In the description of diagnostics as well as in all following sections, the focus is on thermotolerant foodborne Campylobacter species.
A range of commercial diagnostic tests are available, primarily for testing Campylobacter in food samples. Real-time Polymerase chain reaction (PCR) tests are available as kits but need to be used within a laboratory setting. For example, there are commercial PCR-based assays for the detection of C. jejuni, C. coli, and C. lari in meat samples, poultry carcass rinses or/and processed products. Real-time PCR equipment has been developed and test results detecting low numbers of Campylobacter can be obtained within one hour. PCR-based assays have come into use in diagnostic laboratories and, for example in Denmark, to screen broilers. It should be noted that ordinary PCR-based assays detect both viable and non-viable organisms, but there are also PCR-assays described in the literature that detect only viable organisms. Antigen-capture enzyme-linked immunosorbent assays (ELISAs) and other kits have also been developed for detection and rapid species confirmation of Campylobacter.
List of campylobacter diagnostics (Diagnostics For Animals).
BAX® System Real-Time PCR Assay for detection of C. jejuni, C. coli, and C. lari in poultry carcass rinses or processed products. The system is commercially available and has been validated by NordVal. It is performance tested and approved by AOAC. There is also a BioRad kit system IQ Check Campylobacter realtime PCR system for detection of Campylobacter in food samples. It has also AOAC approval.
ISO (International Organization for Standardization) 10272 :2017, Microbiology of food and animal feeding stuffs - Horizontal method for detection and enumeration of Campylobacter spp. - Part 1: Detection method, Part 2: Colony-count technique.
An amendment of ISO 10272:2017 is in progress and is planned to be published in 2022/2023. The amendment includes three PCR methods for identification and/or confirmation of thermotolerant Campylobacter spp. The methods described in the standard have been validated and validation data is included in the standard.
ISO 17995:2019 Water quality — Detection and enumeration of thermotolerant Campylobacter spp.
OIE (Now: WOAH, World Organisation for Animal Health) Terrestrial Manual 2017. Chapter 2.9.3 Infection with Campylobacter jejuni and C. coli Manual of Standards for Diagnostic Tests and Vaccines.
NMKL (Nordic Committee on Food Analysis) No 119 2007, 3. ed. Thermotolerant Campylobacter. Detection, semi-quantitative and quantitative determination in foods and drinking water.
BAM (Bacteriological Analytical Manual) Chapter 7 : Isolation of Campylobacterspecies from Food and Water.
Depends on the potential and whether a legal obligation to screen animals and birds before slaughter will be implemented.
Potential for new diagnostic kits for detection and species identification on farm level. This would make it possible to selectively heat-process or /freeze meat from Campylobacter-positive flocks. Diagnostic kits to be used at farm-level would also be a requisite for a legal obligation to screen animals and birds before slaughter.
There is a process hygiene criterion in the EU as regards Campylobacter on broiler carcasses for food business operators. EN ISO 10272-2 is the reference method in this regulation, but alternative methods can be used provided they are validated against the reference method. A viability qPCR has been validated according to ISO 16140-2 against ISO 10272-2:2017 for thermotolerant Campylobacter spp. in meat rinses (Stingl et al 2021). The live/dead differentiation step is a pre-treatment of the meat rinse with propidium monoazide (PMA), which quenches the signal from dead cells. To ensure proper PMA treatment and eventual loss of DNA during preparation, an internal sample process control (dead cell standard) was established as well.
Rapid detection and identification tests to be used on farms and slaughterhouses are needed.
Commercial diagnostic kits for quantification of Campylobacter validated against ISO 10272-2.
May be required if a vaccine is developed.
Under research only. There is no commercial vaccine available for human or animals except for Campylobacter spp. that cause abortion in sheep. There have been many indications that Campylobacter spp. appear to be commensals in broiler chickens. This, combined with high degree of genetic variability, presents challenges to vaccine development.
No commercial vaccines available to prevent colonisation of Campylobacter in poultry and campylobacteriosis in humans.
Not applicable as no vaccines available.
If a cheap effective vaccine was developed there could be market in the poultry industry to reduce the levels of Campylobacter in birds going for slaughter.
The issues are:
None foreseen unless the vaccine is derived from a genetically manipulated organism.
One vaccine under investigation is a GMO using a Salmonella as a vector of Campylobacter antigens.
Feasible, a market exists especially for free-ranging birds.
Usually, campylobacteriosis is a self-limiting illness in humans and mainly restricted to the gastrointestinal tract. Therefore, antimicrobial therapy is generally not advised. Only in cases of prolonged illness or severe symptoms, especially invasive disease, or in immunocompromised patients, treatment with azithromycin (first choice) or ciprofloxacin (second choice) based on prior susceptibility testing is recommended. A German study noted that 31% of their case patients reported antimicrobial treatment and were most frequently treated with ciprofloxacin (45%) or erythromycin (21%) (Rosner et al. 2017). This agrees in the rest of EU (EFSA 2022).
In most animal species C. jejuni and C. coli exist as a commensal without causing disease, which is also the case for chicken and other poultry. Nonetheless, antibiotics are applied as preventive measures for other diseases and in some countries as growth promotors in intensive poultry meat production (de Mesquita Souza Saraiva et al. 2022). To reduce colonisation and contamination with Campylobacter in animals (to reduce the risk of human illness) alternatives might be used such as bacteriophages and bacteriocins, pre-and probiotics, fatty acids and phytochemicals in chickens. However, prevention of colonisation in poultry mainly rely on strict application of biosecurity measures.
