Hooks and whip worms are the toughies. I have used a massive dose of panacur/ safeguard horse paste, 100#s of paste for every 10# of dog, for three days in a row. It works. This on a rescue german shepard who was reduced to bloody diareha and on the advise of a vet. It's hard on the dog if they are debilitated from the worms, like this one was. Dog had a full recovery, gained about 20#'s in a month, still going strong 5 years later.