I have recently came across some information on giardia, which suggests there is a certain virus commonly associated with this parasite which increases it's pathology. I am certain the same is true of many unicellular parasites.

I would not be suprised if it is some kind of retro virus, but I have not furthered my investigation in that area.

Maybe antiviral meds in combo with traditional antiprotozoan meds could be more effective.

Shroom