Dr. Ian Lipkin, the leading “bug” hunter in the world, dedicated a solid year trying to link a specific pathogen to ME/CFS and failed using his state-of-the-art lab techniques.
Lipkin did not find any parasites as a cause of ME/CFS. He is far more likely to find a virus, in his expert opinion (he is the leading expert in the world having found many of the viruses in the news of late).
Here is his wiki page:
https://en.wikipedia.org/wiki/W._Ian_Lipkin
Here is a 2014 interview with Dr. Lipkin:
http://www.cfscentral.com/2014/05/candid-conversation-with-dr-ian-lipkin.html
Is a spirochete a parasite?