Rickettsia is a cell-wall-deficient bacteria. It is typically transmitted through tick bites. But I'm not convinced that's how I got mine. Very persistent and hard to kill infection. Causes many symptoms you can think are something else (fatigue, "brain-fog", carb sensitivity, hormonal and thyroid problems, etc. etc. etc.).

the mercury one is tricky. In my case I was exposed to high levels of the stuff (lab spill). However, some people believe that certain people (who tend to develops CFS, Fibro etc.) have an impaired ability to remove toxins from their system. Glutathione depletion and other things plays a role. So this means that mercury is accumulated faster than it is disposed so build up occurs where it wouldn't in normal people. There are lots of theories about CFS/Fibro etc. It's all very interesting.

Unfortunately, far too many people try to treat Candida with antifungals and probiotics instead of healing their bodies or treating the underlying cause. I'm trying to set up a website to provide more info about this sort of thing. If you hear anybody say "I've had Candida for years!" they have another problem or they're doing something wrong. Candida really shouldn't be that hard to treat.