and serology. If a disease or infectious agent is identified in a facility or colony, the choice of therapy should be made by the veterinarian in consultation with the investigator. If the animal is to remain in the study, the selected treatment plan should be therapeutically sound and, when possible, interfere minimally with the research process.

Subclinical microbial infections (see Appendix A, Pathology, Clinical Pathology, and Parasitology) occur frequently in conventionally maintained rodents but can also occur in facilities designed and maintained for production and use of pathogen-free rodents if the microbial barrier is breached. Examples of infectious agents that can be subclinical but that may induce immunologic changes or alter physiologic, pharmacologic, or toxicologic responses are noroviruses, parvoviruses, mouse hepatitis virus, lymphocytic choriomeningitis virus, and Helicobacter spp. (Besselsen et al. 2008; Clifford and Watson 2008; NRC 1991a,b,c). Scientific objectives of a particular protocol, the consequences of infection in a specific strain of rodent, the potential for zoonotic disease, and the adverse effects that infectious agents may have on other animals or protocols in a facility should determine the characteristics of rodent health surveillance programs and strategies for keeping rodents free of specific pathogens.

The principal methods for detecting microbial infections in animal populations are serologic tests (e.g., flow cytometric bead immunoassays, immunofluorescent assays) but other methods, such as DNA analysis using polymerase chain reaction (PCR), microbial culture, clinical chemistry (e.g., lactate dehydrogenase virus), histopathology, and other validated emerging technologies, can also be used to make or confirm a diagnosis.

Transplantable tumors, hybridomas, cell lines, blood products, and other biologic materials can be sources of both murine and human viruses that can contaminate rodents or pose risks to laboratory personnel (Nicklas et al. 1993); rapid and effective assays are available to monitor microbiologic contamination and should be considered before introducing such material into animals (Peterson 2008).

Because health monitoring programs are dependent on the size and complexity of the Program, the species involved, and the institutional research focus, it is beyond the scope of the Guide to go into details about health monitoring programs for all species; additional references are in Appendix A (under Disease Surveillance, Diagnosis, and Treatment; Pathology, Clinical Pathology, and Parasitology; and Species-Specific References).


Healthy, well-cared-for animals are a prerequisite for good-quality animal-based science. The structure of the veterinary care program, including the number of qualified veterinarians, should be appropriate to fulfill the

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