Assessing interventions to reduce the risk of Campylobacter prevalence in broilers

Quantifying health risks from ESBL-producing Escherichia coli in Dutch broiler production chains and potential interventions using compartmental models

Extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (E. coli) in animals are considered a human health threat, because this type of bacteria can serve as a reservoir of antibiotic resistant genes and act as a continuous threat of the emergence of new resistant bacteria, in addition to the direct effect of making infection untreatable. Although the prevalence of ESBL producing bacteria in broilers was drastically reduced in the Netherlands, chicken meat still has the highest prevalence among meat products. Therefore, further control of the ESBL-producing E. coli in the broiler production chain is important to reduce public health risks. The main objectives of this study were to evaluate the effectiveness of intervention scenarios to reduce the transmission of ESBL-producing E. coli in the broiler production chain and to quantitatively estimate the risk to public health. In this study, we developed two different types of transmission models that described the observed time-related decline in prevalence during a production round: one with time-dependent decline in susceptibility and one with partial immunity to phylogenetic groups. Both models incorporated the environmental contamination effect between production rounds and within flocks. The parameter values, including transmission rate and recovery rate, were estimated by Approximate Bayesian computation (ABC) method using data from a longitudinal study in a Dutch organic broiler farm. We applied the models to the three production stages in the broiler production chain, beginning from the Parent Stock (PS) farms, the hatcheries, and to the broiler farms. In our models, eggs were collected from different parent stock farms and transported to the hatchery and from there to a broiler farm.The size of a flock and the number of farms were adjusted to the Dutch situation. Both models were able to describe the observed dynamics within and between the production stages equally well, with estimated ESBL-producing E. coli prevalence of 8.98% and 11.47% in broilers at slaughter and 0.12% and 0.15% in humans due to chicken consumption. Both models indicated that improving farm management to eliminate the bacteria from the environment was the most effective intervention, making this outcome robust. Although chicken meat consumption is not a major risk factor for human carriage of the bacteria according to our models, reducing the bacteria in the PS and broiler farm environment to at least one percent can further decrease the prevalence in humans.

Approaches for disease prioritization and decision-making in animal health, 2000-2021: a structured scoping review

This scoping review identifies and describes the methods used to prioritize diseases for resource allocation across disease control, surveillance, and research and the methods used generally in decision-making on animal health policy. Three electronic databases (Medline/PubMed, Embase, and CAB Abstracts) were searched for articles from 2000 to 2021. Searches identified 6, 395 articles after de-duplication, with an additional 64 articles added manually. A total of 6, 460 articles were imported to online document review management software (sysrev.com) for screening. Based on inclusion and exclusion criteria, 532 articles passed the first screening, and after a second round of screening, 336 articles were recommended for full review. A total of 40 articles were removed after data extraction. Another 11 articles were added, having been obtained from cross-citations of already identified articles, providing a total of 307 articles to be considered in the scoping review. The results show that the main methods used for disease prioritization were based on economic analysis, multi-criteria evaluation, risk assessment, simple ranking, spatial risk mapping, and simulation modeling. Disease prioritization was performed to aid in decision-making related to various categories: (1) disease control, prevention, or eradication strategies, (2) general organizational strategy, (3) identification of high-risk areas or populations, (4) assessment of risk of disease introduction or occurrence, (5) disease surveillance, and (6) research priority setting. Of the articles included in data extraction, 50.5% had a national focus, 12.3% were local, 11.9% were regional, 6.5% were sub-national, and 3.9% were global. In 15.2% of the articles, the geographic focus was not specified. The scoping review revealed the lack of comprehensive, integrated, and mutually compatible approaches to disease prioritization and decision support tools for animal health. We recommend that future studies should focus on creating comprehensive and harmonized frameworks describing methods for disease prioritization and decision-making tools in animal health.

A systematic review and meta-analysis of the sources of Campylobacter in poultry production (preharvest) and their relative contributions to the microbial risk of poultry meat

A systematic review and meta-analysis were conducted to idetnify the relative contributions of the sources of Campylobacter in poultry live production to Campylobacter prevalence of broiler meat. The keywords of Campylobacter, prevalence, live production, and broiler were used in Google Scholar to address the research interest. A total of 16,800 citations were identified, and 63 relevant citations were included in the meta-analysis after applying predetermined inclusion and exclusion criteria. A generalized linear mixed model approach combined with logit transformation was used in the current meta-analysis to stabilize the variance. The analysis revealed that Campylobacter is ubiquitous in the poultry house exterior environment including surroundings, wildlife, domestic animals, and farm vehicle, with a predicted prevalence of 14%. The recovery of Campylobacter in the interior environment of the poultry house is far less abundant than in the exterior, with a prevalence of 2%, including litter, water, insects, mice, feed, and air. A lack of evidence was observed for vertical transmission due to the day-old chicks being free of Campylobacter from 4 studies identified. Live birds are the predominant carrier of Campylobacter, with a predicted prevalence of 41%. Transportation equipment used for live haul had an overall prevalence of 39%, with vehicles showing a predicted prevalence of 44% and crates with a predicted prevalence of 22%. The results of this meta-analysis highlight the need to implement effective biosecurity measures to minimize the risk of Campylobacter in poultry meat, as human activity appears to be the primary factor for Campylobacter introduction.

