SPONTANEOUS AND EXPERIMENTAL INFECTIONS IN SCID AND SCID BEIGE MICE

Severe combined immunodeficient (scid) mice are valuable animals to st udy a variety of physiologic and disease processes. Their capacity to support multiple tissue xenografts permits these mice to be used as in termediate models for host-specific, fastidious organisms for which a small animal model has not been available previously. However, because they are unable to mount a normal immune response, they are very susc eptible to a variety of primary and opportunistic microbial pathogens. Fatal, naturally occurring infections with bacteria such as Proteus m irabilis, Streptococcus viridans, and Escherichia coli have been obser ved. In addition, based on observations after experimental or naturall y occurring viral infections, scid and scid/beige mice have been shown to be very susceptible to infections with viruses such as mouse hepat itis virus, Sendai virus, and murine respiratory virus, with resulting mortality. Of the parasitic infections, Pneumocystis carinii is a rel atively common contaminant of the respiratory tracts of scid mice and may complicate research projects, particularly experimental respirator y tract infections. In view of the enhanced susceptibility of these mi ce to infections of this type, it is essential that they be housed und er optimal conditions, which include implementing stringent management practices and a functional barrier system.