Dermo disease confirmed in Quebec, P.E.I. oysters

Cases of a disease affecting oysters have been confirmed in Quebec and Prince Edward Island for the first time.

The Canadian Food Inspection Agency says dermo was detected in oyster samples from Chaleur Bay in Quebec and Egmont Bay, P.E.I.

It says a different disease affecting oysters, known as MSX, was also confirmed in the Quebec samples, another first in the province.

The agency says dermo and MSX don’t pose risks to human health or food safety but can cause increased oyster mortality and decreased growth rates.

Officials say dermo, also known as perkinsosis, can be transmitted from oyster to oyster or from water contaminated with the parasite.

However, they say with MSX it’s presumed there is an unknown intermediary host, making it harder to determine how it’s spread.

This report by The Canadian Press was first published July 4, 2025.

The Canadian Press