Detailed Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Q: Passage: Figure 15.12 Trypanosoma brucei is the causative agent of sleeping sickness in humans. The mRNAs of this pathogen must be modified by the addition of nucleotides before protein synthesis can occur. (credit: modification of work by Torsten Ochsenreiter). Answer: trypanosoma brucei
A:
What is the causative agent of sleeping sickness in humans?