Really bad diarih in new dog...details inside.?

The "breeder" i got this dog from closed down about a year ago. I bought one of her puppies last year. About 2 weeks ago she phoned me about my dogs sire. 5 years old Blue heeler. He was "accidentaly" impregnating her old breeder females. She didnt want anymore pups. Anyway, he is with me and my bf and we finished his food..the breeder feeds !OLD ROY! to both her preg. lactating females and the male dogs and puppies. So you can imagine the fur wasnt in the best shape etc. Anyway, i feed a good food CALL OF THE WILD,AND TUFFYS GOLD. I ran out of his old roy/my dog food mix and just gave him call of the wild. Tonight we took him for his first walk around the neighborhood, he took a poop and it was like water and he was FULL of worms. literaly. Would the worms cause the sudden diarih? Im worried now about my dogs and if they will get worms or get sick? Ill be bringing them ALL in for a fecal. Should i also have heartworm checked? Are my dogs at risk from getting heartworm from him? thanksPrevious question: http://answers.yahoo.com/question/index;_ylt=AmLkyvjD77gP9aK0Z9qfxbPsy6IX;_ylv=3?qid=20100720064504AAfAOhJ

He needs to go to a vet ASAP!!!! And worms do cause diarrhea

Vet now. There are multiple reasons for this kind of bowel movement and one of them is Giardia.Giardia takes a special fecal test and will affect all of your other dogs. Not to scare you, but the dog has worms so he may also have parasites.I don't know where you live? But if you have mosquitoes, your dogs are at risk for heartworms, hon.