Making a difference in the bird flu debate

NIOO-researchers have been collecting bird faeces in the area around Dutch poultry farms infected with bird flu. So far, traces of the H5N8 strain of the virus have been found in samples from two wigeons. But there is more to the story.

This week's and previous week's field research into the link between migratory birds and the H5N8 strain of bird flu was commissioned by the Dutch Economic Affairs ministry, in response to the recent outbreak.

The NIOO's Centre for Avian Migration and Demography was asked to carry out a (large) part of the work because of its long experience in collecting data about swans, ducks and other possible carriers of the virus.

Challenging Assumptions

That experience has prompted the Centre to warn the Dutch media against jumping to conclusions. In the case of migrating mallards, for instance, NIOO's researchers recently found that many of them contract (older strains of) bird flu after they arrive in the Netherlands, not before.

This does not mean migratory birds aren't responsible for spreading the latest strain of the virus. But assumptions about the path it has followed and how widespread it is among migrants may need to be revised, head of the Centre for Avian Migration Henk van der Jeugd said on Dutch radio.

East and West

One of the few things that do appear certain is that H5N8 originated in Southeast Asia. But there is no direct migration route from there to Western Europe, says Van der Jeugd, so the virus could only have arrived via a complicated relay that involved more than one flyway and probably more than one species of bird.

A possible scenario is that birds migrating west to Europe from Northern Siberia were infected last summer by other birds that stop and breed in Siberia from their flyway east. Earlier research showed that migratory birds can be carriers of (mild) bird flu strains without becoming sick themselves.

Structural changes?

Either way, the next step is to establish how widespread H5N8 is in the swan, goose and duck faeces that NIOO's researchers have so far collected from the area around the outbreaks. Samples are sent to the Erasmus Medical Center in Rotterdam for further research.

If H5N8 should indeed turn out to be widespread, this will cause the government policy to be stepped up. More structural changes aimed at reducing the vulnerability of the production system will take time.

(Photograph of mute swan: John Kroll/Flickr)