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Food Inspection Agency investigating after parasite found in P.E.I. oysters

Several sites considered 91Ƶunder suspicion91Ƶ and have been placed under quarantine
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Oysters harvested from a farm are inspected by a worker in Brunswick, Maine, on June 12, 2022. THE CANADIAN PRESS/AP, Robert F. Bukaty

A 91Ƶworrisome91Ƶ parasite has been confirmed in at least one area on Prince Edward Island, and samples from several oyster farms have been sent for testing, says the Canadian Food Inspection Agency.

Danielle Williams, disease technical specialist at the federal agency, said the parasite called multinucleate sphere X 91Ƶ or MSX 91Ƶ has been confirmed in Bedeque Bay on the province91Ƶs south shore.

91ƵWe haven91Ƶt determined the amount of spread yet, but it is worrisome. It is very worrisome,91Ƶ she said in an interview Monday.

Several other sites are considered 91Ƶunder suspicion91Ƶ of having the parasite and have been placed under quarantine as investigation continues to confirm whether it is present, including a location on Malpeque Bay on the province91Ƶs north shore, she added.

91ƵWe have found another location in Malpeque area and so we have a few places under quarantine right now,91Ƶ she said. 91ƵWhat we did was that if a place was under suspicion, we placed it under quarantine until the testing results were finished.91Ƶ

She said the parasite likes to stay in 91Ƶlittle pockets of areas,91Ƶ and if scientists are able to quickly identify and stop it from moving further, they can limit damage to the industry.

The parasite affects the growth of oysters and increases mortality, but there is no human health risk. Typically, cultivated oysters take about three years to reach market size, and the inspection agency said mortality rates from the disease can reach 90 to 95 per cent in older oysters.

The agency said MSX has previously been found in Nova Scotia and British Columbia, but this is the first time it has been detected in Prince Edward Island waters. Testing confirmed the presence of the parasite earlier this month after P.E.I. reported a 91Ƶsignificant91Ƶ oyster mortality in Bedeque Bay this spring.

Cory Deagle, fisheries minister for Prince Edward Island, called the presence of MSX in oysters in Bedeque Bay 91Ƶdevastating news.91Ƶ

91ƵIt isn91Ƶt just about the impact on our oyster industry, it is about the livelihood of Islanders, their families and our communities,91Ƶ he said in a statement last week.

91ƵThis is the first time we have had to deal with MSX in our province, and while MSX has been heavily researched over the years, scientists, researchers, and fishers around the globe still do not understand how the disease spreads. It will take time before we know the full extent of the impact on our industry.91Ƶ

A provincial government study said that in 2019 Prince Edward Island accounted for 32 per cent of the national economic value of oysters 91Ƶ about $54 million.

Peter Warris, executive director of the P.E.I. Aquaculture Alliance, said oyster growers are 91Ƶvery concerned91Ƶ about the presence of MSX, something they have been dreading for years. 91ƵSo it91Ƶs bad news that it91Ƶs finally arrived,91Ƶ he said.

Harvesters have not yet seen significant mortalities, he said, noting that the situation is evolving. 91ƵI think everyone91Ƶs taking a bit of a pause in terms of their activities 91Ƶ waiting to see the results from the testing, to see where it has spread to,91Ƶ he said.

A publication from the Connecticut Department of Agriculture said MSX caused massive oyster mortalities in Delaware Bay in 1957 and two years later in Chesapeake Bay. While the parasite has been found in the United States from Florida to Maine, not all areas have been associated with oyster deaths, it said.

Warris said it is possible to have a thriving oyster industry in spite of MSX. 91ƵThe industry will adapt to the new circumstances,91Ƶ he said.

Rod Beresford, an associate professor at Cape Breton University91Ƶs biology department, said one of the challenges with the parasite is that in spite of it being around since the 1950s, there is not much known about its life cycle.

Scientists have tried to determine if the parasite has an intermediate host that allows it to move, he said. What they do know is that the infection is first seen in the oyster91Ƶs gills 91Ƶ which is where oysters get their food 91Ƶ and replicates, eventually leading to the death of the host.

91ƵFor something that91Ƶs been around for 60 years and caused this much economic and ecological damage, it91Ƶs really, really surprising that we91Ƶve not figured out its life cycle,91Ƶ Beresford said. 91ƵIt91Ƶs really a mystery.91Ƶ

In many diseases, proximity to an infected animal increases the likelihood of infection, but that is not always the case for MSX, said Beresford, who has been studying the parasite.

It is also not known exactly what temperatures, salinity or conditions result in this parasite eventually causing infection and disease. In the past, he said, researchers have put infected and non-infected oysters together in tanks and there was no spread. Oysters free from MSX were injected with tissue from a diseased animal but did not get infected, he added.

91ƵWe91Ƶre missing a piece of the life cycle here,91Ƶ he said. 91ƵWe know so little about this organism, it91Ƶs shocking. 91Ƶ We91Ƶre really stymied by this. It91Ƶs a real challenge.91Ƶ





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