Environmental Health Monitoring
Frequently Asked Questions

It’s normal to have many questions and concerns before switching a facility to environmental health monitoring. Below are answers to the most commonly asked questions our group encounters.

Yes, both types of racks can work for EHM but there is a difference in how to test. For IVC systems that filter at the rack level (e.g., Allentown Inc., TecniplastTM) Exhaust Dust Testing can be achieved via rack plenum swabbing and collar-mounted media. For open top, static, or IVC systems that filter at the cage level (e.g., Animal Care Systems, Inc., Innovive, Inc., Thoren, Inc., Lab Products, LLC.) you can use Sentinel-Free Soiled Bedding Sampling to shake or stir some type of media (swabs or filter) in a cage that holds soiled bedding without the use of sentinel animals. For more information view our Overview Page or Publication Page.

Yes, EHM will also work with static caging. PCR material will need to be collected from a cage that holds dirty bedding by using the filter/media paper or flocked swabs method, but without the use of sentinel animals.  These publications describe these methods Dubelko, 2018; O’Connel 2021; Hanson, 2021; Winn, 2022; Varela, 2022. These publications have shown that this method is equal or more sensitive to soiled bedding sentinels for common rodent pathogens.

For more information view our Overview Page or Publication Page.

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.

For more information view our Overview Page or Publication Page.

Yes, the majority of the available evidence (more than 30 publications) indicates that environmental health monitoring techniques are equally effective or more effective than traditional soiled bedding sentinels. 

Not necessarily, we are aware of two cost analyses that indicated switching to environmental health monitoring was actually LESS expensive than traditional sentinel programs. One has been published (Luchins, 2020). Be sure in your calculations to factor in the cost of housing and caring for sentinel rodents.

In a survey of 78 different institutions, 76% indicated that their institution would accept rodents from other institutions that used environmental health monitoring techniques although some may require additional testing. In talking to institutions that have switched, they have not found any real world issues with rodent transfers.

False positives or negatives are always possible particularly with a very sensitive testing paradigm. We recommend that you always investigate unexpected results further and discuss unexpected results with your diagnostic laboratory.

Yes. PCR assays are very sensitive, and can detect old, or legacy nucleic acids of agents that may no longer be present. This can make interpreting results difficult. Data suggests that you can take a stepwise approach to removing legacy nucleic acids if it is causing problems. This can include manual scrubbing in addition to standard sanitation practices, washing equipment 2 or 3 times in a mechanical washer, use of bulk autoclaves for cage and rack sterilization, and even vaporized hydrogen peroxide (VHP) exposure to degrade legacy nucleic acids on equipment. 

We recommend performing histopathology on any colony animals with unusual phenotypes/signs/illness to help identifying any new or emerging pathogens. However, the diagnostic labs often find greater detection of potential pathogens via environmental health monitoring.

This may depend on the pathogen. Ask your diagnostic laboratory what they recommend. They may recommend testing colony animals by cage perimeter swabs, direct fur swabs, blood, or feces to narrow down positive cages. Alternatively if you are using exhaust dust testing they may suggest pooled plenum swabbing for confirmatory testing.

If you suspect a false positive or residual nucleic acid, then move cages to a clean rack & re-swab in 2-4 weeks.

The number of publications confirming the use of EHM as a more sensitive method for health monitoring increases yearly. However, there is so much more than we need to learn about EHM. Please consider conducing these research projects at your institution and publishing them for all to see!

  1. Confirm adequate sanitation for IVC racks and their cages to ensure the removal or degradation of legacy nucleic acids for different pathogens
  2. The effect of varying air changes per hour and humidity on EDT
  3. Comparing plenum swabbing versus the use of indwelling filter media for EDT
  4. Assessing media trapping efficiency for EDT and SFSB
  5. Assessing rate of rodent pathogen deposition into a racks exhaust system for EDT
  6. Assay detection limits for PCR tested of different pathogens