The BcglltylLsh locus is a major gene controlling early phases of infection with intracellular parasites in mice.Natural resistance associated macrophage protein 1 (Nrampl) has been shown to be the Beg gene in mice. Analysis of a bovine cDNA homolog of murine Nrampb designated as bovine NRAMPI, predicted a 548-amino-acid protein with hydrophobic domains, an amino-terminal SH3-binding domain, and a conserved consensus transport motif. Northern blotting indicated that bovine NRAMP1 was expressed primarily in macrophages and tissues of the recticuloendothelial system. Bovine NRAlqPI was mapped to BTA 2 within syntenic loci conserved on HSA 2q and MMU I.

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Despite traditional disease control measures, losses attributable to infectious diseases continue to impede the livestock industries. An alternative approach to this problem is genetic disease resistance involving both immune and non-immune mechanisms, which is the inherent capacity of a previously unexposed animal to resist disease when challenged by pathogens. Although the nurturing environment influences variability in disease expression, natural resistance has been found to be inheritable and is transmitted from parent to offspring. Thus, an alternative approach to enhancing animal health management systems is to increase the overall level of genetic resistance at herd and population levels by using selective breeding programmes. The purpose of this review is to bring veterinarians, regulatory officials, industry representatives and animal technicians up to date with the principles and applications of genetic resistance as an adjunct to traditional interventions to control bacterial diseases of livestock. Although genetic resistance to bacterial diseases is often regulated by multiple genes controlling different processes of the host-pathogen interaction, the genetics of natural resistance is being unravelled increasingly by identification and characterisation of candidate genes, microsatellite markers and comparative gene mapping, to develop more practical methods of application.

Genetically based natural resistance to brucellosis in cattle provides for novel strategies to control zoonotic diseases. Bovine NRAMP1, the homologue of a murine gene (Bcg), has been identified as a major candidate for controlling the in vivo resistant phenotype. We developed an in vitro model for expression of resistance-and susceptibility-associated alleles of bovine NRAMP1 as stable transgenes under the regulatory control of the bovine NRAMP1 promoter in the murine RAW264.

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