Just looked up the leprosy thing. World Health Org says, because their blood is unique, "the 9-banded armadillo can be infected experimentally, and thus provides a vital source of material for research and vaccine preparation." So, they can catch it (or be "given" it), but they don't "carry" it any more than the average human.
I think armadillos, along with possums, are just so "basic", evolution-wise, that their brain is about the size of a (small) pea ... you can pretty much fill them full of lead before they figure out they're supposed to die.