I've been mowing mine for several years expecting I can get it under control, but can't. I have cut huge trunks of it on many trees and applied round-up poison ivy version, but it keeps coming back. I need to try the 24D spraying in the larger patches on the ground and see if that will get it under control. The root systems on my property are amazing.
I get it at least once a year, usually just from mowing although I cover up very well and do all the shower tricks and inside out clothes as soon as I'm done and home. It pops up all over my body regardless of where I got exposed generally. When I get it, I always have to go to my father-in-law (a PA) and get a shot of cortisone to clear it up.
I actually have my property listed for sale. When/if buying another, I will walk it looking for poison ivy first...