Monday, July 20, 2015

Debating The Humane Methods Of Depopulating Infected Chickens


Credit Mass Depopulation and Euthanasia: Poultry - USDA-APHIS



# 10,241


Although it isn’t making daily national headlines, the USDA, APHIS, CDC, and a host of public and private organizations and agencies – along with thousands of poultry producers around the nation – are gearing up to fight what may soon become America’s greatest zoonotic challenge – the return of avian flu this fall and winter.


While no one can predict the timing, or the impact, of avian flu later this year and next, speaking before the USA Poultry & Egg Export Council (USAPEEC) last month, John Clifford, the chief veterinary officer of the United States warned the USDA  was preparing for a `worst case scenario’

  • A worst-case scenario, he said, would involve the highly pathogenic strain of avian influenza returning in migratory wild birds in the fall of 2015 and infections occurring in all poultry sectors - broilers, turkeys and egg layers - and across the country including in the broiler production regions of the Southeastern U.S. and the Upper Midwest and California.
  • Clifford said another part of such a scenario is if the H5N2 virus were to genetically reassort to present a different strain than the one presently infecting poultry and wild birds in the U.S.

He stressed that while preparing for HPAI’s return this fall could cost millions, failing to prepare could cost billions.  You can view Dr. Clifford’s testimony before the Senate on the steps that are being taken, or contemplated, in my July 8th blog Senate Avian Flu Hearing Video & Testimony.


Although a great many topics were discussed, among them were the need to find faster, more efficient means to depopulate infected poultry farms.   The longer this process takes, the greater the risk that the virus will spread to adjacent farms, or worse, to cullers or farm workers.


Over the spring outbreak, nearly 50 million birds either died or were destroyed, but in some cases it took weeks using existing methods (CO2, Water based foam, Carbon Monoxide) as workers must `suit up’ in full protective gear before entering chicken houses and can only work inside for a short time due to the heat, thus limiting the number of birds that can be culled in a single day.

The use of carbon dioxide - or inert gasses like Nitrogen or Argon - are considered more humane methods than water-based foam.  But not every facility, or situation, lends itself to their use.


During his testimony, Dr. Clifford mentioned the possibility of using VSD (Ventilator Shutdown) as a faster, and safer  alternative.  The USDA’s 2011 publication Euthanasia and Depopulation describes the procedure as:

Ventilation shutdown is defined as the cessation of natural or mechanical ventilation of atmospheric air in a building where birds are housed, with or without action to increase the ambient temperature. Although this method has not yet been addressed by the AVMA, it is approved in the United Kingdom as a killing method for poultry in certain disease control situations. Compelling welfare concerns exist since it has not been determined if birds die from heat stress or suffocation. In addition, time to death has not been definitively established, and there are concerns that prolonged suffering may occur. Thus, this method is not recommended, and other euthanasia methods should be considered.


When this was written, no one was seriously thinking about dealing with 50 or 100 million infected birds.  Times, and conditions, change.

VSD has the advantage of being able to kill tens of thousands of birds with a flip of a switch, and without requiring repeated entries of human cullers into an environment where there are live, infected birds. It also stops the potential airborne dispersal of the virus through the barn’s exhaust system (see CIDRAP Change in pattern of H5N2 spread raises questions).


It is not, however, likely to be either quick or painless for the birds (at least compared to other methods).


As you might imagine, the suggestion that this method might be used has not gone down well with animal rights advocates, and it has resulted in a sharp response from the Humane Society of the United States (HSUS).  You can read an article on the debate in today’s Washington Post, after which I’ll be back with a bit more.


The most gruesome way to kill millions of chickens at once

By Roberto A. Ferdman July 20 at 10:46 AM


Hyperbolic headlines aside (and WaPo changed it from its original `The Uncomfortable Question Of How to Kill Millions Of Chickens’), the stakes here go beyond the fate of tens of millions of unfortunate birds that are caught in the middle. 


Although H5N8 and H5N2 have yet to cause human illness there are no guarantees that North American HPAI H5 will remain a disease only of birds. Earlier this summer in CDC HAN:HPAI H5 Exposure, Human Health Investigations & Response,  the CDC warned:


While these recently-identified HPAI H5 viruses are not known to have caused disease in humans, their appearance in North American birds may increase the likelihood of human infection in the United States. Human infection with other avian influenza viruses, including a different HPAI (H5N1) virus found in Asia, Africa, and other parts of the world; HPAI (H5N6) virus; and (H7N9) virus, has been associated with severe, sometimes fatal, disease.


The CDC currently recommends that all cullers wear protective clothing, are offered antiviral prophylaxis, and are monitored for signs of illness for 10 days after their last exposure. And it is reasonable to assume, the more exposures humans have during the depopulation process, the greater are the chances that someone is going to become infected. 


Somehow officials are going to have to weigh the risks of additional culler exposures, substantially longer eradication times, and risking spreading the virus to neighboring farms against what many will perceive as unnecessarily cruel depopulation methods.


Admittedly, not an easy choice.  But, if this turns out to be the toughest decision that avian flu thrusts upon us, then we should consider ourselves as having  gotten off lucky.

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