# Health Monitoring Programs for Laboratory Animal Facilities


## Key Takeaways

- Health monitoring programs are risk-based, requiring explicit assessment of species, facility barrier levels, research needs, and regulatory standards to define the target agent list, sampling frequency (typically quarterly for barrier facilities), and sentinel animal selection (immunocompetent outbred rodents preferred).
- Sentinel animals provide indirect colony health assessment by exposure to soiled bedding or direct contact, with exposure periods of at least four to six weeks necessary for seroconversion to detect agents shed in feces, urine, or respiratory secretions.
- Diagnostic modalities include serology (ELISA, IFA) for detecting prior exposure, PCR for identifying active infection (essential for immunodeficient animals), parasitology, bacteriology, and histopathology, with method choice dictated by agent biology and transmission routes.
- Program failure modes include silent agent circulation missed by clinical observation alone, inadequate sentinel exposure (e.g., insufficient duration or bedding transfer), and sample degradation or assay errors, necessitating confirmatory testing on fresh samples.
- Common design errors involve overly broad or narrow agent panels, inappropriate sampling strategies (e.g., pooling too many animals, testing only young animals), and treating results as static, underscoring the need for periodic review and consistent sampling cadence.
- Unexpected positive results, especially for agents with zoonotic potential (e.g., LCMV) or those impacting research validity, require immediate escalation to biosafety officers, occupational health, and affected investigators, followed by defined response pathways including confirmation, containment, and eradication or exclusion plans.

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Health monitoring programs are the principal means by which laboratory animal facilities detect, track, and control infectious agents that can compromise research validity and animal welfare. This article provides a procedural reference for veterinary researchers and laboratory animal veterinarians who design, implement, or interpret such programs. It covers the scientific rationale for health surveillance, the selection and placement of sentinel animals, the choice of pathogen screening methods, sampling strategies, and the interpretation of results within the context of institutional biosecurity. Treatment protocols for infected colonies are outside the scope of this article.

The reader is assumed to be familiar with the major pathogens of laboratory rodents and other common laboratory species, including their routes of transmission and their potential to confound experimental data. The focus here is on the decision framework that turns pathogen surveillance from a routine husbandry task into a defensible, risk-based monitoring program. The [Guide for the Care and Use of Laboratory Animals](https://grants.nih.gov/grants/olaw/guide-for-the-care-and-use-of-laboratory-animals.pdf) identifies health surveillance as a component of the veterinary care program and requires that institutions maintain animals free of disease that could interfere with research objectives.

A health monitoring program must answer four questions. What agents are we screening for? Which animals do we sample? How often do we sample? And what action do we take when a result is positive? The answers depend on the species housed, the microbiological status of incoming animals, the barrier level of the facility, the nature of the research being conducted, and the regulatory or accreditation standards that apply. No single program fits all facilities, and the design process is one of explicit risk assessment instead of template adoption.

## At a Glance

| Parameter | Decision or Standard |
|---|---|
| Program objective | Detect agents that threaten research validity or animal welfare, also clinical disease |
| Agent list | Based on species, research use, source colony status, and regional prevalence |
| Sentinel selection | Immunocompetent outbred rodents preferred, immunodeficient animals used only when justified |
| Sentinel placement | Dirty bedding transfer is standard, direct contact used for agents with poor environmental survival |
| Sampling frequency | Typically quarterly for barrier facilities, risk-based adjustment permitted |
| Screening methods | Serology, PCR, parasitology, bacteriology, histopathology, method choice follows agent biology |
| Positive result response | Confirm, contain, trace source, notify stakeholders, implement eradication or exclusion plan |
| Reference framework | [Guide for the Care and Use of Laboratory Animals](https://grants.nih.gov/grants/olaw/guide-for-the-care-and-use-of-laboratory-animals.pdf) and [WOAH terrestrial animal health standards](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) where applicable |

## Purpose and Limitations of Health Surveillance

The primary purpose of health monitoring is not to certify that a colony is pathogen-free. It is to provide ongoing evidence that the colony remains free of the specific agents that the program targets, and to detect introductions early enough to limit spread. Surveillance data also support the health status claims that facilities make when shipping animals to collaborating institutions, and they inform decisions about quarantine, rederivation, and barrier practices.

