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Avian influenza killed several thousand birds of various species in Quebec last year, but it also affected at least three species of marine mammals, official data shows. Experts warn that the virus is likely to strike this wildlife again this year.
If we only trust To confirm “positive” cases Of avian influenza in wildlife species in Quebec, there are 315 of the approximately 1,676 confirmed or suspected cases (the sample tested positive for influenza in a provincial laboratory) in Canada. The problem is that this data, which includes all infected species, represents only a very small sample of affected animals.
This is the case for marine mammals, according to D.s Stéphane Lair, director of the Quebec Center for Wild Animal Health. His team analyzed 64 carcasses of 10 different species of marine mammals last year. “H5N1 virus has been identified as the cause of death for 14 of 22 harbor seals examined, for one of the three gray seals examined and for one of five white-sided dolphins examined,” states Fisheries and Oceans Canada in response to questions from Must.
to seal the harbour, It’s just the tip of the iceberg “, confirms Drs Areen, adding that many of the bodies had not been picked up and analyzed. According to him, it is very likely that the number of infected pinnipeds is greater. He notes that between 2017 and 2021, the Quebec Marine Mammal Emergency Network identified an average of 55 common or unidentified seal carcasses during the months of April to September. In 2022, that number has jumped to 155 bodies.
“This excess of deaths can be largely attributed to avian influenza,” concludes Stéphane Lair, professor emeritus at the University of Montreal’s College of Veterinary Medicine.
‘Suspicious’ cases
However, it is difficult to predict how much the virus might affect a population of harbor seals, which are the only shark species residing in the St. Lawrence and the least abundant of the four that frequent the estuary and bay. Certainly, “it could take several years before we get back to the population from before,” says Dr. Lair. According to Fisheries and Oceans Canada, there are between 20,000 and 30,000 harbor seals.
Thus, Quebec is no exception to what has been observed in the United States and Europe, where seals have been found dead. “We can assume that the seals became infected after coming into contact with carrier seabirds, such as the common eider, with which they share habitat. The impact of these deaths on seal numbers still needs to be determined,” explains Quebec’s Ministry of Environment, Climate Control, and Wildlife. and Parks (MELCCFP).
Moreover, despite some “suspicious” cases in porpoises (the smallest St. Lawrence cetaceans), none of the 23 carcasses examined detected the presence of the virus. There were significant deaths in 2022, Stefan Lair specifies, but they were not attributed to avian influenza. The vet team also did not discover any cases of H5N1 infection in the sea whales during the analysis of the cadavers.
Back in 2023
However, experts will remain vigilant in 2023, as bird flu should continue to kill wild animals in Quebec. “We can expect in 2023 Which would look like the year 2022, whether for birds or marine mammals. It would be great if it were different,” warns Drs air. In Europe, the virus is still present more than two years after the onset of the epidemic.
Same story from Magella Guillemette, professor in the Department of Biology at the University of Quebec in Rimouski, but also from MELCCFP. “It is still possible for other species to continue to be monitored, and other species of varying severity may continue to die intermittently in the coming months,” the ministry said.
But for 2022, authorities cannot give an “accurate estimate of the number of dead wild birds”. One thing is for sure, the deadly virus will hit waterfowl in 2022, including the Canada goose and some species of duck. Snow geese have also been affected, particularly during a surge in cases observed in November, when the species migrates seasonally.
MELCCFP adds: “Predatory birds or scavengers that can feed on waterfowl or their carcasses, such as birds of prey, were also significantly affected by the virus.” Among the affected species, the ministry mentioned the turkey vulture, bald eagle and certain species of hawk.
The H5N1 avian influenza strain has also caused “significant” deaths in St. Lawrence seabirds, particularly gannets, common birds, seabirds, and herrings.
However, Professor Guillemette believes the worst has been avoided for the largest colony of northern gannets in North America, Bonaventure Island. “The effect was very small. We’re talking about a decline of 0.5% to 5%, depending on the variables used. The effect was greatest at the beginning of the year, before decreasing after that,” explains the researcher who leads a team doing annual monitoring of this colony of more than 100,000 birds since 2008.
