Trypanosomes – Flagellates
The trypanosomes are among the serious pathogens that cause high mortality among human populations and domestic animals in Africa and also in South and Central America. Trypanosoma brucei is a wide spread parasite of African mammals (excepting man and baboons), which produces high mortality among domestic animals. T. gambiense and T. rhodesiense both cause sleeping sickness in man. They utilize the tsetse fly of the genus Glossina which transmits them to man during its blood meal.
The organisms get into the circulating blood with the bite of the fly and multiply as trypanomastigote forms in the extracellular blood fluids (blood and lymph). When the fly once again bites man, it also ingests the parasite along with its blood meal. The parasites multiply in the midgut of the fly, after a period of few days they move forward to the salivary glands where they multiply and form the infective stage. When the infected tsetse fly bites a new host, it transmits the infective stage of the parasite into its circulating blood. T. gambiense produces chronic disease ultimately leading to "sleeping sickness" T. rhodesiense infection produces similar but more acute disease and the infected person dies within a few months. Trypanosoma cruzi produces Chagas’ disease in South America.