Is 2 months of colitis normal after 4 months of giardiasis, what else could it have caused?

Giardia. If colitis refers to diarrhea, it may be due to different factors. Persistent giardia, antibiotic associated colitis caused by the antibiotic used for treatment, unmasking of underlying inflammatory bowel disease(uncommon) such as ulcerative colitis or crohn's disease. Consult your doctor to work this up!