Tuberculosis Surveillance in Free-Living Pinnipeds of Patagonia, Argentina

Abstract Tuberculosis is a disease caused by bacteria belonging to the Mycobacterium tuberculosis complex (MTBC), which includes zoonotic agents capable of infecting a wide range of domestic and wild species, including marine mammals. Although tuberculosis in pinnipeds has been documented worldwide, evidence is largely restricted to post-mortem findings, with limited information from active surveillance of live populations. In this study, We conducted an exploratory field-based assessment of tuberculosis exposure in free-ranging South American sea lions ( Otaria byronia ) along the Patagonian coast of Argentina. During the austral summer of 2025, biological samples were collected from 28 neonate pups from four colonies located in Chubut and Santa Cruz provinces, using minimally invasive field procedures. Blood and nasal swab samples were obtained and processed using a combination of serological, bacteriological, and molecular diagnostic approaches. Serological testing was performed using a commercial rapid assay (Lionex Animal TB®) to detect antibodies against MTBC antigens, while nasal swabs were analyzed by bacteriological culture and PCR targeting the IS6110 sequence. Serological reactivity to at least one MTBC antigen was detected in 25.0% (7/28) of the sampled pups, indicating indirect serological evidence of exposure at the colony levelin three of the four colonies. In contrast, all samples were negative by bacteriological culture and PCR. Considering the neonatal age of the individuals and the chronic nature of tuberculosis, the serological findings most likely reflect passive transfer of maternal antibodies rather than active infection in pups. This study offers new evidence on tuberculosis surveillance in live free-ranging pinniped populations, emphasizing the relevance of combining serological, bacteriological, and molecular tools for comprehensive wildlife health monitoring under a One Health approach. Overall, the results reinforce the need for active and integrated surveillance strategies to address zoonotic risks in high-risk wildlife–human interface settings.