Avian campylobacteriosis, prevalence, sources, hazards, antibiotic resistance, poultry meat contamination, and control measures: a comprehensive review

Avian campylobacteriosis is a vandal infection that poses human health hazards. Campylobacter is usually colonized in the avian gut revealing mild signs in the infected birds, but retail chicken carcasses have high contamination levels of Campylobacter spp. Consequently, the contaminated avian products constitute the main source of human infection with campylobacteriosis and result in severe clinical symptoms such as diarrhea, abdominal pain, spasm, and deaths in sensitive cases. Thus, the current review aims to shed light on the prevalence of Campylobacter in broiler chickens, Campylobacter colonization, bird immunity against Campylobacter, sources of poultry infection, antibiotic resistance, poultry meat contamination, human health hazard, and the use of standard antimicrobial technology during the chicken processing of possible control strategies to overcome such problems.

Modelling the introduction and transmission of Campylobacter in a North American chicken flock

Campylobacter is the second leading cause of foodborne illness in the United States. Although many food production animals carry Campylobacter as commensal bacteria, consumption of poultry is the main source of human infection. Previous research suggests that the biology of Campylobacter results in complete flock colonization within days. However, a recent systematic review found that the on-farm prevalence of Campylobacter varies widely, with some flocks reporting low prevalence. We hypothesized that the low prevalence of Campylobacter in some flocks may be driven by a delayed introduction of the pathogen. The objectives of this study were to (a) develop a deterministic compartmental model that represents the biology of Campylobacter, (b) identify the parameter values that best represent the natural history of the pathogen in poultry flocks and (c) examine the possibility that a delayed introduction of the pathogen is sufficient to replicate the observed low prevalence examples documented in the literature. A deterministic compartmental model was developed to examine the dynamics of Campylobacter in chicken flocks over a 56-day time period prior to movement to the abattoir. The model outcome of interest was the final population prevalence of Campylobacter at day 56. The resulting model that incorporated a high transmission rate (β = 1.04) was able to reproduce the wide range of prevalence estimates observed in the literature when pathogen introduction time is varied. Overall, we established that the on-farm transmission rate of Campylobacter in chickens is likely high and can result in complete colonization of a flock when introduced early. However, delaying the time at which the pathogen enters the flock can reduce the prevalence observed at 56 days. These results highlight the importance of enforcing strict biosecurity measures to prevent or delay the introduction of the bacteria to a flock.

The Data Behind Risk Analysis of Campylobacter Jejuni and Campylobacter Coli Infections

Campylobacter jejuni and Campylobacter coli are major causes of food-borne enteritis in humans. Poultry meat is known to be responsible for a large proportion of cases of human campylobacteriosis. However, other food-borne, environmental and animal sources are frequently associated with the disease in humans as well. Human campylobacteriosis causes gastroenteritis that in most cases is self-limiting. Nevertheless, the burden of the disease is relatively large compared with other food-borne diseases, which is mostly due to rare but long-lasting symptoms related to immunological sequelae. In order to pave the way to improved surveillance and control of human campylobacteriosis, we review here the data that is typically used for risk analysis to quantify the risk and disease burden, identify specific surveillance strategies and assist in choosing the most effective control strategies. Such data are mostly collected from the literature, and their nature is discussed here, for each of the three processes that are essential for a complete risk analysis procedure: risk assessment, risk management and risk communication. Of these, the first, risk assessment, is most dependent on data, and this process is subdivided into the steps of hazard identification, hazard characterization, exposure assessment and risk characterization. For each of these steps of risk assessment, information from published material that is typically collected will be summarized here. In addition, surveillance data are highly valuable for risk assessments. Different surveillance systems are employed in different countries, which can make international comparison of data challenging. Risk analysis typically results in targeted control strategies, and these again differ between countries. The applied control strategies are as yet not sufficient to eradicate human campylobacteriosis. The surveillance tools of Campylobacter in humans and exposure sources in place in different countries are briefly reviewed to better understand the Campylobacter dynamics and guide control strategies. Finally, the available control measures on different risk factors and exposure sources are presented.

