Which statement best describes how species can influence disease outcomes?

• A. Pseudorabies is non-fatal in pigs but fatal in dogs
• B. Pseudorabies is equally severe in all species
• C. Pseudorabies is only a respiratory disease in all species
• D. Pseudorabies does not infect dogs

Answer: (A)

Differences in disease outcomes across species show how host factors shape clinical illness. Pseudorabies virus is adapted for pigs as the natural reservoir, and infections in pigs can range from mild to moderate, especially in older animals; death is not universally expected. In dogs, however, infection typically leads to severe nervous system disease and is almost always fatal. This contrast illustrates that the same pathogen can cause very different outcomes in different host species due to differences in susceptibility, immune response, and how the virus interacts with tissues. The other statements don’t fit because the virus can infect dogs and cause fatal disease in that species, its clinical picture is not limited to respiratory disease in all species, and outcomes are not uniformly severe across species.