5 Introduction

In Part II information on the infectious agents of mice and rats is presented by using an organ system approach. This approach was chosen for pragmatic reasons. For most individuals (although not for erudite specialists) concerned with the whole animal, it is easier to organize thoughts around organ system presentations of clinical, pathological, etiological, and other data sets than approaches such as taxonomic groupings of agents. We hasten to add, however, that the organ system approach also has its disadvantages. Many agents do not affect a single organ system by infection or disease expression. Thus, final decisions in deciding groupings sometimes became very arbitrary.

Within the organ system groupings, information on each agent is presented, as much as is feasible, in a standard outline format. The intent has been to provide objective, reliable data applicable to contemporary rodent populations. Data collected 20 or more years ago often are out of date and misleading (except possibly for those few stocks that have never been rederived by cesarean section).

The standard outlines for information on each agent include subheadings with the following definitions and contents:

Significance. An overall appraisal of the real or potential importance of each agent as a research complication for the general biomedical community that uses the host species (mouse or rat). In instances where an agent poses risks unique to research results in one or more specialized disciplines, this is emphasized.



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OCR for page 31
--> 5 Introduction In Part II information on the infectious agents of mice and rats is presented by using an organ system approach. This approach was chosen for pragmatic reasons. For most individuals (although not for erudite specialists) concerned with the whole animal, it is easier to organize thoughts around organ system presentations of clinical, pathological, etiological, and other data sets than approaches such as taxonomic groupings of agents. We hasten to add, however, that the organ system approach also has its disadvantages. Many agents do not affect a single organ system by infection or disease expression. Thus, final decisions in deciding groupings sometimes became very arbitrary. Within the organ system groupings, information on each agent is presented, as much as is feasible, in a standard outline format. The intent has been to provide objective, reliable data applicable to contemporary rodent populations. Data collected 20 or more years ago often are out of date and misleading (except possibly for those few stocks that have never been rederived by cesarean section). The standard outlines for information on each agent include subheadings with the following definitions and contents: Significance. An overall appraisal of the real or potential importance of each agent as a research complication for the general biomedical community that uses the host species (mouse or rat). In instances where an agent poses risks unique to research results in one or more specialized disciplines, this is emphasized.

OCR for page 31
--> Perspective. Key developments in evolution of knowledge concerning infection with each agent including its natural history, host effects, diagnosis, control, and significance. Agent. A listing of those characteristics important to recognition, laboratory manipulation, and control of each agent. Includes taxonomy, strains, morphology, cultural requirements, biochemical reactions (bacteria), stability (viruses), and inactivation (viruses). Hosts. Does the infection occur in mice, rats, or both? Are they the natural, reservoir, or incidental hosts? What other laboratory animals can serve as hosts? Are there reservoir hosts for mice and rats? Epizootiology. Epizootiology of the infection plus consideration of specific ecological niches inhabited by the agent inside and outside of the host(s). Clinical. Clinical signs of infection, if any. The majority of natural infections in mice and rats are subclinical or have only transient clinical signs. Pathology. Strain differences in susceptibility (if known), pathogenesis, gross pathology, histopathology, pathology of infection in immunodeficient or immunosuppressed hosts (if different from that in immunocompetent hosts), and immune response(s). Diagnosis. Direct and indirect methods for agent detection, including serology, culture, and immunofluorescence, with comments on sampling and interpretation of results, as appropriate. Guidelines are given for pathologic workups on diseased animals. Control. Methods most likely to succeed in prevention of infection are emphasized. Approaches to eradicating or limiting spread of established existing infections are also presented. Medications usually are not given as their use may impose additional variables on experiments. Interference with research. A compilation from the literature of specific examples in which the agent was found to complicate research results or alter host responses.