Risk factors for the presence of Campylobacter spp. in Dutch broiler flocks

Campylobacter presence on Dutch broiler farms and associated risk factors

Campylobacter is the most reported zoonotic pathogen in humans in the European Union. Poultry is a major source of human infection with Campylobacter. Although many studies are done on the presence of Campylobacter in broilers and theoretically effective control measures are known, their relative importance at broiler farms remains poorly understood. Therefore, the aim of this study was to investigate the presence of Campylobacter on selected broiler farms in the Netherlands, to determine the moment of introduction, and associated risk factors. A longitudinal study on 25 broiler farms was carried out between June 2017 and December 2020. Fecal samples were collected weekly from 43 broiler houses. In total 497 flocks were sampled. Putative variables on flock and farm characteristics for a risk factor analysis were gathered through questionnaires. Risk factors associated with the presence of Campylobacter in a broiler flock were determined using regression models. In total 30% of the flocks included in the study were positive for Campylobacter. Factors associated with presence of Campylobacter at slaughter age included: season, mowing lawns and presence of agricultural side activities. While summer/autumn and mowing lawns were associated with an increase in Campylobacter presence in flocks, the farmer having agricultural side activities other than poultry production was associated with a decrease. Analysis of the age at which flocks first tested Campylobacter positive revealed that slower growing breeds became positive on average 1 wk later compared to regular growers. This study revealed a delayed introduction of Campylobacter in slower grower vs. regular grower broiler flocks reared indoors. In addition, it confirmed importance of season as major risk factor. The relevance of mowing and preceding positive flocks as risk factors needs further investigation.

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.

Differences in Genotype and Antimicrobial Resistance between Campylobacter spp. Isolated from Organic and Conventionally Produced Chickens in Sweden

Antibiotic resistance is a major challenge worldwide and increased resistance to quinolones in Campylobacter is being reported. Analysis of antibiotic resistance was performed on 157 Campylobacter strains (123 C. jejuni and 34 C. coli) from conventional and organic chickens produced in Sweden. Susceptibility for tetracycline, ciprofloxacin, erythromycin, nalidixic acid, streptomycin, and gentamycin was determined by microdilution. All 77 isolates from organic chickens were sensitive to all antibiotics, except two C. jejuni that were resistant to tetracycline. Of the 80 isolates from conventional chickens, 22.5% of C. jejuni and 11.1% of C. coli were resistant to quinolones and 5.6% of C. jejuni were resistant to tetracycline. Whole-genome sequencing resulted in 50 different sequence types of C. jejuni and six of C. coli. Nine sequence types were found in both organic and conventional chickens. Two of these (ST-19 and ST-257) included isolates from conventional broilers with different resistance phenotypes to the remaining isolates from conventional and organic broilers. There are management differences between the production systems, such as feed, breed, use of coccidiostats, and access to outdoor area. It is unlikely that quinolone resistance has arisen due to use of antimicrobials, since fluoroquinolones are not permitted in Swedish broiler production.

Demographic, Husbandry, and Biosecurity Factors Associated with the Presence of Campylobacter spp. in Small Poultry Flocks in Ontario, Canada

This study is part of a 2 year disease surveillance project conducted to establish the prevalence of poultry and zoonotic pathogens, including Campylobacter spp., among small poultry flocks in Ontario, Canada. For each post-mortem submission to the Animal Health Laboratory, a pooled sample of cecal tissue was cultured for Campylobacter spp., and a husbandry and biosecurity questionnaire was completed by the flock owner (n = 153). Using both laboratory and questionnaire data, our objective was to investigate demographic, husbandry, and biosecurity factors associated with the presence of Campylobacter spp. in small flocks. Two multivariable logistic regression models were built. In the farm model, the odds of Campylobacter spp. were higher in turkeys, and when birds were housed in a mixed group with different species and/or types of birds. The odds were lower when antibiotics were used within the last 12 months, and when birds had at least some free-range access. The effect of pest control depended on the number of birds at risk. In the coop model, the odds of Campylobacter spp. were lower when owners wore dedicated clothing when entering the coop. These results can be used to limit the transmission of Campylobacter spp. from small poultry flocks to humans.

The effectiveness of biosecurity interventions in reducing the transmission of bacteria from livestock to humans at the farm level: A systematic literature review

Zoonotic bacterial infections are a health hazard for people who are in regular contact with livestock at the farm level. Improved biosecurity can limit zoonotic pathogen transmission within farms. The aim of this review was to summarize the effectiveness of farm-level biosecurity interventions in reducing bacterial transmission from animals to people who lived, worked in or visited farms. A systematic literature review was conducted using Embase, Ovid Medline and Agris databases, which were searched on 7^th of July 2019, limited to English language papers but with no time exclusion criteria. A narrative synthesis was undertaken utilizing the Centre for Reviews and Dissemination approach, reported in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Risk of bias within and across the included studies was performed using established checklists. Out of 869 studies retrieved through database searches, 11 studies were selected. In addition, three studies were found through study reference lists. Fourteen studies were therefore included in this review. Biosecurity interventions were grouped into five categories: hand washing, sanitization and hygienic measures (six studies); personal protective equipment (five studies); vaccination (two studies); other interventions (e.g. air ventilation flap) (four studies); and routine farm activities (two studies). Across studies that investigated odds of human colonization or infection (three studies), odds were seen to both be increased and decreased through use of tested biosecurity measures. Large confidence intervals that often crossed the threshold of an odds ratio equal to 1 were found. Most of the studies' overall risk of bias was 'medium risk' (11 studies), with selection bias domains generally being scored 'medium risk.' Biosecurity interventions are potentially beneficial in reducing bacterial transmission from animals to humans. However, more high-quality evidence is needed to increase certainty in which interventions, in which contexts, are most effective from the human health perspective.

