Sunday, April 21, 2013

Food Insecurity, Economics, And The Control Of H7N9

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1 person in 8 is Undernourished Photo Credit – FAO

 

# 7171

 

As the number of `official’ human infections with the emerging avian H7N9 virus rapidly approaches the century mark, epidemiologists and agricultural officials continue to struggle with determining exactly where this virus is hiding in nature.

 

The best guess so far is in poultry and/or wild birds, but test results thus far have only uncovered a handful of positive results (see Branswell On The Paucity Of H7N9 Positive Poultry).

 

Normally, avian flu produces signs of illness or increased mortality in birds, and this serves as a biosecurity early warning system for flock owners that something is amiss and testing is needed.

 

Of concern, these telltale signs of infection in poultry are noticeably absent with the H7N9 virus.

 

While highly pathogenic in humans, this virus produces low pathogenicity in birds, and as a result it makes it extremely difficult to detect and eradicate.

 

On April 5th, the FAO released a statement (see FAO On Biosecurity Challenges Of H7N9) where they explained:

 

"Unlike H5N1, where chickens were dying off on a large scale, with this virus we don't have a red flag that immediately signals an infection. This means farmers may not be aware that virus is circulating in their flock. Biosecurity and hygiene measures will help people protect themselves from virus circulating in seemingly healthy birds or other animals," said Juan Lubroth, FAO Chief Veterinary Officer.

 

 

Assuming you can spot it, the OIE recommended response to any outbreak of a highly pathogenic bird flu in poultry (or any H5 or H7 strain) is to immediately restrict movement of livestock in the area and cull any affected, or potentially exposed birds.

 

The OIE also has a rather extensive FAQ on H7N9 Avian Influenza, portions of which are excerpted below:

 

Can culling be used as a control measure?

If the infection is detected in animals, generally a culling policy is used in the efforts to control and eradicate the disease.

 

Requirements include (and are described in the OIE Terrestrial Animal Health Code):

  • humane destruction of all infected and exposed animals (according to OIE animal welfare standards);
  • appropriate disposal of carcasses and all animal products;
  • surveillance and tracing of potentially infected or exposed poultry;
  • strict quarantine and controls on movement of poultry and any potentially contaminated vehicles and personnel;
  • thorough decontamination of infected premises ;
  • a period at least 21 days before restocking.

In the case of low pathogenic avian influenza like the current outbreaks of H7N9 declared by China, stamping out is generally applied at the level of the infected farm or within a short radius around the infected premises. 

 

Essentially, this quarantine and cull response is precisely what we would see quickly enacted anywhere in the North America, Europe, Australia, and Japan if a farm or region saw a bird flu outbreak.

 

Since it entails considerable expense, the culling of millions of birds is far easier to accept in wealthier nations than in regions where food insecurity runs high and personal incomes are low. 

 

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Food Insecurity map - Source FAO 

 

In many parts of the world - poultry - whether factory farmed or from backyard flocks, represents a major source of income, protein, and accrued wealth for hundreds of millions of people.  

 

Take that away, and you risk destabilizing an entire region.

 

China, which produces more poultry than anyplace else on earth, reportedly raises in excess of 15 Billion birds (cite Vaccines for pandemic influenza as of 2005) each year.

 

Any avian virus, or a culling policy to control that virus, that seriously threatens their poultry industry also raises the specter of mass hunger in the world’s most populous nation.

 

And hunger, as China’s leaders know, often leads to social unrest and political instability.

 

The negative impacts from culling are the main reasons that nations like China, Vietnam, Indonesia and Egypt have adopted poultry vaccination as their preferred method of controlling the H5N1 bird flu virus.

 

For many of these countries, vaccination is viewed as being their only viable option. Not everyone agrees, though:

 

Leading scientists such as Zhong Nanshan of China, have warned,"The existing vaccines can only reduce the amount of virus, rather than totally inactivating it.”

 

Dr. C.A. Nidom, whose name has appeared often in this blog, was quoted earlier in Poultry Indonesia as saying:

 

Poultry Indonesia Printing Edition, March 2009

(excerpts)

Chairul Anwar Nidom, a virologist with the Tropical Disease Centre at Airlangga University in Surabaya, said a common policy on bird flu was lacking among government agencies, making controlling the disease more difficult.

 

Nidom criticized the government’s policy of vaccinating poultry rather than culling, believing that it masks the virus, and ultimately contributes to its mutation.

 

The OIE, perhaps sensing that China and other nations will move towards adding an H7N9 vaccine to their avian flu arsenal, advised.

 

Does OIE recommend vaccination of animals to control the disease?

