[TxVicki]

Well this may explain why he was sick. Like you had posted on the Sick and Injured Forum. Yes your dog could get worms from eating cat poop and can also get many other things as well.
From the sound of it, you are not outside with him when he is out there. You need to be with him at all times to watch him. I never let mine out alone, I am with them at all times, even tho we do have six foot fenced in yard.