Heartworm disease causes severe cardiopulmonary damage and is fatal if untreated, yet it is entirely preventable through monthly prophylactic medication — making prevention one of the highest welfare-per-dollar veterinary interventions.
Heartworm disease causes progressive suffering from the accumulation of parasites in the cardiovascular system. As worm burden increases, exercise tolerance decreases, coughing worsens, and heart function declines. The treatment experience is itself welfare-challenging — immobilization, strict rest, and the risk of worm die-off reactions create weeks of discomfort and stress. Prevention eliminates the entire welfare burden of treatment and disease at minimal cost and risk. The welfare calculus strongly favors prevention: monthly medication prevents weeks to months of treatment suffering and years of life impaired by cardiovascular compromise. Geographic complacency is a welfare risk — climate change is expanding the range of heartworm-carrying mosquitoes, and dogs in previously low-risk areas are increasingly exposed.