{"id":194127,"date":"2023-08-18T07:23:56","date_gmt":"2023-08-18T05:23:56","guid":{"rendered":"https:\/\/ew-nutrition.com\/salmonella-pigs-threat-humans-challenge-pig-producers\/"},"modified":"2023-11-13T12:45:00","modified_gmt":"2023-11-13T11:45:00","slug":"salmonella-pigs-threat-humans-challenge-pig-producers","status":"publish","type":"post","link":"https:\/\/ew-nutrition.com\/us\/salmonella-pigs-threat-humans-challenge-pig-producers\/","title":{"rendered":"Salmonella in pigs: a threat for humans and a challenge for pig producers"},"content":{"rendered":"

By Dr. Inge Heinzl<\/strong>, Editor, EW Nutrition<\/em><\/span><\/p>\n

Salmonellosis is third among foodborne diseases leading to death (Ferrari, 2019<\/a><\/span>). More than 91,000 human cases of Salmonellosis are reported by the EU each year, generating overall costs of up to \u20ac3 billion a year (EFSA, 2023<\/a><\/span>), 10-20% of which are attributed to pork consumption (Soumet, 2022<\/a><\/span>). The annual costs arising from the resulting human health losses in 2010 were about \u20ac90 million (FCC Consortium, 2010<\/a><\/span>). Take the example of Ireland, where a high prevalence of Salmonella in lymph nodes still shows a severe issue pre-slaughter and a big challenge for slaughterhouses to stick to the process hygiene requirements (Deane, 2022<\/a><\/span>).<\/p>\n

Several governments already have monitoring programs in place, and the farms are categorized according to the salmonella contamination of their pigs. In some countries, e.g., Denmark, an economic penalty of 2% of the carcass value must be paid if the farm has level 2 (intermediate seroprevalence) and 4-8% if the level is 3. Other countries, e.g., Germany, the UK, Ireland, or the Netherlands, use quality assurance schemes. The farmers can only sell their carcasses under this label if their farm has a certain level.<\/p>\n

Let’s take a quick look at the genus of Salmonella<\/h2>\n

Salmonellas are rod-shaped gram-negative bacteria of the family of enterobacteria that use flagella for their movement. They were named after the American vet Daniel Elmer Salmon. The genus of Salmonella consists of two species (S. bongori and S. enterica with seven subspecies) with in total more than 2500 serovars (see Figure 1). The effects of the different serovars can range from asymptomatic carriage to severe invasive systemic disease (Gal-Mor, 2014<\/a><\/span>). All Salmonella serovars generally can cause disease in humans; the rosa-marked ones already showed infections.<\/p>\n

\"FigureFigure 1: the genus of Salmonella with Salmonella serovars relevant for pigs (according to Bonardi, 2017: Salmonella in the pork production chain and its impact on human health in the European Union)<\/em><\/span><\/p>\n

Within the group of Salmonella, some serovars can only reside in one or few species, e.g., S. enterica spp. enterica Serovar Dublin (S. Dublin) in bovines (Waldron, 2018<\/a><\/span>) or S. Cholerasuis in pigs (Chiu, 2004<\/a><\/span>). An infection in humans with these pathogens is often invasive and life-threatening (WHO, 2018<\/a><\/span>). On the contrary, serovars like S. Typhimurium and S. Enteritidis are not host-specific and can cause disease in various species.<\/p>\n

The serotypes S. Typhi and S. Paratyphi A, B, or C are highly adapted to humans and only for them pathogenic; they are responsible for the occurrence of typhus.<\/p>\n

Serovars occurring in pigs and relevant for humans are, for example, S. Typhimurium (Hendriksen, 2004<\/a><\/span>), S. Serotype 4,[5],12:I (Hauser et al., 2010<\/a><\/span>), S. Cholerasuis (Chiu, 2004<\/a><\/span>), S. Derby (Gonzalez-Santamarina, 2021<\/a><\/span>), S. Agona (Brenner Michael, 2006<\/a><\/span>) and S. Rissen (Elbediwi, 2021<\/a><\/span>).<\/p>\n

