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While we usually think of birds, pigs, humans, horses, and dogs as the normal hosts of influenza viruses, there are other species that can acquire and potentially spread the infection as well.
Pandemic H1N1 flu has been documented in humans, swine, turkeys, skunks, ferrets, cats, and dogs. For a listing of animal pandemic flu reports you can visit the AVMA Pandemic Flu page.
In That Touch Of Mink Flu I wrote about 11 farms in Holstebro, Denmark that were reported to be infected with a variant of the human H3N2 virus.
And while less commonly reported - camels, whales and seals have all been shown to be susceptible to influenza (cite Evolution and ecology of influenza A viruses R.G. Webster et al.)
In early October media reports indicated that scores of dead seals had been discovered along the shoreline of New England, predominantly from the North Shore of Massachusetts to the southern coast of Maine.
Testing was underway, but this incident reminded some biologists of an outbreak of influenza among seals in the Cape Cod region more than 30 years ago.
In that instance, the culprit turned out to be an H7N7 influenza. (see Isolation of an influenza A virus from seals G. Lang, A. Gagnon and J. R. Geraci)
Over the past month coastal residents were advised to give any dead seals a wide berth, and report their location to authorities as necropsies, and testing for toxins and pathogens was conducted.
Late yesterday, the story emerged that NOAA, the federal agency investigating the incident, had determined that at least 5 of the dead seals had tested positive for an (as yet) unidentified influenza A virus, and that the incident has been declared an Unusual Mortality Event (UME).
You can read several media reports (see here, here, and here) on this announcement. I’ve posted excerpts from the NOAA statement below.
OAA declares string of seal deaths in New England an unusual mortality event
Public reminded to maintain safe distance from seals as investigation continues
November 4, 2011
NOAA announced today that the high number of seal deaths that have occurred along the New England coast since September has been declared an “Unusual Mortality Event.” This will enable the agency to direct additional resources to further investigate the cause of these seal deaths.
“We want to remind people to not get close to seals encountered along the shore, to keep their pets away and to report any sightings to us through our stranding hotline, while we continue to assess whether there is any potential human health risk,” said Dr. Teri Rowles, National Marine Mammal Health and Stranding Response Program Coordinator, NOAA Fisheries Service.
The declaration of an Unusual Mortality Event (UME) was determined after a formal consultation with the Working Group on Marine Mammal Unusual Mortality Events, a panel of international experts established under the Marine Mammal Protection Act to monitor and investigate marine mammal health concerns.
From Sept. 1 to Nov. 3, NOAA’s national Marine Mammal Stranding Network, the New England Aquarium’s Marine Mammal Rescue Program and the University of New England's Marine Animal Rescue Center, have been working with NOAA to respond to a reported 146 seals strandings in Maine, New Hampshire and northern Massachusetts. Most of the animals were harbor seals less than a year old. This is more than three times the average number of strandings that typically occur this time of year.
Preliminary pathology, biotoxin and virology analysis has been conducted on samples from five seals examined by the New England Aquarium. Samples from the five seals has tested positive for the Influenza A virus, while test results for six other viral pathogens and biotoxins were negative.
Even though preliminary results have been received, they are only indicative of those five cases, and additional evaluations are underway to determine whether the influenza virus has played a role in the overall mortalities.
An investigation team of marine mammal experts will work closely with NOAA, New England Stranding Network partners and the Working Group on Marine Mammal Unusual Mortality Events to identify and characterize the specific type of Influenza A virus found in these animals.
In 1984 influenza subtype H4N5 – a strain previously only seen in birds – was determined to be behind the deaths of a number of New England seals in 1982 and 1983 (cite Are seals frequently infected with avian influenza viruses? R G Webster et al.)
And in 1995, in the Journal of General Virology, authors R. J. Callan, G. Early, H. Kida and V. S. Hinshaw wrote of the The appearance of H3 influenza viruses in seals during the early 1990s.
Seals have also been shown susceptible to influenza B (cite Influenza B virus in seals. Osterhaus AD, Fouchier , et al.).
NOAA reminds people along the shoreline that seals - like other marine mammals - are protected under the Marine Mammal Protection Act, and advise that people:
Stay at least 50 yards (150 feet) away from seals or other marine mammals. Keep dogs on a leash and don't allow them to approach seals. Seals and dogs can easily infect each other with diseases since they are closely related species.
We’ll obviously be watching for more information on this case, including the identification of the influenza virus.
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