Surveillance has inherent limitations. Sampling a small number of animals can never prove the absence of an agent from a large population. The sensitivity of the program depends on the prevalence of the agent, the number of animals sampled, the sensitivity of the detection method, and the probability that the sampled animals have been exposed. A negative result means that the agent was not detected under the conditions of sampling, not that it is absent. This distinction matters when interpreting results for institutional oversight bodies and when comparing the health status of incoming animals from commercial vendors.

The [National Antimicrobial Resistance Monitoring System](https://pubmed.ncbi.nlm.nih.gov/28792800/) illustrates a parallel surveillance principle from the public health domain: integrated monitoring programs must adapt their sampling schemes and target lists as threats change. Laboratory animal programs face the same requirement. The agent list that was appropriate when a facility opened may not be appropriate a decade later, as new pathogens emerge, diagnostic methods improve, and the research portfolio shifts.

## Agents Under Surveillance

The target agent list is the foundation of the program. It should be derived from a formal risk assessment that considers the species housed, the source of the animals, the experimental manipulations performed, and the consequences of an undetected infection. Agents that cause high morbidity, spread rapidly, persist in the environment, or confound specific research outcomes warrant inclusion. Agents that are ubiquitous, clinically silent, and of no known research impact may be excluded to conserve resources.

For laboratory rodents, the list typically includes murine norovirus, mouse hepatitis virus, Sendai virus, pneumonia virus of mice, parvoviruses, Theiler's murine encephalomyelitis virus, ectromelia virus, lymphocytic choriomeningitis virus, and selected bacterial agents such as *Mycoplasma pulmonis*, *Cilia-associated respiratory bacillus*, *Helicobacter* species, and endo- and ectoparasites. For rabbits, common targets include *Encephalitozoon cuniculi*, *Pasteurella multocida*, and *Treponema paraluiscuniculi*. The [MSD Veterinary Manual](https://www.msdvetmanual.com/) provides species-specific information on the clinical presentation and pathology of these agents, which informs the selection of screening methods and the interpretation of positive findings.

The list must be reviewed periodically. Changes in the research program, the introduction of new animal strains, or the emergence of newly recognized pathogens all justify revision. The review should be documented, and the rationale for inclusion or exclusion of each agent should be recorded so that the program remains defensible to accrediting bodies and to collaborating institutions that receive animals from the facility.

## Sentinel Animal Programs

Sentinel animals are purpose-placed animals that are exposed to the microbial status of the colony through controlled means, then tested to provide an indirect assessment of colony health. The sentinel program is the most common surveillance strategy in rodent facilities because it avoids the cost and experimental disruption of testing large numbers of colony animals directly. The validity of the sentinel approach depends on the probability that sentinels acquire the same infections as the colony animals they represent.

### Sentinel Selection

Sentinel animals should be immunocompetent, outbred, and of the same species as the colony under surveillance. Outbred stocks such as Swiss Webster or Sprague Dawley are preferred because they are outbred, hardy, and serologically reactive across a broad range of agents. Inbred strains may be used when the colony itself is inbred, but strain-specific differences in susceptibility and antibody response must be considered. Immunodeficient animals should not be used as sentinels for immunocompetent colonies because they may fail to seroconvert to agents that the colony animals control effectively, and they are susceptible to opportunistic infections that do not reflect colony status.

The number of sentinels per room or per rack depends on the agent prevalence that the program aims to detect, the sensitivity of the detection method, and the acceptable level of confidence. Published tables, such as those used in the [Guide for the Care and Use of Laboratory Animals](https://grants.nih.gov/grants/olaw/guide-for-the-care-and-use-of-laboratory-animals.pdf), provide sample size estimates for detecting an agent at a given prevalence with a given confidence level. These estimates assume random mixing of sentinels with colony animals, which is rarely achieved in practice, so most programs sample more animals than the theoretical minimum.

### Sentinel Placement and Exposure

Sentinel animals are housed in cages that receive dirty bedding from colony cages, typically on a rotating schedule so that each sentinel is exposed to material from multiple colony cages over time. The bedding transfer method is effective for agents that are shed in feces, urine, or respiratory secretions and that survive in the environment. It is less effective for agents that require direct contact for transmission, such as ectromelia virus or certain fur mites. For these agents, direct contact sentinels, housed in the same cage as colony animals, may be necessary.

The exposure period must be long enough for sentinels to become infected and to develop detectable antibody. A minimum of four to six weeks of exposure is commonly used for serological detection, with longer periods for agents that transmit slowly or that induce a delayed antibody response. The sentinel cage should be positioned to maximize exposure, for example on the bottom shelf of a rack where airborne particulates and bedding dust tend to accumulate.

