Effectiveness of Interventions and Control Measures in the Reduction of Campylobacter in Poultry Farms: A Comprehensive Meta-Analysis

<i>Campylobacter</i> is a leading foodborne bacterial pathogen, and poultry production is a major reservoir contributing to human exposure. Reducing <i>Campylobacter</i> at farm level is therefore critical to limit downstream contamination. This systematic review and meta-analysis aimed to identify and quantitively summarise the current interventions and control measures applied in poultry farms to control the contamination and bird colonisation by <i>Campylobacter</i>. The Scopus electronic database was accessed to collect primary research articles that focused on observational studies and in vivo experiments, reporting results on <i>Campylobacter</i> concentrations or prevalence in both non-intervened and intervened groups. A total of 4080 studies were reviewed, from which 112 were selected and included in the meta-analysis according to predefined criteria, yielding 1467 observations. Meta-regression models were adjusted to the full data set and by intervention strategy based on the type of outcome measure (i.e., concentration and prevalence). In general terms, the results reveal that the effectiveness to reduce <i>Campylobacter</i> colonisation vary among interventions. A highly significant effect (<i>p</i> < 0.001) was observed in interventions such as organic acids, bacteriophages, plant extracts, probiotics, and organic iron complexes added to feed or drinking water; although drinking water was proven to be a more effective means of administration than feed for extracts and organic acids. In contrast, interventions such as chemical treatments, routine cleaning and disinfection, and vaccination showed both lower and more heterogeneous effects on <i>Campylobacter</i> loads. Vaccination effects were demonstrated to be driven by route and schedule, with intramuscular administration, longer vaccination periods and sufficient time before slaughter linked to greater reduction in <i>Campylobacter</i> colonisation. Probiotics, plant extracts and routine cleaning and disinfection were associated with lower <i>Campylobacter</i> prevalence in flocks. Meta-regression models consistently showed that the interventions were proven more effective when the sample analysed was caecal contents in comparison to faeces (<i>p</i> < 0.001). Overall, the findings of this meta-analysis study emphasise the application of a multi-barrier approach that combines targeted interventions with robust biosecurity and hygiene measures in order to reduce <i>Campylobacter</i> levels in poultry farms.