Rats can carry Leptospirosis, but so does other wildlife. Plague is a problem in the western states, not Tennessee. I just plan to clean out and rebed my coop, which is due to be done anyway; I'm not going to bleach it out. Mice and rats will appear sometimes, and need to be eliminated as much as possible. The chickens will help in daytime, but not at night. I've got a coop foundation issue that will be fixed ASAP. Mary