## Sampling Strategy and Frequency

Health monitoring programs operate on a defined sampling schedule that balances diagnostic sensitivity against animal use and cost. The interval between sampling rounds depends on the agent's transmission dynamics, the colony's barrier status, and the consequences of a missed infection. For rodent colonies maintained behind a specific pathogen free (SPF) barrier, quarterly sampling is a common baseline, but this frequency assumes a stable colony with no new introductions and no clinical signs. Facilities that import animals frequently, maintain immunodeficient stocks, or have experienced a recent breach should shorten the interval to monthly or even biweekly for a defined period.

The sampling schedule must also account for the age of the animals tested. Young animals may clear certain infections or remain seronegative during early exposure, while aged animals may lose detectable antibody titres. Most programs sample adults between 8 and 16 weeks of age, an age window that captures both seroconversion and active shedding for most common rodent pathogens. When immunodeficient animals are present, they should be sampled preferentially because they often harbour infections at higher prevalence and for longer durations than immunocompetent animals.

Sample size calculations should follow the expected prevalence of the target agent. For agents with low expected prevalence, such as murine hepatitis virus in a stable barrier colony, testing a small number of animals per room may fail to detect an incipient outbreak. The [Guide for the Care and Use of Laboratory Animals](https://grants.nih.gov/grants/olaw/guide-for-the-care-and-use-of-laboratory-animals.pdf) emphasizes that surveillance design should be based on the probability of detecting an infection at a given prevalence, not on a fixed percentage of the population. A practical approach is to sample enough animals to detect a prevalence of 5% with 95% confidence, which requires approximately 60 animals per room for a perfectly sensitive test. Because most programs cannot justify sampling 60 animals per room quarterly, they rely on pooled samples, sentinel animals, or environmental sampling to increase coverage without increasing animal numbers.

## Diagnostic Testing Modalities

Serology remains the backbone of rodent health monitoring because it detects prior exposure to viral and bacterial agents with high sensitivity. The choice of serological assay affects both sensitivity and specificity. Enzyme-linked immunosorbent assays (ELISA) and immunofluorescence assays (IFA) are widely used, but multiplexed bead-based assays now allow simultaneous detection of antibodies against many agents from a single small serum sample. Confirmatory testing by western blot or IFA is recommended when screening assays produce positive or equivocal results, particularly for agents with known cross-reactivity such as rodent coronaviruses.

Polymerase chain reaction (PCR) testing complements serology by detecting active infection. PCR is the method of choice for agents that are difficult to culture or that produce transient serological responses, and it is essential for detecting infections in immunodeficient animals that cannot mount an antibody response. PCR can be performed on fecal samples, oral swabs, or tissue samples, and it is particularly valuable for detecting Helicobacter species, fur mites, and pinworms, all of which are poorly detected by serology. Quantitative PCR adds the ability to track shedding intensity over time, which is useful when monitoring the clearance of an agent after a deliberate depopulation or rederivation event.

The interpretation of PCR results requires attention to the sample type and the agent's biology. A positive fecal PCR for Helicobacter species indicates current shedding, but a negative result does not rule out infection because shedding can be intermittent. Multiple sampling rounds may be needed to confirm freedom from infection. For agents such as murine norovirus, which is highly contagious and produces prolonged shedding, a single positive PCR in any animal should trigger a full room-level investigation.

## Sentinel Selection and Exposure

Sentinel animals are the primary means of detecting infections that circulate within a colony without producing clinical signs. The choice of sentinel stock is a critical decision. Outbred stocks such as Crl:CD1(ICR) are commonly used because they are robust, inexpensive, and immunocompetent, but they may not be as susceptible to certain agents as inbred strains. For agents with known strain-specific susceptibility, such as mouse hepatitis virus, the sentinel stock should be selected to match the susceptibility profile of the resident colony. Immunodeficient sentinels are sometimes used to amplify agents that do not infect immunocompetent animals, but they require enhanced biosecurity and are not appropriate for all facilities.

