The cost of prevention is less expensive and more effective than treatment of a condition. This statement is especially true when considering heartworm preventatives for dogs and cats. Heartworms are a serious and possibly fatal condition caused by parasites which are spread by mosquitoes to both dogs and cats. Heartworms have been diagnosed in all fifty states, and are especially prevalent in moist and humid areas where mosquitoes thrive, such as Tennessee. Based on the potentially deadly effects and the high incidence rate in our area, the doctors at Cumberland Animal Hospital recommend yearly heartworm testing in accordance with the American Heartworm Society.