Hookworms in puppies????I am lost?

We adopted a puppy, spaniel/lab ret. He has hookworms and the vet gave him panacur for 3 days. His third day was yesterday. I used to see the eggs, that made his poo look very grainy. He goes back to the vet tomorrow to see if he is okay for the shots that he never got. The vet then wants me to bring in another sample of poo in about a week. I now see little white specs all in his poop. Does anyone know how long it will take to expel these worms? It seems like he has quite a few in his poo. He also steps right into his poo with his hind legs after he goes everytime. We have tried everything to keep him from stepping in the poo. We wash it off very good after he steps in it, but I know that stepping in it is one way the dog contracts it. If we are washing him immediately, is he still able to contract it. We pick up his poo as soon as he poo's and disinfect the area. Is this enough? Anyone have experience with this?