Year: 1998
Type: article
Abstract: Steven H. Weisbroth, D.V.M., is President of AnMed Biosafe Inc., Rockville, Maryland; Robert Peters, Ph.D., is Scientific Director at MA Bioservices, Rockville, Maryland; Lela Riley, Ph.D., is Associate Professor at the University of Missouri, Columbia, Missouri; and William Shek, D.V.M., Ph.D., is Director of Diagnostic Services at Charles River Laboratories, Wilmington, Massachusetts. Steven H. Weisbroth, D.V.M., is President of AnMed Biosafe Inc., Rockville, Maryland; Robert Peters, Ph.D., is Scientific Director at MA Bioservices, Rockville, Maryland; Lela Riley, Ph.D., is Associate Professor at the University of Missouri, Columbia, Missouri; and William Shek, D.V.M., Ph.D., is Director of Diagnostic Services at Charles River Laboratories, Wilmington, Massachusetts. Steven H. Weisbroth, D.V.M., is President of AnMed Biosafe Inc., Rockville, Maryland; Robert Peters, Ph.D., is Scientific Director at MA Bioservices, Rockville, Maryland; Lela Riley, Ph.D., is Associate Professor at the University of Missouri, Columbia, Missouri; and William Shek, D.V.M., Ph.D., is Director of Diagnostic Services at Charles River Laboratories, Wilmington, Massachusetts. Steven H. Weisbroth, D.V.M., is President of AnMed Biosafe Inc., Rockville, Maryland; Robert Peters, Ph.D., is Scientific Director at MA Bioservices, Rockville, Maryland; Lela Riley, Ph.D., is Associate Professor at the University of Missouri, Columbia, Missouri; and William Shek, D.V.M., Ph.D., is Director of Diagnostic Services at Charles River Laboratories, Wilmington, Massachusetts. Participants in the September 1997 Workshop on Opportunistic Infections of Rats/Mice, held in Washington, DC, attempted to deal with the issue of defining “opportunistic” agents. Although they were unable to reach consensus regarding universally applicable guidelines to usefully distinguish between “primary pathogens,” “opportunists,” and “commensals,” they did agree that the issue hinges largely on host constitutional factors of relative resistance and susceptibility to given microbial forms. Impaired immunocompetency was first recognized in the 1950s and 1960s as a physiological consequence of animals undergoing protocols in radiation biology and pharmaceutical corticosteroid and antimetabolite development. Latent, usually clinically silent microbial forms that include Pneumocystis carinii, Corynebacterium kutscheri, Pseudomonas aeruginosa, and Clostridium piliforme became recognized as concomitants of such research ( Weisbroth 1995 ) and were important in prompting development of health surveillance programs. Since then, in addition to chemical modes of impairment of normal rodents, numerous inherited models of immunodeficiency have been developed and used commonly. Examples include athymic (nude) mice and rats and mice with severe combined immunodeficiency (SCID1). Confounding the issue is the proliferating use of mouse and rat inbred strains and transgenics with bioengineered genomes that may have impaired or fragile immunocompetency as a deliberate (or accidental) inherited character. Since the early 1980s, a substantial literature base has accumulated to document disease episodes in immunodeficient rodents with infectious agents that are usually clinically silent in their immunocompetent counterparts. Workshop participants, for example, considered both “primary pathogen” and “opportunistic” as a definition for defining the pathogen status of Pneumocystis carinii . For immunocompetent rodents, Pneumocystis is a rarely encountered opportunist diagnostically; however, for immunodeficients, there is an established record for Pneumocystis as a primary pathogen ( Kitada and Serikawa 1994 ; Weisbroth 1995 ). Additionally, a considerable list of viral, protozoan, bacterial, and helminth pathogens are similarly clinically silent in immunocompetent hosts although they produce disease in immunodeficient rodents. A similar situation has been shown with Sendai virus infection in inbred and outbred mouse strains ( Parker and others 1978 ), and considerable data have accumulated more recently on the role of certain Helicobacter species as pathogens of some mouse strains but not others ( Ward and others 1994b , 1996 ). Thus, the Workshop participants' problem was whether to define “pathogen” at the level of the normatively resistant host or at the level of the most susceptible. For the present, their position is to recognize that issues of infectivity and pathogenicity are influenced as much by host-related factors of resistance and susceptibility as by biological properties of specific infectious agents. Workshop participants acknowledge that health report recipients (investigators and animal facility managers) must be able to understand the significance of positive findings, particularly if clinically inapparent, in making animal colony health management and procurement decisions. They also recognize---and emphasize---that few facile, universally applicable guidelines are available to simplify the