Effect of Critical Processing Stages and Interventions on Campylobacter in Poultry Meat at the Slaughterhouse Level: A Comprehensive Meta-Analysis

Campylobacter spp. are a major foodborne zoonosis, and poultry slaughterhouses are One Health interfaces where animal carriage, environmental reservoirs and worker exposure intersect. We performed a comprehensive systematic review and meta-regression to quantify how slaughter stages and in-plant interventions affect Campylobacter concentration and prevalence on poultry carcasses and meat. The Scopus literature search engine was accessed to collect articles that focused on observational studies and challenge tests, reporting results on Campylobacter concentrations or prevalence in both pre-stage/non-intervened and post-stage/intervened groups. From a total of 4080 studies initially retrieved, 71 were eligible for inclusion in the meta-analysis, yielding 1256 observations. Meta-regression models were adjusted according to the type of outcome measure: log10 reduction for concentration outcomes and ln risk ratio (ln RR) for prevalence outcomes. Meta-analysis showed reductions in Campylobacter counts after scalding (0.898 log10 reduction on neck skin p < 0.001), carcass rinsing with water (0.523 log10, p = 0.043), and after sanitisation combined with chilling (0.692 log10, p < 0.001). Although significant, chilling was found to slightly decrease Campylobacter prevalence by 8% (95% CI: 1–17%; ln RR = 0.082, p = 0.032). Intervention strategies reducing Campylobacter concentrations included processing in colder climates (autumn and winter) (1.927 log10, p = 0.005), application of plant extracts (1.493 log10, p = 0.008), use of organic acids (1.192 log10, p < 0.001) and chemical carcass sanitisation (1.031 log10, p < 0.001). Organic acids also reduced the prevalence of Campylobacter in poultry carcass slaughter groups (ln RR = 1.079, p = 0.009), whereas freezing did not reach statistical significance (0.740 log10, p = 0.288). Environmental synthesis highlighted high pooled prevalence in transport crates (0.833, 95% CI 0.765–0.885) and among operators (0.732, 95% CI 0.404–0.917), supporting their role as reservoirs and vectors. Meta-regressions demonstrated that the measured effectiveness of slaughter stages and intervention strategies were driven by key moderators, namely, sample weight, type of sample, type of chemical/organic acid/extract and its concentration, mode of application and storage time. Despite substantial heterogeneity and small study effects for concentration, the evidence supports the implementation of a multi-barrier One Health strategy combining the control of incoming contamination, hygiene of equipment and personnel, and optimised rinsing/sanitisation and chilling to reduce consumer risks.