There are Campylobacter species, which could cause disease in food-producing animals, such as C. hepaticus that could cause spotty liver disease in chicken, and C. jejuni and C. fetus that can cause abortion in sheep, cattle and goats. As a prevention measure experimental vaccination is applied or treatment with tetracycline, with varying success (Erickson et al. 2017; Menzies 2012). However, due to the emergence of a hypervirulent tetracycline-resistant clone in the United States tulathromycin is increasingly used as an alternative (Yaeger et al. 2021).
Further research and development of curative and preventive therapies (excl antibiotics).
Antimicrobial resistance in thermotolerant Campylobacter is an emerging and increasing threat to human health. In 2017, the World Health Organization (WHO) published a global priority list in order to identify, at global level, the most important resistant bacteria for which there is an urgent need for new treatments. Fluoroquinolone-resistant Campylobacter was placed in priority group 2, i.e., high priority.
More field studies are needed to test the effect of control strategies (vaccination, probiotics, water and feed additives and pre-slaughter phage treatment) against Campylobacter in broilers because results of experimental studies are difficult to extrapolate to the field. Moreover, combining different control strategies should also be tested using field studies.
Development of therapy for humans (excluding antibiotics).
Development of therapies that reduce the colonisation of Campylobacter in poultry.
Feed additives, probiotics etc to reduce the colonisation of Campylobacter in poultry.
Would need to be considered on a case by case basis.
To be explored, depending on industry interest.
Diagnostics should be standardized, sensitive and specific and preferably fast and cheap. Diagnostics should specify if they can differentiate between live and dead organisms or not. A viability qPCR was established and validated according to ISO 16140-2 using ISO 10272-2:2017 as reference for thermotolerant Campylobacter spp. in meat rinses. The qPCR was validated per se within the ISO 10272. The live/dead differentiation step is a pre-treatment of the meat rinse with propidium monoazide (PMA), which in contrast to EMA is passively excluded from viable but transiently inactive Campylobacter and quenches the signal from dead cells. To ensure proper PMA treatment and eventual loss of DNA during preparation, an internal sample process control (dead cell standard) was established as well.
Development of rapid tests for the detection of live Campylobacter (genus and species identification) in different types of samples, even present in low numbers.Rapid methods for the quantification of live Campylobacter.
Medium to long term.
More feasible and easy-to-handle use diagnostic methods, sensitive enough to determine Campylobacter of low counts in different matrices.
More culture-independent diagnostic methods are needed.
There are different diagnostic methods available at present that can rapidly detect Campylobacter, such as qPCR from fecal samples and air-sampling filters, but the application and implementation are not widely adopted by the industry. Methods that are still as sensitive but that can be used directly on-site without laboratory-trained personnel stands bigger chances of adoption by the industry.
Culture-independent methods that can be used directly on-site.
Different approaches are currently under investigation. For vaccine of Campylobater in poultry there is not a requirement for complete prevention of colonisation but to reduce the level in the intestines.
Lack of understanding how the immune system reacts on Campylobacter.
Depending on when a candidate vaccine could be identified.
Problem to produce reproducibly effective vaccine.
Expensive with the need to develop and undertake all the relevant tests to provide data to enable the product to be authorized.
In chickens, several vaccine types (bacterial based, killed whole-cell, cell lysates, subunit and conjugate vaccines) and antigens have been tested so far. Results reported high variability in terms of Campylobacter protection and high inter-individual variability but comparisons between studies are difficult due to differences in vaccination protocols and in assessing vaccine efficacy.Vaccines for the prevention of Campylobacter in human is still ongoing. Numerous vaccine candidates have been tested in different animal models (rats, ferrets, mice, rhesus macaques...), but animal models do not completely reproduce human campylobacteriosis and only a limited number of these antigens have been tested in controlled human infection.
Immune responses of broilers or humans to Campylobacter is not fully understood but it appears to be a prerequisite for developing an effective vaccine.Moreover, Campylobacter is known to be genetically diverse so the targeted antigens should be common among the strains to ensure the vaccine to be protective against a large range of strains.On the other hand, the impact of intestinal microbiota on vaccination has been already demonstrated, and should be evaluated in vaccination against Campylobacter in field studies.
Standardised approach how to do vaccine trials and measured parameters are missing.
Development needed for treating animals by feed additives, probiotics etc to reduce the colonisation of Campylobacter in poultry.
Pharmaceutical need to be developed to reduce the outcome of severe cases in humans.
More knowledge needed regarding resistant strains to currently available antibiotics.
Time to develop would depend on the product and the trials necessary to validate the test. Commercial production would then take further time.
Costly, since new products have to be developed and large-scale studies have to be done.
Alternative antimicrobials are needed for humans with severe cases of campylobacteriosis.
More fields studies are needed to evaluate feed additive efficacy.
Genus Campylobacter consists of a Gram-negative, motile, slender, curved, microaerobic bacteria with a single polar flagellum at one or both ends. Members of the genus Campylobacter can colonise the intestinal tract of a variety of warm-blooded animals. The most important species in terms of food-borne disease are considered to be the Campylobacter species, C. jejuni and C. coli, followed by C. lari. These species are often referred to as “thermotolerant”, because they grow to the same extent in 37 °C as in 42 °C. This document focuses on thermotolerant Campylobacter.
