Longitudinal survey investigating vectors and reservoirs for <i>Campylobacter</i> colonization of chickens on a New Zealand broiler poultry farm

This longitudinal survey followed the life cycle of a New Zealand broiler flock to investigate sources of flock colonization by <i>Campylobacter</i>. Samples were collected at frequent intervals from potential <i>Campylobacter</i> reservoirs and sources, transmission routes for <i>Campylobacter</i> ingress into the broiler shed, and to monitor flock colonization. Of the 738 samples, 200 (27%) tested positive for <i>Campylobacter. Campylobacter</i> species from sample isolates included 316 <i>Campylobacter jejuni</i>, 39 <i>Campylobacter coli,</i> and 8 <i>Campylobacter lari</i> isolates; only <i>C. jejuni</i> was isolated from chickens. <i>C. jejuni</i> isolates (<i>n</i> = 199) were sequenced and consisted of seven sequence types (STs); the most abundant was ST6964 (105 isolates). Most flock isolates were ST6964 (44 isolates) or ST50 (27 isolates). ST6964 isolates closely matched those from the previous flock and another age-matched flock on the same farm, supporting a role for an on-farm reservoir contaminating flocks. There were six STs from catching crew and equipment isolates; the most prevalent were ST6964 (19 isolates) and ST50 (21 isolates). The close genetic match, high <i>Campylobacter</i> prevalence in catching samples (59/130, 45%), and the timing of flock colonization occurring closely following catcher presence in the shed support that catchers and equipment might also contaminate the shed and flock from prior flocks that they visited. There was no evidence for wildlife, feed, drinking water, breeder flock, or shed litter as sources of the <i>Campylobacter</i> genotypes colonizing the flock. Taken together, this study identified key areas where the poultry industry might focus on-farm risk management practices to reduce colonization of broiler flocks by <i>Campylobacter</i>.IMPORTANCECampylobacteriosis is the most frequently notified enteric disease in New Zealand, and New Zealand has one of the highest rates of campylobacteriosis among industrialized countries. Reducing <i>Campylobacter</i> colonization of poultry at the farm level would reduce reliance on processing interventions for reducing <i>Campylobacter</i> contamination of broiler meat. This study aimed to identify on-farm sources of <i>Campylobacter</i> contamination in New Zealand broiler chicken flocks. No evidence was found that wildlife, chicken feed, drinking water, or parent breeder flocks were contaminating sources. Instead, carryover of <i>Campylobacter</i> from the previous flock or other farm flocks, and/or contamination from chicken catching crews and their equipment, may have contributed <i>Campylobacter</i> strains that colonized the study flock. These are key areas where the poultry industry might focus on-farm risk management practices to reduce colonization of broiler flocks by <i>Campylobacter</i>.