Ka1a-azar is a tropical disease which occurs in China, Africa, Southeast Asia, Southern Europe and parts of India, especially in Assam, Madras and regions along the Ganges and Brahmaputra rivers. The disease is probably caused by the bite of a small sand fly (phlebotomus) which carries a minute protozoan parasite called leishmania donovani. It can also be introduced by merely crushing the sandfly on the skin. Smears stained and examined under a microscope reveal this protozoan to be a minute ovoid organism showing characteristic markings. These microscopic parasites enter the cells of the body, especially the bone marrow, liver, spleen and blood-vessels.
The disease may come on suddenly or gradually. With sudden onset there is usually high fever, preceded in some cases by chills or vomiting. The fever may resemble malignant tertian malaria, lasting two to six weeks; or it may come in waves suggesting undulant fever. The spleen usually enlarges first and some months later the liver also becomes swollen. The patient's condition apparently improves, only to be followed by more fever and swelling of the spleen and liver. Finally after months of alternating fever and fever-free periods, there is a persisting low-grade elevation of body temperature.
The patient becomes thin and anremic and has a large, distended abdomen. The native name, kala-azar, means "the black disease," so named because in many cases the skin takes on a peculiar gray color, especially on the feet, hands and abdomen. The hair may fall out and the patient is apt to have bleeding from gums and nose.