Brucella ceti in Common Dolphins (Delphinus delphis) in Portugal – Characterization of First Isolates

This study investigates Brucella ceti infection in marine mammals stranded along the Lisbon and Tagus Valley coast between 2022 and mid-2024, marking the first report of Brucella presence in Portuguese waters. Out of 59 examined marine mammals, B. ceti was isolated in three common dolphins (5.1%), a prevalence rate consistent with previous studies from other coastlines. Pathological findings varied, with one dolphin exhibiting neurobrucellosis-like symptoms and others showing diverse clinical presentations, complicating diagnosis. PCR-based detection indicated a higher infection rate (23.7%), suggesting underestimation in prevalence due to sample preservation status. Multilocus Sequence Typing (MLST) and Multiple-Locus Variable-Number Tandem-Repeat Analysis (MLVA) revealed distinct genetic profiles and close relationships to B. ceti strains from the Atlantic, supporting the hypothesis of specific host-adapted lineages in dolphins. These findings underscore the need for further research and surveillance to understand B. ceti transmission, host range, and impacts on Atlantic cetaceans, as well as to develop effective diagnostic and management strategies to mitigate infection risks in marine environments.