Which disease poses the highest risk of entering and infecting animals in the U.S.?

The correct answer points to a disease with wild birds as a reservoir as posing the highest risk of entering and infecting animals in the U.S. This is primarily due to the migratory patterns of wild birds, which can travel long distances and carry pathogens without exhibiting symptoms. Such diseases can enter new geographic areas and spread rapidly, affecting both wildlife and domestic animal populations.

Wild birds can serve as carriers for various zoonotic diseases, including avian influenza and West Nile virus, which can significantly impact the health of both animals and humans. The movement of these birds across borders makes it challenging to control and monitor the spread of diseases they may carry.

In contrast, diseases with domestic animals as reservoirs or that affect only farm animals are generally more contained within specific environments. They often have established control measures in place due to the high level of monitoring and management in agricultural settings. Similarly, a disease that has been eradicated in other countries presents less immediate risk because eradication usually involves rigorous biosecurity protocols, making the likelihood of transmission lower. Hence, wild birds pose a unique threat due to their mobility and the potential for introducing new diseases into the U.S. ecosystem.