Campylobacter presence on Dutch broiler farms and associated risk factors

Abstract

Campylobacter is the most reported zoonotic pathogen in humans in the European Union. Poultry is a major source of human infection with Campylobacter. Although many studies are done on the presence of Campylobacter in broilers and theoretically effective control measures are known, their relative importance at broiler farms remains poorly understood. Therefore, the aim of this study was to investigate the presence of Campylobacter on selected broiler farms in the Netherlands, to determine the moment of introduction, and associated risk factors. A longitudinal study on 25 broiler farms was carried out between June 2017 and December 2020. Fecal samples were collected weekly from 43 broiler houses. In total 497 flocks were sampled. Putative variables on flock and farm characteristics for a risk factor analysis were gathered through questionnaires. Risk factors associated with the presence of Campylobacter in a broiler flock were determined using regression models. In total 30% of the flocks included in the study were positive for Campylobacter. Factors associated with presence of Campylobacter at slaughter age included: season, mowing lawns and presence of agricultural side activities. While summer/autumn and mowing lawns were associated with an increase in Campylobacter presence in flocks, the farmer having agricultural side activities other than poultry production was associated with a decrease. Analysis of the age at which flocks first tested Campylobacter positive revealed that slower growing breeds became positive on average 1 wk later compared to regular growers. This study revealed a delayed introduction of Campylobacter in slower grower vs. regular grower broiler flocks reared indoors. In addition, it confirmed importance of season as major risk factor. The relevance of mowing and preceding positive flocks as risk factors needs further investigation.

Keywords: broiler; campylobacter; longitudinal; monitoring; risk factor.

Figure 1

Percentage and number of flocks becoming positive for Campylobacter for each study month June 2017 until December 2020. Number of positive flocks and number of flocks tested is indicated above each bar and separated with a slash (number positive/number tested locks).

Figure 2

Frequency diagram of the first positive Campylobacter test result (age in weeks). The figures summarize results of 144 out of 150 positive flocks in the study (for 6 flocks relevant information to estimate age of first positive sample was missing). Flocks were reared in different concepts (59 positive regular flocks, 72 positive slower grower flocks, for 19 flocks the production concept was unknown), thus slaughtered at different ages. The number of positive flocks decreased after wk 6, since regular growers are slaughtered at that age, thus not sampled anymore.