Heartworm disease causes severe suffering and death in dogs. Prevention is simple and highly effective; treatment of established infection is costly, complex, and itself involves welfare costs.
Heartworm disease causes significant and preventable welfare harm. Dogs with established infection experience progressive cardiopulmonary damage — the physical presence of worms in the pulmonary arteries causes inflammation, blood vessel damage, and heart strain that manifests as exercise intolerance, coughing, and eventually heart failure. The welfare harm accumulates silently over years before dramatic clinical signs appear. Treatment of established heartworm infection involves adulticide drugs with serious side effects, strict exercise restriction for weeks, and risk of pulmonary embolism from dead worms. This welfare cost can be entirely avoided through monthly preventive medication — one of the most cost-effective welfare interventions available to dog owners. The medication is safe, well-tolerated, and available as tasty chewable tablets. In endemic regions, year-round prevention is the welfare standard; in areas with seasonal mosquito populations, seasonal prevention covers the risk period. Climate change is expanding heartworm endemic zones — owners in previously low-risk areas should consult their veterinarian about changing risk profiles.