I would also contact your vet as Patty suggested. Not to scare you, but I've heard from several people on the boards, that pups with parvo have horrible smelling BM's. I would just make sure that everything is okay on that front.
Also, it wouldn't hurt to add a tablespoon or so of pumpkin to his meal as well. Use the plain, canned pumpkin...not the kind that has the spices in it for pies.
Brooke