File:Zoonosis Transmission of African Trypanosomes.jpg

English: 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 image . Inside the host, they transform into bloodstream trypomastigotes image , are carried to other sites throughout the body, reach other body fluids (e.g., lymph, spinal fluid), and continue the replication by binary fission image . 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 image , image . In the fly’s midgut, the parasites transform into procyclic trypomastigotes, multiply by binary fission image , leave the midgut, and transform into epimastigotes image . The epimastigotes reach the fly’s salivary glands and continue multiplication by binary fission image . The cycle in the fly takes approximately 3 weeks. Rarely, T. b. gambiense may be acquired congenitally if the mother is infected during pregnancy.