I have been through that recently. Here is one solution, an alternative to the accepted answer, which is also excellent.
Sit in your chair, in front of your monitor, mouse and keyboard. When the person, that you are collaborating with, reaches to touch your mouse, do not move your hand away from it. They will then ask you
--Could I have your mouse to show you something?
--Just tell me how to do it myself - you should reply.
--But it will be so much quicker if I do it!
--I need to learn and develop, please teach me - your response, or any other silly excuse.
I found this causing a little bit less confrontation than wiping the mouse in front of the offender and less anxiety than secretly doing so.