Yersinia enterocolitica – a bacterial pathogen that causes yersiniosis, now the fourth most reported zoonosis in the EU, with more than 8,700 cases in 2023 – presents a major public health challenge.
This article outlines:
- the characteristics of the pathogen, which differs from others in that it is able to grow at very low temperatures
- the symptoms of food poisoning that Yersinia enterocolitica can induce in consumers
- practical advice for consumers on how to prevent infection and reduce the risks of illness that are best avoided.
The analysis continues with an in-depth look at current shortcomings in EU regulations. It also explores the innovative potential of European Data Spaces to apply the ‘One Health’ approach to zoonotic and health surveillance.
1. Yersinia enterocolitica, introduction
Yersinia enterocolitica is a pathogenic bacterium, more specifically a Gram-negative coccobacillus belonging to the family Yersiniaceae, order Enterobacterales. It is the agent of human yersiniosis, a predominantly foodborne disease reported with some frequency in Europe.
Like Listeria monocytogenes and Pseudomonas spp., Yersinia enterocolitica is a psychrotrophic microorganism (from the Greek ψυχρός, psykhros, meaning ‘cold,’ and from τροφή, trophḗ, meaning ‘feeding.’ That is, it feeds or grows in cold environments). And it is indeed able to grow at low temperatures, between 0°C and +7°C, to high numbers. Unlike other pathogens (Salmonella, Escherichia coli, Staphylococcus aureus), which instead require temperatures of at least +7-8°C to proliferate.
The species Yersinia enterocolitica is divided into numerous serogroups, differentiated by somatic antigen O, and six biotypes (1A, 1B, 2, 3, 4, 5) that have variable biochemical characteristics. The strains responsible for most human infections, in Europe, belong to Y. enterocolitica O:3/biotype 4 and Y. enterocolitica O:9/biotype 2.
2. Host animals
The host (or reservoir) animal par excellence is the pig, which harbors Yersinia enterocolitica in the intestine (mesenteric lymph nodes) and pharynx (palatine tonsils). The tonsils, in particular, represent a real ‘niche’ for the bacterium.
Adult pigs do not show symptoms of disease, which may sometimes appear in piglets in the form of diarrhea. Very often the most pathogenic human strains, namely Yersinia enterocolitica O:3/biotype 4 and O:9/biotype 2, are isolated from pigs.
Cattle may in turn harbor Yersinia enterocolitica at the intestinal level, and milk may be contaminated with it at milking. Rodents in turn are host animals of this pathogenic bacterium.
3. Routes of exposure and modes of transmission
Exposure to Yersinia enterocolitica occurs primarily through consumption of contaminated food, particularly raw or undercooked pork, unpasteurized milk, and fruit and vegetables.
However, other routes of exposure include ingestion of contaminated water, direct contact with animals carrying the bacterium (such as pigs, ruminants and rodents) and contaminated surfaces. Transmission can also occur via the fecal-oral route, especially in environments with poor sanitation.
Cases of nosocomial infection and transmission of Yersinia enterocolitica through infected blood transfusions have been documented, underscoring the potential risk to vulnerable individuals (e.g., elderly and immunocompromised).
4. Foods at risk
Foods at risk include mainly pork, consumed raw or undercooked, fresh pork sausages, vegetables contaminated with animal manure during fertigation (simultaneous application of water and fertilizer through the irrigation system), and non-potable water.
In contrast, raw milk – at serious risk of contamination by pathogen bacteria such as STEC and Listeria monocytogenes – has a marginal role in Yersinia enterocolitica infections because the less pathogenic biotype of (1A) is often isolated in it. Consumption of swine offal can in turn promote transmission of Yersinia enterocolitica.
5. Pathogenesis and clinical manifestations of Yersinia enterocolitica infection
Exposure to Yersinia enterocolitica, as noted above, occurs primarily through ingestion of contaminated food. After crossing the gastric barrier, the bacterium reaches the intestine, particularly the ileum and the proximal part of the colon, where the infectious process begins. The infection usually manifests as acute gastroenteritis or enterocolitis, characterized by fever, vomiting and diarrhea. At the level of the intestinal epithelium, Yersinia enterocolitica is able to invade mucosal cells, triggering an immune response with the recall of leukocytes and macrophages, which contribute to inflammation and diarrhea. However, the pathogen possesses evasion mechanisms that allow it to thwart the action of macrophages, cells critical to immune defenses through phagocytosis (or digestion, degradation) of pathogens.
The weakening of the immune defense allows Yersinia enterocolitica to spread to the mesenteric lymph nodes (located in the mesentery, the membrane that connects the small intestine to the abdominal wall), aggravating the clinical picture. Inflammation of the intestinal lymph nodes causes mesenteric lymphadenitis, a condition characterized by intense pain in the right iliac fossa. This clinical picture may mimic acute appendicitis (pseudo-appendicitis), sometimes leading to misdiagnosis and unnecessary surgery in patients without inflammation of the appendix but with lymph node involvement of the ileum.
6. Post-infectious complications and sequelae.
In vulnerable individuals – such as children, the elderly, and immunocompromised individuals – Yersinia enterocolitica infection can evolve, although rarely, into severe forms. All the way to the development of sepsis, a systemic inflammatory response that can cause multi-organ damage with life-threatening outcomes (Seabaugh et al., 2024).
Several studies have shown that Yersinia can alter inflammatory processes, and exploit immune cells to promote various diseases (Chung et al., 2016). Thus, interactions between Yersinia enterocolitica and the intestinal microbiome, for example, are being investigated, with a focus on bacterial metabolites and their possible role in intestinal inflammation and the pathogenesis of Crohn’s disease (Feng et al., 2023).