Review of Quantitative Microbial Risk Assessment in Poultry Meat: The Central Position of Consumer Behavior

Food of animal origin, especially meat products, represent the main vehicle of foodborne pathogens and so are implicated in foodborne outbreaks. Poultry meat is a widely consumed food in various forms, but it is also a reservoir of thermotolerant Campylobacter and Salmonella bacterial species. To assess human health risks associated with pathogenic bacteria in poultry meat, the use of quantitative microbial risk assessment (QMRA) has increased over the years as it is recognized to address complex food safety issues and is recommended by health authorities. The present project reviewed poultry meat QMRA, identified key steps of the farm-to-fork chain with significant impacts on food safety, highlighted current knowledge gaps, and provided risk mitigation advices. A PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses)-based systematic analysis was carried out and enabled the collection of 4056 studies including 42 QMRA kept for analysis after screening. The latter emphasized Campylobacter spp. and Salmonella spp. contaminations during the consumer stage as the main concern. The role of consumer handling on cross-contamination and undercooking events were of major concern. Thus, proper hygiene and safety practices by consumers have been suggested as the main intervention and would need to be followed with regular surveys to assess behavior changes and reduce knowledge gaps.

The transmission dynamics of Campylobacter jejuni among broilers in semi-commercial farms in Jordan

Campylobacter is the leading cause of foodborne bacterial gastroenteritis in humans worldwide, often associated with the consumption of undercooked poultry. In Jordan, the majority of broiler chicken production occurs in semi-commercial farms, where poor housing conditions and low bio-security are likely to promote campylobacter colonisation. While several studies provided estimates of the key parameters describing the within-flock transmission dynamics of campylobacter in typical high-income countries settings, these data are not available for Jordan and Middle-East in general. A Bayesian model framework was applied to a longitudinal dataset on Campylobacter jejuni infection in a Jordan flock to quantify the transmission rate of C. jejuni in broilers within the farm, the day when the flock first became infected, and the within-flock prevalence (WFP) at clearance. Infection with C. jejuni is most likely to have occurred during the first 8 days of the production cycle, followed by a transmission rate value of 0.13 new infections caused by one infected bird/day (95% CI 0.11–0.17), and a WFP at clearance of 34% (95% CI 0.24–0.47). Our results differ from published studies conducted in intensive poultry production systems in high-income countries but are well aligned with the expectations obtained by means of structured questionnaires submitted to academics with expertise on campylobacter in Jordan. This study provides for the first time the most likely estimates and credible intervals of key epidemiological parameters driving the dynamics of C. jejuni infection in broiler production systems commonly found in Jordan and the Middle-East and could be used to inform Quantitative Microbial Risk Assessment models aimed to assess the risk of human exposure/infection to campylobacter through consumption of poultry meat.

Transmission routes of ESBL/pAmpC producing bacteria in the broiler production pyramid, a literature review

Plasmid mediated Extended Spectrum Beta-Lactamase and AmpC Beta-Lactamase (ESBL/pAmpC) producing bacteria are resistant to beta-lactam antimicrobials and are widespread in humans, the environment and animals. Animals, especially broilers, are an important reservoir of ESBL/pAmpC producing bacteria. To control ESBL/pAmpC prevalence in broilers, transmission within the entire broiler production pyramid should be considered. This study, including 103 articles originating from two electronic databases, searched for evidence for possible routes of transmission of ESBL/pAmpC producing bacteria in the broiler production pyramid. Possible routes of transmission were categorised as 1) vertical between generations, 2) at hatcheries, 3) horizontal on farm, and 4) horizontal between farms and via the environment of farms. This review presents indications for transmission of ESBL/pAmpC producing bacteria for each of these routes. However, the lack of quantitative results in the literature did not allow an estimation of the relative contribution or magnitude of the different routes. Future research should be specifically targeted towards such information as it is crucial to guide reduction strategies for the spread of ESBL/pAmpC producing bacteria in the broiler production chain.

A Probabilistic Transmission Model for the Spread of Extended-Spectrum-β-Lactamase and AmpC-β-Lactamase-Producing Escherichia Coli in the Broiler Production Chain

Direct contact between humans and live broilers, as well as the consumption of chicken meat, have been suggested as pathways for transmission of extended-spectrum-β-lactamase (ESBL) and AmpC-β-lactamase (AmpC)-producing Escherichia coli. One approach to design intervention strategies to control the transmission of such bacteria between animals and humans is to study the transmission pathways of such bacteria between the animals themselves. The rationale is that controlling the process of the underlying source, here transmission between animals, can provide hints on how to control a higher-level process, here the transmission between animals and humans. The focus of this article is the transmission of the above-mentioned bacteria between broilers and broiler flocks in meat production with regards to the establishment of possible intervention strategies to reduce the transfer of these bacteria between animals. The objective of this work is to design a mathematical transmission model describing the effects of vertical and horizontal bacterial transmission in the broiler production chain, from the parent generation to the slaughterhouse level. To achieve this objective, an existing transmission model for Campylobacter was adapted for the case of E. coli. The model keeps track of prevalence among flocks (flock prevalence) and of prevalence among animals within one flock (animal prevalence). Flock and animal prevalences show different dynamics in the model. While flock prevalence increases mainly through horizontal transmission in hatcheries, animal prevalence increases mainly at the broiler-fattening farm. Transports have rather small effects just as the vertical transmission from parents to chicks.

