The SVA- Statens veterinärmedicinska anstalt has confirmed the first finding of avian influenza virus in a porpoise. The analysis shows that the porpoise died as a result of the same virus that was behind this summer’s extensive bird flu outbreak among wild birds.
The young male porpoise stranded alive in Kämpersvik, in Tanum municipality, Västra Götaland 28 June 2022. Despite repeated attempts by private individuals to get it to swim out to deeper water again, it was too exhausted, got tangled in seaweed and died later in the evening. The porpoise was transported to SVA for an autopsy. The analysis now shows that bird flu virus was found in several organs and that the virus had caused meningitis. The findings confirm that the bird flu virus was the cause of death.
As far as we know, this is the first confirmed case in the world of bird flu in a porpoise. Unlike seals, where disease outbreaks caused by influenza viruses have been repeatedly demonstrated, there are only isolated reports of influenza viruses in cetaceans. It is likely that the porpoise somehow came into contact with infected birds, says Elina Thorsson, game veterinarian at SVA.
The virus, H5N1, is the same virus that was also behind the extensive bird flu outbreak that is still ongoing among wild birds in Sweden, other parts of Europe and in North America. How the porpoise from Kämpersvik was infected is still unknown, but it was found at the same time as bird flu was causing high mortality among seabirds, especially gannets, on the west coast.
It is an unusual find, and interesting because we get the opportunity to learn more about the virus. At the same time, this is about an individual case, and we have not seen any increased mortality among porpoises. We know that there is a risk that marine mammals can become infected, and have therefore included sampling for influenza in our surveillance program, says Elina Thorsson.
The risk of humans being infected with the variant of bird flu that is now circulating among wild birds is considered to be small.
During the ongoing bird flu outbreak in Europe and North America, in addition to large numbers of dead wild birds, a smaller number of mammals have also been infected and died. The route of infection is suspected to be through close contact with infected birds. Single cases have been detected in red foxes, otters, lynxes and skunks. An increased mortality in both harbor seals and gray seals has been seen in connection with the outbreak in North America, but in Sweden there have been no increased reports of dead seals during the summer.
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