Thursday, December 04, 2014

Media: Canadian Bird Flu Outbreak Identified As H5N2


Map Credit FAO


# 9411

After several days of anticipation – and a good deal of public speculation that Canada’s Fraser Valley bird flu outbreak might have been due to either H5N1 or H5N8 – it was revealed today that this outbreaks is the somewhat less alarming – but far from benign – H5N2 subtype.


The Canadian Press - ONLINE EDITION

Tests confirm avian influenza strain at B.C. farms as H5N2: source

By: The Canadian Press

Thursday, Dec. 4, 2014 at 12:58 PM

VANCOUVER - Tests results have confirmed the strain of avian influenza that has killed poultry on at least two farms in southwestern British Columbia is H5N2.

A turkey farm and a chicken farm located in the Fraser Valley were placed under quarantine earlier this week after the H5 virus was detected, but officials were still awaiting confirmation of the specific subtype.

(Continue . . .)


As of this posting, there is no official statement on the CFIA (Canadian Food Inspection Agency) website, and a more complete analysis of the virus will probably take several days.

On Tuesday, in Fraser Valley B.C. Culling Poultry After Detecting H5 Avian Flu, I described 2 previous H5N2 outbreaks in the same region of Canada – one in 2005 and another in 2009. In 2010, we saw Low-path H5N2 confirmed in Manitoba.  All three outbreaks were quickly contained.


H5N2 is generally found in wild birds, usually as an LPAI (Low pathogenic avian influenza) strain, but when it is introduced into large poultry populations it can evolve into a HPAI. 


It was for this reason that  OIE made both High and Low path H5 & H7 poultry outbreaks a reportable event back in 2004, and why quarantine and immediate culling are the preferred course of action whenever it either is detected. We’ve seen a number of HPAI and LPAI H5N2 outbreaks in the past, notably in Taiwan, China, Canada, the United States, Korea, Japan, and Mexico.


While not normally thought of as a serious threat to public health (see WHO: Human Risk From H5N2 Is Low), we have seen some limited evidence that H5N2 might be able to infect humans.


Nearly three years ago, in Taiwan: Three Poultry Workers Show H5N2 Antibodies, we looked at a report that three poultry workers and officials working in animal quarantine have tested positive for antibodies for the H5N2, but all remained healthy and asymptomatic (note: refer to article for other possible causes of seropositivity).


Some earlier H5N2 studies include:


J Epidemiol. 2008;18(4):160-6. Epub 2008 Jul 7.

Human H5N2 avian influenza infection in Japan and the factors associated with high H5N2-neutralizing antibody titer.

Ogata T, Yamazaki Y, Okabe N, Nakamura Y, Tashiro M, Nagata N, Itamura S, Yasui Y, Nakashima K, Doi M, Izumi Y, Fujieda T, Yamato S, Kawada Y.

Arch Virol. 2009;154(3):421-7. Epub 2009 Feb 3.

Serological survey of avian H5N2-subtype influenza virus infections in human populations.Yamazaki Y, Doy M, Okabe N, Yasui Y, Nakashima K, Fujieda T, Yamato S, Kawata Y, Ogata T.


While these reports are suggestive of prior H5N2 human infection – particularly among poultry workers – we haven’t seen any good evidence that it has produced significant or serious human illness


However, in Human H5N2 bird flu infection: fact or fallacy? (May 2014) by Beuy Joob and Viroj Wiwanitkit, published in the Asian Pac J Trop Biomedicine, the authors argue:


 . . . . the cross species infection from avian to mammal of H5N2 virus has already been confirmed in pigs and the possibility for further genetic reassortment to cause new H5N2 virus that might be highly virulent to human beings is also proposed[9]. It is no doubt that the special concern and appropriate surveillance on the possible emerging human H5N2 bird flu is needed.


Which simply reminds us that influenza viruses are moving targets.  What you can say about one today, may . . .or may not . . .hold true tomorrow.


As far as this current outbreaks is concerned – while there is no such thing as a `good’ H5 avian flu outbreak in poultry – if you were forced to choose between having an H5N1, H5N8, or an H5N2 outbreak . . . .  I’m certain most poultry producers would choose H5N2.

1 comment:

Anonymous said...

You have a talent for organizing and presenting information on a complex topic! I live in WA state, and am curious about why we did not get any commercial farm H5N2 outbreaks, in spite of the fact that a couple of wild birds were found infected, and a few non-confined farms were infected. We do have larger farms near the Canadian border, and the one I'm aware of takes care to be sanitary and to allow their birds enough room to avoid stress. They say they don't need antibiotics because of this.
So perhaps they and a lot of what looks like well-run organic farms in the area provided a buffer even though they were in range of the virus.

I'm curious, too, as to why the BC Fraser Valley commercial farms did so much better at snuffing out the virus than they seem to be doing in the Midwest. Your post has been really helpful in showing that it may be improved biosecurity in Fraser Valley. Since that H7N3 2004 outbreak took out almost their whole commercial population, (17,000,000+), and this current outbreak seems to have ended at 245,000, they must be doing something right. We benefited in WA since once BC's commercial growers were under control, our wild bird and small free-range farm outbreaks ended, too.
I see you have BC's control methods detail in another post so will try to compare them to what is being done in the Midwest.