Test uses oyster waste to track devastating parasite

A team of UK scientists has developed a method to detect a deadly oyster parasite, without harming the shellfish themselves.

The European flat oyster, Ostrea edulis, has fallen in numbers over the past two centuries due to overfishing, habitat loss and disease. They are now rare and protected in the wild. 

Among the most persistent threats is a microscopic parasite called Bonamia ostreae. This causes a condition known as bonamiosis, and can devastate oyster populations, but is harmless to humans. 

Until now, detecting the presence of the parasite has involved dissecting a sample of oysters, an approach that is not only destructive but also impractical for monitoring rare or restoration-targeted populations.

But researchers from the University of Edinburgh’s Roslin Institute and Heriot-Watt University have pioneered a new method that uses oyster waste to screen for parasite DNA. 

By analysing the waste material left after oysters are held overnight in aerated seawater, scientists can determine whether any oysters are infected, without harming any.

The technique is a step forward for oyster conservation and aquaculture biosecurity, according to the team involved.

The team tested the method at several sites across the UK, including Bonamia-positive waters in Essex and West Loch Tarbert in Scotland.

They found the non-invasive method was at least as sensitive as traditional tissue sampling and histology, and often more effective than water-based environmental DNA techniques.

The native flat oyster was once widespread across Europe’s coasts, but has become a conservation priority due to its ecological importance. Oyster reefs provide vital habitat, filter water, and stabilise marine sediments.

But efforts to restore wild oyster populations and expand sustainable farming have been repeatedly thwarted by Bonamia ostreae. The parasite, which invades oyster immune cells, spreads silently and can wipe out populations.

The newly developed method has been validated in field and lab settings and is portable enough to be used on-site with mobile DNA testing kits. It also proved highly accurate in negative control sites, with no false positives detected.

Unlike other DNA-based detection methods, which often rely on complex lab setups, the new approach uses a field-ready extraction and PCR system. 

According to the research team, it is scalable, cost-effective, and may even be adaptable to other marine pathogens.

The scientists are now working on refining the process further and exploring whether similar techniques could be used to detect other diseases or even invasive species.

Their findings were published in the journal Aquaculture and supported by the UK Seafood Innovation Fund and the Sustainable Aquaculture Innovation Centre, with additional funding from the Dornoch Environmental Enhancement Project, supported by The Glenmorangie Company.