I have five cats. The ages are 12, 4, almost 2, and two are 1 1/2. When the 2 youngest cmae into the house they had worms that we didn't know about.The worms that look like spaghetti. All of the cats had the de-worming medicine. About a month after that worms started showing up again and because we didnt know who had them all kitties once again had to have the medicine. And a month after that the same thing happened. It is a moth past the last time and you guesed it...worms, again!!! Why does this keep happening? Would a change in diet help? They never go outside, never eat people food or dairy, we don't have mice in the house. I am at my wits end. I knwo it is medicine for them again this time but what can I do to prevent this from happening again? Thank you.