Friday, June 01, 2018

China MOA: H7N9 Confirmed At Liaoning Poultry Farm

Credit Wikipedia


Based on the limited reporting we get out of China, last year's massive nationwide poultry vaccination campaign - using a newly developed H5 + H7 recombinant AI vaccine - appears remarkably successful, with only 4 human infections (3 H7N9, 1 H5N6) and a handful of poultry outbreaks announced since last October. 
In April we saw an H7N9 Outbreak In Ningxia Provice, while in March we saw Outbreaks Of HPAI H5N6 In Guangxi & H7N9 In Shaanxi.
Today we can add Liaoning Province to this short list of avian flu outbreaks, with the following (translated) announcement from China's MOA, after which I'll return with more on the use of poultry vaccines to control avian flu.
A H7N9 flu outbreak in poultry in Liaozhong District, Shenyang City, Liaoning Province, China

Time: 2018-05-31 

On May 22, a layer of hens raised by a farmer in Liaozhong District, Shenyang City, Liaoning Province experienced suspected avian flu symptoms, with 11,000 morbidities and 9,000 dead. On May 24, the Liaoning Provincial Center for Animal Disease Control and Prevention was diagnosed as suspected of the bird flu epidemic. On May 31, the national bird flu reference laboratory confirmed the epidemic was the H7N9 flu epidemic.

    After the outbreak of the epidemic, the local government did a good job in the handling of the epidemic in accordance with the relevant preplans and technical requirements for prevention and control. It had culled 8,000 diseased chickens and the same group of chickens, and conducted harmless treatment of all chickens in the epidemic site. At present, the epidemic has been effectively controlled.

While we don't have a genetic analysis, based solely on the reported mortality, this appears to have been an HPAI H7N9 outbreak.  LPAI H7N9 is normally asymptomatic in birds, including poultry.

Throughout the United States, and indeed, most of the world, the preferred method of controlling H5 and H7 avian flu outbreaks in poultry has been immediate quarantine and the culling of infected or exposed birds.
Since early in the last decade only a handful of countries have elected to go the vaccination route, with China, Indonesia, Egypt & Vietnam consuming nearly 99% of the world's poultry AI vaccines.
While we'll never know what would have happened had they not elected to go with vaccination, their track record hasn't been all that enviable.  H5 and H7 viruses remain endemic and a perennial problem in these countries after more than a dozen years of vaccine use.  

While it can be argued that these vaccines have saved millions of poultry from culling, have prevented financial ruin for farmers, and has lessened food instability in developing areas of the world, there has also been a downside. 
Poultry vaccines don’t always prevent disease – sometimes they only mask the symptoms of infection, and that can not only allow viruses to spread stealthily, it can also put human health at risk.
And as avian viruses evolve, poultry vaccines become increasingly less effective. Poor vaccine matches can then allow AI viruses to spread silently among flocks, to continue to reassort and evolve, and potentially lead to the emergence new subtypes of avian flu.

A few earlier blogs on that include:
Subclinical Highly Pathogenic Avian Influenza Virus Infection among Vaccinated Chickens, China).

Study: Recombinant H5N2 Avian Influenza Virus Strains In Vaccinated Chickens

EID Journal: Subclinical HPAI In Vaccinated Poultry – China
There are other factors in the creation of new avian subtypes, of course - including the bringing together of different bird species in live markets, the move to larger commercial poultry operations, and poor biosecurity - but vaccine-escape variant viruses appear to be significant driver as well.
While one hopes that the Chinese have hit a home run with their new poultry vaccine, a headline (see Vietnam: Thousands Of Vaccinated Chickens Die Of Suspected H5N1) from last August reminds us that pharmaceutical victories over rapidly evolving viruses and bacteria are often fleeting.
So we'll be watching for more signs of `breakthrough' events, such as the one reported above, in the months ahead.

1 comment:

Les Sims said...


For a recent review of the pros and cons of avian influenza vaccination I suggest you view the webinar I delivered for FAO a few weeks ago. There was a link to this in the latest FAO H7N9 update. Briefly vaccination was introduced to China, Egypt, Indonesia, Bangladesh and Viet Nam because the virus was already endemic and stamping out, as practiced, had not been successful. It was recognised when these countries commenced vaccination that they could not eliminate the virus using other measures. Virus elimination was not the objective in any of these places. For example, Viet Nam had already culled or lost 45 million birds and had not succeeded in virus elimination in 2004 before vaccination was introduced.