Salmonella surveillance in raw pet food and dogs in Great Britain, 2013-2022

Lucy C Snow^1*Andrew D Wales²Susan M Withenshaw¹Joanna R Lawes¹Adrienne Mackintosh¹Francesca Martelli¹

• ¹Animal and Plant Health Agency (United Kingdom), Addlestone, United Kingdom
• ²University of Surrey, Guildford, United Kingdom

Background. The rising popularity of raw meat pet food for dogs in Great Britain has prompted concerns about its potential role in transmitting zoonotic pathogens, particularly Salmonella. Aim. To investigate correlations between Salmonella isolated from dog food (both raw and heat-treated) and from dogs, using historical passive surveillance data from manufacturing plants and clinical samples. Methods. Data collected by the Animal and Plant Health Agency from 2013 to 2022 (phenotypically-determined Salmonella serovars plus their phage types and disc-diffusion antimicrobial resistance profiles) were compared between dog food and canine clinical sources. Results. Over time both the number and serovar diversity of Salmonella isolations from raw meat pet food increased, from 4 isolates of 4 serovars in 2013 to 606 isolates of 39 serovars in 2022, in parallel with a five-fold increase in the number of raw meat pet food plants operating in Great Britain. Between 2021 and 2022, following the implementation of statutory Salmonella reporting in dogs, considerable overlaps in serovar distributions were observed between raw meat pet food and dog samples, with serovars of significant public health importance such as S. Typhimurium, monophasic S. Typhimurium and S. Infantis among the top ten most frequently isolated from both sources. Some clinically relevant serovars, such as S. Typhimurium and S. Dublin, were over twice as frequent among dog isolates. Antimicrobial resistance patterns revealed some correlations between sources for certain serovars, such as S. Typhimurium, while for others (including S. Dublin) resistance patterns were unique to the dog isolates. Resistances to cefotaxime, ceftazidime or ciprofloxacin were rare, although exceptionally 9.9% of S. Infantis isolates from raw meat pet food showed ciprofloxacin resistance. S. Kentucky resistant to cefotaxime, ceftazidime and ciprofloxacin was isolated from a dog sample. Conclusions. Despite limitations for establishing direct transmission pathways, the findings highlight raw meat pet food as a potential vector for Salmonella transmission, emphasising the risks to both animal and public health and underlining the need for vigilant monitoring and hygiene practices. For antimicrobial resistance risk, generally high susceptibility to the extended spectrum cephalosporin and fluoroquinolone classes is reassuring, although the detection of multi-drug-resistant strains highlights ongoing concerns.