The incubation period for campylobacteriosis in humans is usually 2 to 5 days and the symptoms are usually mild to moderate. Most patients have prodromal fever followed by 3-7 days of diarrhea (mild to severe, sometimes frequent, explosive and bloody), abdominal pain, nausea and fever. The clinical symptoms of Campylobacter infection are often indistinguishable from those caused by other enteric pathogens such as Salmonella and Shigella. Most cases of campylobacteriosis are self-limiting within a week, but some cases may require medical treatment including hospitalization. Post-infection complications include arthopathies, neuropathological symptoms (such as Guillain Barre Syndrome (GBS) and irritable bowel syndrome. The frequency of arthritis is low, and no correlations have been found between the severity of gastrointestinal symptoms and the development of Guillain-Barré syndrome.
Both C. jejuni and C. coli have highly diverse populations but there is no known association between human disease presentation and strain variation excepting that some strain types are more frequently associated with GBS than others which appears to be related to antigen mimicry. C. jejuni/coli rarely cause disease in animals.
Host- factors involved in clinical picture need to be clarified. In practice, no animal model is available to mimic human disease and test pathogenicity of strains, in particular for investigation of long-term sequelae.
Some STs are over-represented among human cases – but there is a lack of knowledge if they are more prone to cause disease or just more common.
In the laboratory Campylobacter species are generally very intolerant to high oxygen levels, drying, heat, UV, disinfectants, extremes of pH, etc. However, in natural environments, C. jejuni and C. coli often survive for longer periods of time, depending on the surrounding conditions. Survival is supported by lower temperatures (4-10ºC), darkness and a moist atmosphere. The conditions under which fresh poultry meat is stored at for retail are ideal for survival. Freezing decreases the number of viable bacteria by around 1 log10. Survival potential varies between strains and environmental stresses can affect host colonisation properties. Environmental stress can cause morphological changes from spiral to coccal. It may also render the organisms to enter the viable but non-culturable (VBNC) stage. Coccal and VBNC formation are independent events.
The mechanisms of survival in the environment are unclear but both VBNC state and biofilm formation contribute to survival, and possible also entering unicellular organisms. The repertoire of stress response regulators present in other Gram negative bacteria is limited in the genome of Campylobacter.
Markers of survival capacity required for informing risk assessments.
C. jejuni and C. coli can colonise the intestinal tract of most, if not all, mammals and birds. Also C. lari colonizes birds, including broilers and laying hens. In the laboratory C. jejuni and C. coli grow in the same extent in 37 ºC as in 42 ºC (body temperature of a bird) and seems to be well adapted to the avian gut. Poultry, especially chickens are colonised throughout their gastrointestinal tract and colonisation of the caecum can reach 1010 cfu per gram of caecal contents. These organisms can frequently be recovered from spleen and liver suggesting extra intestinal infection. Nevertheless, this colonisation is asymptomatic and in experimentally challenged birds there are no obvious clinical signs or effect on production criteria.
Campylobacter jejuni or C. coli may be recovered from animals with diarrhea but in the vast majority of cases this is more likely to reflect the washing out of commensal gut organisms due to other infections than to be causative of disease. There are other Campylobacter species that are not thermotolerant and, therefore, not mentioned in this document.
Prevalence of C. coli in chicken.
The mechanisms of pathogenicity to induce diarrhea in humans are not completely known. A number of virulence properties have been described including mobility, adherence, invasion and cytolethal distending toxin (CDT) production. Strains vary in each of these properties but to date none have been able to account for the features of the disease. The major hindrance to understanding pathogenicity has been the absence of a suitable animal model of disease. Conventional laboratory mice bear physiological colonsation resistance exerted by the murine gut microbiota. However, gnotobiotic mice or mice with modified gut microbiota or knock-out mice with increased sensibility towards C. jejuni lipooligosaccharide have been established which exhibit key features of human campylobacteriosis (Heimesaat et al. 2021).
Lack of animal model.
The only test of Koch’s postulates is experimental infections with purified organisms – this has been done with several volunteer studies for a limited number of organisms indicating a dose response relationship to colonization of humans but not to disease.
Evidence of markers confirming pathogenicity (virulence) is lacking.
Arthropods may act as mechanical vectors.
Campylobacter jejuni and C. coli are common asymptomatic gut colonisers of all warm-blooded animals including livestock, domestic pets and wildlife. The fastidious growth requirements for these organisms means that amplification only occurs within a host. Organisms are shed in faeces and survive to become ubiquitous in the environment, including in surface waters. Consequently, Campylobacter is recovered from multiple potential reservoirs and is transmitted to humans and other animals by multiple potential routes and vectors.
The reported prevalence of Campylobacter positive broiler flocks varies between countries. In some countries in the northern Europe the prevalence is about 5% while in middle European countries e.g., the UK it is about 80% and in southern European countries it is about 100%. The prevalence of Campylobacter positive flocks also varies over season with summer peaks in most countries. Prevalence also varies with the production system, organic chicken and broilers in a production with outdoor access had a higher prevalence with up to 100%.
Cattle, sheep and pigs are frequently colonised with Campylobacter; with prevalence at slaughter of 50% to 90%.
There is some host-specificity in thermotolerant Campylobacter species. C. jejuni is commonly found in ruminants and poultry; C. coli is commonly found in pigs and poultry; while C. lari is most often found in wild birds and molluscs, and C. upsaliensis in dogs.
Transmission between hosts occurs via the faecal-oral route. Transmission from animals to humans is mainly through consumption and handling of contaminated animal food products or water and soil but also via direct contact with colonised animals.
In broilers there is no detectable vertical transmission. The infective dose can be less than 10 cfu. Strains that are laboratory adapted are less infective. Transmission within a commercial broiler flock is very rapid and up to 100% of birds can become colonised within 5 days. Interestingly flocks are rarely infected until 2-3 weeks of age. This resistance to infection appears to be related to maternally derived immunity although newly hatched chicks can be colonised by challenges of less than 10 cfu.
