We have pulled 8 dogs in 8 days, 7 are Heartworm postitive, 5 of those have multiple issues on top of the heartworms….. but what is hard to understand is that heartworms are largely preventable. Monthly prevention, acquired from your veterinarian, can be very effective in protecting your pet. Especially in comparison to the treatment once they are positive. Please check with your veterinarian to make sure your pet is covered.