The SPF Pig in Research.

Abstract

The domestic (meat type) pig, Sus scrofa domestica, has become a common research animal used in biomedical research due to similarities to humans in many of the organ systems. So similar, in fact, that axenic, gnotobiotic, and specific pathogen-free pigs are being promoted as potential sources of organs available for xenotransplantation (Ye and others 1994). These 3 levels of microbial status, while having important differences, are commonly confused because many of the derivation and maintenance practices are similar. Pigs, like other laboratory animals, may be produced using 4 basic levels of care. Conventional animals are produced without standardized controls for microbial status. Domestic pigs and miniature pigs produced under conventional practices vary in health status, known genetic background, and level of available herd historical information. Axenic, or germ-free, pigs are produced and maintained free of any known microbial agents. Gnotobiotic animals are produced with a known flora of microbial agents. Axenic and gnotobiotic pigs are surgically delivered and maintained under strict isolation. Gnotobiotic pigs are subsequently inoculated with a known microbial flora. True gnotobiotic and axenic pigs are not generally available commercially as they are very expensive to produce and maintain. Specific pathogen-free (SPF) animals are produced free of specific microbial agents. These animals are derived using gnotobiotic procedures but are then maintained in more conventional facilities. With SPF animals, management and care procedures are geared towards restricting entry of specific indicator disease syndromes. In swine the designation SPF has a proprietary commercial meaning as well. The purpose of this paper is to clarify the definition of domestic SPF pigs, and discuss their appropriateness for biomedical research.