Preface: I am not a doctor, this is just my understanding. Human bites are, on the whole, much worse. You have to consider that the human mouth is full of bacteria that the human immune system hasn't already dealt with, so human bites can infect really bad.
Not that rats don't have awful things in their mouths. Get it looked at either way.
Nice! I had a 3.5 campaign I was running once where one of the major plot points was going to be a guy who was cloning Tarrasques and experimenting on them, but the game fizzled out because of me falling down on the job.
It's the lower level spell to use when someone's been hit with Disintegrate. Much cheaper than True Res.