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Analysis of the baseline survey on the prevalence of Campylobacter in broiler batches and of Campylobacter and Salmonella on broiler carcasses, in the EU, 2008 - Part B: Analysis of factors associated with Campylobacter colonisation of broiler batches and with Campylobacter contamination of broiler carcasses; and investigation of the culture method diagnostic characteristics used to analyse broiler carcass samples

EFSA Journal 2010; 8(8):1522 [132 pp.]. doi:10.2903/j.efsa.2010.1522
European Food Safety Authority Acknowledgment EFSA wishes to thank the members of the Task Force on Zoonoses Data Collection: Andrea Ammon, Marta Bedriova, Susan Chircop, Georgi Chobanov, Veronica Cibin, Jürg Danuser, Kris De Smet, Emma Martín Denia, Matthias Hartung, Birgitte Helwigh, Merete Hofshagen, Simona Iannetti, Patrícia Inácio, Sarolta Idei, Helle Korsgaard, Elina Lahti, Lesley Larkin, Jose Luis Saez Llorente, Peter Much, Edith Nagy, Iona Neghirla, Lisa O’Connor, Rob Van Oosterom, Jacek Osek, Manca Pavšič, Christodoulos Pipis, Saara Raulo, Tatjana Ribakova, Julien Santolini, Petr Šatrán, Joseph Schon, Jelena Sõgel, Snieguole Sceponaviciene, Kilian Unger, Luc Vanholme and Dimitris Vourvidis for the endorsement of the report; the members of the Working Group on the analysis of 2008 broiler carcasses baseline survey: Dirk Berkvens, Enne de Boer, Marjaana Hakkinen, Mary Howell, Annemarie Kaesbohrer, Micheál O’Mahony, Eva Olsson Engvall, Hanne Rosenquist, Moez Sanaa, Mieke Uyttendaele, Arjen van de Giessen and Jaap Wagenaar for the preparation of this EFSA scientific output; Diane Newell and Arie Havelaar for the peer review; the EFSA’s contractors: Lieven De Zutter from University of Ghent, Saskia Litière and Marc Aerts from University of Hasselt and Alessandro Mannelli from University of Turin, and the EFSA’s staff members: Maria Teresa Da Silva Felício, Kenneth Mulligan and Frank Boelaert for the support provided to this EFSA scientific output. Contact zoonoses@efsa.europa.eu
Type: Scientific Report of EFSA On request from: European Commission Question number: EFSA-Q-2008-416B Approved: 22 July 2010 Published: 05 August 2010 Affiliation: European Food Safety Authority (EFSA), Parma, Italy
Abstract

A European Union-wide baseline survey on Campylobacter in broiler batches and on broiler carcasses was carried out in 2008. From each of the 10,132 randomly selected batches, pooled caecal contents samples of slaughtered broilers were taken in 561 slaughterhouses and examined for the presence of Campylobacter. From the same batches one carcass was collected after chilling, from which neck skin together with breast skin was examined for the presence of Campylobacter and the Campylobacter count was determined. Multivariable regression analysis showed that a Campylobacter-colonised broiler batch was about 30 times more likely to have the sampled carcass contaminated with Campylobacter, compared to a non-colonised batch. Also, a higher Campylobacter count on carcasses was strongly associated with Campylobacter colonisation of the batch. Contaminated carcasses could also derive from non-colonised broiler batches. Both the risks for Campylobacter-contaminated carcasses and for Campylobacter colonisation of batches increased with the age of the slaughtered broilers as well as during certain months of the year - with the period July-September being the quarter at most risk. Processing later during the day increased the risk of Campylobacter contamination of carcasses. Batches originating from previously thinned flocks were more at risk of being colonised with Campylobacter. The risks for contamination of carcasses with Campylobacter, for higher Campylobacter counts on carcasses and for colonisation of batches with Campylobacter all varied significantly between countries and between slaughterhouses within countries, even when other associated factors were accounted for. Investigation of the culture method results used to estimate the prevalence of Campylobacter-contaminated broiler carcasses showed that the diagnostic sensitivity of the detection test may have varied between Member States.

© European Food Safety Authority, 2010

Summary

A European Union-wide baseline survey on Campylobacter in broiler batches and on Campylobacter and Salmonella on broiler carcasses was carried out in 2008. A total of 10,132 broiler batches were sampled from 561 slaughterhouses in 26 European Union Member States, plus Norway and Switzerland. From each randomly selected batch, the caecal contents of 10 slaughtered broilers were collected, pooled and examined for the presence of Campylobacter. From the same batch, one carcass was collected after chilling from which the neck skin together with the breast skin was examined for the presence of Campylobacter or Salmonella, and to determine the Campylobacter count. Campylobacter was detected in pooled caecal contents of broilers and on broiler carcasses in all participating countries. The results of the analysis of Campylobacter and Salmonella prevalence have already been published by the European Food Safety Authority on 17 March 2010 in the Part A report. The present Part B report provides the results of the associations of eight batch- or slaughterhouse level factors and Campylobacter colonisation of batches and/or contamination of carcasses. The investigated prevalence was the observed prevalence, meaning that the prevalence estimates did not account for imperfect test characteristics. In addition, further analyses of the identified Campylobacter species distribution across the European Union, and the results of the diagnostic sensitivity investigation of the detection method used to estimate the prevalence of Campylobacter-contaminated broiler carcasses, are included in the current report. A Part B report on Salmonella will be published at a later stage.

