The American Heartworm Society (AHS) has released its latest U.S. heartworm incidence map, based on data collected in 2025 from veterinary practices and shelters nationwide. Results show the highest infection rates remain concentrated in the Gulf Coast and southeastern states, with Texas leading the country, followed by Louisiana, Arkansas, Mississippi, and South Carolina.

Additional high-incidence areas include parts of Florida, the Carolinas, and southern Illinois.

The survey also identified expanding heartworm presence in regions not traditionally considered high risk, including parts of California, Colorado, Wisconsin, and Maine, as well as increases in several western states. Most veterinarians (59 per cent) reported stable incidence rates compared with the previous survey, while others noted increases or decreases.

The findings highlight heartworm disease as a persistent nationwide concern influenced by factors, such as mosquito populations and compliance with preventive care. The updated map is intended to support veterinary education, client communication, and disease prevention efforts.

For more information, visit the AHS website.