Heartworm disease causes chronic cardiovascular suffering in dogs and cats before killing them, and monthly preventive medications are among the highest-value welfare investments available to pet owners.
Heartworm prevention welfare value is exceptional -- a low-cost monthly intervention prevents severe chronic suffering and death. Dogs with heartworm disease experience progressive respiratory distress, weakness, and cardiovascular failure over months. The treatment process for dogs is painful, expensive, and requires enforced rest. Cats face sudden cardiac death with no treatment option. Monthly prevention is the welfare-optimal approach because it is highly effective, low-cost, and avoids both the disease welfare harm and the treatment suffering. The welfare case for consistent year-round prevention, even in lower-risk areas, is strong given the severity of disease consequences.