There is some evidence for Campylobacter strain-associated differences in colonisation potential in livestock. A comparative genomics study indicates that intensified agriculture leads to the evolution of host-adapted strains (Morukas et al. 2020). In this study C. jejuni ST-21 und St-45 complexes have been identified as host-generalists and ST-61 and ST-42 as cattle-adapted strains. A similar study for C. coli from different sources (pigs, chicken and cattle) for French isolates identified clonal complex 828 to be the dominant one (Jehanne et al. 2020).
Differences in colonisation potential (in broilers) need to be clarified.
Routes for transmission between other livestock than poultry needs to be explored further.
More source attribution studies needed.
Campylobacter colonisation in poultry is asymptomatic and in experimentally challenged birds there are no obvious clinical signs or effect on production criteria regardless of age.
In young ostriches' colonisation with C. jejuni can be associated with enteritis and occasional mortality but this is difficult to reproduce experimentally.
In ruminants (cattle and sheep) both C. jejuni and C. coli are recovered from 50-90% of asymptomatic animals. However, in pregnant ruminants, especially sheep, infection with certain highly pathogenic strains can cause abortion with organisms recovered from the abortion products. The incidence of abortion is low and appears to be dependent on the timing of infection, as well as on strain virulence. Abortion tends to occur late in gestation. Abortion induces immunity which is long lasting.
Over 75% of pigs are asymptomatically carrier of C. coli and to a lesser extent C. jejuni. Campylobacter-associated abortion in pigs has very rarely been reported but abortion caused by a similar organism, Arcobacter, has been reported.
C. jejuni and occasionally C. coli have been associated with enteritis in dogs, cats and other animal species, although rationally it could be causative, especially in juveniles and immunocompromised animals' conclusive causative evidence is lacking.
Day-old chicks can be colonized experimentally if they receive Campylobacter orally. In conventional breeding, the chickens are usually colonized at 2-3 weeks of age with a spread to the whole flock within 3-5 days and a maximally colonization of 1010 cfu per g caecal contents. The incubation period in ruminants and pigs is unknown.
There is no mortality associated with Campylobacter in chicks or chickens. The organisms are frequently recovered from the gut, liver and spleen of dead birds but the death is not caused by these bacteria.
In broilers shedding in faeces occurs detectably within 3 days of challenge. Colonisation is often chronic for the life of a conventional broiler (up to 7 weeks of age). Shedding can be erratic and is not a good indicator of colonisation. Colonisation can wane from 9 weeks after challenge which is thought to be associated with acquired immunity. However, some laying hens are still colonized in the caecum at slaughter (1.5 years old).
Quantitative data on shedding especially in free-range birds.
There is no known pathogenicity in broilers.
Campylobacter is a major cause of food-borne bacterial enteritis in humans worldwide. In the United States (US) Campylobacter causes about 1.5 million estimated cases of illnesses each year. The Foodborne Diseases Active Surveillance Network (FoodNet) indicates that about 20 cases are diagnosed each year for every 100,000 people in US.
In Australia, campylobacteriosis is also the highest enteric notified infection and have been since its introduction as a notifiable disease in 2017. A seasonality is found in Australia: the notifications were highest in the warmer months, particularly in November and January. The notification rate was per 100,000: 110.0 in 2020, with a higher rate among males with 123.5 per 100,000 and 56% of all notified cases (OzFoodnet).
In 2020, Campylobacter continued to be the most commonly reported gastrointestinal bacterial pathogen in humans in the European Union (EU) and has been so since 2005. The number of reported confirmed cases of human campylobacteriosis was 120.946 with an EU notification rate of 40.3 per 100,000 population, a 25.4% decrease compared with the rate in 2019, probably due to the COVID-19 pandemic and UK did not report their results due to Brexit. However, the overall campylobacteriosis trend in 2016–2020 showed no statistically significant increase or decrease. There is a significant underreporting of cases, hampering the possibility to calculate the total burden of the disease correctly. The cost of campylobacteriosis to public health systems and to lost productivity in the EU has, however, been estimated by EFSA to be around EUR 2.4 billion a year. WHO refers to studies in high-income countries from which an annual incidence of campylobacteriosis between 4.4 and 9.3 per 1000 population was reported - the true incidence is however more poorly known in low-income countries. The incidence is higher in children (aged 0- 4) and in young adults (15- 24). In 2020, Campylobacter species information was provided for 64.7% of confirmed cases reported in the EU, Iceland and Norway, which was an increase in reporting compared with 2019 (55.2%). Of these, 88.1% concerned C. jejuni, 10.6% C. coli, 0.16% C. fetus, 0.11% C. upsaliensis and 0.09% C. lari. Other Campylobacter species accounted for 0.94% of cases, but the large majority of those cases were reported at the national level as ‘C. jejuni/C. coli /C. lari not differentiated (EFSA and ECDC 2021).
True number of campylobacteriosis in humans.
The vast majority of human cases are sporadic rather than outbreaks. However, outbreaks, or clusters of disease caused by consumption of poultry meat, unpasteurised milk and large water-borne outbreaks have been reported.
Risk attribution studies have been undertaken using a variety of epidemiological methods. Epidemiological investigations, such as case-control and outbreak studies suggest that 20-40% of cases are attributable to the mishandling and consumption of not adequately cooked poultry meat. Scientific reports on risk factors for human infection indicate that the consumption of food (poultry meat, cross contaminated food products, raw milk and contaminated water) is the main source of infection, followed by direct contact with colonized animals.