Approaches to prevent and control Campylobacter spp. colonization in broiler chickens: a review

Campylobacter, Gram-negative bacteria, is the most common cause of acute bacterial enteritis in human beings, both in developing and developed countries. It is believed that poultry, in particular broiler chickens, is the main host of human infection with Campylobacter. Handling and consumption of contaminated chicken meat are the usual modes of transmission. Prevention and reduction of Campylobacter colonization in poultry farms will cut off the road of infection transmission to humans throughout the food chain. With the incidence of antibiotic resistance and with growing concern about superbugs, the search for natural and safe alternatives will considerably increase in the coming years. In this review, we will discuss the prevalence and risk factors of Campylobacter colonization in broiler chickens and sources of infection. This review also provides extensive and recent approaches to prevent and control Campylobacter colonization in broiler chickens, including biosecurity measures, natural feed/drinking water additives with antimicrobial properties, bacteriocins, bacteriophages, antimicrobial peptides, and vaccination strategies to prevent and control the incidence of human campylobacteriosis.

Longitudinal Study of the Distribution of Antimicrobial-Resistant Campylobacter Isolates from an Integrated Broiler Chicken Operation

The aim of this study was to analyze the prevalence, antimicrobial resistance, and genetic diversity of Campylobacter isolates that were obtained from whole chicken production stages in Korea. A total of 1348 samples were collected from 10 production lines. The prevalence of Campylobacter in breeder farm, broiler farm, slaughterhouse, and retail meat products was 50.0%, 3.3%, 13.4%, and 68.4%, respectively, and Campylobacter was not detected at the hatchery stage. Resistance to quinolones/fluoroquinolones was the most prevalent at all stages. Among the multidrug-resistant isolates, 16 isolates (19.8%) from breeder farm were resistant to both azithromycin and ciprofloxacin. A total of 182 isolates were subdivided into 82 pulsed-field gel electrophoresis (PFGE) genotypes with 100% similarity. Diverse genotypes were presented with discontinuous patterns along the whole production chain. Thirty percent of Campylobacter-free flocks became positive after slaughtering. An identical genotype was simultaneously detected from both breeder farm and retail meat, even from different production lines. This study reveals that antimicrobial-resistant Campylobacter contamination can occur at all stages of the chicken supply chain. In particular, the breeder farm and slaughterhouse should be the main control points, as they are the potential stages at which antimicrobial-resistant Campylobacter could spread to retail meat products by horizontal transmission.

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.

Prevalence of and Risk Factors for Campylobacter spp. Colonization of Broiler Chicken Flocks in Greece

The prevalence and risk factors for Campylobacter spp. colonization of broiler flocks and broiler carcass contamination in Greek slaughterhouses were investigated. Over a 14-month period, a pool of 10 ceca and 5 neck skin samples from chicken carcasses were collected from each of 142 batches of broiler flocks slaughtered in 3 different slaughterhouses. Information on potential risk factors for Campylobacter infection in broilers was collected by an on-farm interview and linked according to the Campylobacter contamination status of broiler flocks and differences in farm characteristics and management practices identified from questionnaires. Campylobacter spp. was isolated from 73.94% and 70.42% of ceca (95% CI 65.92-80.94) and carcasses (95% CI 62.19-77.78), respectively. A significant correlation (p < 0.001) between the presence of Campylobacter spp. in broiler ceca and contamination of carcasses was found, suggesting the spread of the microorganism on the skin of carcasses during the slaughtering procedure. A multiple logistic regression showed the disinfection of the poultry house being conducted by unskilled personnel (odds ratio [OR] ¼ = 3.983) as a significant risk factor (p < 0.05) and the use of straw litter as bedding material (OR ¼ = 0.170) and closure of windows during the intervals of production cycles (OR ¼ = 0.396) as significant protective factors (p < 0.05) for broiler flock contamination. These results are important and help further the understanding of the epidemiology of Campylobacter spp. derived from poultry in Greece.

