Description

Leishmaniasis, a parasitic disease caused by obligate intracellular protozoa, is transmitted by the bite of infected female phlebotomine sand flies (1-3). The disease has two major forms: cutaneous leishmaniasis, which causes skin sores, and visceral leishmaniasis, which affects some of the internal organs of the body (e.g., spleen, liver, and bone marrow).

Occurrence

Leishmaniasis is found in approximately 90 countries around the world (4). In the Old World, leishmaniasis is found in parts of Asia, the Middle East, Africa (particularly East and North Africa, with some cases elsewhere), and southern Europe; it is not found in Australia or the South Pacific. In the New World (the Americas), leishmaniasis occurs from northern Mexico (rarely in the southern United States) to northern Argentina; it is not found in Chile, Uruguay, or Canada. More than 90% of the world’s cases of cutaneous leishmaniasis are in Afghanistan, Algeria, Brazil, Iran, Iraq, Peru, Saudi Arabia, and Syria. More than 90% of the world’s cases of visceral leishmaniasis occur in Bangladesh, Brazil, India, Nepal, and Sudan. However, the geographic distribution of cases of leishmaniasis evaluated in countries such as the United States reflects travel and immigration patterns (5-6). For example, more than 75% of the civilian cases about which CDC is consulted are in persons with New World cutaneous leishmaniasis acquired in Latin America.

Risk for Travelers

Persons of all ages are at risk for leishmaniasis if they live in or travel to leishmaniasis-endemic areas. Even persons with short stays in such areas can become infected; the bite of one infected sand fly can result in infection. Leishmaniasis usually is more common in rural than urban areas. However, in some parts of the world, it is found in suburban or urban areas; for example, in the Old World, a particular species of the parasite (Leishmania tropica) that usually causes cutaneous leishmaniasis is common in some urban areas (e.g., in Kabul, Afghanistan, and in Baghdad, Iraq). Risk is highest from dusk through dawn because sand flies typically feed (bite) at night and during twilight hours (see below). Examples of the types of travelers and expatriates potentially at increased risk for infection (especially with the cutaneous form) include adventure travelers, Peace Corps volunteers, missionaries, soldiers, and persons such as ornithologists who do research outdoors at night or during twilight hours.

Clinical Presentation

Cutaneous leishmaniasis is characterized by one or more skin sores, which develop weeks to months after a person is bitten by an infected sand fly (1-3). The sores can change in size and appearance over time. They often develop raised edges and a central crater (or ulcer), which might be covered by a scab. The sores usually are painless but can be painful, particularly if they become infected with bacteria. Some people develop swollen glands near the sores. Even if not treated, the sores usually eventually heal. However, the healing process can take months, sometimes years, and typically results in scarring. Another potential concern applies to some of the species of the parasite found in Latin America: occasionally, the parasite spreads from the skin to the nose or mouth and causes sores there (mucosal leishmaniasis), which might not be noticed until years after the original skin sores have healed. The best way to prevent mucosal leishmaniasis is to treat the cutaneous infection before it spreads.

Visceral leishmaniasis is not common in travelers. The manifestations of visceral leishmaniasis, such as fever, weight loss, hepatomegaly and significant splenomegaly, typically develop months, sometimes years, after a person becomes infected (1-3). Patients usually have low blood counts, including a low red blood cell count (anemia), low white blood cell count, and low platelet count. If untreated, severe cases of visceral leishmaniasis typically are fatal.

Prevention

No vaccines or drugs for preventing infection are currently available. Preventive measures for travelers are aimed at reducing contact with sand flies. Travelers should be advised to avoid outdoor activities when sand flies are most active (dusk to dawn). Although sand flies are primarily nighttime biters, infection can be acquired during the daytime if resting sand flies are disturbed (e.g., if a hiker brushes against tree trunks or other resting sites). Sand fly activity in an area can easily be underestimated because sand flies do not make any noise when they fly. They are small (about one-third the size of mosquitoes), and rare bites might not be noticed.

Travelers should be advised to use protective clothing and insect repellent. Clothing should cover as much of the body as tolerable in the climate. Repellent with DEET should be applied to exposed skin and under the edges of clothing, such as sleeves and pant legs according to the manufacturer’s instructions; repeated applications may be necessary under conditions of excessive perspiration and washing (see Chapter 2).

Contact with sand flies can be reduced by using bed nets and screens on doors and windows. Sand flies are so small that they can pass through the holes in ordinary bed nets. The effectiveness of bed nets is enhanced by treatment with a pyrethroid-containing insecticide (permethrin or deltamethrin). The same treatment can be applied to window screens, curtains, bed sheets, and clothing; clothing should be retreated after five washings. In addition, spraying the room or dwelling with insecticide may provide some protection.

Travelers who have had leishmaniasis should be informed that they can become infected more than once and that they should use these preventive measures whenever they are in leishmaniasis-endemic areas.

Treatment

Travelers should be advised to consult an infectious disease or tropical medicine specialist for diagnosis and treatment. The relative merits of various types of treatment can be discussed with the specialist (1-3). Physicians may consult with CDC to obtain information about leishmaniasis, including diagnostic and other assistance. The parenteral drug sodium stibogluconate is available from the CDC Parasitic Disease Drug Service (404-639-3670), under an Investigational New Drug protocol. (See http://www.cdc.gov/ncidod/srp/drugs/drug-service.html.) Additional information can be found on the Division of Parasitic Diseases’ website: http://www.cdc.gov/ncidod/dpd/parasites/leishmania/factsht_ leishmania.htm.

References

1. Herwaldt BL. Leishmaniasis. Lancet. 1999;354:1191-9.
2. Murray HW, Berman JD, Davies CR, Saravia NG. Advances in leishmaniasis. Lancet. 2005;366:1561-77.
3. Berman JD. Human leishmaniasis: clinical, diagnostic, and chemotherapeutic developments in the last 10 years. Clin Infect Dis. 1997;24:684-703.
4. Desjeux P. Leishmaniasis: public health aspects and control. Clin Dermatol. 1996;14:417-23.
5. Herwaldt BL, Stokes SL, Juranek DD. American cutaneous leishmaniasis in U.S. travelers. Ann Intern Med. 1993;118:779-84.
6. Schwartz E, Hatz C, Blum J. New world cutaneous leishmaniasis in travelers. Lancet Infect Dis. 2006;6:342-9.