Hopefully somebody who has pets on a diatomaceous earth (DE) program will post but, from reading on this site, I understand that pets can be fed DE to control internal parasites, and that DE will kill fleas on ticks on their skin.
That said, please be sure you research this. As I said above, I do not have pets and have not researched this carefully for correct amounts, etc.
One thing I do know, if you are going to add DE to your pets' food, it has to be the feed-grade DE. I don't know where you'd get that.
Again, I sure hope somebody with pets on an organic program answers your posts. Meanwhile, hopefully this answer will get you moving in the right direction and get your kitties some help.
**Take time to stop and smell the flowers
(or... as my ladybug refrigerator magnet says
"take time to stop and eat