The strain of highly pathogenic avian flu that spread through flocks of domestic poultry and wild birds this year could also be behind a spike in seal strandings in Maine, officials said Wednesday. American officials.
Samples from four recently stranded seals – all of which died or were sick enough to require euthanasia – tested positive for the virus.
The strain, officially known as Eurasian H5N1, primarily affects birds. After causing outbreaks in Europe, Africa, the Middle East and Asia, the virus arrived in North America late last year and quickly spread to commercial poultry farms and along migratory bird routes.
Recent outbreaks involving the latest version of the virus have wreaked far more havoc on wild birds than previous rounds. And that has endangered carnivores and scavengers that feed on 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 on the fallout side,” Dr. Julianna Lenoch, national wildlife disease program coordinator for the US Department of Agriculture, told a news conference. Wednesday. “But it’s not unexpected that bird flu occasionally spreads among mammalian species.”
Workers at Marine Mammals of Maine, an organization that responds to reports of stranded sea creatures, began noticing an unusually high number of stranded seals last month. From May 10 to July 4, 92 gray and harbor seals were reported stranded in Maine.
Many seals were found dead. The current rate of dead seal strandings is about three times higher than normal, according to the National Oceanic and Atmospheric Administration. Other stranded seals were sick and exhibited symptoms including lethargy, sneezing and coughing. Some also had seizures – a symptom that has been reported in fox kits infected with bird flu.
Marine Mammals of Maine sent samples from eight stranded seals to Tufts University for lab testing, Lynda Doughty, the organization’s executive director, said during the briefing. Four have tested positive for the virus.
So far, most strandings have been reported in central and southern Maine. “But it’s possible this could spread to our coast as live animals move around,” said Ainsley Smith, stranded marine mammal coordinator at NOAA’s Greater Atlantic Regional Fisheries Office.
The viruses have been responsible for other mass strandings in marine mammals, and previous versions of bird flu have caused deadly 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’s no evidence yet that it happened in Maine, said Bryan Richards, emerging disease coordinator at the US Geological Survey’s National Wildlife Health Center.
“With all mammalian scavengers, and now with seals, I don’t think we have any evidence to suggest that each individual animal is anything other than, literally, a dead end host,” he said.
Although the risk to humans remains low, infection of mammals increases the chance that the virus could mutate in a way that makes it more likely to pose a danger to people. Versions of bird flu that have been isolated from seals in previous outbreaks have shown signs of adapting to mammals.
In the past, similar versions of bird flu tended to disappear in the summer when temperatures rose. It’s too early to tell if that will happen this year, Dr Lenoch said: “This particular bird flu is acting a little differently, so we’ll be on high alert.
In the meantime, authorities have recommended that people – and their pets – stay a safe distance from seals and other sea mammals and report stranded animals to local wildlife authorities.