Monday, May 22, 2023

WOAH: Rethinking Avian Influenza Prevention and Control Efforts



For the past two decades the World Organization for Animal Health (WOAH, formerly the OIE) has stated that the `preferred' method for dealing with HPAI H5 or H7 in poultry is stamping out (culling), and that vaccines should be viewed as a `temporary' solution at best.

Even though they prevented expensive die offs of poultry, vaccines were viewed as suboptimal solutions since they sometimes only masked the symptoms of infection, and could allow  HPAI viruses to spread (and mutate) through flocks.  

In 2009's Avian influenza and vaccination: what is the scientific recommendation?, the OIE reiterated their strong recommendation that humane culling be employed to control avian influenza, and advising that vaccines should only be used as a temporary measure, stating that:

`Any vaccination campaign must include an “exit strategy” i.e. a return to classic disease control measures.'

While most of the world's countries followed that advice, China, Egypt, Indonesia, Vietnam, and Hong Kong - all hotbeds of avian influenza since the early-to-mid 2000s - embraced poultry vaccination instead, with no signs of an `exit strategy'.  

In theory, a comprehensively applied, and frequently updated poultry vaccination program should be an effective strategy against avian flu, at least in captive birds. But in actual practice (see Egypt: A Paltry Poultry Vaccine), those can be difficult standards to maintain.
Instead we've seen dozens of cautionary studies suggesting that improper application, or outdated vaccines have helped to drive the evolution of avian influenza viruses.  A few examples include:  

J. Virus Erad.: Ineffective Control Of LPAI H9N2 By Inactivated Poultry Vaccines - China

PLoS One: Effectiveness of HPAI H5N1 Vaccination in Poultry - Indonesia 

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

In 2013, following the surprise emergence of H7N9 in China (which is asymptomatic in birds, but can be deadly in humans), the OIE softened the language in their recommendations to allow:

'In short, vaccination should be implemented when culling policies cannot be applied either because the disease is endemic and therefore widely present, or the infection in affected animals is too difficult to detect.'

Fast forward another decade and the global avian flu situation has changed radically once again. 

Prior to 2016, H5N1 was primarily a disease of poultry and had trouble maintaining itself for very long in wild and migratory birds (see PNAS: The Enigma Of Disappearing HPAI H5 In North American Migratory Waterfowl), limiting its ability to spread.

But HPAI H5's behavior in wild birds changed markedly following a reassortment event in China/Russia in 2016 - allowing it to persist year-round, and spread efficiently via a variety of avian species.

Over the past 7 years, those host adaptations have only grown stronger.

With H5N1 now ubiquitous in the wild - poultry are no longer the prime drivers of avian flu evolution - rendering many of the reservations about poultry vaccination far less relevant.    

We've already seen a number of countries move towards poultry vaccination in recent months (WUR: 2 of 4 H5 Poultry Vaccines Tested Appear Effective Against H5N1), and this week WOAH will meet in Paris at their 90th General Session of the World Assembly of Delegates to discuss how to approach avian influenza prevention and control methods going forward. 

The following preview comes from WOAH, after which you'll find a link to a 23-page PDF report outlining the challenges ahead. 

I'll have a brief postscript after the break. 

Sharing expertise to rethink avian influenza prevention and control efforts

Avian influenza control 

The current global avian influenza crisis calls for a coordinated response. The upcoming General Session of the World Organisation for Animal Health (WOAH) will bring together international experts and government representatives to discuss the current challenges and opportunities in tackling this major threat.

Over 500 million birds have died from avian influenza since 2005. The deadly bird disease has devastating consequences on the health of domestic and wild birds, as well as on biodiversity and livelihoods. Lately, the global spread of avian influenza has raised growing preoccupation with an unprecedented number of outbreaks reaching new geographical regions, unusual die-offs in wild birds, as well as an increasing number of cases in mammals. Despite countries’ efforts to implement surveillance as well as strict prevention and control measures—such as movement control, enhanced biosecurity, and stamping-out—avian influenza continues to spark concern among the international community.  