In the general population they may then develop post-infectious sequelae, including reactive arthritis and erythema nodosum.
7. Prevention of Yersinia enterocolitica toxin infection
Prevention of Yersinia enterocolitica toxins depends primarily on consumers taking some basic precautions. It is essential to avoid the consumption of raw or undercooked pork and raw (i.e., unpasteurized) milk, unless boiled. Vegetables should be thoroughly washed and disinfected, using chlorine-based products.
These preventive practices are effective in countering the spread of Yersinia enterocolitica, a pathogen whose prevalence is emphasized to be underestimated.
It is important to note that simply storing food at low temperatures is not enough to stop the growth of the bacterium. The only safe method to inactivate Yersinia enterocolitica is proper cooking of foods, paying particular attention to the insides of meats, such as pork burgers and sausages, which must be well cooked even in the deepest areas.
8. Rules in the European Union
The European legislature has not yet introduced harmonized microbiological criteria for Y. enterocolitica in food (Regulation EC 2073/05), nor has it established uniform monitoring plans at the pig slaughter stages.
However, the EU system for monitoring and reporting information on zoonoses requires member States to collect data on zoonoses, zoonotic agents, antimicrobial resistance and foodborne disease outbreaks (Directive 2003/99/EC). The European Food Safety Authority (EFSA) is in charge of reviewing the data, together with the European Centre for Disease Prevention and Control (ECDC), for the publication of the European Union’s ‘One Health Zoonoses’ Report (EUOHZ).
Yersiniosis is indeed included among the zoonoses to be monitored in humans, animals, feed and food. However, monitoring and surveillance are unsatisfactory in several member states (including Italy), which, as noted in the latest ‘One Health’ report on zoonoses in the EU (EFSA, ECDC, 2024), reported only a few dozen cases.
9. Zoonotic surveillance and public health, the potential of EU Data Spaces
Transdisciplinary data from animal surveillance, critical for a ‘One Health’ approach to public health, are still scarce. This situation severely limits the ability to anticipate future threats, particularly those related to zoonotic diseases with pandemic or epidemic potential.
A very recent study (Riccetti et al., 2025) explores the potential of the European Data Spaces framework to improve the availability of animal surveillance data to better address public health threats.
In particular, it is proposed to expand and develop existing initiatives (e.g., Data Spaces for Health, Agriculture, and the Green Deal) to design innovative services. Such services would enable the integration of diverse data sources, supporting research and the development of health policies appropriate to the identified risks.
10. Interim conclusions
In summary, prevention of yersiniosis relies on key consumer precautions, such as avoiding raw pork and unboiled milk, and washing vegetables thoroughly.
It is critical to remember that mere refrigeration is not enough to inactivate Yersinia enterocolitica; only proper cooking ensures elimination of the risk.
This need, combined with awareness of current regulatory gaps at the European level, underscores the need to strengthen the ‘One Health’ approach, including through enhanced zoonotic and sanitary surveillance.
Dario Dongo and Silvia Bonardi
Credit cover: Stocklib, Yersinia enterocolitica
References
- Chung LK, Bliska JB. (2016). Yersinia versus host immunity: how a pathogen evades or triggers a protective response. Curr Opin Microbiol. Feb;29:56-62. doi: 10.1016/j.mib.2015.11.001
- EFSA (European Food Safety Authority), and ECDC (European Center for Disease Prevention and Control). (2024). The European Union One Health 2023 Zoonoses Report. EFSA Journal. 2024;22:e9106. doi:10.2903/j.efsa.2024.9106.
- EFSA (2025). Data collection: zoonoses, antimicrobial resistance and food-borne – Deadlines for 2024 data reporting and validation. https://tinyurl.com/yc85r6dj
- EFSA (European Food Safety Authority), Amore G, Beloeil P-A, Boelaert F, Garcia Fierro R, Rizzi V and Stoicescu A-V (2025). Guigance for reporting 2024 data on zoonoses, foodborne outbreaks and antimicrobial resistance. EFSA supporting publication 2025:EN-9239. 169 pp. doi:10.2903/sp.efsa.2025.EN-9239
- Fang X, Kang L, Qiu YF, Li ZS, Bai Y. (2023). Yersinia enterocolitica in Crohn’s disease. Front Cell Infect Microbiol. Mar 8;13:1129996. doi: 10.3389/fcimb.2023.1129996
- Francesca Piras, Christian Scarano. Yersinia enterocolitica. In: Paparella A., Schirone M., Visciano P. Igiene nei processi alimentari (Hoepli, Milano, 2023)
- Nicola Riccetti, Serena Signorelli, Angela Fanelli, Emanuele Massaro, Manlio Bacco, Wojciech Szewczyk, Dolores Ibarreta, Juan Carlos Ciscar, Alessandro Cescatti, Sandra Coecke, Ilaria Capua (2025). The urgency of addressing zoonotic diseases surveillance: Potential opportunities considering One Health approaches and common European Data Spaces. Data in Brief, 59, 111332, https://doi.org/10.1016/j.dib.2025.111332
- Seabaugh JA, Anderson DM. (2024). Pathogenicity and virulence of Yersinia. Virulence. Dec;15(1):2316439. doi: 10.1080/21505594.2024.2316439
Dario Dongo, lawyer and journalist, PhD in international food law, founder of WIISE (FARE - GIFT - Food Times) and Égalité.
Graduated in Veterinary Medicine and Specialist in Inspection of Food of Animal Origin and in Veterinary Public Health, she is Professor of Inspection and Control of Food of Animal Origin at the University of Parma.
