Easy to prevent. Expensive to treat!
Heartworm disease is a serious and potentially fatal disease in pets in the United States (all 50 States) and many other parts of the world. It is caused by foot-long worms (heartworms) that live in the heart, lungs and associated blood vessels of affected pets, causing severe lung disease, heart failure and damage to other organs in the body.
You could buy 7 years of heartworm preventatives for the same price as treating heartworms one time.