Campylobacter control measures in indoor broiler chicken: critical re-assessment of cost-utility and putative barriers to implementation

As campylobacteriosis is one of the most important foodborne infections, a European Union (EU)-27 level cost-effectiveness model has been developed on the socio-economic costs and benefits of applying certain control measures for the reduction of Campylobacter in broiler meat. This is expected to be a gold standard for food safety policymakers in the EU; hence, the validity of its modelling assumptions is essential. The authors of the present paper conducted an independent review of model input parameters on health and economic burden and found that the model most probably overestimated the burden of human campylobacteriosis. A discounted, quality-adjusted life year (QALY)-based European estimate has been developed for human campylobacteriosis and resulted in 15.23 QALY loss per 1000 human gastroenteritis cases. Country-specific cost of illness estimates have been developed for various countries in the EU-27. Based on these model adaptations, a selected Campylobacter control strategy was re-assessed and its high cost-effectiveness was confirmed at the EU level, and also in all but three Member States. Bacteriocin treatment or vaccination of the animals, two alternative control measures were also re-evaluated, and these strategies seemed to be far less cost-effective than the investigated strategy. Putative barriers to the rapid implementation of the investigated Campylobacter control strategy are discussed, and potential solutions are proposed. Further research is required on stakeholder perspectives pertaining to the realistic barriers and implementation opportunities.

Quantification of Campylobacter jejuni contamination on chicken carcasses in France

Highly prevalent in poultry, Campylobacter is a foodborne pathogen which remains the primary cause of enteritis in humans. Several studies have determined prevalence and contamination level of this pathogen throughout the food chain. However it is generally performed in a deterministic way without considering heterogeneity of contamination level. The purpose of this study was to quantify, using probabilistic tools, the contamination level of Campylobacter spp. on chicken carcasses after air-chilling step in several slaughterhouses in France. From a dataset (530 data) containing censored data (concentration <10CFU/g), several factors were considered, including the month of sampling, the farming method (standard vs certified) and the sampling area (neck vs leg). All probabilistic analyses were performed in R using fitdistrplus, mc2d and nada packages. The uncertainty (i.e. error) generated by the presence of censored data was small (ca 1 log₁₀) in comparison to the variability (i.e. heterogeneity) of contamination level (3 log₁₀ or more), strengthening the probabilistic analysis and facilitating result interpretation. The sampling period and sampling area (neck/leg) had a significant effect on Campylobacter contamination level. More precisely, two "seasons" were distinguished: one from January to May, another one from June to December. During the June-to-December season, the mean Campylobacter concentration was estimated to 2.6 [2.4; 2.8] log₁₀ (CFU/g) and 1.8 [1.5; 2.0] log₁₀ (CFU/g) for neck and leg, respectively. The probability of having >1000CFU/g (higher limit of European microbial criterion) was estimated to 35.3% and 12.6%, for neck and leg, respectively. In contrast, during January-to-May season, the mean contamination level was estimated to 1.0 [0.6; 1.3] log₁₀ (CFU/g) and 0.6 [0.3; 0.9] log₁₀ (CFU/g) for neck and leg, respectively. The probability of having >1000CFU/g was estimated to 13.5% and 2.0% for neck and leg, respectively. An accurate quantification of contamination level enables industrials to better adapt their processing and hygiene practices. These results will also help in refining exposure assessment models.

Mathematical Modeling Tools to Study Preharvest Food Safety

This article provides an overview of the emerging field of mathematical modeling in preharvest food safety. We describe the steps involved in developing mathematical models, different types of models, and their multiple applications. The introduction to modeling is followed by several sections that introduce the most common modeling approaches used in preharvest systems. We finish the chapter by outlining potential future directions for the field.

Chicken Anti-Campylobacter Vaccine - Comparison of Various Carriers and Routes of Immunization

Campylobacter spp, especially the species Campylobacter jejuni, are important human enteropathogens responsible for millions of cases of gastro-intestinal disease worldwide every year. C. jejuni is a zoonotic pathogen, and poultry meat that has been contaminated by microorganisms is recognized as a key source of human infections. Although numerous strategies have been developed and experimentally checked to generate chicken vaccines, the results have so far had limited success. In this study, we explored the potential use of non-live carriers of Campylobacter antigen to combat Campylobacter in poultry. First, we assessed the effectiveness of immunization with orally or subcutaneously delivered Gram-positive Enhancer Matrix (GEM) particles carrying two Campylobacter antigens: CjaA and CjaD. These two immunization routes using GEMs as the vector did not protect against Campylobacter colonization. Thus, we next assessed the efficacy of in ovo immunization using various delivery systems: GEM particles and liposomes. The hybrid protein rCjaAD, which is CjaA presenting CjaD epitopes on its surface, was employed as a model antigen. We found that rCjaAD administered in ovo at embryonic development day 18 by both delivery systems resulted in significant levels of protection after challenge with a heterologous C. jejuni strain. In practice, in ovo chicken vaccination is used by the poultry industry to protect birds against several viral diseases. Our work showed that this means of delivery is also efficacious with respect to commensal bacteria such as Campylobacter. In this study, we evaluated the protection after one dose of vaccine given in ovo. We speculate that the level of protection may be increased by a post-hatch booster of orally delivered antigens.

