Background: Caseous Lymphadenitis (CL) is a chronic infectious and contagious disease that affects sheep and small ruminants, whose prevalence in Argentine Patagonia has been demonstrated over the years. However, this disease continues to be underestimated within the sheep farming sector, causing economic losses due to reduced meat and wool quality, as well as the condemnation of carcasses and viscera. This disease has also begun to spread to wild animals, including species such as the huemul in the Andean region. Reports from Chile suggest a potential impact on the Argentine Patagonian region.
Methods: A total of 1,832 sheep intended for commercial purposes were inspected, and lesions compatible with CL were identified during the 2023–2025 period. A total of 224 samples were collected, from which the causal agent was biochemically identified. Subsequently, the etiological agent was confirmed using the MALDI-TOF method. Additionally, the presence of the gene encoding Diphtheria Toxin was investigated.
Results: Out of a total of 224 samples, 193 isolates were confirmed as Corynebacterium pseudotuberculosis biovar ovis through biochemical tests and MALDI-TOF confirmation. Additionally, the search for the diphtheria toxin gene yielded negative results.
Conclusion: Caseous Lymphadenitis (CL) is established in Argentine Patagonia, with sustained presence in sheep farming. Interaction with wildlife and environmental persistence of the agent may favor its maintenance and dissemination in the region, highlighting the importance of strengthening surveillance and control strategies.