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Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

tetano

tetano

Editor, Senior Moderator
Virology

Volumes 450?451, February 2014, Pages 316?323
Cover image
Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

Keun Bon Kua, b, 1,
Eun Hye Parka, b, 1,
Jung Yuma, b, 1,
Heui Man Kima, b,
Young Myong Kanga, b,
Jeong Cheol Kima, b,
Ji An Kima, b,
Hyun Soo Kimc,
Sang Heui Seoa, b, Corresponding author contact information, E-mail the corresponding author

a Laboratory of Influenza Research, Chungnam National University, College of Veterinary Medicine, 220 Gung Dong, Daejeon 305-764, Republic of Korea
b Institute for Influenza Virus, Chungnam National University, College of Veterinary Medicine, 220 Gung Dong, Daejeon 305-764, Republic of Korea
c Laboratory of Public Health, Chungnam National University, College of Veterinary Medicine, Daejeon 305-764, Republic of Korea



Highlights

?

Replication of H7N9 avian influenza virus in chickens is poor.
?

H7N9 avian influenza virus is transiently shedding from chickens.
?

H7N9 avian influenza virus does not transmit between chickens well.
?

H7N9 avian influenza virus does not transmit from chickens to ferrets well.

Abstract

Previous studies have shown that the H7N9 avian influenza virus cannot be transmitted efficiently between ferrets via respiratory droplets. Here, we studied the infectivity of the H7N9 avian influenza virus in chickens and its transmissibility from infected to na?ve chickens and ferrets. The H7N9 virus (A/Anhui/1/2013) replicated poorly in chickens and could not be transmitted efficiently from infected chickens to na?ve chickens and ferrets. H7N9 virus was shed from chicken tracheae for only 2 days after infection and from chicken cloacae for only 1 day after infection, while the H9N2 avian influenza virus, which is endemic in chickens in many Asian countries, was shed from tracheae and cloacae for 8 days after infection. Taken together, our results suggest that chickens may be a poor agent of transmission for the H7N9 virus to other chickens and to mammals, including humans.
Keywords

Influenza virus;
H7N9;
H9N2;
Transmission;
Chickens


http://www.sciencedirect.com/science/article/pii/S0042682213006855
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

Sic!

From where this virus are coming from, after all?
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

This is a really important study.

The findings of this study implies that chickens are not the primary H7N9 vector in terms of human infections, and I would suggest that a really good look needs to be taken at vermin, which are likely to prevalent in and around wet markets. It is also worth remembering that screening has struggled to find virus in rural farms, and that human cases have been centered to date around cities.

If vermin feed on entrails and discarded food materials that are infected with a fully avian variation, they could become infected, where the virus adapts and subsequently spreads animal to animal i.e they could be our missing vector. Vermin would also disperse widely into residential areas.

Closing wet markets would ultimately work, as they would be the source of infection of vermin. Other possibilities could be stray cats and dogs.

This issue needs a rapid investigation, and calls into question the role of chickens.
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

Turkeys, quails, ducks, geese?

Anyway, even though a chicken sheds H7N9 for few hours, the amount of animals trade and their droppings should be enough to kill an entire city...
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

Pigeon? I still think this is a bird virus (primary host).
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

I vote for an avian host as well.
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

This is consistent with few animal and environmental samples positive, but it is worrying because people become infected despite low exposure to external sources
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

Good point on the other forms of poultry. I would consider quail as they have more similar receptors to humans i.e both forms of sialic acid receptor. Either way, if were to be e.g. quail that was the primary problem, it would be far, far more feasable to carry out a total eradication operation that it would be to try this in chickens. Eradication and containment would be possible.
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

what would happen if it becomes better transmissible between chickens ?
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

Transmission of Avian Influenza A Viruses Between Animals and People
...

Avian influenza A viruses may be transmitted from animals to humans in two main ways:
  • Directly from birds or from avian influenza A virus-contaminated environments to people.
  • Through an intermediate host, such as a pig.
Influenza A viruses have eight separate gene segments. The segmented genome allows influenza A viruses from different species to mix and create a new virus if influenza A viruses from two different species infect the same person or animal. For example, if a pig were infected with a human influenza A virus and an avian influenza A virus at the same time, the new replicating viruses could mix existing genetic information (reassortment) and produce a new influenza A virus that had most of the genes from the human virus, but a hemagglutinin gene and/or neuraminidase gene and other genes from the avian virus. The resulting new virus might then be able to infect humans and spread easily from person to person, but it would have surface proteins (hemagglutinin and/or neuraminidase) different than those currently found in influenza viruses that infect humans.

This type of major change in the influenza A viruses is known as ?antigenic shift.? Antigenic shift results when a new influenza A virus subtype to which most people have little or no immune protection infects humans. If this new influenza A virus causes illness in people and is transmitted easily from person to person in a sustained manner, an influenza pandemic can occur.

