Five waterways in Prince Edward Island (PEI) are now under quarantine following the detection of multinuclear sphere X (MSX), a disease deadly to oysters. 

And a sixth location, in western PEI, has returned a presumptive positive test result for MSX, though it must be confirmed through DNA sequencing, according to the Canadian Food Inspection Agency (CFIA). 

MSX is known for its devastating impact on oyster populations, causing mortality rates of up to 90% in new infections. It was first discovered in the province's waterways six weeks ago, as Undercurrent News reported. The disease is known to have cost at lest one PEI oyster processor, Five Star Shellfish, about CAD 100,000 ($72,954) since it was first detected in Bedeque Bay in early July.

CFIA has implemented primary control zones (PCZs) to restrict the movement of oysters and related equipment, though harvesting is still permitted with proper authorization. The agency also has continued sampling and testing waterways across the province to determine the extent of the infection.

Among the waterways where MSX has been confirmed are: Boughton River in eastern PEI; New London Bay/Stanley Bridge in Queens County; Birds Island to Black Banks, which extends along the North Shore from Lennox Island to the mouth of Cascumpec Bay; Bedeque Bay, where MSX was first detected on July 11; and Darnley Basin on P.E.I.'s North Shore.

The Canadian government has committed up to CAD 1 million for scientific research over the next two years to address gaps in understanding the disease. It will host a science summit this fall to discuss future strategies.