Speaking of personal experience only:
A big female came to me with an RI, and I got her along with another. Housed them in their own tubs in the QT rack: the one was treated and cured of the RI and the other never came down with an RI.
I recently picked up two babies from an expo who both had RIs (came from the same vendor). Each were transported along with seven other pickups that day and also housed in their own tubs in a QT rack setup. None of the others came down with RIs.
I always recommend QT in at least a separate room than your established guys, but if that's not possible I would handle the sick one after you work with your healthy ones and clean and sanitize everything that would come in contact between them. I have a different set of everything for my QT guys vs my established guys (feeding tongs, hides, paper towels, etc). Wash hands, sanitize, and keep the sick one as far away from the healthy ones as possible and keep an eye on your healthy guys.
Reply With Quote