Dog heartworm endemic areas include which geographic region?

• A. Central Valley and Sierra Nevada mountains and foothills
• B. Coastal deserts
• C. Arctic tundra
• D. Tropical rainforest

Answer: (A)

Heartworm is spread by mosquitoes, so areas where mosquitoes are active for a long season and temperatures allow the parasite to develop inside the mosquito are considered endemic. The Central Valley and the Sierra Nevada foothills provide warm summers and plenty of standing water from irrigation, creating abundant mosquito habitats and enabling ongoing transmission to dogs. The other regions either lack reliable mosquito populations (coastal deserts), stay too cold for most of the year (Arctic tundra), or are not the typical endemic focus in educational context (tropical rainforest). Thus, this region best fits where dog heartworm is endemic.