[PennysMum]

Squirrels aren't a primary host for Lepto as far as I know-- it's generally rats and mice. I've heard of raccoons and possums carrying it somewhat often-- in fact, when I used to rehab wildlife back in Michigan, we would vaccinate our raccoons for it before releasing them to the wild.

As far as determining the risk in a particular area, I'd speak with your veterinarian about it. Even within a region or a state, there are little pockets where certain diseases are more or less common-- if you trust your vet, they'd probably be the best one to tell you which diseases they see coming through their door, and which they haven't seen in twenty years.