Sentinel exposure to soiled bedding is the standard method for detecting agents transmitted through fecal, urinary, or respiratory routes. The effectiveness of bedding transfer depends on the volume of bedding transferred, the frequency of transfer, and the duration of exposure. A common protocol transfers a defined volume of soiled bedding from each cage in the room to the sentinel cage on a rotating schedule, ensuring that every cage contributes material at least once per sampling interval. The sentinel is then held for a minimum of four weeks before testing to allow seroconversion. This period is adequate for most viral agents but may be insufficient for agents with delayed seroconversion, such as some bacterial infections.

Direct contact exposure is required for agents that do not survive well in the environment or that require close contact for transmission. Sendai virus and pneumonia virus of mice are transmitted by aerosol and can be detected through bedding sentinels, but agents such as ectromelia virus and lymphocytic choriomeningitis virus may require direct contact for reliable transmission. Some programs use a combination of bedding and contact sentinels, with contact sentinels housed in a single cage that is rotated through the room. The [NC3Rs guidance on refinement](https://www.nc3rs.org.uk/) supports the use of the minimum number of sentinels consistent with adequate detection, and this principle should guide the design of exposure protocols.

## Environmental and Molecular Monitoring

The limitations of sentinel-based surveillance have driven interest in environmental sampling as a complementary approach. PCR testing of exhaust dust from individually ventilated cages (IVC) can detect agents shed by any animal in the rack, providing room-level or rack-level coverage without the use of sentinel animals. This approach is particularly attractive for detecting agents that are shed in high quantities, such as murine norovirus and Helicobacter species, and it aligns with the refinement principle of reducing animal use. However, exhaust dust PCR does not detect agents that are not shed in detectable quantities, and it cannot distinguish between viable and non-viable organizms. A positive exhaust dust PCR should be followed by targeted testing of individual animals to confirm active infection.

The choice between sentinel-based and environmental monitoring depends on the facility's goals and resources. Facilities that prioritize the detection of a broad range of agents with high sensitivity may continue to rely on sentinels, while those that seek to reduce animal use or that house animals in IVC systems may adopt exhaust dust PCR as a primary screening tool. Hybrid programs use exhaust dust PCR for routine screening and retain sentinels for confirmatory testing and for agents that are poorly detected in environmental samples.

## Documentation and Reporting

Health monitoring data must be recorded in a format that supports trend analysis and regulatory review. Each sampling round should generate a report that lists the agents tested, the number of animals sampled, the test methods used, and the results for each agent. Positive results should be accompanied by the confirmatory test result, the affected room or rack, and the action taken. The [AVMA professional practice resources](https://www.avma.org/resources-tools) note that documentation standards should support both internal decision-making and external review by accrediting bodies.

The reporting structure should distinguish between agents that are excluded from the colony, agents that are monitored but tolerated, and agents that trigger immediate intervention. This classification should be defined in the health monitoring plan before results are generated, so that responses are consistent and do not depend on the individual interpreting the data. A positive result for an excluded agent should trigger a defined response pathway that includes confirmation, source tracing, quarantine, and a decision on depopulation versus rederivation.

| Monitoring Parameter | Sample Type | Primary Agents Detected | Frequency | Interpretation |
| --- | --- | --- | --- | --- |
| Serology | Serum | MHV, Sendai, MPV, TMEV, Mycoplasma pulmonis | Quarterly | Positive result requires confirmatory testing, seroconversion window is 2 to 4 weeks |
| Fecal PCR | Feces | Helicobacter spp., murine norovirus, Giardia, Spironucleus | Quarterly or on clinical suspicion | Positive result indicates active shedding, negative result does not exclude infection |
| Exhaust dust PCR | IVC exhaust filter or dust | MHV, MNV, Helicobacter, fur mites | Monthly to quarterly | Positive result indicates rack-level exposure, confirm with individual animal testing |
| Fur pluck or tape test | Fur and skin | Radfordia spp., Myocoptes spp., lice | At each sampling round | Direct visualization of mites or eggs confirms infestation |
| Contact sentinel serology | Serum | Agents requiring direct contact for transmission | Quarterly | Positive result indicates transmission within the room, review husbandry practices |

The health monitoring report should also record the colony's health status classification, such as SPF, defined flora, or conventional, and any changes to that classification during the reporting period. This information is essential for researchers who need to match animal health status to experimental requirements, and it provides the institutional animal care and use committee with the data needed to assess the adequacy of the surveillance program.

