The H5N1 2.3.4.4b strain is also known to infect and kill mammals such as martens, foxes, raccoons, martens and bears.
There has been a mass death among seals in the United States as a result of the avian flu that is currently circulating. A research team from Tufts University in Medford (USA) reports in the journal “Emerging Infectious Diseases” that hundreds of common and gray seals have died of H5N1 in New England, in the northeastern USA. For some time now, the worst wave of avian flu ever documented has been rampant among birds. It spans several continents.
Tens of millions of animals have died, mostly seabirds. The circulating H5N1 strain 2.3.4.4b is known to also infect and kill mammals such as martens, foxes, raccoons, martens and bears. Most often these are individual tests.
3,500 sea lions died in Peru
In Peru, however, according to Tufts University, about 3,500 sea lions have recently died from the virus, and Canada has reported the death of a seal in the St. Lawrence. There have also been reports from Russia of a similar event in seals in the Caspian Sea.
The team led by Wendy Puryear and Kaitlin Sawatzki has now evaluated data on pathogen analyzes of samples from dead, diseased and healthy animals. Avian influenza has been continuously monitored by testing on birds and some mammals in New England since January 2022. Accordingly, in June and July 2022 alone, more than 330 gray seals died from avian influenza line 2.3.4.4b at along the North Atlantic coast.
At the time when seals were dying in New England, the virus was also hitting gulls particularly hard, the scientists explain. Sometimes there are pairs of specimens, sometimes literally from a bird and a seal on the same beach, Puryear explained. A seal can become infected if it comes into contact with the faeces of a sick bird or water contaminated by the bird, or if it eats an infected bird.
Nearly 100 percent lethal in waterfowl
It is known that H5N1 is almost 100% deadly in waterfowl. The study now shows that this could also apply to mammals: all seals that tested positive for the virus were already dead at the time of sample collection or succumbed to the pathogen shortly afterwards.
The question of whether the virus is also transmitted between seals is still being discussed. “It wouldn’t be surprising if seal-to-seal transmission could occur, as this has already happened with low-pathogenic avian influenza,” Puryear said. However, definitive evidence is still lacking – for seals and generally for mammal-to-mammal transmission.
Experts are concerned that the virus might better adapt to mammals and therefore humans. So far, only one death in China has been proven to be attributed to the currently circulating group of avian flu viruses. The Friedrich Loeffler Institute (FLI) recently reported that the woman who died in October had the H5N1 virus group 2.3.4.4b. She was 38 years old and had contact with infected birds. She developed severe pneumonia and died in hospital.
Experts were concerned about an outbreak of avian flu at a Spanish mink farm in October 2022. There were indications in the animals that the pathogen had genetically adapted better to mammals, he said. It is still unclear whether there was transmission from animal to animal on the farm or another route of contagion, for example via food. Mammal-to-mammal transmission would pose a greater risk to humans.
(APA/dpa)