Prevalence and risk factors of Campylobacter infection in broiler and cockerel flocks in Mymensingh and Gazipur districts of Bangladesh

Campylobacter spp. is one of the most frequent causes of foodborne gastroenteritis. This study aimed to estimate the prevalence and to identify the risk factors of farm-level Campylobacter infection in meat-type chicken flocks. A cross-sectional study was conducted in two selected districts of Bangladesh over the period of January to July 2019. A total of 84 pooled cloacal swab samples were collected from 84 broiler and cockerel farms. Data on farm management, biosecurity, and hygiene practices were collected using a structured questionnaire through a face-to-face interview during sampling. Thereafter, Campylobacter spp. were isolated through bacteriological culture and identified by Gram staining and biochemical tests. Furthermore, the isolates were confirmed using the polymerase chain reaction by targeting the 16S rRNA gene. The risk factors were analyzed at the farm level using multivariable logistic regression with the significant levels of P-value ≤ 0.05. Among the 84 farms, 34 were positive to Campylobacter spp.; thus, the prevalence was estimated to be 40.5% (95% CI: 30.1%-51.8%). In risk factor analysis, the following factors were found to be significantly associated with Campylobacter infection: shed older than five years, birds older than 30 days, flock size with more than 1500 birds, downtime less than seven days, no disinfection of shed surroundings during rearing, rice husk as litter materials, and less than 10 years of farming experience. The study identified the factors that could lead to the setting of effective interventions in controlling Campylobacter infection in chickens to reduce campylobacteriosis in humans through meat consumption.

Identification of Transmission Routes of Campylobacter and On-Farm Measures to Reduce Campylobacter in Chicken

An in-depth analysis was performed on Swedish broiler producers that had delivered chickens with Campylobacter to slaughter over several years, in order to identify possible transmission routes and formulate effective measures to prevent chickens being colonized with Campylobacter. Between 2017 and 2019, 626 samples were collected at farm level and Campylobacter was isolated from 133 (21.2%). All C. jejuni and C. coli isolated from these samples were whole-genome sequenced, together with isolates from the corresponding cecum samples at slaughter (n = 256). Core genome multi-locus sequence typing (cgMLST) analysis, using schemes consisting of 1140 and 529 genes for C. jejuni and C. coli, respectively, revealed that nearby cattle, contaminated drinking water, water ponds, transport crates, and parent flocks were potential reservoirs of Campylobacter. A novel feature compared with previous studies is that measures were implemented and tested during the work. These contributed to a nationwide decrease in Campylobacter-positive flocks from 15.4% in 2016 to 4.6% in 2019, which is the lowest ever rate in Sweden. To conclude, there are different sources and routes of Campylobacter transmission to chickens from different broiler producers, and individual measures must be taken by each producer to prevent Campylobacter colonization of chickens.

Characterization and Prevalence of Campylobacter spp. From Broiler Chicken Rearing Period to the Slaughtering Process in Eastern China

Campylobacter is one of the most important foodborne pathogens worldwide, and poultry is regarded as the main reservoir of Campylobacter. The contamination of Campylobacter in broiler chickens at the farm level is closely related to the transmission of Campylobacter in the poultry production chain. This study identified 464 Campylobacter isolates from 1,534 samples from broiler rearing period and slaughtering process including 233 Campylobacter jejuni isolates and 231 Campylobacter coli isolates. We have observed a dynamic distribution of Campylobacter during broiler chicken production, that 66.3% of Campylobacter isolates were C. jejuni during broiler rearing period, while C. coli occupied 60.4% of Campylobacter isolates during the broiler slaughtering process. A tag-label method allowed us to track the dynamic of Campylobacter in each broiler chicken from 31-day age at rearing to the partition step in the slaughterhouse. At the 31-day during rearing, 150 broiler chicken were labeled, and was tracked for Campylobacter positive from rearing period to slaughtering process. Among the labeled broiler, 11 of the tracking broiler samples were able to detect Campylobacter from rearing period to slaughtering. All Campylobacter isolates from the 11 tracking samples were sequenced and analyzed. C. jejuni isolates were divided into four STs and C. coli isolates were divided into six STs. Isolates with identical core genome were observed from the same tag-labeled samples at different stages indicating a vertical transmission of Campylobacter in the early broiler meat production. Meanwhile, the core genome analysis elucidated the cross-contamination of Campylobacter during the rearing period and the slaughtering process. The virulotyping analysis revealed that all C. jejuni isolates shared the same virulotypes, while C. coli isolates were divided into three different virulotypes. The antimicrobial resistance gene analysis demonstrated that all Campylobacter isolates contained at least two antibiotic resistance genes (ARGs), and the ARG profiles were well-corresponding to each ST type. Our study observed a high prevalence of Campylobacter during the early chicken meat production, and further studies will be needed to investigate the diversity and transmission of Campylobacter in the poultry production chain.

Update and review of control options for Campylobacter in broilers at primary production

The 2011 EFSA opinion on Campylobacter was updated using more recent scientific data. The relative risk reduction in EU human campylobacteriosis attributable to broiler meat was estimated for on-farm control options using Population Attributable Fractions (PAF) for interventions that reduce Campylobacter flock prevalence, updating the modelling approach for interventions that reduce caecal concentrations and reviewing scientific literature. According to the PAF analyses calculated for six control options, the mean relative risk reductions that could be achieved by adoption of each of these six control options individually are estimated to be substantial but the width of the confidence intervals of all control options indicates a high degree of uncertainty in the specific risk reduction potentials. The updated model resulted in lower estimates of impact than the model used in the previous opinion. A 3-log10 reduction in broiler caecal concentrations was estimated to reduce the relative EU risk of human campylobacteriosis attributable to broiler meat by 58% compared to an estimate larger than 90% in the previous opinion. Expert Knowledge Elicitation was used to rank control options, for weighting and integrating different evidence streams and assess uncertainties. Medians of the relative risk reductions of selected control options had largely overlapping probability intervals, so the rank order was uncertain: vaccination 27% (90% probability interval (PI) 4-74%); feed and water additives 24% (90% PI 4-60%); discontinued thinning 18% (90% PI 5-65%); employing few and well-trained staff 16% (90% PI 5-45%); avoiding drinkers that allow standing water 15% (90% PI 4-53%); addition of disinfectants to drinking water 14% (90% PI 3-36%); hygienic anterooms 12% (90% PI 3-50%); designated tools per broiler house 7% (90% PI 1-18%). It is not possible to quantify the effects of combined control activities because the evidence-derived estimates are inter-dependent and there is a high level of uncertainty associated with each.

