What route is the highest risk for introducing pathogens into an animal facility?

• A. Introduction of live animals
• B. Contamination brought in by facility staff
• C. Growth of microorganisms in the room's waste containers
• D. Spoilage of feed and bedding

Answer: (A)

Introducing live animals is the highest-risk route because these animals can carry infectious agents that aren’t already part of the facility’s microbial environment. Even with health programs, quarantine, and testing, infections can be latent, asymptomatic, or newly acquired and thus slip past screening. When new animals arrive, they bring potential pathogens directly into the colony, and in the dense, interconnected housing typical of facilities, a single introduction can spread quickly and affect both animal welfare and research integrity.

Other routes are mitigated by strong controls: staff need proper PPE and hygiene to minimize transfer, and waste handling or feed management is governed by sanitation and monitoring to prevent microbial growth or contamination. While those can be problems, they’re less likely to introduce new pathogens into the population compared with bringing in fresh animals.