Food Standards Agency
Friday 19 March 2010
Business campaign
AZ-Directory
What's NewRSS
What is RSS?Listen
Listen to this siteThursday 16 September 2004
This research project aims to undertake a detailed audit of commercial chicken production and processing to determine when broiler chickens become infected with Campylobacter spp .
Study Duration : November 1999 to December 2002
Contractor : University of Bristol
Campylobacter spp. are important human gastro-intestinal pathogens. Although there are a variety of sources of infection, it has been estimated that the most important is contaminated poultry, principally chicken. Infection can result directly from the consumption of under-cooked chicken or indirectly as a consequence of cross-contamination during meal preparation.
Recent surveys indicate that 70-90% of fresh chicken carcasses in retail outlets are campylobacter positive. It would also appear that 60% of housed poultry is colonised with the bacterium at slaughter. There are clear public health benefits to be gained from a reduction in the incidence of campylobacter in the live animal.
Successful control of the colonisation of food animals with bacteria like Campylobacter spp. requires information on how the animals, in this study chickens, become infected and how products derived from them become contaminated. Thus the principle aim of this research project will be to undertake a detailed audit of commercial chicken production and processing to determine when broiler chickens first become infected with Campylobacter spp. and to identify the major sources of flock infection and/or principle risk factors for the introduction of the bacteria. A secondary objective will be to examine poultry processing to identify those points in the slaughterhouse where levels of campylobacter are significantly altered.
These approaches should make it possible to determine the critical points for control on either the farm or in the processing plant and to devise control measures.
1. The study would identify broiler flocks likely to be colonised/infected with Campylobacter and Salmonella spp. and those where colonisation with Campylobacter spp. is less frequent.
2. To use sensitive isolation and enumeration techniques for Campylobacter and Salmonella spp. which maximise the recovery of these zoonotic pathogens.
3. To audit broiler flock colonisation/infection from the status of their parent flock(s) to the day of slaughter by regularly collecting samples from broiler chickens and their feed, water and environment.
4. To explore potential but under-examined, sources of flock infection and horizontal spread of the target pathogens, such as the air in broiler houses by taking air samples.
5. To audit the effects of poultry processing on the numbers and distributions of Campylobacter and Salmonella spp. sub-types on poultry carcass by taking samples at many points on the poultry production line.
6. To examine the distribution of Campylobacter and Salmonella spp. in the atmosphere of poultry processing plants by collecting and analysing air samples.
7. To determine whether immersion scalding is the source of Campylobacter and Salmonella spp. in chicken muscle by taking samples from scald tank water and from carcasses before and after scalding.
8. To carry out detailed typing of the isolates of Campylobacter and Salmonella spp. so that important sources of bird infection/colonisation or carcass contamination can be properly identified.
9. To use the above approaches to identify points of significance within the poultry production chain, which either introduce infection, change its nature or reduce it.
Although this study was not designed to determine the prevalence of campylobacter positive flocks in the UK, 50 of 97 randomly selected housed broiler flocks from one poultry company examined between February and June 2002 were found to be positive for campylobacter.
Random sampling of poultry flocks in one processing plant allowed a comparison of production types in relation to flock prevalence. Results showed that 105 of 109 (96%) of extensively reared flocks were positive for campylobacter compared with 50 out of 97 (52%) conventionally reared broiler flocks. However, there was no significant difference in the numbers of campylobacter present in the caeca, between production systems. Access to the outside and exposure to environmental sources is the most likely major risk factor for the higher prevalence observed in extensively reared birds.
The project investigated the impact of farm management practices on the incidence of campylobacter colonisation. Selected production parameters were compared with campylobacter colonisation rates over sequential flock cycles for two farms exhibiting extremes of colonisation rates, i.e. one farm had a colonisation rate of 1.4% of birds compared with 97% of birds at the other farm over the same period. The difference in hock burn (welfare indicator) over seven flock cycles between the two farms was highly significant (p=0.002). The difference in pad burn over eight flock cycles, was even greater (p < 0.0001). These results could indicate that birds with compromised health are less able to withstand colonisation by campylobacter, or alternatively that flock health factors indicate the amount of care a farmer uses in his work and therefore the level of biosecurity. Further study is required to examine a possible causal link between management practices and the incidence of colonisation.
One of the farmers in the study, who consistently producing negative broiler flocks, used dedicated footwear for each poultry house. This may have reduced transmission from the environment to the birds. This could be a low cost and simple control measure. Another farmer from the same company also producing negative flocks added chlorine dioxide to drinking water. This may be a suitable intervention to control water-borne infection.
The project investigated the effect of the various stages of processing on the carcass load of birds from flocks with high and low levels of campylobacter colonisation. Carcass rinse and neck skin samples were enumerated for campylobacter after the following stages of processing: bleeding, scalding, plucking, removal of viscera, inside-outside washing, chilling and packaging. For positive flocks there was a significant reduction in carcass load between post-pluck and post-chill for three flocks (p=0.02, <0.01 and <0.01). However, there was no significant difference for six flocks tested and there was a significant increase (p=0.01) for one flock. For those positive flocks showing a reduction, in the majority of cases this occurred during the chilling stage and was associated with companies that used Vent-stream chillers. Carcass load of birds from positive flocks at the end of processing was between log 4 and log 7 colony forming units (CFU)/ carcass. For low level colonised flocks the carcass load was several logs lower. Further research is required to identify areas where poultry processing may alter the number of campylobacter on carcasses.
Processing was found to have no significant effect on the levels of carcass contamination.
The project demonstrated that it is possible to produce intensively reared chickens that are free of campylobacter contamination. The participating companies improved in this respect without the need for expensive or complicated control measures. The improvement in the number of campylobacter free flocks, was thought to be based on improved biosecurity and good flock husbandry practices. There will be clear benefits to consumers if the whole of the UK poultry industry could achieve a similar improvement.
The final report is available from the FSA Library and Information centre.
To obtain a copy, please contact the Enquiry Desk, Dr Elsie Widdowson Library and Information Services, Food Standards Agency (tel: 020 7276 8181/8182 or email:
library&info@foodstandards.gsi.gov.uk
)
Contact
: For any enquiries concerning this research project, please contact the relevant Programme contact or email
science@foodstandards.gsi.gov.uk
Find out what our other sites have to offer