## Recognized Complications and Failure Modes

Health monitoring programs fail through predictable mechanisms. The most common is silent agent circulation in a colony that appears clinically normal. Many target agents, including murine norovirus, Helicobacter species, and Sendai virus in immunocompetent mice, produce subclinical infections that are detected only through scheduled sampling. A program that relies on clinical observation alone will miss these agents until they contaminate experimental data or spread to immunodeficient stocks.

False assurance from inadequate exposure represents a second failure mode. Sentinel animals that do not contact soiled bedding, do not remain in the room long enough to seroconvert, or are housed in ventilated cages with filtration that blocks particulate transfer will test negative while the resident colony carries infection. The discriminating check is to compare sentinel serology results against known colony history and to verify that sentinel housing matches the ventilation and caging conditions of the animals they represent.

Sample degradation and assay error produce both false negatives and false positives. PCR results can be suppressed by inhibitors in feces or by improper storage, while serology can yield false positives from maternal antibody in young animals or cross-reacting agents. Detection of a single positive result should trigger confirmatory testing on fresh samples before any colony-level action is taken.

| Observation | Likely cause | Discriminating check |
|---|---|---|
| Sentinel seronegative, resident colony PCR positive | Inadequate sentinel exposure or short exposure period | Verify sentinel age, exposure duration, and bedding transfer frequency, confirm sentinel caging matches colony ventilation |
| Positive PCR on one sample, all other tests negative | Sample contamination or assay artifact | Repeat testing on fresh samples, check extraction blanks and reagent controls |
| Seroconversion in sentinels but no agent found in colony | Sentinel contamination from another room or shared equipment | Review husbandry workflows, staff movement, and equipment sharing between rooms |
| Intermittent positive results across quarters | Low-prevalence agent or environmental reservoir | Increase sample size, test additional sites, and review import and quarantine records |
| Negative results despite clinical disease | Wrong agent targeted or sample type inappropriate | Review clinical signs against the agent panel, consult diagnostic laboratory for sample selection |

## Common Errors in Program Design

Less experienced personnel frequently design panels that are too broad or too narrow. A panel that includes every agent ever reported in the species wastes resources and generates false alarms from environmental contamination. A panel that omits agents endemic to the region or the vendor's colony leaves the facility blind to its most likely risks. The corrective action is to base the panel on a formal risk assessment that considers the source colony's health status, the experimental manipulations in use, and the immunocompetence of the animals housed.

Sampling errors are equally common. Pooling samples from too many animals dilutes low-level infections below the detection threshold. Testing only young animals misses agents that require longer exposure to seroconvert. Collecting samples at the wrong time relative to colony introduction, such as testing immediately after arrival before infections have amplified, produces false reassurance. The corrective action is to follow published sampling schedules that specify animal numbers, age ranges, and collection timing relative to colony establishment.

A third error is treating health monitoring results as static. A single clean quarterly report does not predict the next quarter. Facilities that reduce sampling frequency after a period of negative results lose the ability to detect introduction events early. The corrective action is to maintain a consistent sampling cadence and to increase sampling after any change in colony composition, vendor, or husbandry practice.

## Limitations of Current Evidence

The evidence base for health monitoring programs rests largely on institutional experience and consensus guidance instead of controlled comparative trials. The [Guide for the Care and Use of Laboratory Animals](https://grants.nih.gov/grants/olaw/guide-for-the-care-and-use-of-laboratory-animals.pdf) describes the expectation that institutions monitor colony health but does not prescribe a specific panel or frequency. Expert opinion differs on several points: whether soiled bedding sentinels are superior to direct contact sentinels, whether molecular testing of exhaust dust can replace sentinel animals entirely, and how frequently testing should occur in stable colonies.

The [NC3Rs resources on replacement, reduction and refinement](https://www.nc3rs.org.uk/) emphasize reducing animal use, which has driven interest in environmental sampling methods. However, the comparative sensitivity of exhaust dust PCR versus sentinel serology for all target agents is not fully established, and some agents may be detected more reliably by one method than the other. Facilities should validate any new sampling method against their established program before replacing sentinel animals entirely.

Regional variation also limits generalization. Agents that are endemic in one country may be absent in another, and import regulations affect the risk profile of incoming animals. The [WOAH terrestrial animal health standards](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) address disease surveillance for trade purposes but do not provide laboratory animal specific guidance. Institutions must adapt published recommendations to their local context.

