Veterinary virology — Foot-and-mouth disease (FMD) in cloven-hoofed animals is caused by which type of pathogen?

Introduction / Context:
Foot-and-mouth disease (FMD) is a highly contagious disease affecting cattle, pigs, sheep, goats, and wild ruminants. Identifying the pathogen type is foundational for understanding diagnostics, vaccine strategies, and biosecurity measures.

Given Data / Assumptions:

• FMD outbreaks spread rapidly between susceptible livestock.
• The etiologic agent is small, non-enveloped, and acid-labile.
• Control relies on vaccination, movement restrictions, and surveillance.

Concept / Approach:
FMD is caused by Foot-and-mouth disease virus (FMDV), a positive-sense single-stranded RNA virus (genus Aphthovirus, family Picornaviridae). Its RNA genome encodes structural proteins (VP1–VP4) and non-structural proteins; error-prone replication leads to high diversity, complicating control.

Step-by-Step Solution:

Verification / Alternative check:
Laboratory RT-PCR is the frontline molecular diagnostic, directly indicating an RNA genome; electron microscopy and antigen ELISAs further confirm identity.

Why Other Options Are Wrong:

• DNA virus: inconsistent with picornaviral classification.
• Bacteria/protozoa/fungi: do not match clinical course, structure, or molecular tests for FMD.

Common Pitfalls:
Confusing FMD with vesicular diseases of other etiologies (e.g., vesicular stomatitis, a rhabdovirus), which are also RNA viruses but distinct pathogens.

Final Answer:
RNA virus.