Which disease type would be most difficult to prevent entering and infecting animals in the U.S.?

• A. A disease of swine that has a short incubation period and is highly fatal
• B. A disease of various species that has wild birds as a reservoir
• C. Highly contagious disease of cattle
• D. A disease of cattle transmitted by a tick vector

Answer: (B)

Preventing entry and establishment of a disease hinges on where the pathogen can persist and how it moves between hosts. A disease with wild birds as a reservoir is the hardest to keep out because migratory birds travel long distances and cross borders, continuously introducing pathogens into new areas. This wildlife reservoir means you can’t rely on screening a single species or farm-level biosecurity alone; the pathogen can circulate in wild populations and spill over into domestic animals despite strict import controls. Surveillance, detection, and rapid containment become far more complex when the source is diverse, mobile wildlife that interacts with many species. In comparison, diseases with short incubation in swine, or highly contagious diseases of cattle, or those transmitted by ticks are more controllable through targeted surveillance, movement controls, vaccination, or vector management. Hence, the wild-bird–reservoir scenario presents the greatest preventive challenge.