## Escalation and Referral

Certain findings warrant immediate escalation beyond the routine program. Detection of an agent with zoonotic potential, such as lymphocytic choriomeningitis virus, requires notification of the institutional biosafety officer and occupational health service. Detection of an agent that threatens the validity of ongoing studies requires notification of the principal investigators whose animals may be affected. Detection of a novel or unidentified agent requires consultation with a diagnostic laboratory with expertise in laboratory animal pathogens.

Regulatory reporting obligations vary by jurisdiction and by the agent involved. Agents that are reportable in food animals or wildlife may not be reportable in laboratory colonies, and the reverse also applies. The [MSD Veterinary Manual](https://www.msdvetmanual.com/) provides species-specific guidance on the clinical significance of infectious agents, and the [AVMA practice resources](https://www.avma.org/resources-tools) address professional obligations around disease reporting. When in doubt, the attending veterinarian should contact the relevant regulatory authority to determine whether reporting is required.

Specialist consultation is appropriate when a colony is affected by an agent that is difficult to diagnose, when a disease outbreak does not respond to standard control measures, or when the facility lacks in-house expertise in a particular pathogen. Diagnostic laboratories can provide confirmatory testing, genotyping, and advice on eradication strategies. Consultation is also warranted before implementing a major intervention such as colony depopulation and rederivation, because the decision has substantial financial and animal welfare consequences.

## Frequently Asked Questions

### How Should a Health Monitoring Program Be Prioritized When the Budget Is Limited?

Prioritize agents that threaten research validity or human safety, then those with high morbidity in your specific colony. Direct funds toward testing the highest-risk populations, such as newly received animals and immunodeficient stocks, before expanding sentinel numbers. Environmental sampling of exhaust air dust and soiled bedding can reduce the number of individual animals tested while maintaining sensitivity for many agents. Consider pooling samples from multiple animals within the same housing unit, as this reduces per-sample costs while preserving herd-level detection. The [Guide for the Care and Use of Laboratory Animals](https://grants.nih.gov/grants/olaw/guide-for-the-care-and-use-of-laboratory-animals.pdf) emphasizes that surveillance should be appropriate to the risks posed by the animals and the research, which supports a tiered approach where lower-risk colonies receive less intensive monitoring.

### What Options Exist When Molecular Diagnostics Are Not Readily Available?

Serology and culture remain viable primary tools when PCR is unavailable. Serology detects prior exposure and is well suited to screening sentinel animals for viral agents, while culture with selective media remains the standard for bacterial agents such as *Helicobacter* and *Pasteurellaceae*. Histopathology of target organs, particularly lung, liver, and intestine, can identify lesions suggestive of specific infections, though it lacks sensitivity for subclinical carriage. When using these methods, extend the quarantine period and increase sampling frequency to compensate for lower sensitivity. The [MSD Veterinary Manual](https://www.msdvetmanual.com/) provides species-specific guidance on sample collection and interpretation for conventional diagnostic methods. Confirm any positive serology with a second modality before declaring a colony positive, as cross-reactivity occurs with several common agents.

### How Does Health Monitoring Differ for Non-Rodent Laboratory Species?

Rabbits, ferrets, swine, and nonhuman primates each require species-specific agent panels and sampling strategies. For rabbits, monitor for *Encephalitozoon cuniculi*, *Pasteurella multocida*, and *Treponema paraluiscuniculi*, with sampling of oral and nasal swabs instead of soiled bedding. Nonhuman primates require screening for tuberculosis, herpes B virus, and simian retroviruses, with individual animal testing instead of sentinel-based surveillance because of zoonotic risk and the value of individual animals. Swine and ferrets may carry influenza viruses with zoonotic potential, warranting integration with occupational health programs. The [WOAH terrestrial animal health standards](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) provide internationally recognized guidance on surveillance approaches for species where trade and zoonotic concerns apply. Consult species-specific references before designing any program, as agent prevalence and diagnostic test performance vary substantially across species.

### What Records Must Be Maintained for a Defensible Health Monitoring Program?

Maintain a master document listing the agents screened, testing frequency, sample types, and diagnostic methods for each animal room or colony. Record every test result, including negatives, with dates, animal identifiers, and laboratory accession numbers. Document all interventions taken in response to positive findings, including quarantine dates, re-testing schedules, and colony disposition decisions. Retain these records for at least the lifetime of the colony plus a defined archival period, as institutional audits and regulatory inspections may require retrospective review. The [AVMA practice resources](https://www.avma.org/resources-tools) note that contemporaneous documentation is the foundation of professional accountability in veterinary practice. Ensure that the attending veterinarian and the IACUC have ready access to summary reports and that significant positive findings are communicated within a defined timeframe, typically 24 to 72 hours.

