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. 2024 Sep 17:11:1427773.
doi: 10.3389/fvets.2024.1427773. eCollection 2024.

Non-typhoidal Salmonella among slaughterhouse workers and in the pork value chain in selected districts of Uganda

Velma Kivali  1   2   3 , Kristina Roesel  1   2 , Ian Dohoo  4 , Lordrick Alinaitwe  1   2   5   6 , James Katamba Bugeza  1   2 , Jolly Justine Hoona  7 , Denis Rwabiita Mugizi  1   2 , Clovice Kankya  8 , Sinh Dang-Xuan  1   2 , Istvan Szabo  9 , Uwe Rösler  3 , Anika Friese  3 , Elizabeth A J Cook  1   2
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Non-typhoidal Salmonella among slaughterhouse workers and in the pork value chain in selected districts of Uganda

Velma Kivali et al. Front Vet Sci. .

Abstract

Introduction: Non-typhoidal Salmonella (NTS) is a major cause of gastroenteritis worldwide, often associated with meat consumption and meat processing. Research on NTS infection and circulating serovars in meat value chains in Uganda is limited. We aimed to establish NTS prevalence, antimicrobial resistance, and risk factors among slaughterhouse workers, and to identify potentially zoonotic serovars in the pork value chain.

Material and methods: We conducted a nationwide cross-sectional survey, collecting 364 stool samples from livestock slaughterhouse workers and 1,535 samples from the pork value chain: mesenteric lymph nodes, fecal samples, swabs of carcass splitting floor, cleaning water, meat handlers hand swabs, carcass swabs, raw pork, cooked pork, and mixed raw vegetables. Samples were cultured for isolation of NTS, and subsequently serotyped according to White-Kauffmann-Le Minor scheme. Antimicrobial resistance profiles were determined using tube microdilution and Sensititre® EUVSEC3® plates. Semi- structured questionnaires with 35 questions were used to collect data on demographics, work related risk factors and activities outside the slaughterhouse.

Results and discussion: Overall NTS prevalence was 19.2% (365/1899). Proportions at slaughter were; 46.7% in floor swabs, 30.5% in carcass swabs, 20.5% in pig faeces,19.2% in mesenteric lymph nodes,18.4% in hand swabs, 9.5% in water and 5.2% in slaughterhouse workers. At retail, proportions were 33.8% in pork chopping surface, 33.1% in raw pork, 18.9% in hand swabs, 4.0% in cooked pork and 0.7% in vegetables. Sixty-one serovars were identified, with significant overlap between humans and the pork value chain. Overall, zoonotic S. Zanzibar, monophasic serovars of S. subspecies salamae (II) and subspecies enterica (I), S. Typhimurium and S. Newport, were the most prevalent. S. Typhimurium was predominant in humans and exhibited multi-drug resistance. NTS infection was significantly associated with eating, drinking, or smoking while working (OR = 1.95, 95% CI: 0.67-2.90%, p = 0.004). The detected NTS serovars in slaughterhouse workers could be a potential indicator of circulating serovars in the general population. The persistent presence of NTS along the pork value chain highlights occurrence of cross-contamination and the potential for transmission to consumers and slaughterhouse workers. This emphasizes the need to reduce Salmonella prevalence on pig farms and improve hygiene and pork handling practices at slaughter and retail points.

Keywords: NTS serovars; Uganda; non-typhoidal Salmonella; pork value chain; slaughterhouse workers.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.

Figures

Figure 1
Figure 1
Map of Uganda showing the districts of the study. Source: Stephen Oloo/ILRI. Map drawn in open QGIS version 3.24.2 with a base layer of Uganda districts downloaded from the Humanitarian Data Exchange database (https://data.humdata.org/).
Figure 2
Figure 2
Distribution of the top 15 most prevalent serovars detected at the point of pig slaughter. Illustration: ILRI/Annabel Slater. (Salmonella prevalence at the top is the prevalence per sample type, while the prevalences next to the serovars shows how many of the positives belong to a particular serovar. Serovars in bold were also detected in pig slaughterhouse workers).
Figure 3
Figure 3
Distribution of the top 15 most prevalent serovars detected at the point of pork retail. Illustration: ILRI/Annabel Slater. (Salmonella prevalence at the top is the prevalence per sample type, while the prevalences next to the serovars shows how many of the positives belong to a particular serovar. Serovars in bold were also detected in pig slaughterhouse workers).
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