JAALAS ARTICLE: Comparing Mouse Health Monitoring Between Soiled‐bedding Sentinel and Exhaust Air Dust Surveillance Programs
Soiled-bedding sentinel animals (SBS) are traditionally used to monitor rodent colony health in research facilities. However, several pathogens go undetected through soiled bedding (1), and the act of collection is quite time consuming. As recommended by the Federation of European Laboratory Animal Science Associations (FELASA) for IVC housing, a secondary, more modern approach is testing the exhaust air dust (EAD) via collection media in the exhaust plenum.
The University of Chicago put the two methods to the test in a yearlong study using Allentown’s Jag 75 MicroVent IVC racks. Each quarter, a set of racks were analyzed using EAD PCR, and concurrently, another set of racks were tested through serology (2).
This is the first and only long-term study to compare SBS and EAD colony surveillance by using EAD collection media on IVC racks in a working biomedical research barrier. (A few studies include a limited number of racks and only for just a single quarter – not an entire year.) This study confirmed EAD monitoring is more efficient, sensitive and humane for monitoring the health status of mice, and through that confirmation validated the design, application and performance of Allentown’s Sentinel EAD solution.
Increased Sensitivity (more efficient in detection)
As the EAD collection media accumulates dust particles over the course of three uninterrupted months, it has the potential to collect a much higher concentration of microbes and biological particles generated by microbes, containing nucleic acids detectable by qPCR. Sentinel animals may not shed these microbiological particles at the time of collection, which decreases the likelihood of bacteria detection from the SBS samples.
The study verified EAD testing is more sensitive than SBS in the detection of bacteria, specifically Helicobacter spp and Rodentibacter spp. Bacteria was detected in all 16 racks every quarter via EAD but was only detected through SBS on 5 racks in the first quarter and 1 rack in the third quarter.
Beyond the scope of the study, researchers identified two pathogens that wouldn’t have been otherwise detected by SBS. And, an unexpected pathogen was identified using EAD – lactate dehydrogenase-elevating virus (LDV). As SBS has never tested positive for LDV, a diagnostic laboratory was consulted and confirmed it to be a true positive. (The LDV finding is being submitted as a future paper.)
Some researchers question whether exhaust debris PCR analysis leads to many false positives, a requirement for special rack sanitation practices, or has a higher risk of cross contamination, especially from dead microorganisms present in bedding, feed or IVC plenums. Since implementing EAD throughout the IVC racks at the University of Chicago LAS facilities, a total of four false positives were detected over a two-year period. Of those four, one was a reporting error. Each of the other three were confirmed through follow-up tests, including plenum swabs and direct animal swabs, and collaboration with the testing facility made these situations easy to manage.
Decreased Animal Use (in line with the 3Rs*)
The use of EAD follows the principals of the 3Rs. Using EAD monitoring replaces live sentinel animals in the facilities and greatly reduces the number of animals that otherwise would have been used for health monitoring. Since implementing EAD monitoring, the University of Chicago reduced the need by approximately 1,700 sentinel animals each year. Additionally, EAD reduces the risk of cross contamination during soiled bedding transfer and helps maintain animal well being by indicating when unwanted conditions arise that can be detrimental to the animals’ health.
The replacement of sentinel animals with Sentinel EAD monitoring reduced the costs in this study by 1/3. Significantly reduced were the cost associated with acquisition of the mice, the maintaining of the animals, the time spent on transferring soiled bedding, and the in-house sample collection and diagnostics.
(1) FELASA recommends health monitoring of mouse, rat, hamster, guinea pig and rabbit colonies in breeding and experimental units. Laboratory Animals, 2014, Vol. 48 (3), 178-192
(2) D. Mailhiot et al., Journal of the American Association for Laboratory Animal Science, 2020, Vol 59, No 1, 1–9
*The principles of the 3Rs (Replacement, Reduction and Refinement) were developed over 50 years ago providing a framework for performing more humane animal research. Sentinel EAD is in line with all three main goals: Replacement (methods which avoid or replace the use of animals,) Reduction (methods which minimize the number of animals used per experiment) and Refinement (methods which minimize animal suffering and improve welfare.)
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