The impact of biosecurity and partial depopulation on Campylobacter prevalence in Irish broiler flocks with differing levels of hygiene and economic performance

Background

Campylobacter jejuni is the leading bacterial food-borne pathogen within the European Union (EU), and poultry meat is the primary route for transmission to humans.

Material and methods

This study examined the impact of partial depopulation (thinning), season, and farm performance (economic, hygiene, and biosecurity) on Campylobacter prevalence in Irish broilers over a 13-month period. Ten caecal samples were taken per flock, for a total of 211 flocks from 23 farms during the duration of the study. Campylobacter was isolated and enumerated according to modified published ISO methods for veterinary samples. Biosecurity was evaluated through a questionnaire based on risk factors for Campylobacter identified in previous studies. Hygiene compliance was assessed from audit records taken over the course of 1 year. All information relating to biosecurity and hygiene was obtained directly from the processing company. This was done to ensure farmers were unaware they were being monitored for Campylobacter prevalence and prevent changes to their behaviour.

Results and discussion

Farms with high performance were found to have significantly lower Campylobacter prevalence at first depopulation compared with low-performance farms across all seasons (P≤0.01). Peak Campylobacter levels were observed during the summer season at first thin in both the high- and low-performance groups. Campylobacter prevalence was found to increase to ≥85% in both high- and low-performance farms across all seasons at final depopulation, suggesting that Campylobacter was introduced during the first depopulation. On low-performance farms, four biosecurity interventions were found to significantly reduce the odds of a flock being Campylobacter positive (physical step-over barrier OR=0.17, house-specific footwear OR=0.13, absence of water body within 0.5 km OR=0.13, two or more broiler houses on a farm OR=0.16), compared with farms without these interventions. For high-performance farms, no single biosecurity intervention was identified as significant as this group had full compliance with multiple factors. High-performance farms had significantly better feed conversion ratios compared with low-performance farms (1.61 v 1.67 (P≤0.01)). No differences in flock mortality rates were observed (P≥0.05). This highlights the impact of season, biosecurity, partial depopulation, and farm performance on Campylobacter prevalence in Irish broilers.

Multiple-Strain Approach and Probabilistic Modeling of Consumer Habits in Quantitative Microbial Risk Assessment: A Quantitative Assessment of Exposure to Staphylococcal Enterotoxin A in Raw Milk

Quantitative microbial risk assessment (QMRA) models are extensively applied to inform management of a broad range of food safety risks. Inevitably, QMRA modeling involves an element of simplification of the biological process of interest. Two features that are frequently simplified or disregarded are the pathogenicity of multiple strains of a single pathogen and consumer behavior at the household level. In this study, we developed a QMRA model with a multiple-strain approach and a consumer phase module (CPM) based on uncertainty distributions fitted from field data. We modeled exposure to staphylococcal enterotoxin A in raw milk in Lombardy; a specific enterotoxin production module was thus included. The model is adaptable and could be used to assess the risk related to other pathogens in raw milk as well as other staphylococcal enterotoxins. The multiplestrain approach, implemented as a multinomial process, allowed the inclusion of variability and uncertainty with regard to pathogenicity at the bacterial level. Data from 301 questionnaires submitted to raw milk consumers were used to obtain uncertainty distributions for the CPM. The distributions were modeled to be easily updatable with further data or evidence. The sources of uncertainty due to the multiple-strain approach and the CPM were identified, and their impact on the output was assessed by comparing specific scenarios to the baseline. When the distributions reflecting the uncertainty in consumer behavior were fixed to the 95th percentile, the risk of exposure increased up to 160 times. This reflects the importance of taking into consideration the diversity of consumers' habits at the household level and the impact that the lack of knowledge about variables in the CPM can have on the final QMRA estimates. The multiple-strain approach lends itself to use in other food matrices besides raw milk and allows the model to better capture the complexity of the real world and to be capable of geographical specificity.

