Leishmaniasis is a parasitic disease found in parts of the tropics, subtropics, and southern Europe. Leishmaniasis has several different forms. This section focuses on visceral leishmaniasis (VL), which affects some of the internal organs of the body (such as the spleen, liver, and bone marrow).
VL is caused by obligate intracellular protozoan parasites, particularly by the species Leishmania donovani and L. infantum (considered synonymous with L. chagasi ).
The parasites that cause VL are transmitted through the bite of infected female phlebotomine sand flies. Congenital and parenteral transmission (through blood transfusions and needle sharing) have been reported.
VL is usually more common in rural than urban areas, but it is found in some periurban areas (such as in northeastern Brazil). In the Old World (Eastern Hemisphere), VL is found in parts of Asia (particularly the Indian subcontinent and southwest and central Asia), the Middle East, Africa (particularly East Africa), and southern Europe. In the New World (Western Hemisphere), most cases occur in Brazil; some cases occur in scattered foci elsewhere in Latin America. Overall, VL is found in focal areas of >70 countries, with most (>90%) of the world’s cases in the Indian subcontinent (India, Bangladesh, and Nepal), East Africa (Sudan, South Sudan, Ethiopia, Somalia, and Kenya), and Brazil. More information is available at www.who.int/leishmaniasis/burden/endemic-priority-alphabetical/en.
The geographic distribution of cases of VL evaluated in countries such as the United States reflects travel and immigration patterns. VL is uncommon in US travelers and expatriates. Occasional cases have been diagnosed in short-term travelers (tourists) to southern Europe and also in longer-term travelers (such as expatriates and deployed soldiers) to the Mediterranean region and other areas where VL is found.
Among symptomatic people, the incubation period typically ranges from weeks to months. The onset of illness can be abrupt or gradual. Stereotypical manifestations of VL include fever, weight loss, hepatosplenomegaly (especially splenomegaly), and pancytopenia (anemia, leukopenia, and thrombocytopenia). If untreated, severe (advanced) cases of VL typically are fatal. Latent infection can become clinically manifest years to decades after exposure in people who become immunocompromised (such as HIV infection, immunosuppressive therapy, or biologic immunomodulatory therapy).
Clinicians should consider VL in people with a relevant travel history (even in the distant past) and a persistent, unexplained febrile illness, especially if accompanied by other suggestive manifestations (such as splenomegaly and pancytopenia). Laboratory confirmation of the diagnosis is achieved by detecting Leishmania parasites (or DNA) in infected tissue (such as in bone marrow, liver, lymph node, or blood), through light-microscopic examination of stained specimens, culture techniques, or molecular methods. Serologic testing can provide supportive evidence for the diagnosis.
CDC can assist in all aspects of the diagnostic evaluation, including species identification. For consultative services, contact CDC Parasitic Diseases Inquiries (404-718-4745; email@example.com) or see www.cdc.gov/dpdx.
Infected people should be advised to consult an infectious disease or tropical medicine specialist. Therapy for VL should be individualized with expert consultation. The relative merits of various approaches can be discussed with CDC staff (see the Diagnosis section above for contact information).
Liposomal amphotericin B (AmBisome) is approved by the Food and Drug Administration (FDA) to treat VL and generally constitutes the drug of choice for US patients. The oral agent miltefosine is FDA approved to treat VL in patients who are infected with L. donovani , are ≥12 years of age, weigh ≥30 kg, and are not pregnant or breastfeeding during therapy or for 5 months thereafter; the drug is available in the United States via www.profounda.com. The pentavalent antimonial compound sodium stibogluconate (Pentostam) is available to US-licensed physicians through the CDC Drug Service (404-639-3670) for parenteral administration under an investigational new drug protocol (see www.cdc.gov/laboratory/drugservice).
No vaccines or drugs to prevent infection are available. Preventive measures are aimed at reducing contact with sand flies (see Chapter 3, Mosquitoes, Ticks & Other Arthropods; and Prevention in the previous section, Cutaneous Leishmaniasis). Preventive measures include minimizing outdoor activities, to the extent possible, especially from dusk to dawn, when sand flies generally are the most active; wearing protective clothing; applying insect repellent to exposed skin; using bed nets treated with a pyrethroid-containing insecticide; and spraying dwellings with residual-action insecticides.
CDC website: www.cdc.gov/parasites/leishmaniasis
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Barbara L. Herwaldt, Sharon L. Roy