Friday, April 26, 2019

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

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Zhejiang Province – Credit Wikipedia















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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 Nationwide that 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
Influenza H5/H7 Virus Vaccination in Poultry and Reduction of Zoonotic Infections, Guangdong Province, China, 2017–18
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:
Virology: Receptor Binding Specificity Of H9N2 Avian Influenza Viruses
J. Infect & Public Health: High Seroprevalence Of Avian Influenza H9 Among Poultry Professionals In Pakistan
Vet. Sci.: The Multifaceted Zoonotic Risk of H9N2 Avian Influenza
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.

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