronic stuffiness, and inflamed mucosa or sores; less often the mouth or larynx are involved, manifesting as a brassy cough or hoarseness.

In advanced cases, ulcerative destruction of the mouth, nose, larynx, and pharynx (e.g., perforation of the nasal septum, or laryngeal or tracheal damage) can occur. Thus, any patient with CL caused by a Viannia subgenus from the Western Hemisphere, regardless of symptoms, should undergo a careful examination of mucosal surfaces, including the vocal cords and oronasal pharynx, along with biopsy of any abnormal-appearing tissue, to avoid missing ML cases. Although most commonly associated with species of Leishmania found in the Western Hemisphere, ML has been documented on rare occasions with species of Leishmania found in various countries of the Eastern Hemisphere.

Diagnosis

Consider CL in people with chronic, nonhealing skin lesions who have been in areas where leishmaniasis is found. Clinical signs and symptoms are not sufficiently specific to differentiate CL from other conditions. Obtain an explicit travel history, including, if possible, questioning fellow travelers about similar lesions. Obtain information about duration and progression of symptoms, whether the lesions are painful, prior treatment, and current medications (e.g., immunosuppressive agents); photographs are helpful to assess lesions over time. Conduct a careful physical examination including evaluation of skin, lymph nodes, and mucosal surfaces; referral to a specialist able to conduct an endoscopic laryngeal examination might be warranted if ML is suspected.

Laboratory confirmation of the diagnosis is achieved by detecting Leishmania parasites or DNA in infected tissue through light-microscopic examination of stained specimens, culture techniques, or molecular methods (e.g., PCR); conducting all 3 tests maximizes diagnostic yield. The Centers for Disease Control and Prevention (CDC) can assist in all aspects of the diagnostic evaluation. Because different Leishmania species have different management implications, species identification through molecular testing is important, particularly if >1 species is endemic to areas where the patient traveled.

Serologic testing generally is not useful for CL because the assays are insensitive and cannot distinguish between active and past infection. For consultative services, including collection and packaging of samples for molecular testing, contact CDC Parasitic Diseases Inquiries (404-718-4745; parasites@cdc.gov).

Treatment

The primary goal of treatment is to prevent morbidity. Individualize decisions about whether and how to treat CL, including whether to use a systemic (oral or parenteral) medication rather than a local or topical approach. Treat all cases of ML with systemic therapy. Clinicians can consult with CDC staff about the relative merits of various approaches to treat CL and ML (see the Diagnosis section for contact information). The response to a particular regimen can vary not only among Leishmania species but also for the same species in different geographic regions.

The oral agent miltefosine is approved by the US Food and Drug Administration (FDA) to treat CL caused by 3 Western Hemisphere species of the Viannia subgenus: Leishmania (V.) braziliensis, L. (V.) guyanensis, and L. (V.) panamensis, as well as for ML caused by L. (V.) braziliensis, in adults and adolescents ≥12 years old who weigh ≥30 kg and are not pregnant or breastfeeding during therapy or for 5 months after treatment. Various parenteral options, including liposomal amphotericin B, are commercially available, although not FDA-approved to treat CL or ML. The pentavalent antimonial compound sodium stibogluconate (Pentostam) is no longer available through the CDC Drug Service.

Prevention

No vaccines or drugs to prevent infection are available. Travelers can reduce the risk for CL by using personal protective measures to avoid sand fly contact and sand fly bites (see Sec. 4, Ch. 6, Mosquitoes, Ticks & Other Arthropods). Advise travelers to avoid outdoor activities, to the extent possible, especially from dusk to dawn when sand flies are the most active; wear protective clothing and apply insect repellent to exposed skin and under the edges of clothing (e.g., shirt sleeves, pant legs) according to the manufacturer’s instructions; and sleep in air-conditioned or well-screened areas. Spraying sleeping quarters with insecticide might provide some protection, and fans or ventilators might inhibit the movement of sand flies, which are weak fliers.

Sand flies are small (≈2–3 mm, <1/8 inch) and can pass through the holes in ordinary mosquito nets. Although fine mesh nets are available, these can be uncomfortable in hot climates. The effectiveness of mosquito nets can be enhanced by treating with a pyrethroid-containing (i.e., permethrin) insecticide. The same treatment can be applied to bed sheets and clothing, curtains, and window screens.

CDC website: Leishmaniasis