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OFID: Avian H5, H7 & H9 Contamination Before & After China's Massive Poultry Vaccination Campaign

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  • OFID: Avian H5, H7 & H9 Contamination Before & After China's Massive Poultry Vaccination Campaign

    OFID: Avian H5, H7 & H9 Contamination Before & After China's Massive Poultry Vaccination Campaign


    Zhejiang Province – Credit Wikipedia

    #14,035


    In the summer of 2017, following a disastrous spring surge in H7N9 infections and the emergence of a new HPAI strain, China's MOA announced plans to test a new experimental H5+H7 poultry vaccine in two provinces (Guangdong & Guangxi).
    With fears that H7N9 was creeping ever closer to becoming a pandemic strain, less than a month later the MOA Ordered HPAI H7N9 Vaccine Deployed Nationwidethat fall.
    While previous poultry vaccination programs had yielded varying levels of success, China's dramatic drop in human infections, reported outbreaks in poultry, and virus detection from routine surveillance has exceeded all expectations.

    Illustrating the effectiveness, last October we looked at an EID Journal Dispatch that found a remarkable reduction in H7 virus detection in Guangdong Province:
    Volume 25, Number 1—January 2019
    Dispatch
    Jie Wu1, Changwen Ke1, Eric H.Y. Lau, Yingchao Song, Kit Ling Cheng, Lirong Zou, Min Kang, Tie Song2 , Malik Peiris, and Hui-Ling Yen2

    Abstract

    We compared the detection frequency of avian influenza H7 subtypes at live poultry markets in Guangdong Province, China, before and after the introduction of a bivalent H5/H7 vaccine in poultry. The vaccine was associated with a 92% reduction in H7 positivity rates among poultry and a 98% reduction in human H7N9 cases.
    Given that the immediate goal was preventing an H7N9 pandemic, this was an extraordinary turnaround. But nothing happens in a vacuum, and the impact of China's H5+H7 vaccination program on other avian flu subtypes had yet to be determined.

    And while avian flu activity in China has been greatly suppressed for more than a year, we've seen a few cracks in the veneer.
    All of which brings us to a new study, published two days ago, that looks at the impact of China's H5+H7 vaccination program on prevalence of H5, H7, and H9 viruses in Zhejiang Province.
    As with the above study, this first introduction of an H7 poultry vaccine in China reduced H7N9 detection by well over 90% in Zhejiang Province.
    Today's report also adds that detection of H5 viruses remains pretty much unchanged, while the prevalence of H9N2 viruses has increased significantly. First the abstract (follow the link for the full Provisional PDF), then I'll return with a bit more.
    Comparison of avian influenza virus contamination in the environment before and after massive poultry H5/H7 vaccination in Zhejiang province, China

    Wei Cheng Ka Chun Chong Steven Yuk-Fai Lau Xiaoxiao Wang Zhao Yu Shelan Liu Maggie Wang Jinren Pan Enfu Chen
    Open Forum Infectious Diseases, ofz197, https://doi.org/10.1093/ofid/ofz197

    Published: 23 April 2019

    PDF

    Abstract
    Background

    Information regarding comparison of the environmental prevalence of avian influenza virus (AIVs), before and after massive poultry vaccinations, is limited. Our study aimed to detect differences in the prevalence of AIVs type A and subtypes H5, H7, and H9 before and after the September 2017 massive poultry vaccination, across different sampling places and types.
    Methods