Campylobacter epidemiology from breeders to their progeny in Eastern Spain

While horizontal transmission is a route clearly linked to the spread of Campylobacter at the farm level, few studies support the transmission of Campylobacter spp. from breeder flocks to their offspring. Thus, the present study was carried out to investigate the possibility of vertical transmission. Breeders were monitored from the time of housing day-old chicks, then throughout the laying period (0 to 60 wk) and throughout their progeny (broiler fattening, 1 to 42 d) until slaughter. All samples were analyzed according with official method ISO 10272:2006. Results revealed that on breeder farms, Campylobacter isolation started from wk 16 and reached its peak at wk 26, with 57.0% and 93.2% of positive birds, respectively. After this point, the rate of positive birds decreased slightly to 86.0% at 60 wk. However, in broiler production all day-old chicks were found negative for Campylobacter spp, and the bacteria was first isolated at d 14 of age (5.0%), with a significant increase in detection during the fattening period with 62% of Campylobacter positive animals at the end of the production cycle. Moreover, non-positive sample was determined from environmental sources. These results could be explained because Campylobacter may be in a low concentration or in a non-culturable form, as there were several studies that successfully detected Campylobacter DNA, but failed to culture. This form can survive in the environment and infect successive flocks; consequently, further studies are needed to develop more modern, practical, cost-effective and suitable techniques for routine diagnosis.

Thermotolerant Campylobacter during Broiler Rearing: Risk Factors and Intervention

Thermotolerant Campylobacters are one of the most important bacterial causative agents of human gastrointestinal illness worldwide. In most European Union (EU) member states human campylobacteriosis is mainly caused by infection with Campylobacter jejuni or Campylobacter coli following consumption or inadequate handling of Campylobacter-contaminated poultry meat. To date, no effective strategy to control Campylobacter colonization of broilers during rearing is available. In this review, we describe the public health problem posed by Campylobacter presence in broilers and list and critically review all currently known measures that have been researched to lower the numbers of Campylobacter bacteria in broilers during rearing. We also discuss the most promising measures and which measures should be investigated further. We end this review by elaborating on readily usable measures to lower Campylobacter introduction and Campylobacter numbers in a broiler flock.

A systematic review characterizing on-farm sources of Campylobacter spp. for broiler chickens

Campylobacter and antimicrobial-resistant Campylobacter are frequently isolated from broiler chickens worldwide. In Canada, campylobacteriosis is the third leading cause of enteric disease and the regional emergence of ciprofloxacin-resistant Campylobacter in broiler chickens has raised a public health concern. This study aimed to identify, critically appraise, and synthesize literature on sources of Campylobacter in broilers at the farm level using systematic review methodology. Literature searches were conducted in January 2012 and included electronic searches in four bibliographic databases. Relevant studies in French or English (n = 95) conducted worldwide in any year and all study designs were included. Risk of Bias and GRADE criteria endorsed by the Cochrane collaboration was used to assess the internal validity of the study and overall confidence in the meta-analysis. The categories for on-farm sources were: broiler breeders/vertical transfer (number of studies = 32), animals (n = 57), humans (n = 26), environment (n = 54), and water (n = 63). Only three studies examined the antimicrobial resistance profiles of Campylobacter from these on-farm sources. Subgroups of data by source and outcome were analyzed using random effect meta-analysis. The highest risk for contaminating a new flock appears to be a contaminated barn environment due to insufficient cleaning and disinfection, insufficient downtime, and the presence of an adjacent broiler flock. Effective biosecurity enhancements from physical barriers to restricting human movement on the farm are recommended for consideration to enhance local on-farm food safety programs. Improved sampling procedures and standardized laboratory testing are needed for comparability across studies. Knowledge gaps that should be addressed include farm-level drug use and antimicrobial resistance information, further evaluation of the potential for vertical transfer, and improved genotyping methods to strengthen our understanding of Campylobacter epidemiology in broilers at the farm-level. This systematic review emphasizes the importance of improved industry-level and on-farm risk management strategies to reduce pre-harvest Campylobacter in broilers.

Uncertainty of population risk estimates for pathogens based on QMRA or epidemiology: a case study of Campylobacter in the Netherlands

Epidemiology and quantitative microbiological risk assessment are disciplines in which the same public health measures are estimated, but results differ frequently. If large, these differences can confuse public health policymakers. This article aims to identify uncertainty sources that explain apparent differences in estimates for Campylobacter spp. incidence and attribution in the Netherlands, based on four previous studies (two for each discipline). An uncertainty typology was used to identify uncertainty sources and the NUSAP method was applied to characterize the uncertainty and its influence on estimates. Model outcomes were subsequently calculated for alternative scenarios that simulated very different but realistic alternatives in parameter estimates, modeling, data handling, or analysis to obtain impressions of the total uncertainty. For the epidemiological assessment, 32 uncertainty sources were identified and for QMRA 67. Definitions (e.g., of a case) and study boundaries (e.g., of the studied pathogen) were identified as important drivers for the differences between the estimates of the original studies. The range in alternatively calculated estimates usually overlapped between disciplines, showing that proper appreciation of uncertainty can explain apparent differences between the initial estimates from both disciplines. Uncertainty was not estimated in the original QMRA studies and underestimated in the epidemiological studies. We advise to give appropriate attention to uncertainty in QMRA and epidemiological studies, even if only qualitatively, so that scientists and policymakers can interpret reported outcomes more correctly. Ideally, both disciplines are joined by merging their strong respective properties, leading to unified public health measures.

