the mane reasons for NOT feeding wild caught rats are
1) risk of poisoning
2) risk of parasites
3) risk of disease, not so much to your snakes more to your self
"feral" rats can carry up to 14 different diseases including hepatitis
domesticated or laboratory grade
generally do not carry the diseases that "feral" rats do
they also should be treated regularly and there forth have a less chance of harboring parasites such was tape worm. hook worm and zipper worms. witch can be passed on from the rat to your reptiles. or any thing else that eats them