Pier and Beam issues

[MLF]

Hello everyone! I have a pier and beam home, and we are having the problem of rodents getting under the house and into the walls where sometimes they die. My house will smell dreadful after that for days. We don't really know how to address this problem. How do we keep the rodents from getting under the home or how can we keep them out of our walls? Does anyone have any suggestions on keeping them away? Thank you for your time.