Estimating the time at which commercial broiler flocks in Great Britain become infected with Campylobacter: a Bayesian approach

Campylobacter is a common cause of intestinal disease in humans and is often linked to the consumption of contaminated poultry meat. Despite considerable research on the topic there is a large amount of uncertainty associated with Campylobacter epidemiology. A Bayesian model framework was applied to multiple longitudinal datasets on Campylobacter infection in UK broiler flocks to estimate the time at which each flock was first infected with Campylobacter. The model results suggest that the day of first infection ranges from 10 to 45 days; however, over half had a time of infection between 30 and 35 days. When considering only those flocks which were thinned, 48% had an estimated day of infection within 2 days of the day of thinning, thus suggesting an association between thinning and Campylobacter infection. These results demonstrate how knowledge of the time of infection can be correlated to known events to identify potential risk factors for infection.

Assessing most practical and effective protocols to sanitize hands of poultry catching crew members

Catching crew members can heavily contaminate their hands with organic material. They can act as mechanical vector and spread diseases between farms. Hand hygiene is an important issue for the industry as a whole and for human health by reducing contamination risks. Many studies, in human medicine, tend to make hand rub a standard for hand hygiene. However, few studies have tested the effectiveness of hand hygiene products on visibly contaminated hands. The objective of this study was to evaluate the effectiveness of practical hand sanitization protocols: water and soap, degreasing cream and hand wipes, all combined with alcohol-based hand gel. The use of alcohol-based gel alone was also evaluated. For the reduction of coliforms after washing, there was no statistically significant difference between protocols when the initial level of bacterial contamination was low to moderate. When hands were highly contaminated, the alcohol-based gel alone was less effective than the degreasing cream combined with the alcohol-based gel (p=0.002). As for the reduction in total aerobic bacteria counts, there was no difference between protocols when the initial level of bacterial contamination was low. The water, soap and alcohol-based gel protocol was more effective than the scrubbing wipes and alcohol-based gel protocol when hands were moderately (p=0.002) and highly contaminated (p=0.001). All protocols were effective in neutralizing Salmonella on hands. Reducing the level of bacterial contamination on hands before using an alcohol-based gel seems important to ensure effective hand sanitation for highly and moderately contaminated hands. This can be done by using a degreasing cream or water and soap. Based on the survey, catching crew members preferred using warm water and soap compared to a degreasing cream.

The prevalence of Campylobacter spp. in broiler flocks and on broiler carcases, and the risks associated with highly contaminated carcases

A baseline survey on the prevalence of Campylobacter spp. in broiler flocks and Campylobacter spp. on broiler carcases in the UK was performed in 2008 in accordance with Commission Decision 2007/516/EC. Pooled caecal contents from each randomly selected slaughter batch, and neck and breast skin from a single carcase were examined for Campylobacter spp. The prevalence of Campylobacter in the caeca of broiler batches was 75·8% (303/400) compared to 87·3% (349/400) on broiler carcases. Overall, 27·3% of the carcases were found to be highly contaminated with Campylobacter (≥1000 c.f.u./g). Slaughter in the summer months (June, July, August) [odds ratio (OR) 3·50], previous partial depopulation of the flock (OR 3·37), and an increased mortality at 14 days (≥1·25% to <1·75%) (OR 2·54) were identified as significant risk factors for the most heavily Campylobacter-contaminated carcases. Four poultry companies and farm location were also found to be significantly associated with highly contaminated carcases.

Investigation of prevalence and risk factors forCampylobacterin broiler flocks at slaughter: results from a UK survey

During 2007–2009 a UK-wide, 3-year stratified randomized survey of UK chicken broiler flocks was conducted to estimate the prevalence ofCampylobacter-infected batches of birds at slaughter. Thirty-seven abattoirs, processing 88·3% of the total UK slaughter throughput, were recruited at the beginning of the survey. Of the 1174 slaughter batches sampled, 79·2% were found to be colonized withCampylobacter, the majority of isolates beingC. jejuni. Previous partial depopulation of the flock [odds ratio (OR) 5·21], slaughter in the summer months (categorized as June, July and August; OR 14·27) or autumn months (categorized as September, October and November; OR 1·70) increasing bird age (40–41 days, OR 3·18; 42–45 days, OR 3·56; ⩾46 days, OR 13·43) and higher recent mortality level in the flock (1·00–1·49% mortality, OR 1·57; ⩾1·49% mortality, OR 2·74) were all identified as significant risk factors forCampylobactercolonization of the birds at slaughter. Time in transit to the slaughterhouse of more than 2·5 h was identified as a protective factor (OR 0·52).