Towards a paradigm shift in current avian influenza prevention and control measures? 

The extent and severity of the situation requires the assessment of existing strategies to contain the disease and raises multiple questions. What are the gaps in current disease control strategies? How can they be better tailored to different contexts and settings? Do we need to rethink about the way we rear some poultry species? How can we ensure an early detection of outbreaks? Which complementary control options would be needed at country and regional level? Would the wider use of vaccination in birds be a sustainable solution?

How can poultry and poultry products trade take place safely in the presence of vaccination? How to best optimise resources allocation? 

To address the strategic questions and challenges that impede countries to progress towards the global control of the disease, WOAH will hold its first ever Animal Health Forum dedicated to discuss the topic on 22-23 May, in the framework of the 90th General Session. The Forum will introduce the Technical Item as a common thread and will provide one-of-a-kind chance to take stock of past and current strategies and explore other risk management options, more adapted to the current evolving situation. It will also be a unique opportunity to agree on suitable, science-based alternatives for disease surveillance and control, that can reduce the impact of the disease. 

New concerns arise as the disease evolves 

These past years, an unprecedented and broader range of virus strains has emerged, leading to further evolution of the viruses and thus creating an epidemiologically challenging landscape. Historically, the most severe form of the disease in poultry, high pathogenicity avian influenza (HPAI), used to mostly spread from farm to farm, while its low pathogenicity avian influenza (LPAI) used to mainly circulate among wild birds, often remaining asymptomatic in these bird populations. Nowadays, we observe a persistent threat of HPAI encroaching into wild birds, which can carry the disease viruses over long distances and across country borders. Avian influenza has therefore spread rapidly to new regions, in particular in Central and South America where the disease had not been detected for 20 years. In this region, 10 countries reported the disease to WOAH. Whereas, at global level, 74 countries and territories have notified avian influenza outbreaks since October 2021; this wide geographical spread has no previous historical context. 

Beyond the increased number of cases identified in poultry and wild birds in recent years, avian influenza is now being reported in wild and captive mammals. Recent cases in otters, foxes and mink have sparked animal and public health concerns pertaining to the risk of viruses becoming more adapted to mammals and what this means to humans.  

Sporadic, but severe human cases have also occurred. Although transmission from birds to humans is rare and results from repeated exposure to infected birds, the risk of a pandemic remains.  

Building an effective common response  

Avian influenza is a serious threat to global health, livelihoods, food security, and biodiversity. While there have been significant efforts to prevent and control its spread, there is still much work to be done. The change of epidemiology of the disease these past two years has undermined the use of stamping-out as a main control measure. As we are looking for more sustainable production practices, we must explore collectively alternative methods of disease control, to prevent and mitigate the disease, and consequently, avoid destroying so many animals when food security is becoming a critical issue for many.  

These strategic challenges will be extensively discussed during the upcoming Animal Health Forum on avian influenza. In particular, the topics of surveillance, disease control strategies, ways to ensure safe and fair international trade of poultry and poultry products and regional and global coordination will be debated.  

These important discussions will result in the development of international recommendations and will provide a solid basis for the rehaul of the WOAH/FAO global strategy on high pathogenicity avian influenza developed under the umbrella of the GF-TADs.

We need to ensure that countries can respond to this major health threat under a common framework and that their governments are ready to mobilise sufficient resources to tackle avian influenza. Taking appropriate action will be critical to ensure, a safer, healthier future for everyone. 

To follow the discussions, connect to our Animal Health forum: 



David E Swayne1, Leslie Sims1, Ian Brown1, Timm Harder1, Arjan Stegeman1, Celia Abolnik 1, Mariana Delgado2, Lina Awada2, Gounalan Pavade2 and Gregorio Torres2

While poultry remain victims of HPAI H5, in many ways we have entered a post-poultry avian epizootic, where wild birds (and in a few cases, mammals) are now the main drivers of avian flu. 

As conditions change, so must our tactics. 

But poorly implemented avian flu control strategies of past likely contributed to getting us to where we are today.  Given the stakes, we need to do a lot better going forward.