### How Should Unexpected Positive Results Be Communicated to Investigators?

Communicate the finding first to the attending veterinarian and the facility director, then to the affected investigator in writing. State what was detected, the test method, and the confidence level of the diagnosis. Distinguish between agents that are likely to affect research data, such as mouse hepatitis virus, and those that are incidental, such as some commensal bacteria. Provide a preliminary risk assessment and the proposed response timeline, but avoid making definitive claims about study impact before confirmatory testing is complete. The [NC3Rs resources on refinement](https://www.nc3rs.org.uk/) emphasize that transparent communication about animal health status supports both welfare and research quality. Offer the investigator a consultation to review how the agent might interact with their specific experimental model, and document this communication in the health monitoring records.

### When Should a Colony Be Depopulated instead of Managed by Eradication?

Depopulation is indicated when the agent causes significant clinical disease, when it cannot be reliably eliminated by rederivation or quarantine, or when eradication costs exceed the value of the colony. Agents such as mouse hepatitis virus and Sendai virus in immunodeficient stocks often warrant depopulation because of high morbidity and the difficulty of eliminating infection. Eradication by embryo transfer or cesarean rederivation is preferred when the genetic line is irreplaceable or when the agent is of moderate concern. Consider the availability of clean replacement stock and the time required to re-establish breeding colonies. The [Guide for the Care and Use of Laboratory Animals](https://grants.nih.gov/grants/olaw/guide-for-the-care-and-use-of-laboratory-animals.pdf) states that veterinary judgment must balance animal welfare, research needs, and practical feasibility when making colony disposition decisions. Document the rationale for the chosen approach, as this decision will be reviewed by the IACUC and may be scrutinized during accreditation inspections.

## Related Clinical & Scientific Guides

* [Refining IACUC Protocols to Minimize Animal Pain and Distress](/knowledge/veterinary-medicine/laboratory-animal-science/refining-iacuc-protocols-minimize-animal-pain-distress)
* [Anesthetic Risk Assessment in Laboratory Animals: Preoperative Evaluation](/knowledge/veterinary-medicine/laboratory-animal-science/anesthetic-risk-assessment-in-laboratory-animals-preoperative-evaluation)
* [Selecting Animal Models for Infectious Disease Research](/knowledge/veterinary-medicine/laboratory-animal-science/selecting-animal-models-for-infectious-disease-research)


## References and Further Reading

- [National Antimicrobial Resistance Monitoring System: Two Decades of Advancing Public Health Through Integrated Surveillance of Antimicrobial Resistance.](https://pubmed.ncbi.nlm.nih.gov/28792800/). 2017.
- [Cyanobacteria and algae blooms: Review of health and environmental data from the Harmful Algal Bloom-Related Illness Surveillance System (HABISS) 2007-2011.](https://pubmed.ncbi.nlm.nih.gov/25826054/). 2015.
- [Safety of green tea extracts : a systematic review by the US Pharmacopeia.](https://pubmed.ncbi.nlm.nih.gov/18484782/). 2008.
- [Exposure and effects assessment of persistent organohalogen contaminants in arctic wildlife and fish.](https://pubmed.ncbi.nlm.nih.gov/19910021/). 2010.
- [The Belgian PCB/dioxin incident: analysis of the food chain contamination and health risk evaluation.](https://pubmed.ncbi.nlm.nih.gov/11896663/). 2002.
- [Wildlife as Sentinels of Antimicrobial Resistance in Germany?](https://pubmed.ncbi.nlm.nih.gov/33585611/). 2020.
- [Guide for the Care and Use of Laboratory Animals, 8th Edition](https://grants.nih.gov/grants/olaw/guide-for-the-care-and-use-of-laboratory-animals.pdf). National Academies Press, 2011.
- [NC3Rs Resources on Replacement, Reduction and Refinement](https://www.nc3rs.org.uk/). NC3Rs.
- [MSD Veterinary Manual, Professional Edition](https://www.msdvetmanual.com/). MSD Veterinary Manual.

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> This article is educational professional reference material for veterinary audiences. It is not a substitute for veterinary diagnosis, individual clinical judgment, current product labeling, or applicable regulatory requirements.