Question

1. staar question

in 1898 friedrich loeffler and paul frosch found evidence that the cause of the highly contagious hoof - and - mouth disease in livestock was a microscopic infectious particle; it was discovered that this particle requires a host cell to reproduce.
which pathogen is most likely responsible for causing hoof - and - mouth disease in livestock?

• a prion, because it is microscopic
• a bacterium, because it is contagious
• a fungus, because it infects livestock
• a virus, because it requires a host cell to reproduce

Explanation:

Prions are misfolded proteins (not microscopic particles needing host cells). Bacteria are contagious but can reproduce independently. Fungi infect livestock but don’t require host cells for reproduction. Viruses are microscopic infectious particles that must use host cells to reproduce, matching the description.

Answer:

D. a virus, because it requires a host cell to reproduce