Tuesday, October 27, 2015

Australia: Wild Bird Avian Influenza Surveillance

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If one needs evidence that the avian influenza situation is far from static, up until 11 months ago North America had never reported HPAI viruses in wild or migratory birds.  Low Path (LPAI) viruses are quite common, but they haven’t often posed a big threat to the domestic poultry industry and are fairly easily controlled.

 

The introduction of HPAI H5 from Asia via migratory birds has always been thought possible, of course. But after more than a decade of testing and surveillance -and no positive results – many believed we were adequately protected by the oceans on either side of us.


That is, until it happened.  Now, all bets are off and we await the return of HPAI this winter.


Similarly, Australia has been viewed as being sufficiently separated by water from the rest of the world to largely protect it from HPAI via infected migratory birds. Not a 100% guarantee, of course, but reassuring.

 

According to Australia’s Department of Agriculture (formerly DAFF), the odds of seeing HPAI arrive by migratory birds are `remote’.

 

Avian Influenza or Bird Flu

The Key Facts (excerpts)

  • Avian influenza and human pandemic influenza are different diseases.
  • Avian influenza in birds does not easily cause disease in humans. There have been numerous deaths from H5N1 avian influenza in the world since the virus first emerged in 2003.
  • In 2013 a H7N9 strain of avian influenza in poultry emerged which caused human deaths in China.
  • There is only the most remote possibility of a human pandemic influenza developing in Australia as a result of migratory birds carrying avian influenza virus to Australia. If a human pandemic influenza develops as a result of mutation of an avian influenza virus, it will most likely occur somewhere else in the world and any spread to Australia would be from international travellers.
  • Surveillance continues to show H5N1 avian influenza virus is not present in Australia. Waterfowl, which are the normal hosts of avian influenza and are thought to have had a role in the spread of the H5N1 virus in Europe, Asia and Africa do not migrate to Australia. A number of species of wading birds do migrate to Australia but they are not the normal hosts or spreaders of avian influenza. Australia’s strict quarantine measures prevent the disease coming into Australia through imported birds or poultry products.
  • There is little risk of people in Australia being affected by avian influenza through normal contact with birds. As always, practice good personal hygiene when handling birds.

 

The speed with which H5N8 has spread from South Korea, to Japan, Taiwan, across China, and into both Europe and North America has understandably heightened concerns.  It has spread farther in its first year than H5N1 did in its first decade, and there’s a rogues gallery of other emerging bird flu viruses making inroads in China (H7N9, H5N6, H10N8, etc).

But even if imported migratory birds prove unable to bring these viruses to Australia, the land down under may well have the building blocks – in the form of indigenous LPAI H5 and H7 viruses – to evolve their own.


First this abstract, which appears in the Australian Veterinary Journal, after which I’ll have a bit more.

 

Avian influenza in Australia: a summary of 5 years of wild bird surveillance

VL Grillo1,*, KE Arzey2, PM Hansbro3, AC Hurt4, S Warner5, J Bergfeld6, GW Burgess7, B Cookson8, CJ Dickason9, M Ferenczi10, T Hollingsworth11, MDA Hoque7, RB Jackson12, M Klaassen10, PD Kirkland2, NY Kung13, S Lisovski10, MA O'Dea14, K O'Riley5, D Roshier10, LF Skerratt7, JP Tracey15, X Wang5, R Woods1 and L Post16

Article first published online: 26 OCT 2015

DOI: 10.1111/avj.12379

© 2015 Australian Veterinary Association

Volume 93, Issue 11, pages 387–393, November 2015

Background

Avian influenza viruses (AIVs) are found worldwide in numerous bird species, causing significant disease in gallinaceous poultry and occasionally other species. Surveillance of wild bird reservoirs provides an opportunity to add to the understanding of the epidemiology of AIVs.

Methods

This study examined key findings from the National Avian Influenza Wild Bird Surveillance Program over a 5-year period (July 2007–June 2012), the main source of information on AIVs circulating in Australia.

Results

The overall proportion of birds that tested positive for influenza A via PCR was 1.9 ± 0.1%, with evidence of widespread exposure of Australian wild birds to most low pathogenic avian influenza (LPAI) subtypes (H1–13, H16). LPAI H5 subtypes were found to be dominant and widespread during this 5-year period.

Conclusion

Given Australia's isolation, both geographically and ecologically, it is important for Australia not to assume that the epidemiology of AIV from other geographic regions applies here. Despite all previous highly pathogenic avian influenza outbreaks in Australian poultry being attributed to H7 subtypes, widespread detection of H5 subtypes in wild birds may represent an ongoing risk to the Australian poultry industry.

 

One should note the wild bird surveillance used by this took place between 2007 and 2012 – before the emergence (and/or spread) of H7N9, H5N6, H5N8, or H10N8.  

 

As we’ve discussed before, LPAI (low path) H5 and H7 viruses can – if introduced into the right conditions – mutate into HPAI viruses.   While fairly rare, we saw this happen in Lancashire, England earlier this year (see UK APHA: Epi Report On HPAI H7N7 Outbreak In Lancashire), and this has been observed a number of other occasions as well.  

 

This is the reason why LPAI H5 and H7 viruses are considered `reportable’ to the OIE, and efforts are made to stamp them out whenever they occur in poultry.

 

In addition to the H5’s and H7’s, three years ago in EID Journal: Human Infection With H10N7 Avian Influenza, we learned that the H10N7 avian flu virus had been detected in two poultry abattoir workers in Australia from 2010. Although 7 abattoir workers reported symptoms, only 2 tested positive for the H10 virus.


As further evidence of the diversity of LPAI viruses in Australia, the Queensland Department of Agriculture and Fisheries lists the following non-H5/H7 LPAI detections across the country.

 

The following LPAI (not H5/H7) detections have been made:

  • Antibodies to LPAI H1, H4, H5, H7 and H9 subtypes were detected in ducks on a farm in Victoria in 1992.
  • LPAI (H4N8) was detected on a multi-age, commercial duck farm in Victoria in 1994.
  • LPAI (H6N4) was isolated from a single duck on a property in Queensland in 2006.
  • Chickens in several sheds from a property in New South Wales tested seropositive to LPAI (H6N4) in 2006.
  • LPAI H10N7 was detected in 2010 in a chicken farm in New South Wales, where transmission to abattoir workers during the processing of the poultry was documented.
  • An LPNAI H5N3 virus was detected in a free-range duck flock in Victoria during routine surveillance in 2012. The source of the virus could not been determined, but it is speculated that the primary source may have been wild birds, since wild birds were freely able to access the range area.
  • In April 2012, LPAI H9N2 was confirmed on a turkey farm housing about 26,500 turkeys in three sheds near the Hunter Valley in New South Wales; the source of the infection is unknown.
  • In 2012, LPAI H4N6 virus was found in ducks of several age groups on a multi-age farm of 2,400 ducks located on the north coast of New South Wales.
  • In 2012, an LPAI H10N7 virus was detected in a Queensland poultry flock; the source of the infection is unknown, but it is likely that the primary source may have been wild birds.

 

The 2012 discovery of LPAI H9N2 is particularly interesting, as this same subtype has been linked to the evolution of nearly all of China’s HPAI viruses over the past two decades (H5N1, H5N6, H7N9, etc.).  Whether Australia’s H9N2 virus has the `right stuff’  (mostly internal genes) to do the same is unknown.


Today’s report warns `Given Australia's isolation, both geographically and ecologically, it is important for Australia not to assume that the epidemiology of AIV from other geographic regions applies here.’


Having once seen a platypus, I have to agree that is probably good advice.

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