Where do ducks die

Why the ducks suddenly die

The bird flu seems to have made it back to Europe. A good week ago turkeys suddenly died in Mecklenburg-Western Pomerania, and laying hens in the Netherlands a few days later. A disease quickly brought the animals away. On Monday, the authorities in England reported that an unusually high number of ducks on a farm suddenly died in the Yorkshire region. In all three cases, bird flu was probably the trigger.

All animals in affected stalls were slaughtered. In the Netherlands, the authorities imposed a ban on the transport of eggs, poultry and by-products such as poultry manure for 72 hours. In addition, the poultry transport ban will initially apply for 30 days within a ten-kilometer radius of the farm. In England the authorities are a little less rigorous. The pathogen is likely not as aggressive as the H5N1 virus, which had caused deaths in Asia in Asia. However, it cannot be ruled out that it is the same virus subtype that was found in the Netherlands and Germany. Still, no one thinks the virus is spreading.

The reactions to the outbreak are different - because there are different types of viruses that are differently dangerous. To find out any differences, virologists need to do tests. The experts at the National Reference Laboratory for Avian Influenza (bird flu viruses) at the Friedrich Loeffler Institute (FLI) in Greifswald communicate directly with colleagues from abroad. The researchers want to find out more about the origin of the virus in order to prevent it from spreading.

At least for the Netherlands and Germany it is clear that an influenza virus of the subtype A / H5N8 is responsible for the diseases. So far, this type is only known from Korea. "We are now trying to find the possible contact points through which the virus could come to Europe," says Elke Reinking from FLI. It is unlikely that a bird flew from Korea to England and stopped at poultry farms on its way.

There are different scenarios for virus spread. The virus could have been dragged from one place to the next via poultry transport. Poultry products, eggs or meat can also contain viruses. H5N8 may also have traveled in wild birds that passed it on to other wild birds at roosts. "Wild birds do not necessarily infect the hens or ducks on a poultry farm directly," said Reinking. "But if an employee steps into the droppings of a wild bird with his rubber boots, he can theoretically carry it into the stable."

The genetic makeup of the pathogen changes rapidly

The farms affected are on migration routes for wild geese that have moved from Germany to the Netherlands. "That would fit with the outbreak in the Netherlands." There is also another train route that leads from Iceland via Great Britain to the Benelux countries. "That would fit the outbreak in Great Britain," said FLI President Thomas C. Mettenleiter. When determining where the virus comes from, the researchers rely on genetic data: "This is where molecular epidemiology helps," explains Reinking. Influenza viruses are characterized by the fact that they have a relatively high mutation rate. This means that the genetic makeup of the virus changes quickly.

By comparing the virus genome from South Korea with the genome carried by the viruses in European poultry farms, scientists can ultimately get information on how long the virus took from Asia to Europe. If the gene sequences are very similar, it probably traveled quickly. If there are many mutations, it has probably found its way through several intermediate stations.

When H5N8 spread in South Korea earlier this year, it was discussed that overwintering wild ducks from Russia introduced the virus into Korea's poultry populations. Influenza viruses also circulate in wildlife. Since wild animals and viruses have adapted to each other in the course of evolution, the wild animals do not initially get sick - their immune system has adapted to the viruses. Nevertheless, they are a reservoir for viruses.

If one type of pathogen passes from one bird species to another - through direct contact with the animals or indirectly via faeces - then the second bird species can become sick. Mutations in the genetic material can mean that influenza viruses, which originally only attacked birds, also become dangerous for humans. Influenza viruses are also known to mix with other influenza viruses. In the case of swine flu, which spread to humans around the world five years ago, there was probably a mixture of bird flu and swine flu virus. It is unclear whether the new virus in Europe actually poses a threat to people. So far, no people have been infected from South Korea.