Heartworm disease causes severe suffering and death in dogs but is almost entirely preventable through regular medication, making prevention a clear welfare obligation.
Heartworm disease causes significant chronic suffering in affected dogs. Adult heartworms living in the heart and pulmonary vessels cause progressive inflammation, exercise intolerance, and cardiovascular compromise that worsens steadily over months to years. Affected dogs develop coughing, lethargy, and eventually right-sided heart failure. The treatment for established heartworm disease is itself challenging - it requires strict exercise restriction for months and carries risks of complications as dying worms are absorbed. Monthly preventive medication, by contrast, is safe, effective, and eliminates the welfare cost of the disease entirely. In endemic regions, consistent preventive medication is one of the clearest welfare obligations for dog owners - the cost-benefit calculation strongly favors prevention.