Are there holistic remedies for treating Giardia?

Dear Most Esteemed and Knowledgeable Kitties:
I have two 6-month-old kittens, one of whom tested positive for giardia when he was 10 weeks old. He was subsequently treated three times with Panacur (due to persistent symptoms despite four negative fecals) but he and his brother still have totally evil smelling, runny stools and flatulence to go [...]