Prevalence and potential risk of Salmonella enterica in migratory birds from South Korea

Salmonella is a type of zoonotic bacteria that represents an economic and public health concern worldwide. Difficulties in sample collection from migratory birds mean little is known about their importance as a reservoir of Salmonella. The present study evaluated the prevalence and potential risk of Salmonella enterica in migratory birds. From 2012-2017, 3661 cloacal swabs from migratory birds were collected in South Korea and tested to isolate S. enterica. Strains were tested for antimicrobial resistance and the presence of virulence genes. Thirty-six S. enterica strains, including S. enterica serovar Typhimurium (n = 19), S. Berta (n = 16), and S. Virchow (n = 1), were isolated from 34 birds. Two migratory birds were simultaneously co-infected with two serotypes. S. enterica was isolated from the Mallard duck, Northern pintail, Eurasian wigeon, Spot-billed duck, Eastern great egret, and Intermediate egret. S. Virchow was resistant to ciprofloxacin, with a point mutation (Ser-83-Phe) in the gyrA gene. Ten virulence genes were detected; sixteen strains were positive for all ten virulence genes. Salmonella was isolated from different migratory bird species and geographic locations with up to 100 % similarity of PFGE type. Eight S. Virchow strains taken from migratory birds, poultry farms, and chicken meat showed the same PFGE type. Salmonella was transmitted across species, space, and time in migratory birds. These birds may play a role in the dispersal of pathogenic and antimicrobial-resistant Salmonella and sporadic Salmonella infections in poultry; therefore, they may represent a direct or indirect public health threat.