I've done lots of parasite research and B-vits. as part of treatment has never been mentioned. To the contrary, I've read lots that B-vits should be avoided during treatment as they are food for parasites so much so that the host ends up anemiac because of B12 deficiency.
Here's from an article advising how to check if your fatigue is caused by a B12 deficiency:
"Try a sublingual B12 methylcobolamin supplement of high dose, at least 1mg. If it leads to a greatly increased amount of energy, do the Antiparasitic Regimen and do not take any more supplements containing B vitamins until it is complete."