Author(s): Rebecca Chancey, Sharon Roy, Paul Cantey

Infectious Agents

Visceral leishmaniasis (VL) is caused by obligate intracellular protozoan parasites, primarily Leishmania infantum (considered synonymous with L. chagasi) and L. donovani. Leishmaniasis has several different forms. VL affects some of the internal organs of the body (e.g., bone marrow, liver, spleen).

Transmission

The parasites that cause VL are transmitted through the bite of infected female phlebotomine sand flies. Congenital transmission and parenteral transmission through blood transfusions and needle sharing have been reported.

Epidemiology

Leishmaniasis is a parasitic disease found in parts of the tropics, subtropics, and southern Europe. VL is usually more common in rural than urban areas, but it is found in some peri-urban areas (e.g., in northeastern Brazil). In the Eastern Hemisphere, VL is found in Africa, particularly East Africa; parts of Asia, particularly the Indian subcontinent and central and southwest Asia; southern Europe; and the Middle East. In the 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; most (>90%) cases occur on the Indian subcontinent, in Bangladesh, India, and Nepal; countries in East Africa, including Ethiopia, Kenya, Somalia, South Sudan, and Sudan; and in Brazil. See more information.

The geographic distribution of VL cases evaluated in the United States and other countries reflects travel and immigration patterns. Although uncommon in most US travelers and expatriates, VL can occur in travelers returning from visits to endemic regions in European countries (e.g., France, Greece, Italy, Macedonia, and Spain) and among military personnel returning from the Middle East. Cases have been documented in short-term travelers to the Camino de Santiago in northern Spain and endemic areas of southern France, and in longer-term travelers (e.g., expatriates, deployed soldiers) to the Mediterranean region and Middle East.

Clinical Presentation

Among symptomatic people, the incubation period typically ranges from weeks to months. Illness onset can be abrupt or gradual. Stereotypical clinical manifestations of VL include fever, hepatosplenomegaly (especially splenomegaly), night sweats, and weight loss; lymphadenopathy can occur. Laboratory findings characteristic of VL include pancytopenia (anemia, leukopenia, thrombocytopenia), high total protein, low albumin, and hypergammaglobulinemia. If untreated, severe (advanced) cases of VL typically are fatal. Latent infection can clinically manifest years to decades after exposure in people who become immunocompromised through HIV infection, biologic immunomodulatory therapy, or immunosuppressive therapy.

Diagnosis

Consider VL in the differential diagnosis of people with a relevant travel history even in the distant past, and a persistent, unexplained febrile illness, especially if accompanied by other suggestive manifestations (e.g., pancytopenia or splenomegaly). Hemophagocytic lymphohistiocytosis (HLH) could be a complication and should prompt clinicians to consider VL in patients with the appropriate travel history.

Laboratory confirmation of the diagnosis is achieved by detecting Leishmania parasites or DNA in infected blood, bone marrow, liver, or lymph nodes through light-microscopic examination of stained specimens, molecular methods, or tissue culture techniques. Serologic testing can provide supportive evidence for the diagnosis.

The Centers for Disease Control and Prevention (CDC) can assist in all aspects of the diagnostic evaluation, including species identification. See information on specimen collection and diagnosis of leishmaniasis. For consultative services, contact CDC Parasitic Diseases Inquiries (404-718-4745; parasites@cdc.gov).

Treatment

Refer people with VL to an infectious disease or tropical medicine specialist who can help direct care and provide individualized treatment. CDC staff can discuss the relative merits of various approaches (see the Diagnosis section of this chapter for contact information). Risk for relapse and treatment failure is greater in patients with HIV, but also might occur rarely in immunocompetent patients.

Liposomal amphotericin B (AmBisome) is approved by the US Food and Drug Administration (FDA) to treat VL and is generally the drug of choice for US patients. The oral agent miltefosine is approved by the FDA to treat VL in patients infected with L. donovani who are ≥12 years old, who weigh ≥30 kg, and who are not pregnant or breastfeeding during therapy or for 5 months after treatment; the drug is available in the United States via www.profounda.com. Pentavalent antimonials (e.g., meglumine antimoniate, sodium stibogluoconate [Pentostam]) are used in endemic areas, except for India, where developing resistance is a concern. Pentavalent antimonial drugs are currently not FDA approved and not available for use in the United States; Pentostam is no longer available through the CDC Drug Service.

Prevention

No vaccines or drugs to prevent infection are available. Preventive measures are aimed at reducing contact with sand flies and avoiding sand fly bites (see Sec. 4, Ch. 6, Mosquitoes, Ticks & Other Arthropods, and Sec. 5, Part 3, Ch. 14, Cutaneous Leishmaniasis). Preventive measures include minimizing outdoor activities, to the extent possible, especially from dusk to dawn when sand flies generally are 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: Leishmaniasis