Not to scare you but my sister's chihuahua/beagle mix (NO clue how that happened) got sick after her parvo vaccinations. They told my sister that it was parvo and that she probably contracted it BEFORE the vaccines. Now I haven't researched this at all so I don't know what to make of it but if she gets worse, it might be something to think about. BTW, my sister nursed her back to health which is almost unheard of these days. Most dogs die of parvo.
