Heartworm disease is a serious and potentially fatal parasitic infection in dogs. Prevention is straightforward, but treatment of established infection is challenging and welfare-intensive.
Established heartworm disease causes significant suffering through respiratory compromise, exercise intolerance, and eventually heart failure. Dogs with advanced disease struggle to breathe during even mild activity. Treatment, while curative, is itself a welfare challenge — the injections are painful, and the mandatory exercise restriction causes frustration in active dogs. Dogs that do not complete treatment correctly risk fatal pulmonary embolism as dying worms block lung vessels. The welfare calculus strongly favors prevention: monthly preventive medications are safe, inexpensive, and eliminate the disease entirely. In regions where heartworm is endemic, prevention should be considered a basic welfare standard for all dogs. Failing to prevent heartworm, and then facing the much more expensive and stressful treatment, is a foreseeable and avoidable welfare failure.