ive got breeders that are around 2 years old and all the ones ive grown up. i never had half the issues i have seen. the point to this is that if your going to petco those rats are picked over atleast a handfull of times before, mixed with rats from several sources and shipped to your local store.

mine on the other hand came from an actual ratery thats been around for a very long time and properly cared for. also he selectively picks what he keeps. does not bring any outsiders in and has a vet check his stuff all the time.