An integrated qualitative farm-to-fork approach to rank foodborne pathogens associated with mastitis-affected raw milk from Irish dairy farms to the consumer

A qualitative microbial risk assessment (MRA) framework was applied to evaluate the potential introduction of foodborne pathogens from bovine mastitis raw milk into the dairy chain. In a survey between January and December 2024, 588 raw milk samples were obtained from mastitis affected cows across 66 Irish dairy farms. Following guidelines from the International Dairy Federation and National Mastitis Council, samples were analysed for mastitis pathogens, where 337 positive samples (55.3 %) were further tested for seven foodborne microbial pathogens using a hierarchical testing strategy with ten culture-based methods. A qualitative MRA guided by the FAO/WHO and EFSA framework was developed in this study. Incorporating stages of the risk assessment paradigm that include hazard identification, hazard characterisation, exposure assessment, and risk characterisation through a structured decision-tree approach. For the survey, Streptococcus spp. was most frequently isolated (n = 123), followed by Escherichia coli (n = 76), Staphylococcus aureus (n = 67), and coagulase-negative staphylococci (CNS) (n = 39). Less frequently detected pathogens included Enterococcus spp. (n = 15), Salmonella spp. (n = 4), and Bacillus cereus (n = 1). Exposure assessment and risk characterisation identified S. aureus, E. coli, and Salmonella spp., as high risk, necessitating targeted interventions within dairy chain systems, including processing failures. This study provides novel insights into the risks posed by mastitis-associated foodborne pathogens, facilitating evidence based recommendations for improving dairy safety management in the dairy chain.