Saturday, October 1, 2022

Bird flu may cause seal strandings

The highly pathogenic avian influenza strain, which this year whipped through flocks of domestic poultry and wild birds, may also be responsible for the spike in seal strandings in Maine, US officials said on Wednesday.

Samples from four recently trapped seals – all of whom died or were sick enough to require euthanasia – tested positive for the virus.

This strain, officially known as Eurasian H5N1, mainly affects birds. After spreading to Europe, Africa, the Middle East and Asia, the virus arrived in North America late last year and quickly spread to commercial poultry farms and migratory bird routes.

Recent outbreaks involving the latest version of the virus have had a much greater impact on wild birds than in previous cycles. And it has endangered carnivores and scavengers who eat wild birds and their carcasses. Scientists have now found the virus in a variety of wild mammals in North America, including foxes, bobcats, skunks and raccoons.

“The seal is the first marine mammal we’ve seen at the end of a spillover,” Dr Juliana Lenoch, the US Department of Agriculture’s National Wildlife Disease Program coordinator, said at a news briefing on Wednesday. “But it’s not unexpected that bird flu sometimes moves to mammalian species.”

Those working with Marine Mammals of Maine, the organization responding to reports of trapped seabirds, began seeing unusually large numbers of trapped seals last month. From May 10 to July 4, 92 gray and harbor seals were reported to be trapped in Maine.

Many seals were found dead. According to the National Oceanic and Atmospheric Administration, the current rate of dead seal stranding is about three times higher than normal. Other trapped seals were ill, including lethargy, sneezing and coughing. Some also had seizures – a symptom reported in fox kits infected with avian influenza.

At the briefing, the organization’s executive director, Linda Doughty, said Marine Mammals of Maine sent samples of eight trapped seals to Tufts University for laboratory testing. Four tested positive for the virus.

Most of the strandings to date have been reported in central-to-southern Maine. “But it’s likely to spread to our coast because of live animals,” said Ainsley Smith, coordinator for stranded marine mammals at NOAA’s Greater Atlantic Regional Fisheries Office.

Viruses are responsible for other large-scale trapping events among marine mammals, and previous versions of avian influenza have caused fatal outbreaks in seals. Scientists suspect that seals, like other mammals, catch the virus after eating infected birds.

Seals can spread at least some versions of the flu to other seals. However, there is no evidence yet that this has happened in Maine, said Brian Richards, emerging diseases coordinator at the U.S. Geological Survey’s National Center for Wildlife Health.

“With all scavenging mammals, and now with seals, I don’t think we have any evidence that every individual animal is, literally, anything other than a dead-end host,” he said.

Although the risk to humans remains low, infection with mammals increases the possibility that the virus may mutate in ways that are more likely to pose a risk to humans. Versions of avian flu isolated from seals during previous outbreaks have shown signs of adaptation to mammals.

In the past, similar versions of bird flu tended to end when temperatures rose in the summer. It is too early to say whether that will happen this year, Dr. Lenoch said: “This particular avian influenza is acting a little differently, so we’re going to be on high alert.”

In the meantime, officials recommended that people – and their pets – stay a safe distance from seals and other marine mammals and report trapped animals to local wildlife officials.

Nation World News Desk
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