Marine mammals victims of avian flu

Marine mammals victims of avian flu

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Avian flu caused the death of several thousand birds of different species in Quebec last year, but it also affected at least three species of marine mammals, according to what emerges from official data. And the virus is likely to strike this wildlife again this year, experts warn.

If we relied solely on the confirmed “positive” cases of avian influenza in wildlife species in Quebec, we would identify 315 of the approximately 1,676 confirmed or suspected cases (sample having tested positive for influenza at a provincial laboratory ) in Canada. The problem is that these data, which include all affected species, represent only a very small sample of infected animals.

This is the case for marine mammals, according to the Dr 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. “The H5N1 virus was identified as the cause of death for 14 of the 22 harbor seals examined, for one of the three gray seals examined and for one of the five white-sided dolphins examined”, specifies Fisheries and Oceans Canada in a response to questions from the To have to.

“For the harbor seal, this is just the tip of the iceberg,” says Dr.r Lair, adding that several carcasses were not picked up and analyzed. According to him, it is therefore quite possible that the number of infected pinnipeds was greater. He points out that between 2017 and 2021, the Quebec Marine Mammal Emergency Network identified an average of 55 common or unidentified seal carcasses for the months of April to September. In 2022, that number jumped to 155 carcasses.

“This excess mortality can be largely attributed to avian influenza,” concludes Stéphane Lair, who is notably a full professor at the Faculty of Veterinary Medicine at the University of Montreal.

“Suspicious” cases

However, it is difficult to predict to what extent the virus could affect the population of harbor seals, the only pinniped species resident in the St. Lawrence and the least abundant of the four species that frequent the estuary and the gulf. Certainly, “it could be several years before we get back to the population before,” says Dr. Lair. According to Fisheries and Oceans Canada, there are between 20,000 and 30,000 harbor seals.

Quebec is therefore no exception to what has been observed in the United States and Europe, where seals have been found dead. “We can hypothesize that the seals became infected following contact with carrier seabirds, such as common eiders, with which they share the habitat. The impact that these mortalities will have on the seal population remains to be determined, ”explains the Quebec Ministry of the Environment, the Fight against Climate Change, Wildlife and Parks (MELCCFP).

Furthermore, despite certain “suspicious” cases in harbor porpoises (the smallest cetacean in the St. Lawrence), none of the 23 carcasses examined detected the presence of the virus. There were significant mortalities in 2022, specifies Stéphane Lair, but they were not attributed to avian influenza. The veterinarian’s team also did not detect any cases of H5N1 in belugas during the analysis of carcasses.

Back in 2023

The experts will however remain vigilant in 2023, since the avian flu should continue to kill wild animals in Quebec. “We can expect a year 2023 which will look like the year 2022, whether for birds or for marine mammals. It would be amazing if it were different, ”warns the Dr The air. In Europe, the virus is still present more than two years after the start of the epidemic.

Same story on the side of Magella Guillemette, professor in the Department of Biology at the University of Quebec in Rimouski, but also of the MELCCFP. “It remains possible that other species and other mortality events of varying intensity will continue to be detected sporadically in the coming months,” the ministry said.

For 2022, however, the authorities are unable to give “a precise estimate of the number of dead wild birds”. One thing is certain, the deadly virus hit waterfowl in 2022, including the Canada goose and some species of ducks. Snow geese have also been affected, particularly during an upsurge in cases observed in November, when the species migrates seasonally.

“Predatory or scavenger birds that could feed on waterfowl or their carcasses, such as birds of prey, have also been greatly affected by the virus,” adds the MELCCFP. Among the infected species, the ministry mentions the turkey vulture, the bald eagle and certain species of buzzards.

The H5N1 strain of avian influenza has also caused “significant” mortalities in seabirds in the St. Lawrence, particularly gannets, common eiders, sea gulls and herring gulls.

Professor Guillemette nevertheless believes that the worst has been avoided for the largest colony of northern gannets in North America, that of Bonaventure Island. “The impact was pretty minimal. We are talking about a decline of 0.5% to 5%, depending on the variables used. The impact was greater at the start of the year, before decreasing thereafter,” explains the researcher who leads a team carrying out annual monitoring of this colony of more than 100,000 birds since 2008.

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