Aquaculture

New tech on the west coast

Lavanya describes her recent fieldwork with oysters in Argyll.

23/6/2022

These oysters were tested onsite by Roslin staff.

Postdoctoral researcher Lavanya Vythalingam and her colleagues recently traveled to Argyll for field work. In the 19th century, this area was a large commercial oyster fishery for European flat oysters (Ostrea edulis), but the industry was later crippled due to overexploitation and outbreaks of Bonamia ostreae—a dangerous notifiable pathogen which remains a significant threat to both wild and farmed European flat oysters. Now, people are working to reintroduce the European flat oyster in the area to help rehabilitate oyster reefs. While onsite, Lavanya, Tim Regan, and Tim Bean tested a portable tool developed at the Roslin institute that allows for disease screening to be done non-invasively, and is very sensitive (capable of sentivities greater than 1 disease positive animal among 9 negative animals) to survey oyster beds for the risk of Bonamia ostreae.

Rehabilitation efforts in disease positive sites have been undertaken, but recovery can be damaged by outbreaks of Bonamia and other diseases. However, methods for preventing spread are perhaps not able to keep up with the pathogen; testing only begins once a mass mortality event has taken place—and as Bonamia can endure for long periods of time before causing mortality it is possible for the pathogen to be moved by accident, making it an ever-present threat. “Additionally, conventional testing for the presence of Bonamia takes an extended period of time,” Lavanya explains. “It can be from three days to one week between removing animals from the water to receiving a result and testing isn’t usually done in the field, which further slows any response researchers and farmers can take when faced with the risk of pathogen spread.”

“Ideally, we’d have a tool which can identify disease quickly and onsite and which could be used by scientists and farmers alike, so oysters can be assessed for disease before being moved and before disease presence is suspected,” Lavanya adds. “This would help make our approach preventative rather than reactive.”

Tim Bean's group took to the field while testing samples for Bonamia.

 

Oysters found at the lake are tested methodically for infection.

The tool Lavanya used can confirm the presence of disease with qPCR testing in less than 24 hours, with this timeframe including quarantine and incubation for the sample animals. Assays for Bonamia ostreae, Oyster Herpesvirus type 1 (OsHV), and Vibrio aestuarianus are also in development. Notably, these oysters also do not need to be sacrificed for the sake of the experiment—the testing remains noninvasive despite the breadth of information it can supply.

As expected, the test sites tested were positive for Bonamia ostreae, indicating that the pathogen still lingers. All animals were returned to the water once the oyster weight and measurements were taken. “The presence of parasite could slow down the rehabilitation process,” Lavanya explains. “Nonetheless, the oysters looked healthy and did not show any significant signs of the disease.”

Lavanya is quite optimistic. “This tool will dramatically change the way we deal with oyster disease and help prevent the spread of disease to new sites.” She hopes that one day, UK farmers can collaborate to monitor their farms or oyster restoration sites without scientist assistance. This tool is the first step in improving preventative methods crucial to ensuring the sustainable growth of this industry.