Lately, whole genome sequencing has become a preferred technique for strain characterization (genotyping). Strain typing has been undertaken by multiple phenotypic and genotypic methods to determine risk attribution. Multi-locus sequence typing (MLST) and core genome MLST has become adopted in some laboratories for source attribution studies. The principle behind MLST is that housekeeping or core genes are sequenced of which the combined results indicate statistically a degree of host specificity. Results from surveys where MLST have been used have hence given indications that 50-80% of the human campylobacteriosis cases could be attributable to poultry. Poultry has further been divided into what is direct transmitted via meat, poultry faeces, contaminated water, soil and vegetables and indirect routes i.e., via from other animals including cattle, pigs and domestic pets. Combination of freezing of products from broiler flocks positive on-farm and enhanced biosecurity reduced incidence of domestically acquired campylobacteriosis in Iceland by 90%, indicating much higher attribution of human cases to fresh broiler chicken.
The relative importance of various reservoirs may vary between countries. Travel is also a major risk factor but is a confounder for many factors such as different “reservoirs” and differences in immunostatus. Direct contact with colonised animals or material contaminated by their faeces may also contribute to human campylobacteriosis.
Source attribution studies have only been performed in some countries. Difficult to get a clear picture, partly due to use of different methods (protocols) for strain characterization.
More detailed information would be provided by source attribution based on WGS data.
The infectious dose of campylobacteriosis is low, a few as 500 organisms have been reported to cause illness. The symptoms of the disease in humans varies from mild gastrointestinal distress that resolves within 24 hours to a fulminating or relapsing colitis. The most common symptoms of infection include diarrhea, abdominal pain, fever, headache, nausea and vomiting. Symptoms usually start 2–5 days after infection, and is usually self-limiting after 3–6 days. Relapses can occur in approximately 10-25% of cases. For 2020, a hospitalization rate of 21% was reported in EU (EFSA and ECDC 2021).
Complications are uncommon but occur, such as, Guillain-Barré syndrome, reactive arthritis, irritable bowel syndrome and septicemia for further rare complications. Immunosuppressed individuals are at a high risk for severe or recurrent infections or for septicemia.
Deaths are rare in C. jejuni infections and are seen mainly in patients with multiple diseases or other underlying conditions (eg cancer, AIDS, chronic liver disease). The estimated case/fatality ratio for C. jejuni infections is one in 1,000. The incidence of Guillain-Barré syndrome (GBS) per 100,000 population is 0.6- 1.9; up to 5 % of these patients may die.
Person-to-person transmission is unusual but can occur if personal hygiene is poor and has been reported in nurseries and homes for elderly persons. C. jejuni is found in the faeces and can be shed for as long as 2 to 7 weeks, humans rarely become chronic carriers.
In general there is no disease issue with chickens or the majority of livestock for thermotolerant Campylobacter. Abortion in ruminants could happen but is infrequent. Control measures in conventional broilers currently only involve enhanced biosecurity. Vaccination, bacteriophages and bacteriocins have all been suggested as control measures at the farm level and research is ongoing.
There are studies that have found an association between poorer animal welfare and presence of Campylobacter in broilers, although the underlying mechanisms are not well understood.
Research required on the impact of vaccination, bacteriocins and bacteriophages as control measures to animal welfare.
More studies regarding a possible association between animal welfare and Campylobacter colonisation need to be carried out in order to out rule confounding factors.
The organisms are ubiquitous in animals and the environment worldwide. The disease affects humans worldwide.
Campylobacter is endemic in the world. In low-income countries infection is usually limited to children, suggesting that a high level of exposure in early life or constantly exposed leads to the development of protective immunity.
Sero-epidemiological studies in Europe suggest that exposure is also common in the high-income countries with a person being exposed at least once per year. Since the implementation of whole genome-based surveillance outbreak clusters have been identified that were genetically closely related to animal isolates. Studies indicates that genome-based surveillance of Campylobacter isolates may be able to identify clusters, which may very likely represent outbreaks.
Outbreaks in humans are not always noticed and reported. In 2020, Campylobacter was the fourth most frequent cause of foodborne outbreaks reported by 17 member states (MS) at EU level. Outbreaks have been mainly attributed to milk and milk products, contaminated water or meat and meat products as point sources. Waterborne outbreaks tend to include large numbers of cases, last a short time and are usually related to failure in chlorination (or breakdowns at water plants). In a large sentinel surveillance study in the UK, at the most 5% of cases were estimated to be associated with household outbreaks. There are several published studies pointing out broilers as the source of campylobacter outbreaks in humans. Poultry-meat associated outbreaks occur and can be due to multiple strains or single strains.
Colonisation in a broiler house could be considered as an outbreak although the chickens do not show any symptoms of disease. The rate of spread in these conditions is very rapid (about 3-5 days). Spread to adjacent broiler houses is also very rapid and common.
Disagreement/ different opinion about the occurrence (and size of) of outbreaks in household and/or due to poultry meat. Could be due to differences in study design, different interpretation of data, and lack of harmonisation of typing methods.
Situation with transboundary spread between animals between different countries is not very relevant, but theoretically possible by international trade of colonized live animals and contaminated food.
The majority of flock colonisation result from horizontal transmission from the environment. Campylobacter can be easily spread from bird, or other animal, to bird through a number of routes including common water sources or through contact with contaminated faeces. Molecular epidemiology has demonstrated the presence of strain types in the poultry farm environment (i.e., in puddles or cattle) before the flock becomes positive with the identical type (Frosth et al 2020). There is no evidence that vertical transmission exists, at least not in a significant way.
