chend2,
Any aquarium decoration, rock, substrate, etc. can transmit parasites. When the parasite is in its 'off-the-fish' stages, the parasite can cling to rock (living or dead), plastic decorations, plants, underwater pumps, substrate, etc.
If those items are moved from an infected tank to a non-infected tank, there is a good probability that the parasite will tag along.
It gets worse, I'm afraid. The transfer doesn't even have to be a solid object. Just transferring infected water is enough to bring the parasite along. When the parasite is in its free-swimming stage, it can infect water such that a teaspoon (or less!) of infected water being put into an uninfected system, will infect it.