Way to jump to the worst possible scenario. Puppies get sick, if it's only been a day, it's really not that big of a deal. Dogs usually get parvo from ingesting another dogs feces or in rare cases a mosquito bite. Most likely your pup is constipated or something, if he doesn't return to normal in the next couple of days you should take him in. not that it really matters.
It's important to make sure that your stool does not contain any blood as this could be a number of things. First, stink your finger up your rectum, then smell it. Does it smell like blood? If so contact a doctor immediately.
It's a shame that he's not in Houston anymore. I'm sure he could give you great advice an poop problems.
I had food poisoning that bad before. Got the runs for 4 days straight. I don't eat at a certain freebirds down at Austin anymore... Finally went to the doctor on the fifth and she prescribed me some "extra strength" immodium. I think it was hard for her to keep a straight face about it, even tried to push me some plastic toilet contraption. At that point, I was getting better on my own so I only took it once or twice since I'm assuming that stuff it powerful to make the reverse rock hard. So....take immodium, if it has little effect or you're still having symptoms a week later, go to a real doctor. P.S. Salmonlella can last in your system for 3 or more weeks. In the meanwhile, you could help your condition with the BRAT diet. Might or might not help...not sure. Good times, bro. Good times.
The awesome thing about it is the more you stress about it, the worse you make it. A doctor visit may be in order, but if you'd like to try to fix it at home: Pepto Bismol is still the best stomach medicine made. It's safe, and if you DO have a bacteria, pepto actually has the ability to kill it, not just treat the symptoms. The trick is to not stop yourself up by taking too much.
It seems better in the last day or so. I'm pooping less, and they're getting more solid. Still have the cramps and gas, though. I think it was a bad case of traveller's diarrhea.