Food and Drug Administration and Matt Miller, College of Veterinary Medicine, Texas A&M University
Heartworms can grow up to 12 inches long while festering in a dog's heart and lungs. Untreated, heartworm causes heart failure and death in dogs and cats.
Courtesy of Leeann Plikuhn
Leeann Plikuhn of suburban Indian Head Park treats Chloe (left) and Bebe with heartworm preventatives every summer, even though she admits the cost is a little high.