Heartworm disease is a serious and sometimes fatal infection of dogs and cats. Year round heartworm prevention is recommended by the Center for Disease Control, American Heartworm Society, American Animal Hospital Association and this hospital. Our hospital requires yearly heartworm testing to determine infection status. Heartworm prevention is not always 100% effective. We are also discovering that some heartworms may be becoming resistant to preventative. Yearly testing allows us to determine the efficacy of the heartworm preventative being used and if the test is positive, it allows us to institute treatment early. The following are our more specific heartworm testing guidelines: All dogs and cats are started on prevention at 7-8 weeks of age. Any dog over 6 months of age with an unknown history of heartworm preventative will be required to be tested before starting heartworm preventative and then again 6 months later. Any dog with lapses in prevention will be required to be retested 6 months after resuming heartworm preventative. If the owner wishes to switch heartworm preventatives, then the dog will need to be tested at the time of the switch and again 6 months later. These guidelines are in place to help determine efficacy of the heartworm preventative that are being used and to comply with heartworm preventative manufacturer’s product guarantee and to treat infections early. Please visit www.heartwormsociety.org for more information.