Thread by @thijskuiken

1/ Worldwide, a #poultry-origin disease is causing high mortality in wild birds. The disease is called highly pathogenic avian #influenza (#HPAI). It is important to record the scale of wild bird mortality in order to help prevent such disasters in the future. Here is a thread.

2/ In general, HPAI viruses emerge in intensive poultry production systems by mutation from relatively innocent viruses (aptly called ‘low pathogenic avian influenza viruses). Of 39 known HPAI mutation events detected, 37 are from such poultry farms.

3/ The cause of the current wild bird mortality is the descendant of a HPAI virus that emerged in a commercial farm of domestic geese in Guangdong, China, in 1996. The virus spread widely across poultry farms in Asia, and then spilled over into wild waterbirds.

4/ Over time, HPAI viruses evolving from this Goose/Guangdong lineage spread across the world, often causing high mortality, both in poultry and wild birds. Now these viruses are found in wild birds in Europe, Asia, the Middle East, Africa and North America.

5/ Breeding colonies of wild birds are the most recent niche where these HPAI viruses cause death. Affected species include northern #gannets, sandwich #terns, great #skuas and Dalmatian #pelicans. Because these species are long-lived, their populations may take years to recover.

6/ Current #surveillance systems for HPAI in wild birds record the detection of HPAI virus in a wild bird mortality event, but *not* the numbers of wild birds found dead. That means that these systems are blind to the impact of HPAI on wild bird populations. This needs to change!

7/ To help policy makers around the world to make decisions how to transform the poultry sector into a more sustainable activity, well-documented records of mortality events in wild birds due to HPAI are needed.

8/ Just to be clear: such records will not help to decrease the current wild bird mortality, but they may provide part of the factual basis for new policies to avert future HPAI outbreaks in poultry that can spill over into wildlife.

9/ People professionally involved in monitoring wild bird populations can help by recording the number of wild birds found ill or dead during HPAI mortality events. Additional relevant data include age category, sex, and the numbers of any leg bands on affected birds.

10/ In addition to recording the scale of wild bird mortality, at least a few carcasses should be tested for HPAI. Submission of carcasses for testing must be coordinated with the relevant national authorities, and include taking appropriate hygiene measures.

11/ It also is relevant to record clinical signs in ill birds. Clinical signs like walking or swimming in circles, holding the head at an angle, and repeated trembling or shaking of the head are highly suggestive for HPAI, although virus detection is needed to prove it 100%.

12/ An example: we performed a study on the scale of wild bird mortality from HPAI in the Netherlands in 2016/2017. Estimated wintering population mortality was up to 5% for tufted ducks and Eurasian wigeons, 2%–10% for great black-backed gulls, and 11%–39% for peregrine falcons.

13/ The main conclusion from our paper was: “These latest outbreaks have shifted the paradigm of wild birds as unaffected agents of HPAI viruses, with increasing concerns about potential effects on their populations."

14/ “The Netherlands and other important staging areas for migratory waterbirds across Eurasia ... are at risk for substantial numbers of bird deaths during future HPAI outbreaks...”

15/ “...International responsibilities regarding migratory bird populations should stimulate national authorities to avert HPAI outbreaks not only in poultry and humans but also in wild birds.”

16/ Given the scale of recently observed die-offs in colonial breeding birds around the world, these recommendations are even more widely relevant now, and may apply both to migratory and resident wild birds in HPAI-affected areas.

17/ References for this thread:
1: DOI: 10.1126/science.abo1232
2: doi: 10.3389/fvets.2018.00084
3: doi: 10.1006/viro.1999.9820
4: DOI: 10.1126/science.aaf8852

18/ References continued:
5: vogelbescherming.nl/actueel/berich… (sandwich terns, Netherlands)
bbc.com/news/uk-scotla… (northern gannets, U.K.)
unep-aewa.org/en/news/avian-… (Dalmatian pelicans, Greece)
6: doi:10.2903/j.efsa.2022.7289
10: DOI: 10.3201/eid2312.171086