Systemic salmonellosis in 3 pine siskins from Louisiana during the 2020-2021 songbird mortality event.

During the 2020-2021 irruption year, pine siskins (Spinus pinus) experienced widespread mortality across North America, attributed to Salmonella enterica subsp. enterica serovar Typhimurium. In March 2021, 3 pine siskins were admitted to the Louisiana State University Wildlife Hospital (Baton Rouge, LA, USA) because of lethargy, respiratory distress, diarrhea, and inability to fly. All birds died on or shortly after presentation. Postmortem examination revealed necrotizing and granulomatous esophagitis (3), hepatitis (3), splenitis (2), enteritis (1), cloacitis (1), and stomatitis/rhinitis (1) with intralesional gram-negative bacilli. Immunohistochemistry revealed abundant extracellular and intracellular Salmonella sp. lipopolysaccharide antigen in affected organs. Salmonella Typhimurium was isolated from livers (3), cloacal swabs (2), and a spleen (1). One case had concurrent trichomonosis with erosive pharyngitis and necrotizing esophagitis. These cases are a subset of the larger 2020-2021 salmonellosis outbreak in passerines and are among the few reported from Louisiana.