No association between partial depopulation and Campylobacter spp. colonization of Dutch broiler flocks

Aims: To determine whether an association exists between partial depopulation of a flock and increased Campylobacter colonization in that flock. Methods and Results: Data from 1737 flocks of two Dutch integrators were used. Flocks that experienced partial depopulation were defined as 'exposed' and those that did not as 'nonexposed'. Multivariable modelling was accomplished with, in addition to 'exposure', the independent variables 'age of broilers at slaughter' and 'season' to adjust for possible confounding. The response variable was 'Campylobacter colonization'. The odds ratio (OR) for partial depopulation for integrator A was 0.8 [95% CI (0.4, 1.8)]; for integrator B the OR = 0.8 [95% CI (0.5, 1.3)]. Age and season were confounders: the difference in Campylobacter status between exposed and nonexposed flocks of integrator A could be explained by both variables; for integrator B, only season was associated with Campylobacter status. Conclusions: We found no significant association between partial depopulation and an increased risk of Campylobacter colonization among broiler flocks at final depopulation. Significance and Impact of the Study: This study demonstrates that Campylobacter colonization in a broiler flock is not influenced by the partial depopulation of that flock.