Heartworm disease, transmitted by mosquitoes, causes progressive heart and lung damage in dogs and is entirely preventable through monthly prophylactic medication, making it primarily a preventive welfare issue.
Heartworm disease causes progressive, cumulative welfare harm over the months to years of untreated infection. Affected dogs experience exercise intolerance, respiratory compromise, and cardiac dysfunction that progressively limits their ability to engage in normal activities. The adult worms physically occupy and damage cardiac and pulmonary structures. Treatment, while effective, requires strict rest for 4-8 weeks — a welfare cost in itself for dogs who cannot understand why their activity is suddenly restricted. Dogs that die from untreated heartworm disease experience progressive respiratory and cardiac failure. The entirely preventable nature of the disease through consistent monthly prevention makes heartworm-related suffering a welfare failure attributable to inconsistent preventive care — a significant proportion of affected dogs were either never started on prevention or had lapsed preventive medication.