When appropriate vaccines are available, vaccination aims to protect the susceptible bird populations from potential infection. Vaccination reduces viral excretions by animals and the virus’ capacity to spread. Vaccination strategies can effectively be used as an emergency effort in the face of an outbreak or as a routine measure in an endemic area. Any decision to use vaccination must include an exit strategy, i.e. conditions to be met to stop vaccination.

 

Careful consideration must be given prior to implementing a vaccination policy and requires that the recommendations from the World Organisation for Animal Health (OIE) on vaccination and vaccines are closely followed (www.oie.int\downld\AVIAN INFLUENZA\Guidelines on AI vaccination.pdf).

 

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.

 

 

That said, few nations already using poultry vaccines to combat the H5N1 virus have shown any signs of moving towards an `exit strategy’.

 

Despite the downsides to poultry vaccines - without them - countries like China, Indonesia, and Egypt believe they would lose huge portions of their badly needed protein supply, risking both starvation and political upheaval.

 

Assuming that the H7N9 virus is, or will eventually become, well entrenched and widespread in China’s poultry (which is not necessarily a given) – it would require an immense amount of political will, and no small amount of economic hardship, to bring it under control.

 

While we worry most about its pandemic potential, even as a disease primarily of poultry, H7N9 could seriously impact the health and wealth of millions of people in the years to come.

 

And while unpredictable, the economic and political ripple effects of that could extend far beyond Asia.

 

Facing hard choices, what the Chinese are are able (or willing) to do to halt the spread of H7N9 could have huge implications – not just in China – but around the world.

 


Stay tuned.

 

For more on food insecurity in the world, follow the link below to read the:

 

2012 Hunger Report

The State of Food Insecurity in the World raises awareness about global hunger issues, discusses underlying causes of hunger and malnutrition and monitors progress towards hunger reduction targets.

3 comments:

Tom DVM said...

Hi Mike

Congratulations on your continued excellent and much needed contributions to public health.

It would be interesting if you could find an expert to comment on the effect of influenza vaccines with low efficacy on the potential skewed and accelerated evolution of influenza viruses.

I believe that the usage of primitive vaccines (that in my opinion, would not be accepted for the treatment of any other disease like polio smallpox or rabies etc) and the wide usage of these vaccines in animals (and humans) along with the greater concentration of much larger pig and chicken farms in smaller geographic areas ensures a wave of pandemics in this century.

Michael Coston said...

Welcome Back Tom,

It's been a long time.

I'm not an expert in vaccines, but base on what I've read I share the OIE's concerns that they should only be a temporary measure in the control of avian flu.

Unfortunately, getting countries with low food security to move away from them is a tough sell.


Like CAFOs and overuse of antibiotics, expediency tends to trump wisdom in the short run.


Tom DVM said...

Thanks Mike

I probably should have used different examples.

I am quite sure that a whooping cough, measles or mumps vaccine would never be released to the general public with an efficacy-effectiveness of the current egg-based influenza vaccines.

Once a pandemic starts, it really doesn't matter. You throw everything you have in the toolbox and hope something sticks...

...but in the interpandemic period, it is essential to not have unintended consequences with respect to 'pushing' virus evolution.

Correct me if I am wrong but did they not say that H5N1 achieved full pandemic potential with five passages through ferrets. (ferret to ferret to ferret to ferret to ferret to full potential).

So how is this affected when using vaccines of questionable efficacy?

The virus circulates and replicates but does not kill the animal.This results in the increased potential for many generations of evolution in one individual. It also is 'targeted' evolution because the vaccine virus is at least partially suppressed promoting the survival of mutations instead.

Under these circumstances, it is likely that virus will be shed for longer periods, increasing the odds of infecting other individuals and infecting another potential evolutionary vessel.

Also, there is an opportunity to create supershedders which would shed huge amounts of virus without showing any outward signs of disease.

All of this is not unimportant when we still have the 'elephant in the room' H5N1 that in bilogical terms, really requires very little to achive pandemic potential.

In the past two years, we have several new viruses with the ability to give H5N1 what it needs to finish its evolutionary cycle.

With the very large chicken and pig farms, we have replicated the conditions at the end of the First World War, only in animal populations this time.

I have heard many say that The Spanish Flu was a one-off.

I am pretty sure they are completely wrong.

H5N1 is still the endgame in my opinion and using such vaccines in animal populations are going to ensure that it gets there.

Bottom line is that we need a better vaccine and in a hurry.

We have probably lined up the next two or three pandemics that will be unavoidable...but the monster is not out of the bag yet.

Take it easy and Thanks again for the info!