I want to know the answer to the following question:
What is it difficult to demonstrate the presence of in Chagas disease?
All the background I'm provided with is that "Chagas disease is the most significant example, because it is difficult to directly demonstrate the presence of the causative agent, Trypanosoma cruzi in a patient, which therefore makes it difficult to definitively make a diagnosis.". Is that enough to answer the question?
Answer: yes