Campylobacteriosis – a gastrointestinal disease caused by bacteria belonging to the genus Campylobacter – is the most frequently reported zoonosis in the European Union. Among the various species of the genus Campylobacter, Campylobacter jejuni is certainly the one responsible for the majority of human food poisonings.
1) Foodborne infections by Campylobacter in the European Union, the data
European Union One Health 2023 Zoonoses report– compiled by EFSA (European Food Safety Authority) and ECDC (European Centre for Disease Prevention and Control) – indicates over 148.000 cases of human campylobacteriosis and estimates an incidence of 45,7 cases per 100.000 inhabitants in 2023 (1,2).
The EFSA and ECDC’s One Health report states as many as 229 outbreaks of foodborne campylobacteriosis, but only in 27 cases have the products from which the outbreaks originated been identified with ‘strong evidence’ – that is, with epidemiological certainty:
- 15 out of 27 outbreaks were caused by the consumption of chicken meat,
- 3 from red meat,
- the remainder from various foods such as milk, cheese, mixed chicken and pork meat, turkey meat, eggs and fish products.
1.1) Surveillance in the EU
The surveillance of human campylobacteriosis is active and effective throughout the territory of the EU Member States which report a significant incidence as
– Luxembourg (129,4 cases/100.000 inhabitants, in 2023),
– Czech Republic (125,2),
– Slovakia (104,4),
– Denmark (87,6),
– Ireland (70,9),
– Germany (47,5).
However, other countries, despite applying health surveillance actions extended to the entire territory, report very low incidences, such as Latvia (9,3 cases/100.000 inhabitants), Greece (6,1), Poland (2,3).
1.2) The Italian case
Italy reported only 2.363 cases of human campylobacteriosis in 2023. A very small number compared to the 40.000 cases reported in Germany and the 29.000 notified in Spain, although increasing compared to previous years (1.539, 1.541, 1.418, respectively, in 2022, 2021 and 2020).
This apparently positive data should instead be understood as a sign of ineffectiveness of surveillance of food poisoning in Italy, with the inability to offer coverage across the entire national territory.
Data provided by Italy are therefore not sufficient to estimate the incidence of campylobacteriosis in the population and it is no coincidence that Italy is the only Member State not to report this data.
2) Risky foods, microbiological criteria and controls
Campylobacter is mainly present in the intestines of chickens and turkeys. It can also be found in cattle (rarely in pigs) and thus be transmitted to both meat and cow’s milk, through slaughter and milking operations.
The most at-risk foods of animal origin include raw or undercooked poultry meat, but also raw milk and raw milk cheeses (which present the intrinsic risk of contamination by much more aggressive pathogens such as STEC and Listeria monocytogenes, as we have seen. See notes 4,5).
Occasional reports of campylobacteriosis then derive from the consumption of raw molluscs (oysters, mussels), due to the contamination of sea water by aquatic birds, which are in turn common hosts of C. jejuni.
2.1) Chicken, contamination accepted
Microbiological Criteria Regulation (EC) 2073/2025 requires mandatory monitoring of chicken carcasses for Campylobacter contamination in slaughterhouses.
The limit of 1.000 CFU/g must be evaluated on 50 sample units, to be taken in ten sampling sessions. And the result is defined ‘acceptable’ if the limit is not exceeded by 30% of the samples, which is reduced to 20% (10/50) starting from 1 January 2025. (3)
This means that Campylobacter contamination is considered inevitable, in the slaughter of chicken, and is accepted within the percentage quota mentioned. And only when this quota is exceeded must the plant manager adopt corrective actions to improve the hygienic conditions of slaughter.
2.2) Discrepancies between official controls and those of operators
Significant discrepancies emerge once again – as already for Salmonella (6) – between the results of the analyses carried out by the authorities responsible for official controls and those carried out by those responsible for slaughterhouses.
In Italy for example, in 2023, 22% of the samples taken by the National Health Service (Veterinary Service) were outside the limits, while slaughterhouse managers certified the percentage of ‘unacceptable’ samples at 14%.
Similar discrepancies among the results of official controls and those of analyses carried out in self-control by food business operators have also been recorded in other Member States such as Belgium, Greece, Ireland, Latvia, Poland and Spain.
3) Campylobacter jejuni, an enigma for microbiologists
C. jejuni– despite numerous studies conducted over the years – remains an enigma for microbiologists. In fact, this pathogen:
– adapts poorly to normal atmospheric conditions, since its development requires a low concentration of oxygen (microaerophilia);
– is very sensitive to sodium chloride (common table salt), of which it tolerates very low quantities;
– requires large amounts of free water to survive;
– to cope with hostile environments turns into ‘latent’ forms, with a reduced metabolism, which cannot be cultivated in the laboratory. (7)
It is hypothesized that such a fastidious bacterium can spread so widely in the human species thanks to the role of birds, both domestic and wild, which represent the most efficient natural reservoir since they can host several billion C. jejuni in their intestine without showing signs of disease.
