We have 3 semi ferals that I'm sure need worm meds...Is there any thing over the counter or from the vet that would be easy to give? These 3 have been spayed/neutered and at that time were given the meds, but that's been about 3-4 years...There is no way I could get them to a vet so I need something that will be easy. I've seen some in different pet magazines but I really don't like to order on line unless recommended....Thanks for any help....