It is important to ensure that rodent colonies are free of adventitious infectious agents to support high quality, robust research & safety data. Over the last 50 years, health surveillance has been typically performed using sentinel animals. More recently, molecular-based diagnostics combined with environmental monitoring strategies have been adapted by many institutions to either supplement or replace the more traditional methods. These newer approaches can significantly replace the number of rodents used in maintaining specific-pathogen-free colonies.
Replace Sentinel Mice
More Accurate Results
Reduce Labor & Cost
Reduce Emotional Fatigue
Several reputable, large academic, pharmaceutical, and government organizations have replaced live soiled bedding sentinel rodents with environmental monitoring technology. This includes institutions such as University of Washington, University of Florida, University of Colorado Anschutz Medical Campus, Emory University, University of Chicago, Yerkes National Primate Research Center, Research Institute of the McGill University Health Centre, Medical College of Wisconsin, Northwestern University, Benaroya Research Institute, UT Southwestern Medical Center, and many more.
Advantages = Initially less costly than exhaust plenum media holders (i.e. collars mounted media.)
Challenges = Some rack brands/designs are easier to implement environmental monitoring than others (e.g., not effective with rack designs with cage level exhaust air filtration). May not be sensitive enough for pathogens that are at low prevalence.
Advantages = Operator variability is minimized & minimal handling is required. Detects Helicobacter & MNV with similar sensitivity to swabbing. Media helps increase dust collection. Acceptable for 3-month collection. Provides a history of pathogens that were present over the previous 3 months. Presumably reduced ergonomic effort.
Challenges = Can be physically difficult to place/collect collar mounted media from single-sided racks. Collars/media must be placed AFTER racks are washed & collected BEFORE wash which requires coordination (alternatively you can wait to wash racks until they test positive and then clean once the potential outbreak is resolved). May be costly.
Exhaust air duct monitoring is not an option for static cages or racks that filter at the cage level (Bauer, 2016; Dubelko, 2018). In this case, PCR material must be collected from the cage. These methods are described in 3 key references: Dubelko, 2018; O’Connel 2021; or Hanson, 2021.
Overall, the best option may be to place 10 flocked swabs or a large piece of filter paper inside an additional cage (where sentinel animals would usually be placed) and then transfer soiled bedding as usual. Soiled bedding should be shaken or stirred with the swabs after cage change. Flocked swabs or filter paper can be tested at 1-3 months after placing them.
Research shows that PCR testing of flocked swabs was as effective or MORE effective than PCR testing from sentinel mice.
Thus far these methods have been used to detect pinworms, fur mites, mouse hepatitis virus (MHV), murine norovirus (MNV, minute virus of mice (MVM), mouse parvovirus (MPV), Theiler murine encephalomyelitis virus (TMEV), Helicobacter spp*, Syphacia obvelata, Aspiculuris tetraptera, Rodentibacter spp.*, Entamoeba muris, and Spironucleus spp.
This method is still reliant on soiled bedding transfer & dependent on personnel shaking cages or stirring. However, it is still an effective replacement for soiled bedding sentinel mice.
If animals from approved vendors will only be on-site for a short period of time (e.g., <1-2 months) then health monitoring may not be necessary. You could also consider collecting fecal samples, fur swabs +/- oral swabs directly from colony animals.