I've been researching Giardia and was (and was not) surprised to see that there is a chronic form to this bug. I've found some good links below. The preferred effective MD treatment seems to be Tinidazole. From what I've read Flagyl/Metronidazole has no activity on Giardia.
"Tinidazole is indicated for the treatment of giardiasis in adults with a single 2 g dose and with 50 mg/kg single dose in children over 3 years of age. In eight randomized comparative studies totalling 299 adult and pediatric patients, the average cure rate for tinidazole in giardiasis was 90%.2-8"
(Other Giardia links at the bottom)
Giardia is supposed to feed off Lecithin and Ox Bile (perhaps human bile?).
In researching giardia I found out about some other protozoans that are causing chronic problems very similar to what Cpn and Lyme patients deal with. These are: Dientamoeba fragilis and Blastocystis hominis.
The symptoms are similar to Giardia as well as the chronic symptoms of Lyme and CPN. This site: http://www.badbugs.org/ has a lot of information about these critters, testing and cure. You'll notice how many have attempted drugs and cocktails (including Flagyl and some of our other favorties here) even done several rounds of them (pulse) to try to cure themselves.
Jackie Delaney at badbugs seems to have found a triple abx cocktail that is having some success. The difference in treatment between lyme/cpn and these bugs if that, if effective, the cure takes 10 days.
If you are interested in the drug combination without having to run through the Jackie gauntlet see this thread for the drug combo: http://curezone.com/forums/fm.asp?i=1209928#i
Link to full blog entry: http://cfsjourney.com/index.php