Leishmaniasis, also spelled leishmaniosis, is a disease caused by protozoan parasites of the genus Leishmania and spread by the bite of certain types of sandflies.The disease can present in three main ways: cutaneous, mucocutaneous, or visceral leishmaniasis. The cutaneous form presents with skin ulcers, while the mucocutaneous form presents with ulcers of the skin, mouth, and nose, and the visceral form starts with skin ulcers and then later presents with fever, low red blood cells, and enlarged spleen and liver.
Infections in humans are caused by more than 20 species of Leishmania. Risk factors include poverty, malnutrition, deforestation, and urbanization. All three types can be diagnosed by seeing the parasites under the microscope.Additionally, visceral disease can be diagnosed by blood tests.
Leishmaniasis can be partly prevented by sleeping under nets treated with insecticide. Other measures include spraying insecticides to kill sandflies and treating people with the disease early to prevent further spread.The treatment needed is determined by where the disease is acquired, the species of Leishmania, and the type of infection. Some possible medications used for visceral disease include liposomal amphotericin B, a combination of pentavalent antimonials and paromomycin, and miltefosine. For cutaneous disease, paromomycin, fluconazole, or pentamidine may be effective.
About 12 million people are currently infected in some 98 countries. About 2 million new cases[ and between 20 and 50 thousand deaths occur each year. About 200 million people in Asia, Africa, South and Central America, and southern Europe live in areas where the disease is common.[The World Health Organization has obtained discounts on some medications to treat the disease. The disease may occur in a number of other animals, including dogs and rodents.
Leishmaniasis is diagnosed in the laboratory by direct visualization of the amastigotes (Leishman-Donovan bodies). Buffy-coat preparations of peripheral blood or aspirates from marrow, spleen, lymph nodes, or skin lesions should be spread on a slide to make a thin smear and stained with Leishman stain or Giemsa stain (pH 7.2) for 20 minutes. Amastigotes are seen within blood and spleen monocytes or, less commonly, in circulating neutrophils and in aspirated tissue macrophages. They are small, round bodies 2–4 μm in diameter with indistinct cytoplasm, a nucleus, and a small, rod-shaped kinetoplast. Occasionally, amastigotes may be seen lying free between cells. However, the retrieval of tissue samples is often painful for the patient and identification of the infected cells can be difficult. So, other indirect immunological methods of diagnosis are developed, including enzyme-linked immunosorbent assay, antigen-coated dipsticks, and direct agglutination test. Although these tests are readily available, they are not the standard diagnostic tests due to their insufficient sensitivity and specificity.
Several different polymerase chain reaction tests are available for the detection of Leishmania DNA. With this assay, a specific and sensitive diagnostic procedure is finally possible.
Most forms of the disease are transmitted only from nonhuman animals, but some can be spread between humans. Infections in humans are caused by about 21 of 30 species that infect mammals; the different species look the same, but they can be differentiated by isoenzyme analysis, DNA sequence analysis, or monoclonal antibodies.