Heartworm disease caused by Dirofilaria immitis is a serious, preventable parasitic infection causing progressive cardiopulmonary damage and significant suffering in untreated dogs.
Heartworm disease causes a long, slow deterioration in cardiopulmonary function. Affected dogs experience progressive exercise limitation, coughing, breathing difficulty, and fatigue that restricts activity and enjoyment. Advanced disease causes right-sided heart failure with severe welfare implications. Treatment, while effective, carries its own welfare cost: 8 weeks of strictly enforced rest to prevent clots as dying worms are reabsorbed. Dogs during this period cannot engage in normal exercise and social activity. Prevention eliminates the disease entirely and is simple, safe, and inexpensive — making preventive failure a particularly avoidable welfare outcome. Regular testing ensures early detection before significant cardiopulmonary damage occurs.