Which department regulates the entry of dogs used in livestock handling, including inspection for tapeworms?

The Animal and Plant Health Inspection Service (APHIS) is responsible for protecting and promoting U.S. agricultural health, regulating the entry of animals and plants into the country, and ensuring the proper inspection for diseases like tapeworms, which can affect livestock. This agency plays a critical role in monitoring and controlling diseases that could spread through animal movement. Specifically, regarding dogs used in livestock handling, APHIS sets the guidelines for health inspections, ensuring that these animals do not pose a risk to livestock or public health.

In contrast, other agencies like the Department of Agriculture primarily focus on agricultural practices and policies but do not specifically handle the entry regulations and inspections for animals. The Department of Homeland Security addresses broader security concerns, including border protection, but does not specialize in health inspections related to livestock. The Centers for Disease Control primarily focuses on human health and communicable diseases, rather than the health status of animals entering the country. Hence, APHIS is the correct choice, as it directly pertains to the regulation and inspection processes for dogs involved in livestock handling and related health risks.