NSW: 400K Birds To Be Culled For H7N2 Outbreak

 

# 7868

 

An update to Tuesday’s report of avian flu at a poultry farm in New South Wales, Australia (see NSW: H7 Avian Influenza Reported In Poultry), we now know that the virus has been identified as HPAI (highly pathogenic) H7N2 and the decision has been made to cull 400,000 birds and destroy upwards of 3,000,000 eggs.

 

Highly pathogenic avian viruses are a concern because they cause a high mortality rate among infected birds and are easily spread among flocks, but even low pathogenic (LPAI) H7 and H5 avian viruses are reportable diseases, because of their their ability to mutate from a low pathogenic virus to highly pathogenic virus.

 

The latest update from the NSW DPI reads:

 

Current situation

Updated: 17 Oct 2013

Avian Influenza confirmed in an egg production flock near Young

H7 Avian Influenza has been confirmed in a flock of 400,000 layer hens near Young.

This is not the highly pathogenic H5NI strain that has gained worldwide attention – nor is it closely related to that strain.

The egg farm has been placed under strict quarantine and movements on and off the property are being controlled.

More than 18,000 chickens on the site died as a result of the virus.

Agreement has been reached on the eradication of the virus and the depopulation of the remaining birds has now commenced.

The Department of Primary Industries and the Livestock Health and Pest Authority are continuing surveillance and tracing to confirm the virus has not spread.

If you notice sick or dead birds you need to contact your local veterinarian or call the Emergency Animal Disease Watch Hotline 1800 675 888.

 

Amid the testing and quarantine at this poultry facility, a bit of a kerfuffle has erupted between the media and government officials over the lack of quarantine signage at the farm, and alleged `trespassing’ by reporters after being told not visit the farm.

We’ve two audio reports from ABC news, the first including a testy exchange between DPI Chief Veterinarian Ian Roth and Michael Condon (6 minutes), and the second (4 minutes) with the director CSIRO's Animal Health Laboratory, Kurt Zuelke, explaining the testing process for avian flu.

 

DPI confirms chickens will be destroyed

 

New South Wales Department of Primary Industries chief vet, Ian Roth tells Michael Condon that more than 400,000 chickens will be destroyed after a bird flu outbreak on an egg farm near Young, and responds to reports that the DPI didn't erect 'keep out' signs on the property as soon as it was quarantined.

Scientist explains how bird flu was tested

 

Director of the CSIRO's Animal Health Laboratory, Kurt Zuelke explains to Lucy Barbour how his team tested and confirmed the H7 avian influenza found on an egg farm near Young, in south-west New South Wales.

 

 

Although human infection with H7 avian influenza isn’t unheard of, it has been fairly rare and the risk to the public from these avian viruses is generally considered low.  The exception to this rule being the recently emerged H7N9 virus in China, which has proven unexpectedly pathogenic in humans.

 

On October 7th, the World Health Organization  published an updated Influenza at the human-animal interface Summary and assessment,  which contained the following risk assessment on H7 avian viruses in response to the recent report of 3 poultry workers in Italy contracting H7N7 ( ECDC Update & Assessment: Human Infection By Avian H7N7 In Italy).

 

Influenza A(H7) viruses have been detected in poultry populations in many countries throughout the world. Occasionally, human cases of infection with A(H7) viruses have been detected, mainly in people directly exposed to infected poultry or contaminated environments. Generally, these infections cause conjunctivitis or mild influenza like illness, however in rare cases of human A(H7) infections, notably with A(H7N9), severe and fatal disease was reported.

Overall public health risk assessment for this influenza A(H7N7) virus: Further human cases and small clusters may be expected if the virus continues to circulate in poultry. The current likelihood of community level spread of this virus is considered low.

 

Any country experiencing outbreaks of influenza virus infection in animals should implement appropriate biosafety measures to protect people working with or living nearby infected and potentially infected animals. Collaboration with animal health partners is necessary to optimally control this disease and decrease risks to public health.

Close monitoring of people at risk (cullers, people working on affected farms, veterinarians) and their close contacts is warranted to detect potential human to human transmission.

 

For more on H7 avian viruses in general, you may wish to revisit last March’s Brief History Of H7 Avian Flu Infections.

