What type of diseases does the CDC primarily regulate in imported animals?

The Centers for Disease Control and Prevention (CDC) primarily regulates zoonotic diseases when it comes to imported animals. Zoonotic diseases are infections that can be transmitted between animals and humans, and the CDC's focus is on protecting public health by preventing the spread of these diseases.

The regulation of zoonotic diseases is essential because many of these infections can have significant health impacts on human populations. By monitoring and controlling the diseases associated with imported animals, the CDC works to minimize the risk of outbreaks that could arise from exposure to infected animals or their products.

In contrast, the other options refer to more narrow categories of diseases. Diseases solely affecting livestock may not pose an immediate threat to human health, and while the CDC may have an interest in endemic diseases in the U.S., its regulatory role is more focused on preventing the introduction of zoonotic diseases. Contagious diseases among pets are important as well, but the scope of CDC's regulatory efforts extends beyond just pets to include all animals that may pose a zoonotic risk.