What large complex single celled organism causes African sleeping sickness?

Answer 1

Sleeping sickness is also known as trypanosomiasis or African sleeping sickness. It's caused by a protozoan that leads to a serious infection in the brain and the meninges (the covering of the brain and spinal cord).
Both species of Trypanosoma are transmitted from human to human through the bite of the tsetse fly (Glossina) which is only found in rural parts of Africa.
However, trypanosomes can also be transmitted from mother to child as the parasite can cross the placenta in the blood and infect the baby while it is still in the womb.
Contaminated needles can also contribute to the spread of trypanosomes, but this is rare.
Communities most at risk of trypanosomiasis live in rural areas where the tsetse fly is found. These communities often depend primarily on agriculture, fishing and hunting to survive and have limited access to health services and education. As a result, many cases of trypanosomiasis go undiagnosed.

The trypanosome parasite is first introduced into the mammalian host when a tsetse fly takes a blood meal and secretes parasite-filled saliva into the host’s skin. The neurological phase begins when the trypanosome parasites cross from the blood-brain barrier into the spinal fluid, infecting the central nervous system including the brain. Once the brain is affected it results in
changes in behavior, confusion, poor coordination, difficulties with speech and disturbance of sleep (sleeping through the day and insomnia at night), hence the term ‘sleeping sickness’.
Trypanosomiasis is curable if treatment is given quickly, however if left untreated the disease is fatal.

Answer 2

Trypanosoma brucei (gambiense and rhodesiense)

However the parasite is transferred to humans though a bite from an infected Tsetse fly.