Transmission of Salmonella mostly happens via contaminated food<\/h2>\n

The way of transmission to humans depends on the serovar:
\nHuman-specific and, therefore, only in humans and higher primates residing serovars S. Typhi and Paratyphi A, B, or C (typhoidal) are excreted via feces or urine. Therefore, any food or water contaminated with the feces or urine of infected people can transmit this disease (Government of South Australia, 2023<\/a><\/span>). Typhoid and paratyphoid Salmonellosis occur endemic in developing countries with the lack of clean water and, therefore, inadequate hygiene (Gal-Mor, 2014<\/a><\/span>).<\/p>\n

Serovars which can cause disease in humans and<\/strong> animals (non-typhoidal), can be transmitted by
\n– animal products such as milk, eggs, meat
\n– contact with infected persons\/animals (pigs, cows, pets, reptiles\u2026) or
\n– other feces- or urine-contaminated products such as sprouts, vegetables, fruits\u2026.<\/p>\n

Farm animals take salmonellas from their fellows, contaminated feed or water, rodents, or pests.<\/p>\n

Symptoms of Salmonellosis can be severe<\/h2>\n

In the case of typhoid or paratyphoid Salmonellosis, the onset of illness is gradual. People can suffer from sustained high fever, unwellness, severe headache, and decreased appetite, but also from an enlarged spleen irritating the abdomen and dry cough.<\/p>\n

A study conducted in Thailand with children suffering from enteric fever caused by the typhoid serovars S. Typhi and Paratyphi showed a sudden onset of fever and gastrointestinal issues (diarrhea), rose spots, bronchitis, and pneumonia (Thisyakorn et al., 1987<\/a><\/span>)<\/p>\n

The non-typhoid Salmonellosis is typically characterized by an acute onset of fever, nausea, abdominal pain with diarrhea, and sometimes vomiting (WHO, 2018<\/a><\/span>). However, 5% of the persons \u2013 children with underlying conditions, e.g., babies, or people who have AIDS, malignancies, inflammatory bowel disease, gastrointestinal illness caused by non-typhoid serovars, and hemolytic anemia, or receiving an immunosuppressive therapy can be susceptible to bacteremia. Additionally, serovars like S. Cholerasuis or S. Dublin are apt to develop bacteremia by entering the bloodstream with little or no involvement of the gut (Chiu, 1999<\/a><\/span>). In these cases, consequences can be septic arthritis, pneumonia, peritonitis, cutaneous abscess, mycotic aneurysm, and sometimes death (Chen et al., 2007<\/a><\/span>; Chiu, 2004<\/a><\/span>, Wang et al., 1996<\/a><\/span>).<\/p>\n

In pigs, S. Cholerasuis causes high fever, purple discolorations of the skin, and thereinafter diarrhea. The mortality rate in pigs suffering from this type of Salmonellosis is high. Barrows orally challenged with S. Typhimurium showed elevated rectal temperature by 12h, remaining elevated until the end of the study. Feed intake decreased with a peak at 48h after the challenge and remained up to 120h after the challenge. Daily gain reduced during the following two weeks after infection. A higher plasma cortisol level and a lower IGF-I level could also be noticed. All these effects indicate significant changes in the endocrine stress and the somatotropic axis, also without significant alterations in the systemic pro-inflammatory mediators (Balaji et al., 2000<\/a><\/span>)<\/p>\n

To protect humans, Salmonella in pork must be restraint<\/h2>\n

There are three main steps to keep the contamination of pork as low as possible:<\/p>\n

    \n
  1. Keeping Salmonella out of the pig farm<\/li>\n
  2. Minimizing spreading if Salmonella is already on the farm<\/li>\n
  3. Minimizing contamination in the slaughterhouse<\/li>\n<\/ol>\n

    1. How to keep Salmonella out of the pig farm?<\/h3>\n

    To answer this question, we must look at how the pathogen can be transported to the farm. According to the Code of Practice for the Prevention and Control of Salmonella on Pig Farms (Ministry of Agriculture, Fisheries and Food and the Scottish Executive Rural Affairs Department), there are several possibilities to infiltrate the pathogen into the farm:<\/p>\n