黑热病的病原,是一种椭圆形的黑热病原虫。此种原虫,侵入人体血液内,特别是网状内皮细胞系统的组织和脏器里,如脾脏、肝脏、骨体和淋巴腺等处,发育增殖,因而慢慢肿胀,使人发病。感染此病后,—般经过5—9个月即开始发烧,常可在一天内发两次高热,夜间出汗,时有腹泻,精神 The pathogen of kala-azar is an oval black fever pathogen. This protozoa invades the human blood, especially in the tissues and organs of the reticuloendothelial system, such as the spleen, liver, bone and lymph glands, where it proliferates, and thus slowly swells and causes disease. After the infection, it usually takes 5 to 9 months to start a fever, often with two high fevers in one day, sweating at night, diarrhea, and spirit