Study of Salmonella detection in laying hens using a Bayesian model

Area of Science:

• Veterinary Public Health
• Food Safety
• Epidemiology

Background:

• National Control Programmes (NCPs) are crucial for reducing Salmonella prevalence in UK poultry.
• Statutory testing monitors Salmonella, particularly serovars Salmonella Enteritidis (SE) and Salmonella Typhimurium (ST), linked to human illness.
• Effective testing balances sensitivity for detection with resource efficiency.

Purpose of the Study:

• To estimate the sensitivity of Operator and Competent Authority (CA) Official sampling methods for detecting infected poultry flocks.
• To determine the true prevalence of Salmonella-infected commercial laying flocks in Great Britain annually from 2009-2018.
• To analyze trends in Salmonella prevalence for both SE/ST and non-SE/ST serovars.

Main Methods:

• A Bayesian model was developed using National Control Programme (NCP) data from 2009-2018.
• The model estimated the sensitivity of Operator and CA Official sampling.
• True prevalence of infected holdings and annual trends were calculated.

Main Results:

• Operator sampling sensitivity was low (~9%), while CA Official sampling sensitivity was higher (~44%).
• True prevalence of non-SE/ST infected holdings decreased from 3.9% to 1.6% annually; SE/ST decreased from 0.8% to 0.2%.
• Annual reductions in true prevalence averaged 10.6% for non-SE/ST and 15.9% for SE/ST.

Conclusions:

• The NCP has been effective in reducing Salmonella prevalence in commercial laying flocks.
• Salmonella prevalence reductions met or exceeded the target of 10% per annum for regulated serovars.
• True prevalence of SE/ST remained below the target of 2% throughout the study period.