Where is dog heartworm endemic?

• A. Central Valley and Sierra Nevada mountains and foothills
• B. Coastal plains of California
• C. Great Plains
• D. Southeastern coastal states

Answer: (A)

Heartworm transmission depends on the presence of mosquitoes that can carry and deliver the parasite to dogs. The parasite needs to develop inside the mosquito and then be transmitted during a bite, and this development is temperature- and environment-dependent. The Central Valley and Sierra Nevada foothills provide conditions with irrigation, standing water, and warm-season windows that support stable mosquito populations year after year. That combination allows the heartworm life cycle to persist in dogs in that area, making it a region where the disease is considered endemic. In contrast, areas with cooler winters, less reliable mosquito habitats, or shorter warm seasons don’t sustain continuous transmission as readily, so they are less typically described as endemic.