Actually, we have lice ridden, disease carrying Norwegion rats. In the PI, Thailand and VN (Probably others) they have rats that only eat rice and other vegetable matter. Quite tasty, actually. I went on a rat hunt in a Thailand rice paddy and it was interesting, ecological and had a hell of a feast with Thai Rangers.
Did it taste like, well, you know?...............
When I was in the Peace Corps in Thailand (’77 - ‘79), the government promoted the eating of field rats. Saw quite a few grilled rats for sale here and there.