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Five weeks ago, in NOAA Investigating Unusual Seal Strandings & Deaths In New England we looked at reports of an unusual spike in seal mortality along the Maine, New Hampshire, and Massachusetts coastlines, which was reminiscent of a 2011 event caused by a novel H3N8 avian flu (see New England Seal Deaths Tied to H3N8 Flu Virus).
A week later, NOAA announced that avian influenza (subtype not specified), along with Phocine Distemper virus, was confirmed as being present in at least some of the seals recovered in this latest die off (see NOAA: Seals in New England Test Positive for Avian Flu & Phocine Distemper Virus).Earlier this month, with the number of dead seals continuing to climb, NOAA Declared An Unusual Mortality Event - Harbor & Grey Seals In The Northeast.
NOAA's latest update - 2018 Pinniped Unusual Mortality Event along the Northeast Coast - now implicates Phocine Distemper, and minimizes the likely role of avian flu, in these deaths.
Why are seals stranding?
Full or partial necropsy examinations have been conducted on some of the seals and samples have been collected for testing. Based on tests conducted so far, the main pathogen found in the seals is phocine distemper virus. Phocine distemper virus is not zoonotic, which means it cannot be transferred to humans, but it may still be able to affect pets.The test results do not provide strong evidence that avian influenza virus is a cause of the current Northeast Pinniped UME. We are continuing additional testing to identify any other factors that may be involved in this event and will share those findings when available.As part of the UME investigation process, an independent team of scientists (Investigative Team) is being assembled to coordinate with the Working Group on Marine Mammal Unusual Mortality Events to review the data collected and provide guidance for the investigation.
(Continue . . . )
Although we've seen high seal mortality in the past with avian viruses (see H3N8 in New England and H10N7 in Europe), two years ago in Emerg. Microbes & Inf.: Prevalence Of Influenza A in North Atlantic Gray Seals we looked at a study showing that some seals can carry certain types of influenza A viruses - including avian subtypes - without obvious signs of illness.
Essentially, they found a high level of influenza A infection in the sampled seal population, but with little or no sign of illness. Grey seals in particular, were found to carry these viruses without ill effect.And in 2013 we saw a report (and a study) from UC Davis showing the human 2009 pandemic H1N1 virus had jumped to wild California Elephant Seals just one year after that virus emerged (see The 2009 H1N1 Virus Expands Its Host Range (Again)).
All of which means that the detection of avian influenza in sick seals could end up being an incidental finding, and not the cause of their illness.As this latest update mentions, additional tests are underway, and so we'll keep an eye on this story for any additional developments.
