My dog has had giardia. My vet doesn't believe in fenbendazole as a treatment for
it. He says, based on some research that was being done at LSU when he was in vet school there, that fenbendazole for
giardia just doesn't work. He uses Metronidazole
(Flagyl). We treated my dog with that, and she hasn't had a recurrence.
The Merck Veterinary Manual states that "Metronidazole
(25 mg/kg, PO, bid for
5-7 days) is ~65% effective in eliminating Giardia spp from infected Dogs