A highly contagious form of bird flu continues to feed through seabird colonies on the North Sea and in the northeastern Atlantic. In the meantime, it has also reached breeding grounds on the south-west coast of Ireland, where observers can find hundreds of dead or dying gannets and representatives of other species. Since the early summer of 2022, scientists and bird conservationists have been worried about terns, boobies and other seabirds that have already died by the tens of thousands – including on the German coast. Claire Teitelbaum from the US Geological Survey and her team have now identified mercury as a factor that can potentially weaken the animals' immune system and make them more susceptible to the responsible virus, as they report in the "Proceedings of the Royal Society B".
Pulling wild ducks are suspected of spreading the pathogens of bird flu: on the one hand they are a natural reservoir for the viruses, on the other hand you can infect yourself with breeding poultry. Then carry the germs on the train and put on other birds across types. The team around Teitelbaum therefore tested 750 ducks from eleven species that were shot in the Bay of San Francisco, whether they had come into contact with the bird flu and how much they were stressed with mercury.
In fact, the probability that one of the animals had antibodies to avian flu was five times higher if it was contaminated with the liquid metal. In addition, the prevalence of bird flu was higher among the species, which were also more contaminated with mercury on average. After all, none of the animals carried the highly pathogenic virus strain H5N1, which is raging in Europe in 2022. The results are therefore not directly transferable to the situation at the North Sea and the North Atlantic.
However, mercury weakens the immune system and thus increases the likelihood that animals are infected with pathogens. Birds and other organisms usually absorb the liquid metal in the form of methyl mercury, which forms in nature through biomethylation and accumulates in the food chain. The mercury is entered, for example, by mining or the combustion of coal.
The highly pathogenic H5N1 strain appeared around 1996 in Asia in commercially used geese and spread under poultry in the early 2000s in Europe and Africa. Probably also in East Asia he jumped to wild birds, which also continued to wore the virus. Since then there has been a mass extinction like 2022 again and again. Scientists are particularly worried because it also appeared for the first time in summer, where bird flu activity would decrease.