Biosecurity-based interventions and strategies to reduce Campylobacter spp. on poultry farms

The prevention and control of Campylobacter colonization of poultry flocks are important public health strategies for the control of human campylobacteriosis. A critical review of the literature on interventions to control Campylobacter in poultry on farms was undertaken using a systematic approach. Although the focus of the review was on aspects appropriate to the United Kingdom poultry industry, the research reviewed was gathered from worldwide literature. Multiple electronic databases were employed to search the literature, in any language, from 1980 to September 2008. A primary set of 4,316 references was identified and scanned, using specific agreed-upon criteria, to select relevant references related to biosecurity-based interventions. The final library comprised 173 references. Identification of the sources of Campylobacter in poultry flocks was required to inform the development of targeted interventions to disrupt transmission routes. The approach used generally involved risk factor-based surveys related to culture-positive or -negative flocks, usually combined with a structured questionnaire. In addition, some studies, either in combination or independently, undertook intervention trials. Many of these studies were compromised by poor design, sampling, and statistical analysis. The evidence for each potential source and route of transmission on the poultry farm was reviewed critically, and the options for intervention were considered. The review concluded that, in most instances, biosecurity on conventional broiler farms can be enhanced and this should contribute to the reduction of flock colonization. However, complementary, non-biosecurity-based approaches will also be required in the future to maximize the reduction of Campylobacter-positive flocks at the farm level.

Retention of Campylobacter (Campylobacterales: Campylobacteraceae) in the house fly (Diptera: Muscidae)

The house fly (Musca domestica L.) may transmit Campylobacter to broiler flocks. We assessed the retention time of house flies for Campylobacter jejuni at five temperatures and three doses. Flies were inoculated individually at their proboscis with 1.6 x 10(7) CFU (colony forming units) of C. jejuni and incubated at 15, 20, 25, 30, and 35 degrees C. Furthermore, a dose experiment was conducted at 25 degrees C where individual flies were inoculated in three series: 6.5 x 10(6), 6.0 x 10(4), and 8.2 x 10(2) C.jejuni CFU. Whole flies were tested for C. jejuni carriage at 0, 6, 12, 18, and 24 h by initial preenrichment in Bolton broth, which afterwards was streaked on modified mCCDA agar plates and incubated under micro-aerobic conditions. The results showed that the time C. jejuni remained in flies declined over time with ascending temperatures and when reducing the inoculation dose. All flies stayed Campylobacter positive 24 h postinoculation at 15 degrees C whereas only one-third of the flies were positive at 20 degrees C and few to none at 25, 30, and 35 degrees C. When combinations of temperature and retention time were expressed as accumulated day-degrees, data could be adequately fitted using a generalized linear mixed model that included a linear effect of day-degrees and the difference between the lowest and the two highest doses. Based on model predictions of selected combinations of temperature and dose, the time for 50% and 1% of flies containing Campylobacter was calculated. It is suggested that house flies are mainly short distance carriers of C. jejuni.

Danish strategies to control Campylobacter in broilers and broiler meat: facts and effects

Thermotolerant Campylobacter spp. have been the most common bacterial cause of human gastrointestinal disease in Denmark since 1999. In 2003, the Danish voluntary strategy to control Campylobacter was intensified. The focus was on biosecurity, allocation of meat from Campylobacter-negative broilers to the production of chilled products, and consumer information campaigns. From 2002 to 2007, the percentage of Campylobacter-positive broiler flocks at slaughter decreased from 43% to 27%. After processing, Campylobacter-positive samples of chilled broiler meat fell from 18% in 2004 to 8% in 2007. Furthermore, the number of registered human Campylobacter cases decreased by 12%; from 4379 cases in 2002 to 3865 cases in 2007. We believe that the observed decrease in the occurrence of Campylobacter in broilers and broiler meat and the coincidental fall in the number of registered human cases is, in part, a result of the implemented control strategy.

Effectiveness and efficiency of controlling Campylobacter on broiler chicken meat

Campylobacter bacteria are an important cause of foodborne infections. We estimated the potential costs and benefits of a large number of possible interventions to decrease human exposure to Campylobacter by consumption of chicken meat, which accounts for 20-40% of all cases of human campylobacteriosis in the Netherlands. For this purpose, a farm-to-fork risk assessment model was combined with economic analysis and epidemiological data. Reduction of contamination at broiler farms could be efficient in theory. However, it is unclear which hygienic measures need to be taken and the costs can be very high. The experimental treatment of colonized broiler flocks with bacteriophages has proven to be effective and could also be cost efficient, if confirmed in practice. Since a major decrease of infections at the broiler farm is not expected in the short term, additional measures in the processing plant were also considered. At this moment, guaranteed Campylobacter-free chicken meat at the retail level is not realistic. The most promising interventions in the processing plant are limiting fecal leakage during processing and separation of contaminated and noncontaminated flocks (scheduling), followed by decontamination of the contaminated flock. New (faster and more sensitive) test methods to detect Campylobacter colonization in broilers flocks are a prerequisite for successful scheduling scenarios. Other methods to decrease the contamination of meat of colonized flocks such as freezing and heat treatment are more expensive and/or less effective than chemical decontamination.