Sometimes if they eat something that upsets their stomach, you car feed them bread to help absorb it out of their system. But i guess you would have to know they ate it, this sounds a little more serious though.
Our dog got Parvo when it was a puppy. It had even received the shot and still got the virus. It confused the heck out of the Vet. He said that if the dog died we had to pay nothing and he would refund the cost of the vaccine. If it lived $1150. Our dog is now alive and well with a little bit of arthritis. Hope all is well. Oh BTW, you can't have any new dogs at your place for up to 2 years now because of the virus.
I'm off to work there now since it'* 9:21, and we work from 10-12, and then 2-4. I'll print this out and take it with me today to give you a free exam of sorts. Good luck. Call me at 317-213-8358 to get direct & free access to a vet.