Leishmaniasis

Description

Leishmaniasis is a parasitic disease transmitted by the bite of some species of sand flies. It is an obligate intracellular protozoan. The disease most commonly manifests either in a cutaneous (skin) form or in a visceral (internal organ) form.

Occurrence

Leishmaniasis is found in approximately 90 tropical and subtropical countries around the world and in 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. However, approximately 75% of the cases that are evaluated in the United States were acquired in Latin America, where leishmaniasis occurs from northern Mexico (rarely in rural southern Texas) to northern Argentina. 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 or the South Pacific.

Risk for Travelers

Travelers of all ages are at risk for leishmaniasis if they live in or travel to these areas. Leishmaniasis usually is more common in rural than urban areas, but it is found in the outskirts of some cities. Risk is highest between dusk and dawn. Adventure travelers, Peace Corps volunteers, missionaries, ornithologists, 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 characterized 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 anemia, typically develop months, but sometimes years, after a person becomes infected. If untreated, symptomatic visceral leishmaniasis typically is fatal.

Prevention

Vaccines and drugs for preventing infections are not currently available. Preventive measures for the individual traveler 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. Sand fly activity in an area can easily be underestimated because sand flies are noiseless fliers and rare bites might not be noticed.

Travelers 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 tolerated in the climate. Repellent with N,N-diethylmetatoluamide (DEET) should be applied to exposed skin and under the edges of clothing, such as under the ends of sleeves and pant legs. DEET should be applied according to the manufacturer's instructions; repeated applications may be necessary under conditions of excessive perspiration, wiping, and washing (see Protection against Mosquitoes and Other Arthropods). Although impregnation of clothing with permethrin can provide additional protection, 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 aerosol can provide some protection, as can spraying dwellings with insecticide.

Treatment

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

— Barbara Herwaldt