A Systematic Review of Literature on Pork Chain Epidemiology

This systematic review identified areas in the pork production chain where research is repetitive or lacking, and what can be done to “fill in the gaps” in risk assessment models. The process of systematic review reduces bias in the selection of research studies by the comprehensiveness and reproducibility of the search strategy and the transparent selection of articles included in review.

Co-funded by the Pork Checkoff

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Objectives

The objective of the review was to describe, based on all available studies identified, the points of introduction and amplification of Salmonella spp. in the pork production chain. The pork production chain was divided into slaughter-to-cooler, and post-cooler to-finished raw product prior to retail. Studies relevant to the review were those that reported measuring Salmonella spp. at multiple points on the same processing chain.

Conclusions

The slaughter-to-cooler review identified 15 publications describing 40 studies that evaluated the prevalence of Salmonella spp. on carcasses.  The review provides little evidence that Salmonella is introduced into the pork product as it moves along the processing chain to the cooler.  On the contrary, the aggregated data across the studies suggest that the processes employed from slaughter to the cooler are associated with steady decreases in Salmonella spp. prevalence.

The post-cooler to finished raw product review was unable to identify sufficient studies for an aggregate analysis, similar to that conducted for the slaughter-to-cooler review. From 713 references identified during the literature search, only four manuscripts describing 12 studies reported evaluating Salmonella spp. prevalence at multiple points in the post-cooler production process. This paucity of publically available information has previously been noted. Berands et al  (1998) noted that information about cutting plants was rare and “practically all of which is published in confidential reports in Dutch or in specialized books of limited circulation”¹.

Deliverable

There are two potential impacts of this project on the meat industry. First, the slaughter-to-cooler review provides publically available empirical evidence for the efficacy of the procedures employed in modern pork production systems to control Salmonella spp (Figure 1). The finding that Salmonella spp. prevalence consistently decreases during processing, even in a variety of settings, provides evidence that the processes are robust. This information could be used to convey to the consumer, the efficacy of the measures taken to control Salmonella spp. from slaughter to the cooler.

The results of the post-cooler to finished raw product review indicate a paucity of publically available information about this aspect of pork production. The reviewers acknowledge that it is possible this information is available but subject to confidentiality agreements. The impact of the paucity of available data is that empirical evidence of efficacy of control programs in the post-cooler side of pork processing is not available.

If the industry or consumers are interested in a public document that summarizes the ecology of Salmonella spp. post-chilling in pork then more data are needed. If the reviewers are correct and much of this data is available but confidential, then it may be efficient to develop a mechanism, by which, data from already completed confidential studies which have evaluated post-cooling Salmonella spp. prevalence could be available for an aggregate analysis, similar to that conducted in the slaughter-to-cooler review.  If the reviewers are incorrect and the studies have not been conducted, then primary research in this area could be needed.