17.07.2025

Zoonoses and Public Health, 2025

A new study published in Zoonoses and Public Health presents the first comprehensive analysis of the outcomes of France’s National Control Programme (NCP) for Salmonella in laying hen flocks, following the implementation of EU-harmonized regulations in 2013. Covering 108,718 sampling events conducted in 4,744 poultry houses between 2013 and 2021, the study aimed to identify risk factors associated with the detection of target Salmonella serovars (STS), including S. Enteritidis, S. Typhimurium, its monophasic variants, and S. Kentucky. 
Key Findings:
- STS were detected in 0.68% of sampling events, with an increase from 0.48% in 2013 to 0.99% in 2020.
- Cage production systems were associated with a significantly higher risk of STS detection compared to on-floor, free-range, and organic systems (OR = 1.6).
- Samples collected by the Competent Authority (CA) showed a markedly higher detection rate (OR = 3.1) compared to those collected by Food Business Operators (FBOs), attributed to targeted, risk-based sampling strategies and more comprehensive sampling protocols.
- Sampling events involving six or more samples were associated with a higher likelihood of detection (OR = 2.8).
- The risk of detection was higher in the third and fourth quarters of the year and in the eastern and southern regions of France.
- The years 2016, 2020, and 2021 showed significantly higher detection rates, partly correlating with regulatory changes in confirmation sampling practices.
- The 2018 revision of the French NCP, which limited confirmation sampling following a positive result, contributed to an increase in the number of officially recorded positive cases.

Remark:
No information on flock characteristics, such as flock size, hen age at the time of sampling, or Salmonella vaccination status, was available. The use of live Salmonella vaccines remained strictly restricted until 2023.