Oh it can happen. Gus must of had em when I took him in, months later I found my former dog Shyler teeming with em. We found em a bit on the digs when I was over in the Pueblo area Summer of 2015. Thing is alot if kitties, particularly kittens, in feral colonies have upper respiratory issues, conjunctivitis and run down immunity so the threat of fleas and ticks is alot more real for them specially with rundown immune systems