It is possible that the process of genetic reassortment could occur in a person who is co-infected with an avian influenza A virus and a human influenza A virus. The genetic information in these viruses could reassort to create a new influenza A virus with a hemagglutinin gene from the avian virus and other genes from the human virus. Influenza A viruses with a hemagglutinin against which humans have little or no immunity that have reassorted with a human influenza virus are more likely to result in sustained human-to-human transmission and pose a major public health threat of pandemic influenza. Therefore, careful evaluation of influenza A viruses recovered from humans who are infected with avian influenza A viruses is very important to identify reassortment if it occurs.

Although it is unusual for people to get influenza virus infections directly from animals, sporadic human infections and outbreaks caused by certain avian influenza A viruses and swine influenza A viruses have been reported.

http://www.cdc.gov/flu/avianflu/virus-transmission.htm
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

but remember the big sampling from the Hongkong team. (~Aug.2013)

They found lots of H7N9 and H7N7 etc. in chickens
in Rizhao, Wenzhou,Jiangxi
and sequenced it and you could see how it reassorted
and how the strains emerged

link

http://www.flutrackers.com/forum/showthread.php?t=202737

posts 24ff
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12515.html


> The overall pattern of the prevalence of H7 and H9 viruses at the sampling sites was that H7
> isolates were only, and H9 isolates were predominately, found in markets, not in farms or
> wetlands. Both H7 and H9 isolates were predominately found in chickens and predominately
> from oropharyngeal samples
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

I think the point may be overlooked here. As far as I can see

1. Avian H7N9 IS widespread in chickens and is a silent infection.

2. When this study took an isolate associated with the H7N9 human infections, (A/Anhui/1/2013) they found that variant did not transmit easily between chickens or from chickens to ferrets. Chickens also only shed virus for ONE day, so are unlikely to be releasing huge amounts of virus for onward transmission i.e they are an unlikely vector for the current outbreak

It is this fact that suggests that the culprit for onwards human infections is not a smoking chicken, but a smoking ?quail? goose? ANother animal.

Whilst H7N9 in its fully avian form is widely dispersed amongst chickens, this particular variant looks unlikely to be readily/ easily transmitted through chicken populations. i.e whilst chickens are likely to be the ultimate source of infections, we have an intermediary of some sort IMHO, whether avian (different form of poultry or birds) or mammalian. An experts interpretation of the full paper would be welcome.
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

this E627K(PB2) (or that other mutation in HA) reduces transmission
in chickens so much ?!?

they should have also tested a chicken strain with 627E (did they ?)


if it mutates to 627K in humans it should also mutate back to 627E in chickens

or maybe we have lots of H7N9 with 627K in humans but it's asymptomatic and only
rarely it mutates to 627E and becomes severe
what did serology say (I forgot much from last year now)
 
Virology. Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets.

Virology. Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets.

[Source: US National Library of Medicine, full page: (LINK). Abstract, edited.]


Virology. 2014 Feb;450-451:316-23. doi: 10.1016/j.virol.2013.12.022. Epub 2014 Jan 14.

Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets.

Ku KB<SUP>1</SUP>, Park EH<SUP>1</SUP>, Yum J<SUP>1</SUP>, Kim HM<SUP>1</SUP>, Kang YM<SUP>1</SUP>, Kim JC<SUP>1</SUP>, Kim JA<SUP>1</SUP>, Kim HS<SUP>2</SUP>, Seo SH<SUP>3</SUP>.

Author information: <SUP>1</SUP>Laboratory of Influenza Research, Chungnam National University, College of Veterinary Medicine, 220 Gung Dong, Daejeon 305-764, Republic of Korea; Institute for Influenza Virus, Chungnam National University, College of Veterinary Medicine, 220 Gung Dong, Daejeon 305-764, Republic of Korea. <SUP>2</SUP>Laboratory of Public Health, Chungnam National University, College of Veterinary Medicine, Daejeon 305-764, Republic of Korea. <SUP>3</SUP>Laboratory of Influenza Research, Chungnam National University, College of Veterinary Medicine, 220 Gung Dong, Daejeon 305-764, Republic of Korea; Institute for Influenza Virus, Chungnam National University, College of Veterinary Medicine, 220 Gung Dong, Daejeon 305-764, Republic of Korea. Electronic address: seos@cnu.ac.kr.