Other livestock including cattle, sheep and pigs become rapidly colonized with Campylobacter after birth by acquiring infection from their dams. They also have maternally derived immunity which appears to protect from disease.
Improvement of understanding the transmission and spread of Campylobacter to poultry and the relative importance of food borne and non-food borne campylobacteriosis.
Arthropods may act as mechanical vectors for humans and livestock.
For conventionally reared broilers major risk factors include poor biosecurity, age of birds, season, other livestock nearby, multiple species farming, raising without all in-all out system (i.e., thinning) and free-ranging at any stage. In some studies (possibly country related) drinking water is a risk factor.
In humans, protective immunity to Campylobacter enteritis occurs after primary infection but is short lived and strain specific. However, the epidemiology of disease in low-income countries and in occupationally-exposured individuals clearly indicates that repeated exposure results in cross-reactive immune protection. The human humoral immune response includes the rapid induction of anti-Campylobacter IgG, IgM, and IgA antibodies in serum, as well as secretory IgA from the intestinal mucosa, directed against a number of surface antigens including flagellin and the major outer membrane protein. Proinflammatory cytokines are also induced and there is an inflammatory response to infection in the intestinal mucosa. The self-limiting nature and rapid resolution of the disease in most humans suggests that this immune response is extremely effective. There is however a possibility of immunopathological/autoimmune sequelae: Guillain-Barré syndrome (GBS) is an idiopathic postinfectious neuropathy that leads to progressive motor weakness due to damage to the myelin sheath, most frequently caused by Campylobacter jejuni (Huizinga et al 2015).
In chickens similar humoral and cellular immune responses occur though an inflammatory response is not seen. These responses have been well characterized. The colonisation is persistent suggesting that this immunity is poorly effective at eliminating the infection. Balance between the Th1 and Th2 immune responses against C. jejuni explain the bacterial persistence in the ceca and the absence of pathology in Campylobacter-challenged birds (Mortada et al 2021).
Immune responses to colonisation in other livestock than chicken is poorly understood.
There are no serological assays in routine use for the detection of colonisation of C. jejuni/C. coli in livestock. However, antigen-capture enzyme-linked immunosorbent assays (ELISAs) have been described in the literature for all host species. A standardised assay has recently been described in humans for use in sero-epidemiological studies.
Sanitation and management can help prevent colonization in intensively reared poultry. The main factor is biosecurity and all in-all out system, with decontamination of housing between flocks. This needs to include house-dedicated clothing, with changing of footwear, clothes and wash hands before entering the broiler house, which should also be applied on catchers during thinning. Visitors should be avoided and high housing standards with a high level of tidiness in and around the broiler houses should be applied.
Livestock such as cattle and pigs are often carriers of Campylobacter. Avoiding livestock at the farm or in the surroundings prevent transmission of Campylobacter into broiler houses via farm workers, especially if biosecurity is deficient or via vectors such as insects. Fly-screens have proved effective in some countries. Effectiveness of fly screening of ventilation inlets is most dramatic when applied in conjunction with careful broiler house entry biosecurity. Both flies and poor farm biosecurity can independently lead to high flock prevalence. Exclusion of rodents and other wild animals and wild birds and insect populations should also be controlled.
Problems with implementing all biosecurity measurements and make the farmer fully aware of the need for the strict actions.
Good hygiene and disinfection should be used to prevent spreading Campylobacter from one house to another by farmers or on fomites during an outbreak.
Chlorination and acidification of drinking water and removal biofilm inside the water pipes may help to prevent water-borne transmission. UV treatment of drinking water provides a more effective and low maintenance solution.
There is no evidence that vertical transmission exists, at least not in a significant way.
Two ISO (International Organization for Standardization) procedures for detection and enumeration of Campylobacter exist: a horizontal method for detection and enumeration of Campylobacter in food and animal feeding stuffs (ISO 10272 Part 1 and Part 2: 2017), and a procedure for the detection and enumeration of Campylobacter from water (ISO 17995:2019).
In mammals and birds with a high number of Campylobacter in the intestines, detection of intestinal colonisation is based on direct culture from faeces, rectal swabs and/or caecal contents. Alternatively, their high motility can be exploited using filtration techniques for isolation. Enrichment techniques are mostly used when analysing environmental samples and other samples where a low number of Campylobacter or high number of background flora is expected for example food or environmental samples. Preliminary confirmation of isolates can be made by phase-contrast microscopy, Campylobacter have a characteristic rapid corkscrew-like motility. Biochemical, molecular tests and mass spectrometry can be used to confirm various Campylobacter species. Polymerase chain reaction assays also can be used for the direct detection and identification of C. jejuni and C. coli.
Reliable diagnostic tests that can be used onsite (in farm, on equipment etc.).
There are no effective vaccines available for the prevention of Campylobacter colonization in birds or mammals. However, vaccination using Salmonella as a vector for Campylobacter antigens or subunit vaccines with appropriate mucosal adjuvants are under active research.
Today there are no effective vaccines available for livestock (including poultry).
Human cases are usually not treated with antibiotics unless patient is bacteraemic or disease develops into life threatening condition. Use of antibiotics enhances development of resistance. However, antibiotics are never used as treatment of animals that are colonised with thermotolerant Campylobacter.
