ABSTRACT
The Germfree (GF) animal makes it possible to conduct clean “endpoint studies”: no uncontrolled microbial infection will affect the disrupted or declining functional capabilities of the animal under study. It was thus recognized early on that the GF animal, and for that matter also the GN animal, are models of choice for studies in, e.g., radiation, lethal trauma, and aging. The absence of an otherwise undefined microflora makes it possible to create gnotobiotes harboring the offending organism and to study the resulting pathology in a microbiologically controlled environment. Diseases of viral origin create additional problems in the pork industry. J. E. Collins et al. described the pathology resulting from infection with the swine infertility and respiratory syndrome virus. P. G. Halbur et al. have described the syndrome caused by porcine respiratory coronavirus porcine respiratory coronavirus, characterized by necrotizing and proliferative bronchointerstitial pneumonia.
