The effect of presence of infected neighbouring farms for the Campylobacter infection status in Danish broiler farms

Neighbourhood risk factors for Campylobacter infection in Danish broilers were evaluated. Campylobacter infection status of a flock was identified by PCR analysis of cloacal swab samples collected as a part of national surveillance program. Included into the study were, in total, 10,876 broiler flocks sent by 226 farms to processing plants from 2007 to 2009. A multivariable logistic regression model with autocorrelation structure was used to model the effect of exposure variables on the probability of being tested positive to Campylobacter. Results showed a significant protective effect with the absence of infected neighbours within a distance of 2 km. The analysis was adjusted for potential confounding factors. Seasonal cyclic patterns of the Campylobacter infection was accounted for by using sine and cosine function. Predicted probability maps showed a heterogeneous spatial and temporal risk of Campylobacter infection in Danish broiler.

► Absence of infected neighbour in 2 km radius is protective.
► Negative test status of the farm in previous month is related with lower risk.
► There was observed a difference in risk in different processing plants.
► Predicted probability maps showed a heterogeneous temporal and spatial risk.