Avian flu is now also causing massive deaths among shorebirds. Complete breeding colonies of the Sandwich Tern, a Red List species, have already been wiped out. Epidemiologist Armin Elbers of Wageningen Bioveterinary Research sees the situation as not very rosy. According to Elbers, no specific mutation is known, but the host range of the virus does appear to be broadening.
The colonies of terns and gannets that are now dying en masse have come into contact with the still circulating virus. Previously, the bird flu season in the Netherlands lasted from October to April. But in recent years, the circulation of the virus has continued for longer and, in addition to resident birds, birds that migrate to the Netherlands to breed have also become infected. Because these species breed closely together in large groups, the infection spreads quickly.
Infected wild birds further contribute to the circulation of the virus. This means that the situation remains risky for poultry farming. The confinement obligation prevents direct contact between wild birds and the poultry, but this does not rule out contamination. The virus can still end up in the stable via the outside environment, although it is not yet known exactly how that works.
In the Netherlands, wild birds are infected by other wild birds through direct contact, or indirectly through ingestion of the virus through contamination of surface water or contaminated soil. The virus will continue to circulate in the wild bird population, even if all the world’s poultry were vaccinated.
According to Elbers, the most important preventive measure is to combat poultry infections in certain areas in Southeast Asia. A large part of the commercially kept poultry there is vaccinated there, but because the vaccines do not protect enough, there are still large-scale outbreaks. They are not combated as thoroughly as in Europe, which means that transmission to wild birds takes place. At the moment, there is no prospect that the situation in Southeast Asia will change any time soon.
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