Study reports first hemoplasma detection in European cetaceans

Hemotropic Mycoplasma has now been documented in cetaceans from European waters for the first time, according to a paper published October 14, 2026, in Veterinary Sciences. The study examined stranded cetaceans from two Spanish regions and found PCR evidence of infection in a subset of dolphins from the Mediterranean coast, marking a notable expansion in the known range of these bacteria. (mdpi.com)

The report builds on a gap that marine mammal pathologists had already flagged. A 2025 conference abstract from some of the same research network described 20 cetaceans stranded along the Cantabrian coast that all tested negative in preliminary spleen screening, while noting that hemoplasmas had previously been described in cetaceans from the Americas, not Europe. That earlier work framed the question now answered by the full paper: whether cetaceans in European waters also carry these blood-associated bacteria. (europeancetaceansociety.eu)

In the new study, investigators analyzed spleen and lung samples from 68 stranded cetaceans from Cantabria (n=20) and the Valencian Community (n=48). The animals represented the families Delphinidae, Phocoenidae, Kogiidae, and Ziphiidae. Overall, 8 of 68 animals were positive, for a prevalence of 11.8%, and all positives were striped dolphins from the Valencian Community. The authors also reported two nucleotide sequence types: one matched a hemoplasma previously found in a Brazilian short-beaked common dolphin, while the other showed 96.1% identity to hemoplasmas reported in Bolivian river dolphins, raccoons, and South American camelids. (mdpi.com)

That geographic and genetic context matters because hemoplasmas are a broad group, and their clinical role can be hard to pin down. Merck Veterinary Manual describes hemoplasmas as wall-less bacteria that attach to erythrocytes, with disease expression ranging from asymptomatic infection to immune-mediated anemia, often influenced by host status and co-morbidities. In marine mammals, prior literature has suggested Mycoplasma may contribute to disease in some cases, but often alongside other pathogens or stressors rather than as a clean, single-agent diagnosis. (merckvetmanual.com)

Published marine mammal pathology reports support that caution. A U.S. Navy-supported Pacific stranding review described Mycoplasma as a novel pathogen in that regional dataset and linked it to a melon-headed whale calf with interstitial pneumonia, while also noting prior Scottish and Florida reports in cetaceans with respiratory disease, co-infections, and heavy parasitism. In other words, the European detection is epidemiologically important, but it doesn't yet establish that hemoplasma was driving illness or stranding in these Spanish dolphins. That interpretation is an inference from the available evidence, not a direct claim of the paper. (navymarinespeciesmonitoring.us)

Why it matters: For veterinary professionals, especially those in wildlife health, diagnostic pathology, and aquatic animal medicine, this study expands the pathogen map for stranded cetaceans in Europe. It suggests hemoplasma testing may have value in post-mortem workups, particularly in striped dolphins and in cases involving anemia, immunosuppression, respiratory compromise, or suspected mixed infections. It also reinforces the importance of coordinated stranding networks and standardized tissue collection, because prevalence estimates and clinicopathologic interpretation will depend heavily on which tissues are sampled and whether blood, histopathology, and co-pathogen data are available. (mdpi.com)

The finding also lands in a broader surveillance environment in southern Europe, where stranded cetaceans are already being monitored for pathogens such as cetacean morbillivirus, herpesvirus, and Brucella. That doesn't mean these agents are directly connected in this study, but it does underscore why marine mammal diagnostics increasingly rely on multiplex, ecosystem-level surveillance rather than single-pathogen thinking. (visavet.es)

What to watch: The key next questions are whether additional European surveillance finds hemoplasma in live or stranded cetaceans beyond striped dolphins, whether prevalence differs by region or species, and whether future studies can connect PCR positivity with hematologic changes, lesions, or co-infections strongly enough to clarify clinical relevance. (mdpi.com)