I am fairly sure, in my case at least, that the candida came before the parasites. I received large doses of IV Antibiotics for a skin infection during a hospital stay ten years ago and when I returned home from the hospital I had huge Sugar and carb cravings (sure sign of candida overgrowth). Until that hospital stay my health was generally excellent; looking back in retrospect I can see how my health problems snowballed after the hospital stay.
I'm of the opinion that the two scourges (candida and parasites) work together to bring you down--i.e., whichever one gets a grip on you first holds the door open for the other by beating your immune system down.