Using Sterile Flocked Swabs as an Alternative Method for Rodent Health Monitoring

Routine health monitoring is an integral part of managing SPF rodent colonies. In recent years, rack-level environmental sampling has been introduced as an adjunct method or replacement for exposure of sentinel rodents to soiled bedding. However, rack-level environmental monitoring is not compatible with rodent housing systems that have cage-level filtration. The current study investigated whether exposure of sterile flocked swabs to soiled bedding can be an alternative sampling method for routine health monitoring in mice, thus replacing the use of sentinels in soiled-bedding cages. Flocked swabs were placed in cages containing pooled samples of soiled bedding but no mice; swabs remained there for 90 d, with weekly agitation and biweekly swabbing of the cage floor to mimic the agitation of soiled bedding by sentinel mice and facilitate the collection of dust particles. Fecal samples were collected from both colony and sentinel mice. For environmental samples, exhaust debris was collected from the rack plenum, and dust samples were collected from the exhaust hose. All samples were collected on days 88 through 91 and were tested for multiple pathogens by using real-time PCR assays. To determine the diagnostic agreement of flocked swab sampling with the other methods, we used κ statistics to compare the test results from flocked swabs with those from sentinel feces, exhaust debris, and colony animal feces; we found excellent agreement between the colony feces and the flocked swab methods. The sterile flocked swab method detected all enzootic pathogens in the colonies tested. Results from flocked swab samples had the least agreement with sentinel feces, which also failed to detect the presence of fur mites. This study supports the use of sterile flocked swabs as alternative to using sentinel mice, thus conforming to the guiding principles of replacement and reduction in the use of animals for routine colony health monitoring.