Final answer:
Sleeping sickness, known as African trypanosomiasis, is caused by the tsetse fly and results from the protozoan Trypanosoma brucei. Untreated, it causes severe neurological symptoms and is fatal.
Step-by-step explanation:
The disease caused by the tsetse fly is sleeping sickness, also known as African trypanosomiasis. This illness is endemic to certain regions in sub-Saharan Africa and is caused by the hemoflagellate Trypanosoma brucei. There are two types of African trypanosomiasis, East African trypanosomiasis (EAT) and West African trypanosomiasis (WAT), with WAT being more chronic. The T. brucei protozoa enter a person's bloodstream through the bite of an infected tsetse fly, eventually leading to confusion, difficulty in sleeping, lack of coordination, and without treatment, it is invariably fatal. T. brucei evades the immune system by frequently changing its surface glycoproteins, preventing the immune system from effectively clearing the infection.