Prevalence of Campylobacter spp. in Poultry in Three Spanish Farms, A Slaughterhouse and A Further Processing Plant

The present study was conducted to investigate the prevalence of Campylobacter spp. in a selection of poultry flocks and the corresponding broiler carcasses as well as the possible impact of contamination during slaughter and processing. Samples of the same flock at different ages in three farms (A, B and C) were taken for the determination of Campylobacter spp. The same broiler flocks were examined at different stages of one slaughterhouse and at a further processing plant. The slaughterhouse environment and processing equipment were sampled. Campylobacter spp. was not detected in 7 and 14-day-old broilers in any of the three farms studied. However, Campylobacter spp. was detected in 35 and 42-day-old broilers at two farms (Farm A and B). This pathogen was detected in both dirty and clean transport crates, in scalding water, and on the defeathering machine and the working table at the end of the working day, but not at the beginning. After defeathering, Campylobacter spp. was detected in all of the sampled carcasses. Campylobacter spp. was detected in all of the carcasses and the poultry meat portion samples from Farm C, although it was not detected at the farm level. This suggests that Campylobacter spp. infected flocks may be a source of these bacteria in the corresponding carcasses, but a cross-contamination during the transportation and slaughter process is also very important.

Influence of lauric acid on the susceptibility of chickens to an experimental Campylobacter jejuni colonisation

Among the organic acids, lauric acid has shown a high level of in vitro activity against Campylobacter jejuni. The prevalence and intensity of C. jejuni excretion at slaughter often becomes lower with increasing age. In higher-aged broilers on organic farms which often use other breeds, in turn, the prevalence of C. jejuni is sometimes higher at slaughter. The question then arises as to whether a diet with higher lauric acid concentrations, the age alone or the genetic breed might have an effect in the spread and intensity of an experimental C. jejuni infection in vivo. Therefore, two complete diets with or without 2% lauric acid from palm kernel fatty acids were offered to 450 chickens (ten subgroups à 15 birds, repetitions: n = 3) of two broiler and two layer breeds (Ross 308, Hubbard JA 757, Lohmann Dual and Lohmann Brown-Classic). All breeds were reared for 42 days, Lohmann Brown-Classic also for about 98 days. Twenty-one days before dissection, three seeder birds per subgroup were orally infected with a 1 mL inoculum of C. jejuni (4.46±0.35 log10 CFU/mL). Qualitative detection of C. jejuni in cloacal swabs was performed at days 2, 4, 7, 14 after inoculation and at dissection in all birds. Quantitative detection was performed on excreta samples of seeder birds at days 2, 11 and 17 after experimental challenge and on caecal samples of all birds at dissection. Two days after experimental inoculation, C. jejuni prevalence was higher in control birds without lauric acid supplementation (48.9% vs. 39.6%; P = 0.0462). Depending on age, two days after inoculation the C. jejuni prevalence in young Lohmann Brown-Classic chickens was significantly lower (37.8% vs. 61.1%) whereas at dissection it was higher (99% vs. 67%). At day 2 after inoculation C. jejuni counts in the excreta of young Lohmann Brown-Classic were lower in comparison to those in old ones (log10 CFU/g: 3.30±2.68 vs. 5.24±1.56). Eleven (log10 CFU/g: 5.14±1.13 vs. 4.16±0.82) and 17 days after inoculatioin (log10 CFU/g: 3.77±2.02 vs. 1.72±1.87) it was the reverse situation. At dissection, the carriage of C. jejuni in caecal content was higher in younger than in older birds (log10 CFU/g: 8.57±0.46 vs. 6.66±1.43). An effect of genetic breed on C. jejuni prevalence was seen at dissection, this being lowest in Lohmann Dual chickens (91% vs. 98.9% in other breeds). At d 17 after challenge, C. jejuni counts in the excreta of young Lohmann Brown-Classic were lower in comparison to Ross 308 and Hubbard JA 757 (log10 CFU/g: 3.77±2.02 vs. 5.21±0.85 and 5.62±0.90). Lohmann Dual chickens showed an intermediary excretion, this being only significant lower compared to Hubbard JA 757 (log10 CFU/g: 4.31±0.89). In summary, the effect of lauric acid is limited to the initial phase after experimental inoculation. A higher age at infection seems to lead to a more rapid limitation of the infection. The excretion of C. jejuni appears to decrease more rapidly in layer breeds than in broiler lines after experimental inoculation.

