I need some advise on using Advantage Multi on my elderly cat, now 15. I have had some problems with ear mites on the outside cats, and am sure they have worms, I have seen signs. My inside cats, including the elder do go outside at times, and catch mice and rabbits several times a week. I want to know if I should treat my elder cat, mainly for worms, when I treat the others, or is it too risky? He has not been treated for a couple of years, and then I used Profender. I wanted Advantage multi this time to treat for ear mites if any of them are starting a new epidemic. Has anyone had any trouble with this product? My vet suggested he wouldn't until I saw 'signs', but how could he NOT have worms when he is around the others that do? Maybe I should have a stool sample examined, how reliable are they? Thank you for any advise on this matter.