The Girls went to the vet because one spewed a worm. We got two different kinds of worm medicine and had them on it for ten days. We took in a stool sample to retest and they found another parisite I think she said ws toxidia? Well anyway I have to go get the medicine tommorow and they'll be on it for five days. These poor cats.. Should I heave the litterbox and get a new one? we have had it for ten years.