How to remove cat nip off Cat Condo

Hi



I have four feral 4 month old kittens living in my back yard. I trapped
them and then took them to the human society / spca last week and got the
tested, shots and fixed. The have been released and are doing great.



Someone donated a cat condo to me, and it seems like the previous owner
might have rubbed or put catnip on the top.



Once in a while a kitten will jump to the top and rub its face into the top
of the cat condo and then start freaking out a bit. When this happens the
freaked out kitten will go up to another kitten and kinda start attacking
it, not sure if they are playing out what.



Is there any way to get the catnip off? Take a damp towel and wipe it down,
or take a vacuum attachment to it?



Thanks