Leishmaniasis

Description

Leishmaniasis, a parasitic disease caused by obligate intracellular protozoa, is transmitted by the bite of some species of phlebotomine sand flies. The disease most commonly manifests as either a cutaneous (skin) form or a visceral (internal organ) form.

Occurrence

Leishmaniasis is found in approximately 90 countries around the world, including countries in the tropics, subtropics, and southern Europe. 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. Leishmaniasis is not found in Australia, the South Pacific, or Southeast Asia. The geographic distribution of cases of leishmaniasis evaluated in the developed world reflects travel and immigration patterns. For example, approximately 75% of the cases of leishmaniasis that are evaluated in the United States (non-military associated) and are reported to CDC are cases of cutaneous leishmaniasis that were acquired in Latin America, where it occurs from northern Mexico (rarely in rural south-central Texas) to northern Argentina.

Risk for Travellers

Travellers of all ages are at risk for leishmaniasis if they live in or travel to leishmaniasis-endemic areas. Leishmaniasis usually is more common in rural than urban areas, but it is found in the outskirts of some cities. In the Old World, transmission of a particular species of the parasite (Leishmania tropica) that usually causes cutaneous leishmaniasis is common in some urban areas (e.g., Kabul, Afghanistan and Baghdad, Iraq). Risk is highest between dusk and dawn. Adventure travellers, Peace Corps volunteers, missionaries, ornithologists, and other persons who do research outdoors at night, and soldiers are examples of those who might have an increased risk for leishmaniasis, especially the cutaneous form. Even persons with short stays in leishmaniasis-endemic areas can become infected.

Clinical Presentation

Cutaneous leishmaniasis is characterised by one or more skin sores (either painful or painless, with or without a scab) that develop weeks to months after a person is bitten by infected sand flies. If untreated, the sores can last from weeks to years and often eventually develop raised edges and a central crater. The manifestations of visceral leishmaniasis, such as fever, weight loss, enlargement of the spleen and liver, and anaemia, typically develop months, but sometimes years, after a person becomes infected. If untreated, symptomatic visceral leishmaniasis typically is fatal.

Prevention

No vaccines or drugs for preventing infections are currently available. Preventive measures for the individual traveller are aimed at reducing contact with sand flies. Travellers 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. Sand fly activity in an area can easily be underestimated because sand flies are noiseless fliers and rare bites might not be noticed.

Travellers should be advised to use protective clothing and insect repellent for supplementary protection. Clothing should cover as much of the body as possible and be tolerable in the climate. Repellent with N,N-diethylmetatoluamide (DEET) should be applied to exposed skin and under the edges of clothing, such as sleeves and pant legs. DEET should be applied according to the manufacturer's instructions; repeated applications may be necessary under conditions of excessive perspiration and washing. (See Protection against Mosquitoes and Other Arthropods.) Impregnation of clothing with permethrin can provide additional protection, but it does not eliminate the need for repellent on exposed skin and should be repeated after every five washings.

Contact with sand flies can be reduced by using bed nets and screens on doors and windows. Fine-mesh netting (at least 18 holes to the linear inch; some sources advise even finer) is required for an effective barrier against sand flies, which are about one-third the size of mosquitoes. However, such closely woven bed nets might be difficult to tolerate in hot climates. Impregnating bed nets and window screens with permethrin can provide some protection, as can spraying dwellings with insecticide.

Treatment

Travellers should be advised to consult with an infectious disease or tropical medicine specialist for diagnosis and treatment. The relative merits of various treatments, including parenteral, oral, local, or topical treatments, can be discussed with the specialist. Physicians may consult with CDC to obtain information about the diagnosis and treatment of leishmaniasis. The parenteral drug sodium stibogluconate is available from the CDC Drug Service (404-639-3670) under an Investigational New Drug protocol. Additional information can be found on the Division of Parasitic Diseases' website: http://www.cdc.gov/ncidod/dpd/parasites/leishmania/factsht_leishmania.htm.

Bibliography
  • Berman JD. Human leishmaniasis: clinical, diagnostic, and chemotherapeutic developments in the last 10 years. Clin Infect Dis 1997;24:684-703.
  • Desjeux P. Leishmaniasis: public health aspects and control. Clin Dermatol 1996;14:417-23.
  • Herwaldt BL. Leishmaniasis. Lancet 1999;354:1191-9.
  • Herwaldt BL, Stokes SL, Juranek DD. American cutaneous leishmaniasis in U.S. travellers. Ann Intern Med 1993;118:779-84.

- Barbara Herwaldt

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