Context: In the absence of suitable plate culture techniques, some microbes require culture within live animals. Bacteria such as Mycobacterium leprae and Treponema pallidum can be grown in animals, although serological and microscopic techniques make the use of live animals unnecessary. Viruses are also usually identified using alternatives to growth in culture or animals. Some viruses may be grown in embryonated eggs. Another useful identification method is Xenodiagnosis, or the use of a vector to support the growth of an infectious agent. 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. In this case, xenodiagnosis involves the use of the vector of the Chagas agent T. cruzi, an uninfected triatomine bug, which takes a blood meal from a person suspected of having been infected. The bug is later inspected for growth of T. cruzi within its gut.

Question: What are live animals required by?
Answer: some microbes

Question: What can Mycobacterium leprae and Treponema pallidum be grown in?
Answer: animals

Question: What type of eggs may some viruses be grown in?
Answer: embryonated

Question: What is Xenodiagnosis?
Answer: use of a vector to support the growth of an infectious agent

Question: What is it difficult to demonstrate the presence of in Chagas disease?
Answer: the causative agent

Question: What are live animals unnecessary for?
Answer: Unanswerable

Question: What can Mycobacterium leprae and Treponema pallidum never be grown in?
Answer: Unanswerable

Question: What type of eggs may no viruses be grown in?
Answer: Unanswerable

Question: What does Xenodiagnosis avoid doing?
Answer: Unanswerable

Question: What is simple to demonstrate the presence of in Chagas disease?
Answer: Unanswerable