#13,461
We've been following the summer die-off of harbor seals in Maine & New Hampshire for nearly a week (see NOAA Investigating Unusual Seal Strandings & Deaths In New England), and today NOAA Fisheries has released the first laboratory findings, which finds evidence of both phocine distemper virus (PDV) and an (as yet unidentified) avian flu virus.
While potentially significant, these findings don't necessarily tell us if these pathogens were the primary cause of these recent seal deaths and strandings.Although we've seen unusual mortality events (UMEs) in seals due to avian influenza (see here and here) and PDV in the past, we've also seen evidence that some seals can carry and tolerate Influenza A Virus infection (see Emerg. Microbes & Inf.: Prevalence Of Influenza A in North Atlantic Gray Seals), including many avian influenza strains.
From the above mentioned study, the authors wrote:
All of which has raised questions over whether seals and other marine mammals - who often come in contact with bird species - could serve as `mixing vessels’ for influenza, much in the same way as pigs are viewed.An in vivo study using experimental infection with a seal-derived H7N7 found that while harbor seals developed disease, gray seals and harp seals (Pagophilus groenlandicus) were resistant to disease,7 reminiscent of the low pathogenicity seen in avian natural reservoirs.15Also impressive was the array of Influenza A viruses detected in this study. Again from the study:
The most frequently recognized subtypes were pH1N1, seal H3N8, H13 and H16. However, a large proportion of seropositive pups recognized H6, adults frequently recognized H2N3, and animals from Sable Island had a strong response to H4N6.
While harbor seals do appear to be more prone to morbidity and mortality from avian influenza infection than some other seal species, there remain a lot of unanswered questions. Not the least of which is what subtype of avian flu was detected.Here is what we know as of today, from NOAA.
Thursday, August 23, 2018
Seals in New England Test Positive for Avian Flu and Distemper
Some of the first batch of sampled seals that stranded in Maine, New Hampshire, and Massachusetts during the last several weeks have tested preliminarily positive for either avian influenza or phocine distemper virus. In addition, four seals so far have tested positive for both viruses. These are preliminary results based on the first set of samples analyzed by the Tufts University and University of California, Davis laboratories. We have many more samples to process and analyze, so it is still too soon to determine if either or both of these viruses are the primary cause of the mortality event.
Past seal mortality events in northeastern U.S. coast have been linked to avian flu and phocine distemper virus. However, avian flu and phocine distemper virus have also been detected at low levels in seals along the northeastern U.S. coast in non-outbreak years.
If you see a new sick or injured seal, please call the NOAA hotline: 866-755-NOAA (6622). Please be patient, as the stranding response teams are very busy.
For your safety and theirs, don’t touch a stranded seal, don’t allow pets to approach the seal, and observe the animal from a safe distance of 100 yards.
For more information on these viruses, please read our Frequently Asked Questions.
Stranding Numbers for July 1-August 21, 2018
Maine
July: 43 live, 65 dead
August: 41 live, 179 dead
New Hampshire/Massachusetts
July: 17 live, 30 dead
August: 14 live, 58 dead
Total live: 114
Total dead: 313
Total: 447
Tuesday, August 21, 2018
Stranding Numbers for July 1-August 20, 2018
Maine
July: 43 live, 65 dead
August: 40 live, 170 dead
New Hampshire/Massachusetts
July: 17 live, 30 dead
August: 14 live, 48 dead Total live: 114
Total dead: 313
