How do tsetse flies transmit Trypanosoma brucei between hosts?

Tsetse flies transmit the protozoan Trypanosoma brucei between hosts through a biological cycle involving the fly's digestive and salivary systems.12

The transmission process occurs as follows:

• Acquisition: A tsetse fly becomes infected when it feeds on the blood of an infected human or other mammal.1
• Development: Once ingested, the trypanosomes multiply by binary division within the fly's midgut. This developmental period typically lasts 12 to 15 days.1
• Migration: After multiplying, the parasites migrate from the midgut to the fly's salivary glands.1
• Transmission: When the now-infective fly bites a new host, it injects the parasites into the host's bloodstream via droplets of saliva.1

Once transmitted, the parasites enter the host's circulatory system, eventually invading the lymph nodes, spleen, and eventually the central nervous system, leading to sleeping sickness.12