Multivariable regression analysis showed a strong positive association at European Union level between the likelihood of Campylobacter contamination of broiler carcasses with the presence of a Campylobacter-colonised batch. A Campylobacter-colonised broiler batch was about 30 times more likely to have the sampled carcass contaminated with Campylobacter, compared to a non-colonised batch. Also, a higher Campylobacter count on carcasses was strongly associated with Campylobacter colonisation of the batch. These findings indicated an important effect of Campylobacter colonisation of broiler flocks on both the frequency of occurrence as well as on the contamination levels of Campylobacter on carcasses. Contaminated carcasses could also derive from non-colonised broiler batches, suggesting a potential for cross-contamination in the slaughterhouse environment.

The analyses further showed that the risk for Campylobacter-contaminated carcasses increased with the age of the slaughtered broilers, with processing later during the day and during certain months of the year, with the period July-September being the quarter at most risk. The analyses also showed that the time (in hours) between sampling and testing increased the risk of detecting Campylobacter from the carcass samples. For country-groups having a prevalence lower or higher than the EU median[1], there was variation in the factors found associated with Campylobacter contamination of broiler carcasses and also in the level of importance of these factors. More factors were significant for the group of countries having a higher prevalence.

The risks for contamination of carcasses with Campylobacter and for higher Campylobacter counts on carcasses varied significantly between countries and between slaughterhouses within countries, even when other associated factors, such as the prevalence Campylobacter-colonised batches, were accounted for. These findings indicate that certain slaughterhouses are more capable than others in preventing Campylobacter contamination and in controlling the contamination and/or the Campylobacter counts on the carcasses. This implies that slaughterhouse processing offers an opportunity for Campylobacter risk mitigation.

Factors that were included in the analysis, but which were not significantly associated with Campylobacter contamination of carcasses were flock production type, thinning of flocks, capacity of slaughterhouse, type of chilling of the carcass, and Salmonella-contamination results on the broiler carcass. Moreover, the analyses of the Campylobacter contamination carcasses showed that, in the case of Campylobacter-non-colonised broiler batches, 18% of the unexplained variance (in Campylobacter-contamination results) was attributable to slaughterhouse-specific factors for which no data were gathered during the survey. For Campylobacter-colonised broiler batches, this proportion was higher (50%). In the case of the analyses of the counts on contaminated carcasses, the only potential risk factor was the Campylobacter colonisation status of the batch. Factors that were included in the analysis but that were not significantly associated with higher counts of Campylobacter on carcasses, were flock production type, thinning of flocks, age of broilers, quarter of sampling, time (hour) of processing during the day, time (in hours) between sampling and testing, capacity of slaughterhouse, type of chilling of the carcass, and Salmonella-contamination results on the broiler carcass. For some of the factors the power of the analyses was low due to too few samples in some specific categories.

The analyses of the batch level prevalence survey showed that slaughter batches of previously thinned flocks were at a significantly higher risk of colonisation by Campylobacter. Age of broilers also emerged as a risk factor, and the risk of Campylobacter colonisation of batches increased with the age of the slaughtered broilers and during certain months of the year, with the period July-September being the quarter at most risk. The analyses also showed that the time (in hours) between sampling and testing increased the risk of detecting Campylobacter from the caecal contents samples. There was no variation in the factors found associated with Campylobacter colonisation of broiler batches for country-groups having a lower or higher prevalence than the EU median. The risk of Campylobacter colonisation of batches also varied significantly between countries and between slaughterhouses within countries, even when other associated factors were adjusted for.

Factors that were included in the analysis, but which were not significantly associated with Campylobacter colonisation of batches were flock production type and the time (hour) of sampling during the day. For some of these factors the power of the analyses was low due to too few samples represent in some specific categories. Moreover, the analyses showed that 25% of unexplained variance (in Campylobacter-colonisation results) was attributable to slaughterhouse-specific factors for which no data were gathered during the survey.

Investigation of the culture methods results used to estimate the prevalence of Campylobacter-contaminated broiler carcasses showed that the diagnostic sensitivity of the detection test may have varied between Member States. Thus the true prevalence of Campylobacter-contaminated carcasses might be underestimated for some Member States. Consequently, caution is needed when interpreting the results of the European Union level analyses of factors associated with the prevalence of Campylobacter-contaminated broiler carcasses and of Campylobacter-colonised broiler batches, because the analyses did not correct for test (misclassification) bias.

It is recommended that Member States consider the factors found to be associated with Campylobacter-contaminated broiler carcasses and/or with Campylobacter-colonised broiler batches at EU level in this survey, when they are designing national Campylobacter control programmes for broiler meat or broiler flocks. An integrated control programme that addresses both the primary production and the slaughter process would seem to be important in strategies to prevent or reduce subsequent contamination of the broiler carcass and to improve protection of public health. Further national studies to identify more closely, at batch- and slaughterhouse level, the factors that put broiler batches and carcasses at risk of becoming respectively colonised or contaminated with Campylobacter in a country are recommended. The standardisation of the time between sampling and testing, as well as of the quality control of laboratory testing methods, should be considered of importance by Member States when designing national Campylobacter control programmes. In particular, it is recommended that Member States investigate further the sensitivity of the Campylobacter detection method.

Keywords

Campylobacter, broiler batches, broiler carcasses, chicken, baseline survey, risk factors, EU