Diatomaceous earth can be added to their food as well as sprinkled around their bedding. This will only help with fleas. As for ticks you will need a topical flea/tick product such as Frontline. To apply this you need to be able to handle the cats. http://wolfcreekranch1.tripod.com/defaq.html
Does anyone have a way of treating fleas on ferals? I feed 4 or 5 different ones that come into my yard and I want to try to keep the fleas and ticks at bay.
Thanks