Bird Flu: On the trail of the disease trails

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Bird Flu: On the trail of the disease trails
Bird Flu: On the trail of the disease trails

On the trail of the plague trails

The excitement surrounding H5N1 is slowly dying down. However, how the bird flu pathogen found its way to Germany and finally spread to livestock is still unclear. A Munich laboratory is on the trail of the pathogen. French President Jacques Chirac reluctantly put his fork in his mouth: at a press conference he had to demonstratively try a Bresse chicken. Because the news had just made the rounds, which was tantamount to a catastrophe among France's gourmets: In February, the bird flu had infected the first farm animals in Europe - of all things the famous free-range chickens from the Bresse region, which the French rave about as a delicacy. Chirac had to show his nation that poultry was still safe to eat in order to avert greater economic damage. But how did this happen despite increased vigilance? And how did the H5N1 bird flu virus first get into a German livestock population at the beginning of April?

So far, scientists, such as those at the Friedrich Löffler Institute, have only been able to determine whether a dead animal died from the highly pathogenic variant of the H5N1 virus, but the pathogens could not be assigned to a regional origin. Experts from the new molecular biology laboratory at the Bavarian State Office for He alth and Food Safety (LGL) in Munich recently succeeded in completely decoding the genes responsible for the production of the surface proteins hemagglutinin (H) and neuramidase (N). Since these genes differ depending on their origin, the spread of the disease can now be traced.

Question of Origin

"By decoding the gene sequences, the H5N1 viruses of dead wild birds and scavengers can be compared with one another," explains Heinz Rinder, physician and scientist in the new laboratory."In this way it can be found out whether the virus types on Rügen and in Bavaria match to a large extent or whether they are so different that we have to conclude that they come from different sources." If as many gene sequences as possible of bird flu viruses are elucidated from all countries where the epidemic has previously occurred, the path of spread can be tracked by comparing them.

The theory is crumbling that bird flu spreads particularly during migration

(Heinz Rinder) This has now become very important because two new developments have emerged, Rinder states: "On the one hand, the theory that bird flu spreads particularly during bird migration is crumbling." Because the dead and infected birds on Rügen were found in the middle of winter, i.e. not at the time when migratory birds arrive.

On the other hand, it is completely unclear how the bird disease got into the Saxon breeding farm. These questions could be answered much better with the decoding of the genes, especially for haemagglutinin. However, until that happens and more precise statements can be made, many laboratories still have to sequence these genes and enter them in an international database. According to Rinder, this is the only way to comprehensively identify similarities and differences in the viruses and to track the development of the mutations that the genes of the pathogens are constantly undergoing. "Our publication [in the database] should also be an initial spark for other laboratories to get involved and make their sequencing more widely known," emphasizes the virus expert.

Two Ways

The virus may have migrated to Germany via two different paths. The first gene sequence of the virus that was published in Germany, i.e. that of the Munich laboratory, comes from a dead mallard duck from the district of Bad Tölz-Wolfratshausen. It is 99.3 percent consistent with the viral variant of a mallard duck from Italy. The viruses of the dead birds on Rügen, on the other hand, appear to be more similar to the pathogens from Mongolia and China.

Researchers worldwide can enter and retrieve information and data via the digital database "GenBank". There, the American National Center for Biotechnology Information (NCBI) archives genome codes, develops analysis software and brings together research activities.

No Brainpower

No "brains" are needed to sequence the genes, machines often do that, says Rinder, "but we're proud that we were the first to publish the sequences." This happened relatively quickly because the molecular biology laboratory at the LGL developed a method with which the regional variants of the virus can be determined in just two to three days by skilful work with gene regions and without growing the virus.

The new laboratory is ultra-modern - a level 3 safety laboratory - and so far unique in Germany, as Rinder explains."We have the best working conditions here, because the laboratory has more than 100 square meters and is very well equipped." In four independent laboratory sections, doctors and veterinarians, food chemists, laboratory technicians and technical assistants can scrutinize a wide variety of substances, from substances suspected of being bioterrorists to tuberculosis pathogens.

Even if the excitement about H5N1 is slowly dying down again - the Munich researchers will not run out of work.

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