    We collected 55,130 environmental samples from 11 cities in Zhejiang Province (China) between March 2013 and December 2018. Multivariate logistic regression analyses were conducted to determine the prevalence of AIV type A and subtypes H5, H7, and H9 across different sampling places and types, before and after massive poultry vaccination.
    Results
    After the vaccination, contamination risk of AIV type A (aOR=1.08, 95%CI: 1.03-1.14) and subtype H9 (aOR=1.58, 95%CI: 1.48-1.68) increased, and that of subtype H7 (aOR=0.12, 95%CI: 0.10-0.14) decreased.
    Statistically significant decreased risk for H7 subtype contamination and increased risk for H9 subtype contamination were observed in backyard poultry flocks, live poultry markets, and slaughtering/processing plants.
    Swabs from poultry cages and slaughtering tables showed a statistically significant increased risk for H5 subtype contamination. The prevalence of H7 subtype decreased statistically significantly, while that of H9 subtype increased across the five sample types (poultry cages swabs, slaughtering table swabs, poultry feces, poultry drinking water, and poultry sewage).
    Conclusions

    Despite the sharp decrease in H7 subtype prevalence, reduction measures for avian influenza virus circulation are still imperative, given the high type A prevalence and the increase in H9 subtype contamination across different sampling places and types.
    (Continue . . . )


    These results mirror pretty much what we've observed over the past year.
    H7N9 cases and outbreaks are down dramatically, H5N6 cases and outbreaks have remained roughly unchanged, and we've seen an increasing number of H9N2 human cases since December of 2017.
    The authors offer several possible explanations for the H5 and H9 results, and take note of H9N2's modest pandemic potential and reputation for being a gene donor to many HPAI reassorted viruses.

    A few past blogs on this include:All of which means that while H7N9 has been - at least temporarily - suppressed, there are other viral gears in motion in China, and the battle is far from won. New reassorted viruses are likely to arise over time, H5N6 could gain additional human adaptations, and H7N9 could stage a comeback.

    Because with novel influenza A viruses, the story is always evolving.

    http://afludiary.blogspot.com/2019/0...amination.html
    All medical discussions are for educational purposes. I am not a doctor, just a retired paramedic. Nothing I post should be construed as specific medical advice. If you have a medical problem, see your physician.

  • #2
    I wonder how much good it will do in the longer term. Natural Selection will do what it always does and favour those mutations which are less well matched to the vaccine. The result is vaccines aid drift away from the vaccine strain and therefore aid diversification and so increase the virus' pallet and scope for novel recombination or reassortment into possibly pandemic strains.

    Mike do you know if vaccine capacity was switched from H9N2 to this H7/H5 combo or did they have additional capacity coming on stream. It would account for the H9N2 uptick if less vaccine was produced.

    Comment


    • #3
      I can't answer directly, because the Chinese don't tend to offer up those sorts of details, but we've been watching the antigenic diversification of H9N2 viruses for a number of years. H9 vaccines appear to provide limited protection - if any - against many of the wild-type variants. This from a 2017 BMC Veterinary Research review:
      Current situation of H9N2 subtype avian influenza in China

      • Min Gu?,Lijun Xu?, Xiaoquan Wang and Xiufan Liu
      Even though vaccination remains one of the primary strategies to control H9N2 subtype AI in China, the majority of vaccine recipients are actually still under siege of wild-type variants. Therefore, disease outbreaks would still occur in vaccinated flocks in case of descended protection level or different kinds of immune failure.
      I would also speculate thatwhatever efforts were directed towards the 2017 emergency H5+H7 vaccination program probably stole from the manpower/resources needed to maintain regular H9 vaccination schedules, and I've no idea how old the current H9 poultry vaccine in use there really is. If they aren't updated regularly, they are probably just masking the outward signs of infection.

      Last Fall (see WHO: Candidate Vaccines For Pandemic Preparedness - Sept 2018) the WHO announced the need fo create a new, human H9N2 Candidate Vaccine (A/Anhui-Lujiang/39/2018-like A(H9N2) CVV) - the 7th iteration since 1999 - due to its continual evolution.

      I agree that poultry vaccination programs - even very successful ones - tend to produce temporary, and often fleeting success. Nature always bats last.
      All medical discussions are for educational purposes. I am not a doctor, just a retired paramedic. Nothing I post should be construed as specific medical advice. If you have a medical problem, see your physician.

      Comment


      • #4
        Many thanks, as always.

        Comment

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