Abstract

Previous studies have shown that the H7N9 avian influenza virus cannot be transmitted efficiently between ferrets via respiratory droplets. Here, we studied the infectivity of the H7N9 avian influenza virus in chickens and its transmissibility from infected to na?ve chickens and ferrets. The H7N9 virus (A/Anhui/1/2013) replicated poorly in chickens and could not be transmitted efficiently from infected chickens to na?ve chickens and ferrets. H7N9 virus was shed from chicken tracheae for only 2 days after infection and from chicken cloacae for only 1 day after infection, while the H9N2 avian influenza virus, which is endemic in chickens in many Asian countries, was shed from tracheae and cloacae for 8 days after infection. Taken together, our results suggest that chickens may be a poor agent of transmission for the H7N9 virus to other chickens and to mammals, including humans.


Copyright ? 2014 Elsevier Inc. All rights reserved.

KEYWORDS: Chickens, H7N9, H9N2, Influenza virus, Transmission

PMID: 24503095 [PubMed - in process]


-
-------
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

> The H7N9 virus (A/Anhui/1/2013) replicated poorly in chickens
> and could not be transmitted efficiently from infected chickens
> to naïve chickens and ferrets. H7N9 virus was shed from chicken
> tracheae for only 2 days after infection and from chicken cloacae
> for only 1 day after infection

this seems to be counterintuitive. Why should a poorly
replicating strain be so widespread ?
It seems also to be in conflict with previous studies.

Now, the natural thing would be to ask other experts for comments
and reviews. What do those say who previously published studies
about this ? Is it just the 627K(1) ?

Unfortunately we have built a scientific system where such comments
and reviews and discussions are not appreciated and encouraged and rewarded.


from previous studies:
A/Shanghai/2/2013(H7N9) replicates well in mice without prior adaptation, less pathogenic than H5N1
A/Anhui/1/2013 A(H7N9) its airborne transmissibility in ferrets is between human and avian viruses.
A/Anhui/1/2013 and A/Shanghai/1/2013 (H7N9) both replicated to higher titre in human airway
epithelial cells and in the respiratory tract of ferrets compared to seasonal H3N2.
They had greater infectivity and lethality in mice compared to H9N2
They were readily transmitted to naive ferrets through direct contact but not by droplets.
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

gs it makes sense - after a fashion - if you assume
The virus has a wild avian host in which it is well adapted, mild/asymptomatic & sheds freely.
This host has little or no direct contact with humans, but fairly regularly interacts with poultry or their environment - water, feed.
The virus can infect & replicate reasonably efficiently in poultry even if they do not shed much.
Then all that is needed is poor/moderate chicken to human transmission, given high viral load in an infected chicken and the enormous number of chickens eaten and the level of contact.

I was not surprised by the findings and it fits with the recent release of the the chicken tests in which 33,000 chickens were tested with only 5 positives.

That we have not found my putative wild host is also not surprising as I have not seen any evidence that any great effort has been made to look.
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

there are some problems with that.

1.) they searched a lot but didn't find that avian wild host
2.) there are no multiple introductions, one HA and NA were given, the rest evolved in chickens
3.) the inner segments are totally adapted to chickens, you won't find wild avian hosts
with such inner segments
4.) all flu frequently reassorts in wild avian hosts (=ducks, what else), but we only see
chicken-like-inner segments (from H9N2)
5.) we have several reassortments of H7N9, that didn't spread. Usually one new different inner
segment from (poultry-) H9N2 was acquired.
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

gsgs said:
there are some problems with that.

1.) they searched a lot but didn't find that avian wild host
2.) there are no multiple introductions, one HA and NA were given, the rest evolved in chickens
3.) the inner segments are totally adapted to chickens, you won't find wild avian hosts
with such inner segments
4.) all flu frequently reassorts in wild avian hosts (=ducks, what else), but we only see
chicken-like-inner segments (from H9N2)
5.) we have several reassortments of H7N9, that didn't spread. Usually one new different inner
segment from (poultry-) H9N2 was acquired.
Click to expand...

1) Do you have any info on what and where they searched? Also where are the sequences, even if they did not find any H7N9 they should have found some AIs and there is nothing in the database.
2-5) I agree about where the RNA strands came from, and that would fit with poor transmission but good replication within an infected host. As we have seen in the Passerine paper some terrestrial wild birds look like they are more than capable of being a reservoir.
 
Re: Virology: Transmissibility of novel H7N9 and H9N2 avian influenza viruses between chickens and ferrets

i searched a bit ...

http://www.ncbi.nlm.nih.gov/pubmed/22422062
http://www.flutrackers.com/forum/showpost.php?p=502839

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3148691/figure/F3/


--------------edit-----------
Ducks played key role in China's H7N9 flu outbreak, scientists say
http://articles.latimes.com/2013/aug/21/science/la-sci-sn-bird-flu-ducks-chickens-h7n9-20130821
Lam et.al.: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12515.html
China has about 65 percent of the world's domestic ducks
47 million domestic ducks
 
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