Prevalence of Salmonella spp. in broiler chicken flocks in northern Poland in 2014-2016

Zoonotic serotypes of Salmonella enterica subsp. enterica are an important biological factor that poses a threat to public health, and broilers are often asymptomatic carriers of these bacteria. The aim of this study was to analyze the prevalence of Salmonella spp. and Salmonella serotypes in broiler chicken flocks in northern Poland in 2014-2016. The study was conducted on commercial flocks monitored by the Institutes of Veterinary Hygiene in Gdańsk and Olsztyn in 2014-2016. A total of 4,331 samples were investigated. Identification of Salmonella spp. was performed by a culture-dependent method followed by biochemical and serological confirmation tests, in accordance with Polish Standards. The total percentage of infected flocks in northern Poland reached 1.57%. The prevalence of Salmonella spp. in broiler chickens decreased from 2.19% in 2014 to 1.22% in 2016. The percentage of flocks infected with S. Enteritidis and S. Typhimurium was 1.18% and 0.12%, respectively (S. Enteritidis and S. Typhimurium were detected in 1.29% of flocks). The most common serotypes that had not been covered by the control programme were S. Mbandaka (0.14%), S. Infantis (0.07%) and, sporadically, S. Kentucky and S. Anatum. The percentage of infected flocks was higher (by 0.26%) in the Pomeranian Region than in the Region of Warmia and Mazury, and it increased over the analyzed period – the highest number of positive samples were found in 2016 (2.04%). In the Region of Warmia and Mazury, the percentage of infected flocks was highest in 2014 (3.08%); in 2014-2016, the number of positive samples decreased steadily to reach 0.41% in 2016. In the analyzed regions, the incidence of human salmonellosis was correlated with the percentage of infected broiler flocks.