Parasites are just as much a part of the natural world as rabbits are. Virtually all wild animals carry parasites; that's just how it is. Who are we to say that hosts are any more worthy of life than parasites? If you truly view this rabbit as a "wild rabbit," then you must accept it in its wild state. If you insist on cleaning it up, it will become a pet, and wild animals should not be kept as pets.
Keeping wild animals is usually not legal without a permit, even if you intend to release them, and most people aren't qualified to do so properly. It sounds as if you ought to turn the rabbit over to a licensed rehabilitator. You can find a wildlife rehabilitator near you at the site below.
We do not condone outdoor cats because they take a tremendous toll on wildlife. Please keep your cats indoors or under direct supervision. Thank you.