My mother had one visit her campsite at Sauble Beach PP in the early to mid 90's. It came at nite, routing around probably for food or bugs.
I have been told if a farm or barn discovers one has been on the hay that is fed to horses, that it has to be all destroyed(the hay that is and the opposum, if it gets caught), as the opposum carry a parasite that gives horses EPM (sorry don't know the long term) and it can be fatal.
The barn where I keep my horse has told us, if we ever see one on the property, come arunnin' to the house to get someone!!!!!!!!!