Washington State University

Institutional Animal Care and Use Committee

Rodent Colony Health Monitoring Guidelines [VS-002]

Number of Sentinels and Identification: There should be a cage of 2 sentinel co-housed mice per rack or one-two co-housed sentinel rats per full standard rack or one sentinal cage per side for a full ventilated rack. Two sentinels are used so that one animal can be tested and serum from the second animal saved in the event of an equivocal or positive result from the first animal.  Multiple sentinel cages per room maximizes our ability to detect infection. Sentinels cages must be labeled properly (i.e. strain, source, date of sentinel placement, date of birth/age, sex, etc.) and the cage card should indicate the sentinel rodents are not to be used for any research purpose.  

Caging, Housing and Handling: Sentinel rodents must be housed similar to the standard housing of the room. If the colony is housed in open-top rodent cages, sentinels should be housed in open-top rodent cages (i.e. without filter bonnets or micro-isolator tops). Colonies with closed microisolators or ventilated cages should house sentinels in closed microisolators or ventilated housing as well and provide the same bedding and the feed as the experimental rodents in the room. Handling of sentinel animals (e.g. cage changing, examination, etc.) should be performed after care has been provided for all other animals in the room. This is especially important if the sentinels are in a room housing immunocompromised or irreplaceable (e.g. transgenic) animals. Once a group of sentinel rodents has been placed in a room on a particular rack, they must remain with that same group of animals. Sentinels should never be moved from room to room and/or rack-to-rack between different populations/sources of rodents.

Exposure: Sentinel rodents are to be housed on a composite sample of dirty bedding from cages in the room housing experimental/breeding animals. EVERY TIME the cages are changed in the room, small samples of dirty bedding (i.e.1-2 teaspoons per cage) should be removed from every experimental rodent cage and placed in the sentinel rodent cages.   If a large number of cages need to be sampled into a single sentinel cage, a rotation system can be used where 10-15 cages are sampled per week.   If a rotation system is used, it is critical that all the cages within the colony are sampled within 2 months to allow exposure and seroconversion to occur in the sentinel animals before they are tested.   The composite sample should always include feces and urine. Sentinel animals should be maintained in 100% previously utilized bedding as described.  This ensures the sentinel rodents are exposed to any and all potential pathogens in the room. Thus, sentinel rodent bedding should never look clean.

Sentinels can serve as contact or indirect sentinels:   Contact sentinels share the housing, whereas indirect sentinels are exposed to dirty bedding.   It is noted that some viruses and agents are poorly transmitted through contaminated bedding (Sendai virus and some external parasites).

Placement in the room: Sentinel rodent cages should be placed on the lowest shelf of the rack under the experimental rodents. We request the bottom right corner of the rack for system standardization.  This ensures any dust, dander, aerosols, microorganisms, parasites, etc. drift down into the sentinel cages, enhancing exposure to potential pathogens.

Replacement of Sentinels: When sentinel rodents are removed by the OCV Staff for routine rodent health monitoring, you must replace these with newly acquired sentinel rodents within one week.   OCV will notify vivarium managers when sentinels are removed from a vivarium.

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