If you're not in Hantavirus country, though, all joking aside, our earlier observations are valid. Agricultural products get stuff all over them all the time, and I'm unaware of any hazard other than disgust posed by rodent byproducts.
Breweries and feed stores have always regarded mice in the grain as safe and nontoxic, though undesirable as they eat the stock with no payment rendered. What's not safe is a poisond mouse corpse in the grain. That's why cats have been the preferred deterrent.