Persistent Environmental Reservoirs on Farms as Risk Factors for Campylobacter

Commercial broiler flocks were most likely to become positive for Campylobacter from other infected animals such as cattle, dogs, wildlife and rodents on the farm, according to recently published research from the UK.

22 August 2011

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Campylobacter is the most common known source of human bacterial enteritis in the developed world and poultry is considered the main source, according to Dr J. Ellis-Iversen of AHVLA and co-authors from the same organisation, the University of Bristol and SAC in a paper published online in Epidemiology and Infection.

Broilers often become colonised with Campylobacter during rearing, and then contaminate the farm environment, they explain. The objective of their study was to identify Campylobacter-positive environmental reservoirs on farms, as these pose a risk to broiler flocks becoming colonised with Campylobacter. The researchers considered the temporal aspects of exposure and colonisation.

A longitudinal study monitored six conventional rearing farms over two years. The broiler flocks, catchers' equipment, vehicles, shed surrounds, shed entrance, other equipment, farm entrance, other animals, puddles, dead birds, mains water and drinkers were systematically sampled two to four times per flock. A multivariable generalised estimating equation model was used to assess associations between contaminated environmental sites and colonised broiler flocks. The associations were adjusted for confounders and other known risk factors.

To further assess temporality of contamination, the sequence of contamination of the different environmental sites and the flocks was established.

Contaminated shed entrances and anterooms, contaminated drinkers and shedding of Campylobacter by other animals such as cattle, dogs, wildlife and rodents were significantly associated with positive flocks, concluded Ellis-Iversen and co-authors. They added that the reservoir of 'other animals' was also the reservoir most commonly positive before the flock became colonised. The other sites usually became contaminated after the flock was colonised.

Reference

Ellis-Iversen J., A. Ridley, V. Morris, A. Sowa, J. Harris, R. Atterbury, N. Sparks and V. Allen. 2011. Persistent environmental reservoirs on farms as risk factors for Campylobacter in commercial poultry. Epidemiology and Infection (article in press) DOI: 10.1017/S095026881100118X