Heartworm disease causes severe cardiopulmonary damage and significant suffering in infected dogs, but is almost entirely preventable through monthly medication - making every case a welfare failure.
Dogs with heartworm disease experience progressive cardiopulmonary compromise. As worm burden grows, exercise intolerance develops into frank heart failure - dogs that once ran freely cannot walk without distress. Coughing, labored breathing, and fatigue characterize advanced disease. Treatment itself causes welfare costs - the killing of adult worms requires strict exercise restriction for months and causes inflammatory reactions. Dogs that experience treatment complications can develop pulmonary embolism - an acute welfare emergency. The complete preventability of this disease makes each case a system failure.