If an adult cat is on yearly heartworm prevention and an inside only cat, we recommend checking a fecal yearly and not performing deworming. Heartworm preventions also prevents intestinal parasites. It is important to note no dewormer kills all parasites, thus the need to check fecals yearly. Kittens should be dewormed their first 3 visits and then start on heartworm prevention at 8 weeks. Generally we use a broad spectrum deworming like strongid.