Kala-azar is an infectious disease characterized by irregular, intermittent and long-continued fever, leukopenia, progressive anemia, enlargement of the spleen and liver, gradual loss of strength and emaciation. It is caused by the protozoon Leishmania donovani, and these organisms are found in the reticuloendothelial cells of the spleen, liver, bone marrow and other tissues. In heavily infected patients they may be found in the mononuclear leukocytes of the peripheral blood.
Leishmania donovani grows on N. N. N. culture medium kept at 22 C., and in culture flagellate forms are present. These forms have been found in the midgut and pharynx of certain species of the sandfly Phlebotomus, which is apparently the insect vector involved.
Kala-azar is widespread in the Eastern Hemisphere. The most heavily infected areas are in eastern India, in the provinces of Assam, Madras, Bengal and Bihar, and in China north of the Yangtse River. It is also found