Appropriate cleaning, safe handling of litter and manure, elimination of standing water around houses. Appropriate use of house dedicated clothing, changing boots and safe handling and storage of feed avoiding wild birds and rodents close to the broiler houses. Prevention of the entrance of animals (including wild birds and insects) by the ventilation systems into broiler houses.
Different aspects and development of on-farm educational program including a film with instructions about dos and don were performed within the EU project CamCon: http://www.camcon-eu.net/
A process hygiene criterion for Campylobacter in broiler carcases aims at keeping under control contamination of carcases during the slaughtering process was implemented in EU 2018. The EFSA estimates that a public health risk reduction from the consumption of broiler meat of more than 50 % could be achieved if carcases complied with a limit of 1 000 cfu/g and highlights that significant different contamination levels exist between neck skin and breast skin samples.
Domestic and commercial kitchen practices are of the utmost importance when Campylobacter is introduced into the kitchen environment. Contaminated broiler chicken, together with poor hygiene practices, can lead to more cases of campylobacteriosis.
Crucial gaps in consumer knowledge regarding storage temperatures, food pathogens, reheating, cleaning, and handling of risk foods.
Surveillance program regarding Campylobacter in chickens is implemented in many countries in Europe but is not harmonized within EU. One harmonized baseline survey of broiler flocks and broiler carcasses was carried out in Europe 2008. Many national surveys have been conducted on poultry flocks, as well as cattle, sheep and pigs at slaughter. EFSA’s BIOHAZ Panel has published scientific opinions assessing the public health impact of control measures as well as a report presenting the economics related to different interventions which could be used to reduce the occurrence of Campylobacter in chickens and chicken meat. The experts also evaluated how reduction targets for Campylobacter in chickens in EU may lead to a fall in the number of human cases of campylobacteriosis associated with the consumption of chicken meat.
Limited number of countries have a surveillance program for animals.
It is difficult to control Campylobacter colonization in animals and birds using biosecurity alone. Nevertheless, decreasing prevalence are seen in countries where biosecurity is implemented as part of a national action plan.
A normative cost-effectiveness analysis estimated the cost-effectiveness ratio of using probiotics, prebiotics, or synbiotics in broiler production in Denmark, the Netherlands, Poland, and Spain. The cost-effectiveness ratio was defined as the estimated costs of probiotics, prebiotics, or synbiotics use divided by the estimated public health benefits expressed in euro (€) per avoided disability-adjusted life year (DALY). Simulation results revealed that the costs per ‘avoided disability-adjusted life year’ were lowest in Poland and Spain (€ 4,000–30,000) and highest in the Netherlands and Denmark (€ 70,000–340,000) at an efficacy ranging from 10 to 20%. (Wagenberg et al 2020).
Studies of cost-effectiveness of biosecurity.
Only bovine campylobacteriosis is notifiable.
There is a significant economic impact through loss of working time as a result of infection with campylobacter. EFSA estimated the cost of campylobacteriosis in the EU was ~EUR 2.4 billion a year, due to public health effects and lost productivity. United States estimated an economic burden from health losses at $1.56 billion (Scharff et al., 2012).
Cost-of-illness of food-related pathogens were estimated and presented 2011, with disease burden expressed in Disability Adjusted Life Years, the direct healthcare cost of campylobacteriosis €76 million/year (Mangen et al., 2015). Swedish Institute for Food and Agricultural Economics (Sundström, 2015), estimated a cost of both direct (medicine and hospital treatment and non-institutional care) of 629 million SEK, for 80,000 true cases of campylobacteriosis per year in Sweden. In the United Kingdom, estimated costs to patients and the health service at 2008–2009 were £50 million for Campylobacter and indirect costs (decreased productivity).
Better information about what food has been consumed by affected people.
In general, the impact on human individuals is merely a case of dealing with diarrhoea for a few days. Where the disease progresses, antibiotic treatment may be required and ultimately hospitalisation. For 2020 a hospitalization rate of reported cases was 21% and case fatality 0.05% in EU (EFSA and ECDC 2021). Severe sequelae, such as the Guillain-Barré syndrome might occur in 1 out of 1000 acute cases.
Country specific costs of treatment and control of Campylobacter.
No direct impact, chickens with Campylobacter show now symptoms of disease or increased mortality.
Costs of biosecurity and hygiene practices in broiler houses and abattoirs. Controlling Campylobacter in primary production are expected to be greater than control later in the chain as the bacteria may also spread from farms to humans by other pathways than broiler meat.
Country specific costs.
The specific costs differ among countries. In 2017, the Swedish broiler industry received negative attention in the media due to doubling of the number human cases infected in Sweden. It was due to domestic chickens contaminated with Campylobacter. This resulted in headlines in the newspaper, radio and television, telling that Swedish chickens is a risk factor. The public health officials (County Medical Officers) proposed that Swedish consumers should avoid to eat Swedish poultry meat that have not been frozen. This kind of attention lead to a reduction in the consumption of Swedish chicken.
No overall cost benefit analyses have been done.
Currently low impact, since except for the process hygiene criterion set into force in 2018, no other specific regulation exists for thermotolerant Campylobacter spp. However, for ready-to-eat food, the basis regulation §14 VO (EG) No.178/2002 that prevents the trade of harmful food (e. g. contaminated by Campylobacter spp.) has to be considered. The OIE Terrestrial Animal Health code only refers to bovine genital campylobacteriosis. There are no trade standards for other campylobacter infections.
None at the moment.
No impact at the moment.
Studies indicate relationships between high prevalence of Campylobacter in chicken flocks and increased temperature and/or rainfall.
More studies are required to understand how, and if, colonisation of Campylobacter is linked to climate factors.
