Campylobacter is the most reported bacterial cause of gastrointestinal disease in humans in Sweden, as well as in the rest of Europe. Campylobacter can be transferred to humans directly after contact with animals or through consumption and handling of contaminated food products. Poultry meat can become contaminated with Campylobacter during slaughter if the live chickens carries the bacterium in their intestines. In Sweden, all chicken flocks are tested for the presence of Campylobacter at slaughter since 1991. The proportion of chicken flocks with Campylobacter has decreased until 2013 (9 %), after which there has been an increase to 15.4 % (2016). However, there are big variations between producers, 30-40 % of the producers basically never deliver chickens with Campylobacter to slaughter, while a few (5-10 %) producers deliver chickens with Campylobacter relatively often (>30% of the flocks).
The aim of this study was to perform an in-depth analysis of two producers (A and B), that have delivered chickens with Campylobacter during several years, to identify possible transmission routes. Sock- and swab samples were collected from the in- and outdoor environment adjacent to the broiler houses. All samples were cultured for Campylobacter (ISO10272-1) and suspected isolates were confirmed by MALDI-TOF MS. Next-generation sequencing was performed on obtained isolates using Illumina technology.
Results show that Campylobacter of several different sequence types (ST:s) were detected from both producers. Cattle and contaminated water were identified as potential sources of infection for producer A, whereas wild boar and water from a pond on the premises, which was frequently visited by wild birds matched the ST:s of a number of the samples from chicken from producer B.
In conclusion, this study identified possible reservoirs of Campylobacter with a risk of transmission to broilers such as cattle nearby, contaminated drinking water, wild boars, and wild birds.