im sorry to hear of your pup i lost my bull terrier to weils disease it shows itself over a couple of days ie the dog was off colour i debated wether to take her to the vet but she pulled round and looked spot on again two weeks later she took on a yellow appearance i rushed her to the vet but it was to late,you have to catch it as soon as it shows if you dont it's to late. she didnt pass any blood it sounds like parvo either way innoculations deal with both,i hope you find another pup.