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Risk Factors for Campylobacter Colonisation in Danish Broiler Flocks

05 May 2015

Poultry Science journal

A recent study from Denmark highlights the need for better biosecurity to reduce the prevalence of Campylobacter on broiler farms. Poor general hygiene, adverse litter storage conditions and a chimney inlet to the ventilation system were the factors most likely to increase the risk of a bacteria-positive result.

Campylobacter infections are the most frequently reported bacterial cause of human enteritis in the European Union, with Campylobacter jejuni the species most frequently isolated (85 to 95 per cent) followed by C. coli, according to Marianne Sandberg of the Danish Agriculture and Food Council.

Working together with co-authors from the Council, Chittagong Veterinary and Animal Sciences University in Bangladesh and the University of Southern Denmark, they aimed to establish the prevalence of Campylobacter-positive farms in Denmark and to acquire updated knowledge about risk factors for the introduction of Campylobacter into the flocks.

The work was published recently in the journal, 'Poultry Science'.

As background, Sandberg and her co-authors wrote that it has been estimated that 80 per cent of human cases originate from the poultry reservoir although only 20 to 30 per cent originate from the consumption of chicken meat.

They proposed that, on broiler farms, the most likely reason for a Campylobacter problem is inadequate compliance with general biosecurity, and in this study, they set out to identify the factors that increase the risk of a positive Campylobacter result by studying the conditions on almost 200 broiler farms in Denmark in two studies carried out between September 2010 and September 2011.

Of the 25 farms they visited in the first part of the study, 17 had delivered Campylobacter-positive flocks during the study period, and eight farms had no Campylobacter-positive flocks. The flock prevalence of Campylobacter was 17 per cent.

An electronic survey was returned by 164 broiler farms was the basis for the second part of the study, from which 63 per cent of the farms were Campylobacter-positive and the flock prevalence was 14 per cent.

Using information from the farms, the researchers explored a wide range of conditions that may be linked to the Campylobacter result for each flock on these farms.

They found that the risk of a Campylobacter-positive test result was significantly higher:

  • in summer than winter
  • if the previous flock was positive for Campylobacter rather than negative
  • if litter is delivered to the farm shortly before the arrival of the chicks rather than it is stored on the farm, and
  • where the broiler house ventilation inlet was a vertical chimney rather than through inlets in the side of the building.

The first of these factors confirms previous findings, according to Sandberg and co-authors, that have shown Campylobacter survival to be better when the temperature is above 6°C and there is rainfall, which would be typical of a Danish summer.

The higher probability of a current flock acquiring Campylobacter-positive status given that the previous flock in the house was positive can be explained by the fact that house cleaning between flocks was inadequate. There may be a range of reasons relating to the house design or materials that make thorough washing and disinfection challenging, the researchers say. It is also possible that the bacteria are brought into the house from the outside each time.

The link between a Campylobacter-positive test and the location of litter storage suggests that the material may be contaminated on the farm before it is used in the broiler house. Plastic wrapping and/or indoor storage at the farm may provide a more rodent- and bird-proof solution. The researchers point out, however, that the microbiological quality aspects of litter have been neither investigated nor regulated thoroughly.

Sandberg and co-authors suggested that the higher prevalence of Campylobacter in flocks housed in buildings with vertical chimneys could be linked to the easier entry to the building of flies or rain. Droppings from wild birds might have been an explanation but the chimneys of the poultry houses in these studies were covered by hoods to exclude the entry of wild birds and their droppings.

The findings could contribute to achieving the reduction target set in the New Action Plan against Campylobacter in Danish broilers for 2013 to 2016, concluded the researchers.

The Danish Action Plan against Campylobacter

This plan was initiated in 2008 to reduce the prevalence of the bacteria in the country's poultry, explained Sandberg and co-authors.

Since 2010, testing has been based on the collection of faecal material on tube gauze socks from the floor of the broiler house seven to 10 days prior to sending a flock to slaughter and cloacal samples at slaughter, which are analysed by real-time PCR. Positive flocks identified pre-slaughter by the sock sample test are allocated to freezing or heat treatment (called 'scheduled slaughter')

However, this strategy has been hard to implement because of the high demand for fresh meat, especially in the summer when the prevalence of Campylobacter tends to be higher.

This led to the development of a new slaughter programme – Action Plan 2013 to 2016 – which only requires the collection and analysis of cloacal swabs at the time of slaughter.

For the new Danish action plan to succeed, there needs to be a better understanding of interventions at both the production and slaughter/processing levels, and this was the justification for this study, its authors added.

The paper 'Risk factors for Campylobacter colonization in Danish broiler flocks, 2010 to 2011' by M. Sandberg, L.L. Sørensen, B. Steenberg, S. Chowdhury, A.K. Ersbøll and L. Alban was published in 'Poultry Science', volume 94, p447-453.

Further Reading

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May 2015

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