Skip directly to search Skip directly to A to Z list Skip directly to site content
CDC Home
For questions about DPDx, contact us

DPDx is an education resource designed for health professionals and laboratory scientists. For an overview including prevention and control visit

Trypanosomiasis, African

[Trypanosoma brucei gambiense] [Trypanosoma brucei rhodesiense]

Trypansoma brucei ssp. in thick blood smears stained with Giemsa.

Trypansoma brucei ssp. in a thick blood smear stained with Giemsa.

Trypanosoma brucei ssp. in a thin blood smear stained with Giemsa. The trypomastigote is beginning to divide; dividing forms are seen in African trypanosomes, but not in American trypanosomes.

Trypanosoma brucei ssp. in a thin blood smear stained with Giemsa.

Causal Agents

Protozoan hemoflagellates belonging to the complex Trypanosoma brucei. Two subspecies that are morphologically indistinguishable cause distinct disease patterns in humans: T. b. gambiense causes West African sleeping sickness and T. b. rhodesiense causes East African sleeping sickness. (A third member of the complex, T. b. brucei, under normal conditions does not infect humans.

Life Cycle

Life cycle of Trapanosomiasis African

During a blood meal on the mammalian host, an infected tsetse fly (genus Glossina) injects metacyclic trypomastigotes into skin tissue. The parasites enter the lymphatic system and pass into the bloodstream The Number 1. Inside the host, they transform into bloodstream trypomastigotes The Number 2, are carried to other sites throughout the body, reach other body fluids (e.g., lymph, spinal fluid), and continue the replication by binary fission The Number 3. The entire life cycle of African trypanosomes is represented by extracellular stages. The tsetse fly becomes infected with bloodstream trypomastigotes when taking a blood meal on an infected mammalian host The Number 4, The Number 5). In the fly’s midgut, the parasites transform into procyclic trypomastigotes, multiply by binary fission The Number 6, leave the midgut, and transform into epimastigotes The Number 7 . The epimastigotes reach the fly’s salivary glands and continue multiplication by binary fission The Number 8. The cycle in the fly takes approximately 3 weeks. Humans are the main reservoir for Trypanosoma brucei gambiense, but this species can also be found in animals. Wild game animals are the main reservoir of T. b. rhodesiense.

Geographic Distribution

T. b. gambiense is found in foci in large areas of West and Central Africa. The distribution of T. b. rhodesiense is much more limited, with the species found in East and Southeast Africa.

Clinical Presentation

Infection occurs in 3 stages. A trypanosomal chancre can develop on the site of inoculation. This is followed by a hemolymphatic stage with symptoms that include fever, lymphadenopathy, and pruritus. In the meningoencephalitic stage, invasion of the central nervous system can cause headaches, somnolence, abnormal behavior, and lead to loss of consciousness and coma. The course of infection is much more acute with T. b. rhodesiense than T. b. gambiens.

Back to Top

For questions about DPDx, contact us
  • Page last reviewed December 28, 2015
  • Page last updated December 28, 2015
  • Content source: Global Health - Division of Parasitic Diseases and Malaria
  • Notice: Linking to a non-federal site does not constitute an endorsement by HHS, CDC or any of its employees of the sponsors or the information and products presented on the site. The U.S. Government's Official Web PortalDepartment of Health and Human Services
Centers for Disease Control and Prevention   1600 Clifton Road Atlanta, GA 30329-4027, USA
800-CDC-INFO (800-232-4636) TTY: (888) 232-6348 - Contact CDC–INFO