The shelter where we got Chloe was a very large county shelter. I think they tried to vet check the animals, but sometimes they missed something. They would adopt out unaltered animal, but you had to sign a contract to have them altered within 30 days of adoption. You had to bring in proof of the surgery signed by a vet. (They are very particular about this in the Atlanta area. If you don't have it done, they will send the authorities after you.) Anyway, after we adopted Chloe, we found out that she was pregnant and that she had a serious URI. She was not pregnant enough to show at that point, and the URI symptoms didn't manifest themselves until we got her home.