Most campylobacteriosis cases in humans are sporadic, peaking in the summer months. However, clear seasonal patterns of human infections are identified in EU, but not in the same extent in the southern part of Europe.
In general, in Europe, Campylobacter prevalence in chicken flocks is higher in countries with a longer summer period. The percentages of Campylobacter are increasing from 2% in chicken flocks from northern Europe to 97% in the Mediterranean countries.
More studies are required to understand how geography may be linked to Campylobacter colonisation and spread.
Heavy rainfalls may cause problems for water purification systems and recreational exposure and could lead to outbreaks (Hyllestad et al 2019).
The geographical variation in the timing of the seasonal peak suggests that climate may be a contributing factor to Campylobacter transmission.
Campylobacter incidences seem to be linked to increases in temperature and precipitations. Both temperature and precipitations will be affected by the ongoing climate changes, which should consequently lead to an escalation of campylobacteriosis cases, especially in northern Europe. Countries in the northern hemisphere may experience a doubling of Campylobacter cases by the end of the 2080s, corresponding to around 6,000 excess cases per year caused only by climate changes. Considering the strong worldwide burden of campylobacteriosis, it is important to assess local and regional impacts of climate change in order to initiate timely public health management and adaptation strategies (Kuhn et al 2020).
Studies of how local and regional climate change have impact on Campylobacter risks are needed.
World Health Organization (WHO) published a global priority list in order to identify, at global level, the most important resistant bacteria for which there is an urgent need for new treatments. Fluoroquinolone-resistant Campylobacter was placed in priority group 2, i.e., high priority.
The cause of increased resistance, which has also been shown in countries that do not treat animals with antimicrobials for preventive purposes, should be clarified.
Usually, campylobacteriosis is a self-limiting illness in humans and mainly restricted to the gastrointestinal tract. Therefore, antimicrobial therapy is generally not advised but used for severe human cases.
There are no commercial vaccines available for humans or poultry. Bacteriophages, bacteriocins and competitive microbiota have been suggested as control measures at farm level, most likely they reduce the number of Campylobacter in feces, but there will still be high amount of Campylobacter in the intestines.
Commercial vaccines easily distributed to broilers.
Chickens colonised with Campylobacter are not treated by antimicrobials.Severe human cases are treated with antimicrobials. Antimicrobial resistance poses an additional risk because infections caused by Campylobacter resistant to antimicrobial may lead to longer hospitalizations, higher treatment failures, and increased morbidity and mortality.
Alternative to fluoroquinolone in the treatment of severe cases in humans.
Under the EU's Zoonosis Directive 2003/99/EC, all member states are required to ensure effective monitoring of zoonoses, including Campylobacter. EFSA and ECDC publish a report every year containing data about human cases of disease, data from the entire food production chain as well as data concerning foodborne outbreaks.
Following a request from the European Commission, EFSA and ECDC are in the process of developing the joint collection and analysis of new molecular typing data from food, animal and human isolates of Salmonella, Listeria monocytogenes and STEC. Joint data collection and analysis of Campylobacter isolates are expected to follow later on.
EpiPulse - the European surveillance portal for infectious diseases, including campylobacteriosis. EpiPulse is an online portal for European public health authorities and global partners to collect, analyse, share, and discuss infectious disease data for threat detection, monitoring, risk assessment and outbreak response.
An electronic reporting system and database for monitoring zoonoses is established for the EFSA/ECDC collection of zoonoses data.
All data are available in the annual EU Summary Report (on-line).
The collection of zoonoses data could vary between countries, (except for in EU harmonized surveillance programmes).
Since the number of human campylobacteriosis cases and colonization rates in chicken may increase in a warmer climate, there is a risk for increased number of outbreaks which means that greater care should be considered for hygiene in general.
Higher costs for hygiene measures and ventilation of broiler houses.
Probably no effect at all.
Today, there is no such surveillance on a global basis.
Could be valuable to have such surveillance in humans.
For genotyping by MLST, there are platforms.
Further development needed.
Is performed for source attribution.
Further development needed.
Today no such platforms exist. Questionable if needed.
See above (21.1), about EU zoonosis monitoring and EpiPulse. On a global basis, WHO is the main body for communication.
Existing strategies could be improved. The level awareness of consumers is not the same in the different EU MS.
Campylobacter infections in humans, campylobacteriosis, is a zoonosis and the most frequent cause of foodborne bacterial enteritis in humans. Globally, the incidence varies among countries and the true incidence of campylobacteriosis is largely unknown, particularly in low-income countries. There are multiple reasons for this, e.g., underreporting, difficulties with diagnosis, differences in reporting systems and in surveillance. Nevertheless, campylobacteriosis is regarded a disease with considerable socio-economic implications. Poultry meat can become contaminated with Campylobacter during slaughter if live chickens are intestinal carriers. However, there is a need for more knowledge about sources and transmission routes and to what extent various species of Campylobacter and animal sources contribute to the human Campylobacter disease situation. Some of these gaps are relevant worldwide, whereas others are more related to problems encountered with Campylobacter in high- income countries.
The mechanisms behind pathogenicity of Campylobacter are poorly understood. Studies of virulence factors or virulence associated genes in Campylobacter have so far not given conclusive evidence of genes correlated to the disease in humans. There is no simple animal model available that mimics human disease for studying and possibly discriminating between (for humans) pathogenic and non-pathogenic strains. In spite of all the research and surveillance done in the last decades, there is still a need for further investigation of various tools for control of Campylobacter in order to prevent campylobacteriosis in humans.
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