I wouldn't chance it. I would toss em. Also any reputable rodent dealer will package his rodents well and clean them before packaging. If I bought a package of frozen rats and they were covered in pee and poo and smelled like it, I would definitely complain about it I mean sure a snake isn't going to be eating a sterilized piece of meat in the wild but then again, in the wild they are exposed to a lot more parasites and "junk" that their immune systems can build up against. in captivity, our pets aren't subjected to that kind of inoculation. Not to mention if I pay for rats, I expect them to be in a presentable condition, not covered in pee and poo.