Risk perceptions of public health and food safety hazards in poultry husbandry by citizens, poultry farmers and poultry veterinarians

Differences in risk perceptions of public health and food safety hazards in various poultry husbandry systems by various stakeholder groups, may affect the acceptability of those husbandry systems. Therefore, the objective was to gain insight into risk perceptions of citizens, poultry farmers, and poultry veterinarians regarding food safety and public health hazards in poultry husbandry systems, and into factors explaining these risk perceptions. We surveyed risk perceptions of Campylobacter contamination of broiler meat, avian influenza introduction in laying hens, and altered dioxin levels in eggs for the most commonly used broiler and laying hen husbandry systems in Dutch citizens (n = 2,259), poultry farmers (n = 100), and poultry veterinarians (n = 41). Citizens perceived the risks of the three hazards in the indoor systems higher and in the outdoor systems lower than did the professionals. Citizens reported higher concerns regarding aspects reflecting underlying psychological factors of risk perception compared to professionals. Professionals indicated a relatively low level of personal control, which might imply risk denial. Of the socio-demographic characteristics, gender and childhood residence were associated with risk perceptions. The influence of other factors of risks perception are discussed. It is suggested that risk perceptions of all stakeholder groups are influenced by affect, stigma, and underlying values. To adapt current or new husbandry systems that can count on societal support, views of key stakeholders and multiple aspects such as animal welfare, public health, food safety, and underlying values should be considered integrally. When trade-offs, such as between animal welfare and public health have to be made, insight into underlying values might help to find consensus among stakeholders.

Campylobacter in the Food Chain

Currently Campylobacter is the most commonly reported zoonosis in developed and developing countries. In the European Union, the number of reported confirmed cases of human campylobacteriosis was 246,307 in 2016, which represents 66.3 cases per 100,000 population. The genus Campylobacter includes 31 species with 10 subspecies. Within the genus Campylobacter, C. jejuni subsp. jejuni and C. coli are most frequently associated with human illness. Mainly, the infection is sporadic and self-limiting, although some cases of outbreaks have been also reported and some complications such as Guillain-Barré syndrome might appear sporadically. Although campylobacters are fastidious microaerophilic, unable to multiply outside the host and generally very sensitive, they can adapt and survive in the environment, exhibiting aerotolerance and resistance to starvation. Many mechanisms are involved in this, including pathogenicity, biofilm formation, and antibiotic resistant pathways. This chapter reviews the sources, transmission routes, the mechanisms, and strategies used by Campylobacter to persist in the whole food chain, from farm to fork. Additionally, different strategies are recommended for application along the poultry food chain to avoid the public health risk associated with this pathogen.

Cleaning and disinfection programs against Campylobacter jejuni for broiler chickens: productive performance, microbiological assessment and characterization

Detailed cleaning and disinfection programs aims to reduce infection pressure from microorganisms from one flock to the next. However, studies evaluating the benefits to poultry performance, the sanitary status of the facilities, and the sanitary quality of the meat are rarely found. Thus, this study was designed to evaluate 2 cleaning and disinfecting programs regarding their influence on productive performance, elimination of Campylobacter, and characterization of Campylobacter jejuni strains when applied to broiler chickens’ facilities. Two subsequent flocks with 960 birds each were distributed into 32 pens containing 30 birds each. In the first, the whole flock was inoculated with a known strain of Campylobacter jejuni in order to contaminate the environment. In the second flock, performance and microbiological evaluations were done, characterizing an observational study between 2 cleaning and disinfection programs, regular and proposed. The regular program consisted of sweeping facilities, washing equipment and environment with water and neutral detergent. The proposed cleaning program consisted of dry and wet cleaning, application of 2 detergents (one acid and one basic) and 2 disinfectants (250 g/L glutaraldehyde and 185 g/L formaldehyde at 0.5% and 210 g/L para-chloro-meta-cresol at 4%). Total microorganism count in the environment and Campylobacter spp. identification were done for the microbiological assessment of the environment and carcasses. The positive samples were submitted to molecular identification of Campylobacter spp. and posterior genetic sequencing of the species identified as Campylobacter jejuni. The birds housed in the facilities and submitted to the proposed treatment had better performance when compared to the ones in the regular treatment, most likely because there was a smaller total microorganism count on the floor, walls, feeders and drinkers. The proposed program also resulted in a reduction of Campylobacter spp. on floors, drinkers and birds. Moreover, it was possible to identify 6 different Campylobacter jejuni strains in the facilities. The proposed treatment resulted in a positive influence on the birds’ performance and reduction of environment contamination for broiler chickens.

