Dog Heartworm: Prevention, Treatment, and Welfare

Heartworm disease causes serious cardiopulmonary damage in dogs and is entirely preventable through regular prophylactic medication.

Key Facts

Heartworm (Dirofilaria immitis) is transmitted by mosquitoes and causes adult worms in the heart and pulmonary arteries
Disease is endemic throughout the Americas, Mediterranean Europe, Africa, and Asia
Signs develop slowly - exercise intolerance, cough, and weight loss appear as worm burden increases
Treatment is expensive and risky, requiring restricted exercise for months during adulticidal therapy
Monthly or 3-monthly preventatives are highly effective and low-risk compared to treatment
Climate change is expanding heartworm endemic areas northward in North America and Europe

Welfare Considerations

Heartworm causes progressive deterioration of cardiopulmonary function resulting in exercise intolerance, respiratory distress, and heart failure if untreated. The welfare cost of untreated heartworm disease is substantial and prolonged. Prevention is the welfare-optimal approach - monthly preventatives eliminate the risk entirely at low cost and minimal side effect risk. The expanding geographic range of heartworm due to climate change means prevention is relevant in more regions than ever before.

What You Can Do

Start heartworm prevention before your dog is 8 weeks old in endemic areas
Use year-round prevention even in seasonal climates - coverage gaps create risk windows
Test annually for heartworm even on consistent prevention - break-through infections occur
Choose between monthly or 3-monthly injection prevention based on your lifestyle and compliance
Never stop prevention without veterinary guidance - restarting after a gap requires testing
Report neighborhood mosquito problems to local authorities if they may affect pet health