Identification of Transmission Routes of and On-Farm Measures to Reduce in Chicken.

An in-depth analysis was performed on Swedish broiler producers that had delivered chickens with to slaughter over several years, in order to identify possible transmission routes and formulate effective measures to prevent chickens being colonized with Between 2017 and 2019, 626 samples were collected at farm level and was isolated from 133 (21.2%). All and isolated from these samples were whole-genome sequenced, together with isolates from the corresponding cecum samples at slaughter ( = 256). Core genome multi-locus sequence typing (cgMLST) analysis, using schemes consisting of 1140 and 529 genes for and , respectively, revealed that nearby cattle, contaminated drinking water, water ponds, transport crates, and parent flocks were potential reservoirs of A novel feature compared with previous studies is that measures were implemented and tested during the work. These contributed to a nationwide decrease in positive flocks from 15.4% in 2016 to 4.6% in 2019, which is the lowest ever rate in Sweden. To conclude, there are different sources and routes of transmission to chickens from different broiler producers, and individual measures must be taken by each producer to prevent colonization of chickens.