Canadian oyster farms and wild oyster harvesters across three provinces are grappling with pathogens detected by the Canadian Food Inspection Agency (CFIA), roughly one year after the detection of multinuclear sphere X (MSX) in Prince Edward Island (PEI).
The CFIA has reported the detection of Dermo – also known as Perkinsosis – in oyster samples in locations in PEI, Quebec, and Newfoundland and Labrador. The announcements from the CFIA also revealed it detected MSX in oysters in Quebec, adding it to previous detections in PEI and New Brunswick.
The detections of Dermo in the three provinces also add to the earlier detection of Dermo in New Brunswick in November 2024, which at the time was the first detection of the pathogen in Canada.
The CFIA said it detected Dermo in Egmont Bay, PEI; Chaleur Bay, Quebec; and Notre Dame Bay, Newfoundland and Labrador. All three instances were the first time the pathogen had been detected in the respective provinces.
CFIA said it, Canada’s Department of Fisheries and Oceans (DFO), and the governments of each province are working together with partners to continue monitoring the situation and take necessary actions.
“These actions are part of the Government of Canada's One Health approach to prepare for, detect, and manage animal diseases,” CFIA said.
Response measures on the problem could include applying movement controls on oysters from the provinces, further investigation on the sources of the detections, engaging scientists and oyster producers to monitor the health of mollusks in the region, and ensuring any information on detection is readily available to all oyster producers in the affected areas.
Dermo and MSX both pose no health risks to humans and are not food safety concerns. However, both pathogens can cause increased oyster mortality and decreased growth rates in oysters in the region.
The DFO announced plans to provide up to CAD 1 million (USD 729,000, EUR 623,000) in funding to support scientific research on MSX in 2024 after the pathogen – which is caused by the parasite Haplosporidium nelsoni – was first detected in PEI. According to the CFIA, mortality rates are typically in a range between 50 percent and 75 percent, and there is currently no treatment for it.
Oyster growers and harvesters in Canada have faced an uncertain future since the first MSX detection, which has a varied effect on oysters. Past data on MSX infection has showed the mortality timeline varies – from just a few weeks to over 10 years.
The CBC reported test runs on the wild oyster fishery in Bedeque Bay, PEI, found “devastating” results as a large crew found an extremely small number of oysters.
PEI Shellfish Association President Bob MacLeod told the CBC a large crew, including three dories, three directors from the association each with one other person, and three people from the province all tested the area.
“Between the whole crew of them and the time they spent, in total they found around 30 oysters. It was pretty devastating news, really,” MacLeod said.
He said the area used to be the heart of the fishery, with plenty of oysters for the 70 to 80 fishers who would target it.
"There'd be millions and millions of oysters in Bedeque. That was one of the places you could go and fish over and over and over and over, and you could always make a day's pay,” MacLeod said. “To send a crew out with that many dories and with that many people and come up with 30 oysters – that's just heartbreaking."
