External contamination of broilers by Campylobacter spp. increases from the farm to the slaughterhouse.

1. In this study classical and molecular microbiological methods for detection and quantification of Campylobacter spp. were used to estimate their prevalence in faecal samples and skin swabs collected from 31 broiler flocks (20 farms) in Portugal, and measure the impact of transport-related factors on the expected rising excretion rates from the farm to the slaughterhouse.2. Data on husbandry practices and transport conditions were gathered, including time in transit, distance travelled, or ante-mortem plant holding time.3. A generalised linear mixed model was used to evaluate the significance of a potential post-transport rise in Campylobacter spp. counts and to assess risk determinants.4. At least one flock tested positive for Campylobacter spp. in 80% of the sampled farms. At the slaughterhouse, Campylobacter spp. were detected in all faecal samples, C. jejuni being the most commonly isolated.5. A post-transport rise of Campylobacter spp. counts from skin swabs was observed using classical microbiological methods (from a mean of 1.43 to 2.40 log10 CFU/cm2) and molecular techniques (from a mean of 2.64 to 3.31 log10 genome copies/cm2).6. None of the husbandry practices or transport-related factors were found to be associated with Campylobacter spp. counts.7. This study highlights the need for more research to better understand the multi-factorial nature of Campylobacter spp., a public health threat that was found to be highly prevalent in a sample of Portuguese poultry farms.