MONITORING OF SALMONELLA, HEPATITIS E VIRUS (HEV) AND VIRAL INDICATORS OF FECAL CONTAMINATION IN FOUR ITALIAN PIG SLAUGHTERHOUSES, 2021-2022

Food safety is one of the most important topics of the European politics, guaranteed by strict set of official controls aimed to verify compliance with EU regulations and directives. The safety of food of animal origin is supported by survey of the whole food chain from farm to table. In the pork production chain, the control at slaughterhouse aims to ensure safe food thanks to proper hygienic conditions during all steps of the slaughtering. Salmonella is one of the main foodborne pathogens in the EU causing a great number of human cases, and pigs also contribute to its spreading. Another important and still poorly know foodborne pathogen is the zoonotic hepatitis E virus (HEV). Pig is the main reservoir and HEV can be present in liver, bile, feces and even rarely in blood and muscle. The presence of the virus can determine direct contamination of food and indirect cross-contamination due to improper handlings procedures. Salmonella is present in pork gut and lymph nodes and can easily spread through feces, for improper handling and, during transport and lairage, can be transmitted among pigs. Aim: The aim of this study was to assess the presence of both Salmonella and HEV in several points of the slaughtering chain including transport, lairage, carcasses and utensils by collection of swab samples. Other viruses hosted in the gut flora of pigs and shed in feces were also assayed (porcine adenovirus PAdV, rotavirus, norovirus, and mammalian orthoreovirus MRV). Torque teno sus virus (TTSuV) present in both feces, liver and blood was also considered. Methods: Four Italian pig abattoirs were sampled in 12 critical points, five of which were the outer surface of carcasses before processing. Viruses were detected by target-specific Real-Time PCRs on nucleic acids isolated from swabs by Nuclisens Magnetic Extraction System (BioMerieux, Marcy-l’Étoile, France). For Salmonella, sponges were sampled separately analysed by real-time PCR after pre-enrichment. Positive samples were confirmed according to ISO 6579- 1:2017/Amd 1:2020. Results: HEV and rotavirus were not detected. Norovirus was detected once. Salmonella was detected in two of the 4 abattoirs: in the two lairage pens, in the site of evisceration and on one carcass, indicating the presence of Salmonella in carcasses if improper handled. The sites positive for Salmonella were also positive for PAdV. The latter was present in all abattoirs, in 10 sampled points including 5 outer surfaces of carcasses. MRV was detected in 10 swabs, from only two abattoirs, mainly in outer surface of carcasses (7). TTSuV was also detected in all abattoirs, being widely spread among both utensils and carcasses surfaces, highlighting possible cross contamination with blood of infected pigs. Conclusions: This pilot study provides the evidence of fecal contaminations during slaughtering by using viruses hosted in gut of asymptomatic pigs as indicators. Salmonella can be present and PAdV could be used as fecal indicator, being frequently associated with the presence of Salmonella. In addition to the process hygiene criteria defined in Commission Regulation (EC) 2073/2005, it would be useful to evaluate the role of certain viruses, which could reflect presence of both viral and bacterial pathogen for humans. This work was partially supported by funding from the European Union’s Horizon 2020 grant agreement No 773830: One Health European Joint Programme and by the Italian Ministry of Health Progetto di Ricerca Finalizzata grant: RF-2016-02361926.