Heartworm is a serious parasitic infection causing progressive heart and lung disease. Prevention is simple and highly effective, making most cases entirely avoidable welfare problems.
Heartworm disease causes progressive welfare deterioration through exercise intolerance, cough, respiratory distress, and cardiovascular compromise. Advanced cases develop severe pulmonary hypertension and right heart failure causing profound suffering. Treatment of established heartworm infection involves multiple injections of melarsomine over months with a period of strict exercise restriction that is itself a welfare challenge. Worm die-off causes acute pulmonary reactions requiring emergency management in some cases. Prevention through monthly medication is the most welfare-positive approach for dogs in endemic regions, entirely avoiding the complex welfare challenge of treatment.