Your dog can make himself fatally ill by eating the feces of other animals, even his own.
My dog used to do this as a puppy, I asked my Vet what could be done about it. He prescribed me a little bag of powder to add to her food called "forbid"(in Canada), I added it to the food of every pet in the house. Started again recently, when I got my first cat, they could not stay out of the box of tasty cat treats. When put in the food, the animal rarely tastes the powder, but when it has gone through their system, it makes the smell and taste of poo not so appealing, should they ingest it again, they could be sick as well. Not that I can understand what is so appealing in the first place. After about 2 days of feeding her the forbid with her food, she stopped sniffing poo entirely.
Where your dog is eating other animals feces, it is hard to ensure the other animals have this additive in their food. All I can recommend, is to keep a closer eye on him when he is around places where he can find tasty little snacks to eat.