In reverse, in humans, the infectious dose is very low, sometimes estimated at a few hundred microorganisms. This last factor can also be a determining factor in favouring the spread of the infection in the human species. (8)
4) Campylobacteriosis, symptoms and prevention
From a clinical point of view Campylobacteriosis manifests itself with watery or sometimes bloody diarrhea, together with abdominal cramps, nausea and fever.
In particularly fragile subjects this food poisoning can also manifest as meningitis and bacteremia. In rare cases, an autoimmune neuropathy may appear after the enteric symptoms, which is part of Guillain-Barré Syndrome and manifests itself with paresis in various parts of the body.
Most Campylobacter infections occur in the summer season, with a peak in the months of July and August, as well as in January, due to increased consumption and barbecues related to the holidays (2).
Prevention of food poisoning by Campylobacter – as well as by Salmonella, an equally and even more widespread pathogenic bacterium, as we have seen (9) – is very important for the protection of public health, also taking into account the growing spread of antibiotic-resistant strains of the pathogens in question, already reported in the ‘European Union Summary Report on Antimicrobial Resistance in Zoonotic and Indicator Bacteria from Humans, Animals and Food in 2018/2019’ (EFSA, ECDC, 2021). (10,11)
Since both bacteria are thermosensitive, the prevention of human infections requires some simple precautions to be strictly followed.
5) Practical recommendations
In the Kitchen – as well as in the laboratories of food processing, distribution and supply companies, including food service and food delivery (12) – it is essential to respect:
– cooking meat at risk. Not only chicken but also turkey (still exempt from the microbiological controls required for chicken). To inactivate C. jejuni and Salmonella, meat must reach and maintain 70°C for two minutes in all its parts, including the innermost ones. Particular attention must be paid to thicker cuts and meat preparations, as well as hamburgers, and to some cooking methods (e.g. barbecue); (13)
– separation of cutlery, utensils and work surfaces. It is equally important to avoid ‘cross-contamination’, that is, the transfer of pathogens from their vectors (e.g. raw chicken and turkey meat) to other foods not intended for cooking (e.g. salads, vegetables, cheeses) through cutlery, knives, cutting boards, etc. Utensils and worktops must be sanitized, after contact with at-risk foods, before being put into contact with other foods.
– hand washing. Hands can also transfer pathogens from risky foods to other foods, as well as to the person themselves. Careful hand hygiene is therefore necessary after handling risky foods.
Silvia Bonardi and Dario Dongo
Footnote
(1) Marta Strinati. EU, One Health Report 2023. Listeriosis, salmonellosis and other zoonoses on the rise. FT (Food Times). December 15, 2024
(2) EFSA, ECDC. The European Union One Health 2023 Zoonoses report. EFSA Journal. 2024;22:e9106. doi: 10.2903/j.efsa.2024.9106
(3) Commission Regulation (EC) No 2073/2005 of 15 November 2005 on microbiological criteria for foodstuffs. OJ L 338, 22.12.2005, p. 1–26. http://data.europa.eu/eli/reg/2005/2073/2020-03-08
(4) Silvia Bonardi, Dario Dongo. Malga cheeses and fresh raw milk cheeses, the STEC danger. GIFT (Great Italian Food Trade).
(5) Silvia Bonardi, Dario Dongo. Listeria and listeriosis, an in-depth study. GIFT (Great Italian Food Trade).
(6) See paragraph 2 (Salmonella) in the article cited in note 1
(7) Omole Z, Dorrell N, Elmi A, Nasher F, Gundogdu O, Wren BW. Pathogenicity and virulence of Campylobacter jejuni: What do we really know? Virulence. 2024 Dec;15(1):2436060. doi: 10.1080/21505594.2024.2436060.
(8) Igwaran A, Okoh AI. Human campylobacteriosis: A public health concern of global importance. Heliyon. 2019 Nov 14;5(11):e02814. doi: 10.1016/j.heliyon.2019.e02814
(9) Silvia Bonardi, Dario Dongo. Salmonella, the most widespread pathogen in Europe, ABC. FT (Food Times). October 1, 2018
(10) Marta Strinati. Salmonella and Campylobacter increasingly resistant to antibiotics. FT (Food Times). April 9, 2021
(11) European Food Safety Authority, & European Center for Disease Prevention and Control. (2021). European Union Summary Report on Antimicrobial Resistance in Zoonotic and Indicator Bacteria from Humans, Animals and Food in 2018/2019 [Data set]. Zenodo. http://doi.org/10.5281/zenodo.4557180
(12) Dario Dongo. Food delivery, food safety risks. GIFT (Great Italian Food Trade).
(13) Marta Strinati. A perfect barbecue against food poisoning. GIFT (Great Italian Food Trade).
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.
Dario Dongo, lawyer and journalist, PhD in international food law, founder of WIISE (FARE - GIFT - Food Times) and Égalité.