process. For example, although there is universal consensus that a sustained finding of antibodies to lymphocytic choriomeningitis virus or isolation of Salmonella typhimurium for and there is such consensus for such as Helicobacter or . is that the to the issue of in rodents. of the health status of rats and mice may be as the of given of species a specific of agents of disease to define the health status of the of is to of disease and to the microbial status of of such data on a forms the on to the microbial status of and procurement for on animal health and the health status of research animal undergoing or in research and of health surveillance is to by of or more the in a of pathogen a specific of infectious agents. an is in the the as the or research animal be considered (or with the is the to of a specific of agents and research may be to be a list of that and have is to the of for of of the as the of animals (or the with also on a for the health status of at of research and of to in the status of such or to that there have been of health surveillance is established ( ; and ; and 1997 ; and others 1994 ; and ; ; and others 1996 ; ; and others 1994 ; and others ). the for the and of ( 1996 ), used as the for by the for and of a health as of animal is some however, in the such are the and of agents considered of to have on the the of animals or in the the of and the and of animals in the is surveillance the of of is to the surveillance to specific and to the the available for the of on the of pathogen the to the health status of rodents to of disease and to the status of animal health and animal at to the of specific in of the be considered in the significance of clinically pathogens as positive on significance of such is on in the literature and of to hosts of the not on animal health but also to the physiological of such microbial as a in the research process. to of the (or of that animal the to such in of of to to and to by the infectious is an important and in the that the of a positive finding or an animal with a be not for specific at an a or but also more in of the animal research as a are for and to the or with of the and of the of the may have on the and of the animals ( Weisbroth and others ). the for is important to a that the of the the the and strains the and status of the and and in the as of the or of the and be most animals for health surveillance be clinically normal in if factors are in of and in the surveillance to use for a For example, is to a for virus athymic or rodents. of to be used is by of the of agents for on the the have or of agents to agents for in the the to be and be for of of the animal be to (or and to the an of for a health surveillance the may between but most a similar to that shown in . of for a health surveillance of for a health surveillance of pathogens in animals is a of For the for of was of the a or biological of the of the Since that a of have been developed and are used to pathogens in mice and used to a specific on a of the of the of the the status of the the or of of the in the and the that have been developed to and the of agents is by as or with the and the in to are by and to a of to the specific and species of colony certain are on a to of a pathogen or of in the For if Helicobacter is or are that the of Although in of species is some species are to in they or the of For example, a and piliforme not on but the of certain For is more and such as or are also be by in of agents be by the of are primary and established are by an the the and with to the a are or to primary be a of in be for most to to a or more are usually with are on the of the of the others are they are to of a of are for to and for the of virus by the of in the such as and of the of or of are a but be recognized by of with or of some in is particularly For or may be used as to were used for with the development of are used for or are similar to primary that the is not with to the the virus to in but the to to a a that may for some have been shown to be particularly for isolation of some ( and others ; and ). be in or is mouse must be in in mice ( ). virus isolation is and in is used as a primary Although of is the with are are used to infectious agents in animals and biological ) and rat ) have been used to the of infectious virus in biological such as or ( and ; ; and others ). and mice or rats are with the held for to of an to agents in the and is for the of antibodies to Although and an for virus they are more virus isolation ( and ; ). to as a is that is to and rodents must be and held in a for or is also used to the animal is with an such as or of is on the that rodents with a disease of the host of the has been used to pathogens piliforme ( ; and others ) and carinii ( and others ). 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Source: ILAR Journal
Authors: S. H. Weisbroth, R. Peters, L. K. Riley, W. Shek
Language: English
Subfield: Microbiology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: bronze
OpenAlex ID: W2316659925