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Measures and best practice to minimise infection of remaining birds with campylobacter when broiler flocks are thinned
Project Code: B15004
Division of Farm Animal Science, Department of Clinical Veterinary Science, University of Bristol,
Allen, V ;
Silsoe Research Institute
Previous FSA-funded work has indicated that ‘thinning’ of broiler flocks (depopulation of the poultry house over a period of days) is associated with an increase in prevalence of Campylobacter infection in those birds left after the initial period of catching. This current project was intended to examine this hypothesis by undertaking a detailed review of current industry practices and procedures coupled with a programme of microbiological tests for Campylobacter. The overall objective of the work was to produce recommendations suitable for the production of guidance material for thinning procedures and suggest any suitable intervention measures.
Before the programme of farm visits began, a review of existing codes of practices and standard operating procedures was undertaken by the research team. The objective of this part of the study was to establish what recommendations and guidance was already available and/or in use for hygiene and biosecurity during thinning. In the event, it transpired that no such specific recommendations existed and that most companies relied on applying existing standards for general hygiene and biosecurity to the thinning process.
Following this initial review of information, the Advisory Panel comprising representatives from the broiler companies, the FSA and the research team developed a generic hygiene and biosecurity standard operating procedure (SOP). This document was specifically geared towards catching and thinning and containing detailed requirements for farm managers, catchers and transport drivers. In the subsequent review of the findings of the farm audits, this generic SOP was used as the benchmark when assessing compliance with procedures.
The main part of the project was to undertake visual farm audits during thinning and to take a series of samples to test for the presence of Campylobacter. Accordingly, a programme of 51 farm visits was made between June and October 2005 (‘Year 1’) and February to November 2006 (‘Year 2’) to collect information on hygiene and biosecurity practices and procedures and to collect samples to test for the presence of Campylobacter.
The isolation of Campylobacter on vehicles, equipment and personnel entering and leaving the farm before and after the thinning process clearly indicated areas of risk. Seven flocks which became positive after thinning had Campylobacter isolated from equipment and/or personnel associated with the thinning process. With all these flocks, some Campylobacters isolated from samples collected during the thinning process were indistinguishable following molecular typing (PFGE using the restriction enzyme SmaI) from those which subsequently colonised the flock. All flocks which were negative at the thinning process (~60% of those examined) became positive after the process and almost all within two to six days. The examination of culled birds indicated a rapid spread through the flock with high numbers of the organism in the caeca. However two flocks were negative at slaughter despite some birds being colonised with the organism a few days following thinning. Due to the lack of negative flocks following the process it was impossible to carry out statistical correlations between the subsequent incidence of Campylobacter and procedures and practices adopted on farm during the process.
In October 2005 there was an urgent awareness of the need for increased biosecurity, and for this reason, the programme of farm visits was suspended. From this point onwards, there was a widespread tightening of hygiene and biosecurity throughout the industry. Following discussions with the industry, the programme of visits restarted in February 2006.
The information-gathering was carried out by the research team via a series of interviews with farm managers and catching teams using a questionnaire developed by the Advisory Panel and covering 138 different areas of enquiry. In addition to the verbal responses provided by the farm managers, where appropriate the research team recorded their own observations – particularly where there was a degree of subjectivity involved e.g. cleanliness of protective equipment. The data were recorded and analysed using ‘SNAP’ survey software with additional statistical analysis undertaken using binary logistic regression.
The overall results were evaluated firstly by looking for any differences in Campylobacter incidence between Year 1 and Year 2, and secondly by looking at any effects of procedures and practices on overall incidence of Campylobacter per se.
It was clear that there was a significant tightening-up of standards between Year 1 and Year 2, although not all the trends identified were statistically significant. Over the same period, there was a reduction in the recovery of Campylobacter immediately prior to thinning, although once again, this reduction could not be significantly correlated with individual changes in procedures, probably due to the multifactorial impact.
Despite the heightened awareness of the catchers and the strengthening of procedures and practices between Year 1 and Year 2, the adoption of the generic SOP was at best ‘patchy’. Whilst some aspects of the SOP were applied more thoroughly and systematically than others, in the event, there was not a single aspect of the SOP that was being universally applied across the industry. Whilst, at first sight this may appear to be a disappointing finding, it has to be viewed in the light of the SOP only having become available part-way through the project, and the likelihood that the industry will have had limited opportunities to provide its staff with suitable training on the provisions of the new document.
In addition, one of the main reasons for gaps in the application of the generic SOP is undoubtedly due to practical difficulties and obstacles faced by the catchers (and farm managers) in implementing the specified procedures. Time pressures on catching teams, less-than-ideal availability of equipment and facilities etc. all conspire to make it difficult for catchers to implement the requirements. One of the key recommendations therefore is a need to ensure that facilities and equipment are readily accessible, and that greater onus is placed on the responsibility of farm managers in this respect.
Once the facilities and equipment issues have been addressed, it is clear that catching teams will need to be provided with additional training in the new SOP requirements. When this has been done and the new measures are in place, it is recommended that greater responsibility should be placed on catching team foreman/leading hands to make sure that their teams are actively and consistently working to the required standards. Finally, it is also recommended that senior management should establish more systematic and thorough methods of monitoring compliance – something that again, is somewhat patchy at the moment.
There is every reason to believe that if these recommendations are taken on-board by the industry, there is significant potential for raising standards of hygiene and biosecurity which should deliver real benefits in terms of reduction of both avian and zoonotic diseases.
The findings of the farm audits against the incidence of Campylobacter at thinning revealed little in the way of statistically significant trends. There was some evidence that hand sanitisation, vehicle disinfection and positioning of modules were associated with a reduced incidence of Campylobacter immediately prior to thinning. These issues are already largely addressed within the generic SOP, and therefore the introduction and application of a more robust version of the SOP should go a long way towards addressing these issues.
In terms of possible interventions, only water treatment appeared to be significantly correlated with a reduction in Campylobacter at thin. Given the potential benefits that such an intervention could provide, it is recommended that this be issue be explored further.
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