Final answer:
The causative agent of East African trypanosomiasis is Trypanosoma brucei. It is a parasitic protist transmitted by tsetse flies and is responsible for African sleeping sickness in humans. It can evade the host immune system by altering its surface proteins with each generation.
Step-by-step explanation:
The causative agent of East African trypanosomiasis is Trypanosoma brucei. Trypanosoma brucei is a parasitic protist that causes African sleeping sickness in humans. It is transmitted by tsetse flies and can evade the host immune system by altering its surface proteins with each generation, making it difficult for the immune system to mount a specific antibody defense against it.