I use oregano and once in awhile mixed with desert parsley. With cats you have to be careful, the old sick cat can be so much worms that when you kill the worms too quickly the constipated old house cat will die in its own waste. Catfood destroys the intestines of the cat. cats should be LEAN killing machines, if a cat weighs more than 5# then it is probably a house cat or otherwise poisoned cat. These 20# house cats are a disgrace to nature.