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Campylobacter spp. in housed broiler flocks, the influence of flock husbandry practices on the frequency of colonisation

Project Code: B15001

31/08/2006

Food Microbiology Collaborating Unit, Health Protection Agency, School of Clinical Veterinary Science,University of Bristol
Bull, S ;
University of Bristol
Thomas, A; Lovell, R;
Health Protection Agency
Jorgensen, F;
University of Bristol
Dennis, L; Smith, M; Humphrey, T

This project represented one of the largest and most comprehensive studies into the epidemiology of campylobacter in housed broiler production ever undertaken and examined 789 flocks. The study ran from December 2003 to the end of March 2006 and included three poultry companies with a good geographical spread of farms. ~13 &~037; of farms rearing housed flocks in GB were sampled at least once and details of flock health and management data for each flock were obtained. This, together with climatic and farm structure information, made it possible to examine a wide range of potential risk factors for campylobacter infection. The examination of 30 caeca individually for each flock allowed an estimated detection limit for flock colonisation of 10 % and also made it possible to ascertain the proportion of colonised birds within a flock. The project explored the hypothesis that flocks, which are poorly managed, suffering from underlying disease or have poor welfare are more likely to be campylobacter-positive. Data from the project can be summarised as follows:

Only a minority (35 %) of flocks sampled at first de-population were campylobacter-positive
Only 6 % of flocks were fully infected (all caeca positive) at first de-population
There was marked seasonality in flock infection rates with significantly (p < 0.05) more being campylobacter-positive in summer and autumn
Data from farms located mainly in the SW of England suggested that the proportion of infected flocks on these farms is falling (from 76 % in 1993 to 21 % in 2005). This is primarily due to a reduction in the 'low risk' periods of winter and spring
Some farms were consistently able to produce either campylobacter-negative flocks or ones with only a low level of positive caeca
A number of health indicators were significantly (p < 0.05) associated with campylobacter infection. The most important of these were diseases believed to be caused by avian pathogenic Escherichia coli (APEC)

The above data suggest that there has been quite a marked change in the epidemiology of campylobacter in housed broiler flocks in GB over the last 5-10 years. The results of this project also begin to challenge the dogma that campylobacter are 'normal' flora in broilers. Data suggest that the pathogen may be better able to infect the gut of a compromised avian host and the reasons for this need to be established.

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