What is the minimum age for sentinel animals?

• A. 3 weeks old
• B. 4-8 weeks old
• C. 8-12 weeks old
• D. 6 months old

Answer: (C)

Sentinel animals must be old enough to have a mature immune system and stable health so monitoring tests reliably reflect the colony’s status. Around 8 to 12 weeks old is when mice and rats reach young adulthood, are typically weaned, and can undergo sentinel exposure and subsequent testing (like serology or PCR) with reliable results. If they’re much younger, their immune response may be immature and tests less reliable; if they’re much older, age-related changes can complicate interpretation and the monitoring timeline. Therefore, the minimum age is 8–12 weeks.