Rare contagious cancer in mussels spreading across the Atlantic Ocean

28 Nov 2019

Image: © Rob/Stock.adobe.com

Scientists have discovered that a type of contagious cancer in mussels is likely hitching a ride aboard massive cargo ships.

One of Ireland’s most beloved shellfish species is under threat following the discovery of a type of contagious cancer in locations on either side of the Atlantic Ocean. Scientists from the Columbia University Irving Medical Center have published their findings to eLife, based on analysis of different mussel species along the coasts of Argentina, Chile, France and the Netherlands.

In all of these locations, they found similar cases of contagious cancers. In some mussel colonies, the cancer was so contagious that it had infected 13pc of the population. One of the most surprising findings of the research came as a result of comparing the French and Chilean mussels.

Despite Chilean mussels hailing from the Pacific Ocean and French mussels from the Atlantic, they had identical cancer cells. This means the cancer somehow travelled more than 11,000km across hemispheres and oceans to infect other organisms.

The cancer clone had even spread into species of mussels that were different from the species in which the cancer first arose, the researchers said.

Still safe to eat

Scientists believe that while ocean currents would typically prevent cancer cells from travelling huge distances, they’ve been able to hitch a ride aboard the mussels stuck to the hulls of ships, delivering their deadly payload to other parts of the world.

Contagious cancers are very rare and have so far only been seen in three types of creature – the Tasmanian devil, dogs and shellfish – and cannot be transmitted to humans. This also means that shellfish with the cancer cells are still safe for humans to eat.

Shellfish are more prone to contagious cancers because the malignant cells easily travel in water. Also, mussels are pumping and filtering huge quantities of water on a daily basis and have a limited immune system, making them vulnerable to disease.

“There are parallels between how cancers spread in the ocean and how cancer cells metastasise within humans,” said Stephen Goff, co-author of the paper and an expert in transmissible cancers. “Learning more about contagious cancers in shellfish could help us find ways to prevent the metastatic spread of tumours to new sites in the body.”

Colm Gorey was a senior journalist with Silicon Republic