Knowledge gaps in control of Campylobacter for prevention of campylobacteriosis

Campylobacteriosis is an important, worldwide public health problem with numerous socio-economic impacts. Since 2015, approximately 230,000 cases have been reported annually in Europe. In the United States, Australia and New Zealand, campylobacteriosis is the most commonly reported disease. Poultry and poultry products are considered important sources of human infections. Poultry meat can become contaminated with Campylobacter during slaughter if live chickens are intestinal carriers. Campylobacter spp. can be transferred from animals to humans through consumption and handling of contaminated food products, with fresh chicken meat being the most commonly implicated food type. Regarding food-borne disease, the most important Campylobacter species are Campylobacter jejuni and Campylobacter coli. In humans, clinical signs of campylobacteriosis include diarrhoea, abdominal pain, fever, headache, nausea and vomiting. Most cases of campylobacteriosis are sporadic and self-limiting, but there are post-infection complications, for example, Guillain-Barrés syndrome. This review summarizes an analysis undertaken by the DISCONTOOLS group of experts on campylobacteriosis. Gaps were identified in: (i) knowledge of true number of infected humans; (ii) mechanisms of pathogenicity to induce infection in humans; (iii) training to prevent transfer of Campylobacter from raw to ready-to-eat food; (iv) development of effective vaccines; (v) understanding transmission routes to broiler flocks; (vi) knowledge of bacteriocins, bacteriophages and antimicrobial peptides as preventive therapies; (vii) ration formulation as an effective preventive measure at a farm level; (viii) development of kits for rapid detection and quantification of Campylobacter in animals and food products; and (ix) development of more effective antimicrobials for treatment of humans infected with Campylobacter. Some of these gaps are relevant worldwide, whereas others are more related to problems encountered with Campylobacter in industrialized countries.

Explanatory Variables Associated with Campylobacter and Escherichia coli Concentrations on Broiler Chicken Carcasses during Processing in Two Slaughterhouses

This study aimed at identifying explanatory variables that were associated with Campylobacter and Escherichia coli concentrations throughout processing in two commercial broiler slaughterhouses. Quantative data on Campylobacter and E. coli along the processing line were collected. Moreover, information on batch characteristics, slaughterhouse practices, process performance, and environmental variables was collected through questionnaires, observations, and measurements, resulting in data on 19 potential explanatory variables. Analysis was conducted separately in each slaughterhouse to identify which variables were related to changes in concentrations of Campylobacter and E. coli during the processing steps: scalding, defeathering, evisceration, and chilling. Associations with explanatory variables were different in the slaughterhouses studied. In the first slaughterhouse, there was only one significant association: poorer uniformity of the weight of carcasses within a batch with less decrease in E. coli concentrations after defeathering. In the second slaughterhouse, significant statistical associations were found with variables, including age, uniformity, average weight of carcasses, Campylobacter concentrations in excreta and ceca, and E. coli concentrations in excreta. Bacterial concentrations in excreta and ceca were found to be the most prominent variables, because they were associated with concentration on carcasses at various processing points. Although the slaughterhouses produced specific products and had different batch characteristics and processing parameters, the effect of the significant variables was not always the same for each slaughterhouse. Therefore, each slaughterhouse needs to determine its particular relevant measures for hygiene control and process management. This identification could be supported by monitoring changes in bacterial concentrations during processing in individual slaughterhouses. In addition, the possibility that management and food handling practices in slaughterhouses contribute to the differences in bacterial contamination between slaughterhouses needs further investigation.

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.

The transmissible spongiform encephalopathies of livestock

Prion diseases or transmissible spongiform encephalopathies (TSEs) are fatal protein-misfolding neurodegenerative diseases. TSEs have been described in several species, including bovine spongiform encephalopathy (BSE) in cattle, scrapie in sheep and goats, chronic wasting disease (CWD) in cervids, transmissible mink encephalopathy (TME) in mink, and Kuru and Creutzfeldt-Jakob disease (CJD) in humans. These diseases are associated with the accumulation of a protease-resistant, disease-associated isoform of the prion protein (called PrP(Sc)) in the central nervous system and other tissues, depending on the host species. Typically, TSEs are acquired through exposure to infectious material, but inherited and spontaneous TSEs also occur. All TSEs share pathologic features and infectious mechanisms but have distinct differences in transmission and epidemiology due to host factors and strain differences encoded within the structure of the misfolded prion protein. The possibility that BSE can be transmitted to humans as the cause of variant Creutzfeldt-Jakob disease has brought attention to this family of diseases. This review is focused on the TSEs of livestock: bovine spongiform encephalopathy in cattle and scrapie in sheep and goats.

Campylobacter in Poultry: Ecology and Potential Interventions

Avian hosts constitute a natural reservoir for thermophilic Campylobacter species, primarily Campylobacter jejuni and Campylobacter coli, and poultry flocks are frequently colonized in the intestinal tract with high numbers of the organisms. Prevalence rates in poultry, especially in slaughter-age broiler flocks, could reach as high as 100% on some farms. Despite the extensive colonization, Campylobacter is essentially a commensal in birds, although limited evidence has implicated the organism as a poultry pathogen. Although Campylobacter is insignificant for poultry health, it is a leading cause of food-borne gastroenteritis in humans worldwide, and contaminated poultry meat is recognized as the main source for human exposure. Therefore, considerable research efforts have been devoted to the development of interventions to diminish Campylobacter contamination in poultry, with the intention to reduce the burden of food-borne illnesses. During the past decade, significant advance has been made in understanding Campylobacter in poultry. This review summarizes the current knowledge with an emphasis on ecology, antibiotic resistance, and potential pre- and postharvest interventions.

