Heartworm disease causes severe cardiopulmonary damage in dogs and is entirely preventable through monthly medication, making prevention the most important welfare intervention.
Heartworm disease causes progressive welfare harm from coughing, exercise intolerance, and eventual right heart failure in untreated dogs. Treatment itself requires prolonged strict rest to prevent fatal pulmonary thromboembolism as dying worms are broken down, creating a treatment welfare burden separate from the disease itself. Prevention through monthly medication is so effective and comparatively low-cost that any dog experiencing heartworm disease represents a preventable welfare failure. Expanding geographic range means prevention is becoming important in regions that previously had minimal risk.