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Research facilities that house rodents have traditionally used soiled bedding sentinel health-monitoring programs to detect rodent pathogens that could affect research results. Why is there a need to change this established program? Soiled bedding sentinels have limitations in terms of accuracy, require the use of live animals, and can be costly and time consuming. Environmental health monitoring is a fantastic alternative that has many advantages and overcomes some of these limitations.
Environmental health monitoring involves the surveillance of rodent colonies for pathogens without the use of sentinel animals. These methods replace live animal sentinels with sampling and swabbing techniques from dust, debris, and pooled soiled bedding to be analyzed by very sensitive and specific molecular tests (i.e., PCR). Environmental health monitoring is now recognized for its efficacy in detecting multiple rodent pathogens when used as an adjunct or complete replacement to soiled bedding sentinel health monitoring programs (see the publications tab on the website).
3Rs: Replace Sentinel Mice
Improve Pathogen Detection
(Earlier & More Accurately)
Reduce Labor & Cost
One Welfare: Reduce Emotional Fatigue
Many institutions, from both Canada and the United States, have replaced their soiled bedding sentinel health monitoring programs with EHM programs.
US institutions that have shared their replacement of sentinels with us include: University of Washington, Pfizer Comparative Medicine sites (Kendall Square, La Jolla, Pearl River, Groton), University of Florida, University of Colorado Anschutz Medical Campus, Emory University, University of Chicago, University of Illinois – Chicago, University of Texas at Austin, University of Southern California, Emory National Primate Research Center, Medical College of Wisconsin, Northwestern University, Benaroya Research Institute, UT Southwestern Medical Center, University of Alabama at Birmingham, University of Arizona, Seagen, GSK, and Chapman University.
Canadian institutions include: The Research Institute of the McGill University Health Centre, Comparative Medicine Animal Resources Centre at McGill, Montreal Clinical Research Institute, and University of Saskatchewan.
The first step to implementing EHM is to determine your type of caging. Multiple EHM sampling methods can be used, and the best method(s) are dictated by the type of caging that you have. Ultimately, an environmental sample is collected and analyzed for rodent pathogens by PCR testing.
Below we briefly describe each environmental health monitoring method.
The exact method of exhaust dust dusting depends on if you have Allentown or Tecniplast caging.
Exhaust Dust Testing with Allentown Caging
Allentown has developed two different sample capture units to collect particles moving from the cage to the exhaust filtration system to perform environmental health monitoring that can be integrated in Allentown IVC plenum chamber. The original SentinelTM system works with all available air handling options including rack mounted or trolley mounted blowers as well as facility exhaust. The newer Sentinel2 mounts to the top of the exhaust plenum or on the blower inlet allowing users to access the removable media without entering the exhaust plenum itself. In both situations, the collection media stays for a specific period of time (typically 3 months) and then is submitted to a diagnostic laboratory for PCR analysis. Please see our universal SOP for more details on using this system.
Exhaust Dust Testing with Tecniplast Caging
Tecniplast has developed the Interceptor system to collect particles moving from the cage to the exhaust filtration system to perform environmental health monitoring that can be integrated with Tecniplast caging. The Interceptor works with the Tecniplast air handling units via a stainless-steel frame designed to hold an irradiated cardboard folder containing a sliding filter. Some facilities may have Tecniplast IVCs controlled by a centralized ventilation system. In these situations, a plenum attachment (instead of the stainless-steel frame) is required to house the cardboard folder containing the sliding filter. In both situations, the Interceptor filter is exposed to exhaust air for a specific period of time (typically 3 months) and then submitted to a diagnostic laboratory for PCR analysis. Please see our universal SOP for more details on using this system.
Exhaust dust testing is not an option for static cages, open top cages, or for racks that filter at the cage level. In these cases, sentinel-free soiled bedding testing can be used. In short, soiled bedding from colony animals can be added to a dedicated animal-free cage (where sentinel animals would usually be placed) or dedicated sampling bin (e.g., PathogenBinderTM) at each cage change. After a specific period of time (typically 3 months), some type of media (swabs or filter, e.g., ReplaceTM) is placed in that cage and shaken or stirred. This media is then submitted to your diagnostic laboratory of choice for PCR analysis. Please see our universal SOP for more details on using this system. Sensitivity of this method may be increased by also submitting pooled fecal samples in conjunction with the choice of media.
Despite this method still being reliant on soiled bedding transfer and potentially regular agitation, it is still an effective replacement for the use of sentinel rodents. In addition, these methods are similar to historical husbandry operations involving sentinel mice with little alteration to staff schedule and time gained due to lack of sentinel mouse ordering, associated care, and more complicated sample coordination.
Direct Colony Sampling can also be used to routinely monitor colony health with all cage and rack designs. However, this method is NOT a historic method of sampling and therefore should be used under the direction of a diagnostic laboratory or a veterinarian well-versed in rodent colony health surveillance. Direct colony sampling involves non-invasive or minimally invasive collection of samples taken directly from research animals instead of using soiled bedding sentinels. These samples can include feces, pelt swabs, and/or oral swabs, which are analyzed by PCR. This method is commonly used for rodent quarantine health monitoring of newly arrived rodents to a facility. It is also commonly used for confirmatory testing after a positive test by a different environmental health monitoring method. Sensitivity of this method may be increased by also microsampling blood from colony animals. Please see our universal SOP for more details on using this system.
Health monitoring methods may be complemented with the use of Room & Equipment Monitoring. It should be used under the direction of a diagnostic laboratory or a veterinarian well-versed in rodent colony health surveillance. This involves direct sampling and testing of the laboratory animal facility environment, including walls, floors, room filters, and equipment such as dump stations, biosafety cabinets, or behavioral testing equipment that has rodent contact. The type of structures and equipment, number, and frequency of testing should be considered based on the risks of infection by various agents, their route of exposure and transmission, other surveillance methods used, and facility-specific characteristics such as type of housing. Please see our universal SOP for more details on using this system.