Comparison of different sampling types across the rearing period in broiler flocks for isolation of Campylobacter spp

Campylobacter is the most common bacterial cause of human gastrointestinal disease in most developed countries. It is generally accepted that poultry products are a significant source of foodborne Campylobacter infections in humans. Assessing the effectiveness of any potential intervention at farm level requires monitoring of the Campylobacter status of broiler flocks, using appropriate sampling methods. The aim of this study was to assess the influence of the sample type across the rearing period for the detection of Campylobacter spp. at farm level. During this study, 21 commercial broiler farms were intensively sampled. Each farm was visited and sampled at different times during the rearing period (d 1, 7, 14, 21, 28, 35, and 42). On the first day of rearing, the status of the house and the day-old flock was evaluated, and environmental and cecal samples were collected. During rearing, 4 different sample types were collected: feces with sock swabs (sock swabs), feces directly from the litter (feces), cloacal swabs, and cecal content. All samples were analyzed according to ISO 10272-1:2006 (Annex E) and also by direct culture. The results of this study showed that Campylobacter spp. were detected in all of the sample types on d 14 of rearing. From this point on, the detection increased significantly, with a maximum detection rate by the end of rearing, regardless of the sample type. All samples that were negative upon direct culture were also negative after pre-enrichment. At the end of rearing, the percentage of samples positive for Campylobacter spp. was 71.4% for cecal samples, 61.9% for cloacal swabs, 45.2% for sock swabs, and 69.1% for fecal samples. C. jejuni was detected in all the sample types, with positive rates ranging from 67.1 to 76.0% for cecal samples and cloacal content, respectively. Cecal samples, cloacal swabs, and fecal samples cultured by direct plating onto modified charcoal cefoperazone deoxycholate agar (mCCDA) without pre-enrichment have the same sensitivity for detection of Campylobacter spp. in broiler flocks independent of the day of rearing.

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.

An epidemiological investigation of Campylobacter in pig and poultry farms in the Mekong delta of Vietnam

Campylobacter are zoonotic pathogens commonly associated with gastroenteritis. To assess the relevance of Campylobacter in Vietnam, an economically transitioning country in SE Asia, we conducted a survey of 343 pig and poultry farms in the Mekong delta, a region characterized by mixed species farming with limited biosecurity. The animal-level prevalence of Campylobacter was 31·9%, 23·9% and 53·7% for chickens, ducks and pigs, respectively. C. jejuni was predominant in all three host species, with the highest prevalence in pigs in high-density production areas. Campylobacter isolates demonstrated high levels of antimicrobial resistance (21% and 100% resistance against ciprofloxacin and erythromycin, respectively). Multilocus sequence type genotyping showed a high level of genetic diversity within C. jejuni, and predicted C. coli inter-species transmission. We suggest that on-going intensification of animal production systems, limited biosecurity, and increased urbanization in Vietnam is likely to result in Campylobacter becoming an increasingly significant cause of human diarrhoeal infections in coming years.

Analysis of factors important for the occurrence of Campylobacter in Danish broiler flocks

For more than a decade human campylobacteriosis has been the leading zoonosis in many developed countries. Consumption of poultry or poultry products has been identified as the primary source of infection in humans. This study was conducted to identify risk factors for the occurrence of Campylobacter in Danish broiler flocks. The study was based on a large data set consisting of Campylobacter positive status for nearly 6000 broiler flocks and 43 explanatory variables. Data were obtained from the Danish Campylobacter surveillance programme in poultry and from the responses to a standardized questionnaire answered via interviews with broiler farm owners. Two hundred and forty broiler farms, comprising 539 broiler houses, were included in the study and their Campylobacter status was followed over a 2-year period (1999-2000). The large number of observations made it possible to carry out a multivariate analysis including all 43 variables. A multivariate analysis was conducted using a generalized linear model, and the correlations between the houses from the same farms were accounted for by adding a variance structure to the model. The procedures for analyses included backward elimination, forward selection and expanding of the number of observations used in the variance analysis along with the reduction of the number of parameters in the model. The unit of analysis was 'broiler house', meaning that all results from a broiler house were aggregated into one prevalence figure (number of positive flocks/total number of flocks delivered over the 2-year period). The following factors were found to be significantly associated with the occurrence of Campylobacter in the broiler flocks: old broiler houses, late introduction of whole wheat in the feed, relatively high broiler age at slaughter, improper rodent control, large number of chimneys on the broiler house, farm located in an area with a high density of cattle farms, having more than one broiler house on the farm, and improper storage of wheat. This large-scale study confirms several risk factors identified in previous studies. The results concerning chimneys may be explained by the easier access that flies have to the broiler houses, which seems in agreement with recent Danish studies on the significance of fly-screens to reduce Campylobacter in broiler flocks. The results of this study may be used in identification of effective interventions aimed at controlling Campylobacter in Danish broiler flocks.

