Visceral Leishmaniasis (Kala-Azar). This is a chronic febrile disease caused by Leishmania donovani, transmitted by the bite of a sandfly (Phlebotomus). The visceral form results in emaciation, anemia, hepatomegaly and splenomegaly and is often fatal. It is prevalent among children and young adults in Mediterranean countries, eastern India and northern China. Leisliman-Donovan bodies, two to four microns in diameter, are found in macrophages in the liver and spleen. In the sandfly the flagellate organism (leptomonad form), which develops in the gut, migrates to the buccal cavity and is discharged through feeding. The sandfly becomes infected by ingesting the leishmanian forms described above.The incubation period of the disease is from six weeks to several months. A high fever for several weeks alternates with longer periods of remission. By the end of six months, the liver and spleen are markedly enlarged. The regional lymph nodes are appreciably enlarged, only if cutaneous leishmaniasis (so-called Oriental sore) develops. The bone marrow is hyperplastic. The intestinal villi may be enlarged by foci of the disease.
