In spite of effective heartworm preventatives available, heartworm disease has been increasing in incidence, and spreading to new areas of the United States

Every three years, the American Heartworm Society (AHS) gathers data on heartworm testing to understand the impact heartworm is having nationwide, as well as in specific regions. Testing data from thousands of veterinary practices and shelters is used to create a detailed map showing the average number of heartworm-positive cases per clinic. Click on each map for more details. Please keep your pets on year round heartworm prevention to avoid infection!!