Survival of Campylobacter jejuni in naturally and artificially contaminated laying hen feces

Infected laying hens regularly excrete large amounts of Campylobacter jejuni with their feces, which represent a reservoir of infection within the flock and for animals in the region. However, the knowledge about survival times of C. jejuni in these feces is still scarce. Therefore, orienting laboratory experiments were carried out under controlled conditions to estimate the survival times of C. jejuni both in artificially and naturally contaminated laying hen feces. In 6 different laying hen flocks (3 Campylobacter-free and 3 Campylobacter-positive flocks), fresh excreta were randomly collected and pooled in 20-g samples per flock. In the laboratory, each of the 3 pooled samples from the Campylobacter-free barns were homogenized and mixed with 10 mL of a freshly prepared C. jejuni suspension (3 × 10(8) cfu/mL). The other 3 samples were homogenized only. The 6 samples were stored at 20 ± 1°C and 40 to 60% RH in 2 different incubators. Specimens of 2 g were taken from all 6 samples 1 h after storage and daily at the same time during the next 10 consecutive days and investigated on culturable C. jejuni. The survival times of culturable C. jejuni ranged from 72 to 96 h in artificially inoculated feces and varied from 120 to 144 h in naturally colonized flocks. The flaA typing by RFLP confirmed that the isolates from the artificially contaminated feces were identical with the added strain. A total of 5 different flaA types were identified from the naturally contaminated feces, and survival of these isolates was dependent on flaA type. The demonstrated survival times indicate that contaminated fresh feces are an important reservoir of C. jejuni, representing a permanent source of infection over at least 6 d after excretion. It shows the considerable potential of fresh feces in transmitting the agent within and between flocks during that period. This 6-d span should be considered when poultry manure is applied to land as organic fertilizer.

Colonization of Campylobacter spp. in broiler chickens and laying hens reared in tropical climates with low-biosecurity housing

The onset and prevalence of Campylobacter colonization in broilers and layers at commercial farms with low biosecurity in tropical climates were tested. Despite the presence of positive animals at the same farms, the broiler flocks tested negative until, on average, 21 days. Prelaying flocks showed a higher prevalence than laying flocks.

Farm and slaughterhouse characteristics affecting the occurrence of Salmonella and Campylobacter in the broiler supply chain

Based on a data set on Campylobacter and Salmonella prevalence in the broiler supply chain, collected during the period 2002 through 2005 in the Netherlands, farm- and slaughterhouse-specific characteristics were tested for their effect on Campylobacter and Salmonella prevalence at different stages of the broiler supply chain. Three different sampling points were considered: departure from the farm, arrival at the slaughterhouse, and the end of the slaughterline. Strong associations were found between Salmonella and Campylobacter prevalence at a particular sampling point and their prevalence at the preceding point of the chain. Statistical analyses showed that the country of origin of the broiler farm had a significant effect on the prevalence of Salmonella and Campylobacter at slaughterhouse arrival. The feeding company delivering to the farm also showed a significant effect on the occurrence of both pathogens at departure from the broiler farm. The prevalence of Campylobacter decreased with an increasing number of birds per flock, whereas the prevalence of Salmonella increased with an increasing number of birds per flock. The number of flocks processed within a specific slaughterhouse was not associated with an increased or decreased prevalence of Campylobacter and Salmonella. The results provide more insight into factors related to the occurrence of both pathogens and in understanding their epidemiology. The results can be supportive in decision making on measures to reduce the contamination of broiler products with Salmonella and Campylobacter.

Spatio-temporal patterns of Campylobacter colonization in Danish broilers

Despite a number of risk-factor studies in different countries, the epidemiology of Campylobacter colonization in broilers, particularly spatial dependencies, is still not well understood. A series of analyses (visualization and exploratory) were therefore conducted in order to obtain a better understanding of the spatial and temporal distribution of Campylobacter in the Danish broiler population. In this study, we observed a non-random temporal occurrence of Campylobacter, with high prevalence during summer and low during winter. Significant spatio-temporal clusters were identified in the same areas in the summer months from 2007 to 2009. Range of influence between broiler farms were estimated at distances of 9.6 km and 13.5 km in different years. Identification of areas and time with greater risk indicates variable presence of risk factors with space and time. Implementation of safety measures on farms within high-risk clusters during summer could have an impact in reducing prevalence.

Effect of climate and farm environment on Campylobacter spp. colonisation in Norwegian broiler flocks

Campylobacteriosis is the most frequently reported zoonosis in the EU. A recent report states that between 50% and 80% of the human campylobacteriosis cases could be attributed to broiler as a reservoir. The current study was conducted to investigate associations between the presence of Campylobacter spp. in Norwegian broiler flocks and factors related to the climate and the farm environment. Data from 18,488 broiler flocks from 623 different farms during 2002-2007 were included in the study. A logistic regression analysis was conducted where Campylobacter spp. status of a broiler flock at the time of slaughter was defined as the dependent variable and farm was modelled as a random effect. The following factors were found to increase the probability for a broiler flock to test positive for Campylobacter spp.: daily mean temperature above 6°C during the rearing period, private water supply, presence of other livestock farms within a distance of 2 km, presence of other broiler farms within a distance of 4 km with flocks positive for Campylobacter spp. within 30 days prior to slaughter, heavy rainfall 11-30 days prior to slaughter, region and year. Daily mean temperature below 0°C reduced the probability. The study emphasises the importance of the farm environment and the climate for the occurrence of Campylobacter spp. in broiler flocks. The farm environment is probably a part of the Campylobacter spp. pathway into and between broiler flocks where farmyard run-off and humans or flies entering the houses might constitute vehicles transporting the organism. Fly activity is temperature-driven and flies might be a part of the explanation of the increased risk for Campylobacter spp. related to increased temperature demonstrated in the study.

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).

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.

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.