Seaports are hotspots of contagious cancer in mussels


Seaports act as hubs for the global spread of MtrBTN2,1  a rare contagious cancer affecting mussels. In this disease, cancer cells can be transmitted, like parasites, from one mussel to another nearby. While, in nature, such contagion mainly occurs between mussels in the same bed, ports and maritime transport facilitate the spread of MtrBTN2 to other locations, through biofouling, whereby diseased mussels attach themselves to ship hulls. This finding, the fruit of research by a team led by scientists from the CNRS and the University of Montpellier,2  will be published in Proceedings of the Royal Society B on February 21.

Higher incidence of the disease in ports was noted after studying 76 mussel populations along the coast of southern Brittany and the Vendée, within both natural and artificial habitats.

The research team asserts that their discovery argues in favour of biofouling mitigation policies, to stem the spread of the disease and preserve coastal ecosystems.

Mytilus edulis mussels on floating dock pile in French port of Croisic.
© Nicolas Bierne
MtBTN2 cells under microscope (× 100 magnification). They are characterized by their large size, prominent nucleus, and scarce cytoplasm. In contrast, a healthy cell—a haemocyte of smaller size with more abundant cytoplasm—is visible on the bottom right.
© Maurine Hammel


  • 1MtrBTN2 = Mytilus trossulus Bivalve Transmissible Neoplasia 2
  • 2These scientists are affiliated with the Institut des Sciences de l'Évolution de Montpellier (CNRS / IRD / University of Montpellier) and the Interactions Hôtes-Pathogènes-Environnements research unit (CNRS / IFREMER / University of Perpignan Via Domitia). Their fellow team members are from the MIVEGEC research unit (CNRS / IRD / University of Montpellier) and the research support firms Eurêka Mer and Cochet Environnement.

Marine transmissible cancer navigates urbanised waters, threatening to spillover. M. Hammel, F. Touchard, E. A. V. Burioli, L. Paradis, F. Cerqueira, E. Chailler, I. Bernard, H. Cochet, A. Simon, F. Thomas, D. Destoumieux-Garzón, G. M. Charrière et N. Bierne. Proceedings of the Royal Society B, 21 February 2024.


Nicolas Bierne
CNRS Researcher
Maurine Hammel
Université de Montpellier PhD student
Aurélie Meilhon
CNRS Press Officer