NSW: H7 Avian Influenza Reported In Poultry

 

# 7860

 

With the caveat that all H7 viruses are not created equal - and that with the exception of H7N9 - H7 viruses are generally considered to pose only a low threat to human health, Australian authorities are reporting an outbreak of an H7 virus (N subtype not specified) at a poultry farm in New South Wales. 

 

First the report from the NSW  Department of Primary Industries, after which I’ll return with more.

 

Avian Influenza confirmed at Young egg farm

15 Oct 2013

H7 Avian Influenza has been confirmed in a flock of 400,000 layer hens near Young, NSW Chief Veterinary Officer Ian Roth said today.

"The results were confirmed by the NSW Department of Primary Industries’ (DPI) State Veterinary Diagnostic Laboratories at the Elizabeth Macarthur Agricultural Institute and CSIRO’s Australian Animal Health Laboratory," Mr Roth said.

"The results confirm that this virus is the H7 Avian Influenza strain, NOT the highly pathogenic H5N1 strain that has gained worldwide attention.

"The property has been quarantined and DPI's First Response Team has been activated to oversee the response and work with the property owners and the egg industry.

"The remaining birds on the property will now be culled in-line with national agreements.

"Control restrictions are now in place within a 10km radius of the quarantined egg farm and extensive surveillance and tracing is now underway to ensure the virus does not spread.”

"The NSW Food Authority has confirmed that there are no food safety issues and that poultry and eggs remain safe to eat.

"There is no evidence that eating food from farms that have been affected by avian influenza have ever caused human illness," NSW Food Authority Chief Scientist, Lisa Szabo said.

Mr Roth said Australia has previously had a small number of outbreaks of H7 Avian Influenza viruses which were all quickly and successfully eradicated.

"Late last year, the DPI and Livestock Health and Pest Authority (LHPA) successfully eradicated an outbreak of H7 Avian Influenza at an egg farm near Maitland," Mr Roth said.

People who notice sick or dead birds should contact their local veterinarian or call the Emergency Animal Disease Watch Hotline 1800 675 888.

 

 

Although human infection with H7 viruses have been only rarely reported, and (with the exception of H7N9 in China) have caused mostly mild symptoms, H7 viruses over the past decade have been increasingly viewed as having at least some public health implications.

 

In 2008 we saw a study in  PNAS that suggested the H7 virus might just be inching its way towards better adaptation to humans (see Contemporary North American influenza H7 viruses possess human receptor specificity: Implications for virus transmissibility).

 

You can read more about this in a couple of blogs from 2008, H7's Coming Out Party and H7 Study Available Online At PNAS.

 

The emergence of a highly pathogenic (in humans) H7N9 in China last spring has increased these concerns, as has the revelation that a new H7N7 strain emerged in Chinese poultry at roughly the same time (see Nature: Genesis Of The H7N9 Virus).

 

Ten years ago, the largest known H7 outbreak of human cases (at least until H7N9 in China) was recorded in the Netherlands. In that outbreak, the culprit was H7N7 (albeit from a different lineage than the H7N7 virus described in this Nature Journal letter above).

 

Details on that cluster were reported in the December 2005 issue of the Eurosurveillance Journal (see Human-to-human transmission of avian influenza A/H7N7, The Netherlands, 2003). Roughly 30 million birds residing on more than 1,000 farms were culled to control the outbreak. One person - a veterinarian who visited an infected farm – died a week later of respiratory failure.

 

The rest of the symptomatic cases were relatively mild.

 

The Fraser Valley, British Columbia H7N3 outbreak of 2004 resulted in at least two human infections, as reported in this EID Journal report: Sporadic human cases of avian H7 virus infection linked to outbreaks in poultry have also been reported the UK, Mexico, and most recently Italy (see ECDC Update & Assessment: Human Infection By Avian H7N7 In Italy).

 

Again, cases were generally mild, with conjunctivitis being the most commonly reported symptom.

While most H7 viruses are currently considered primarily a threat to the poultry industry, H7 flu strains - like all influenza viruses - are constantly mutating and evolving. What is mild, or relatively benign today in humans, may not always remain so. 

 

Which is why we take note of outbreaks such as the one reported today in NSW.

 

For more on the history of H7 viruses, you may wish to revisit A Brief History Of H7 Avian Flu Infections.