The Practice of Culling to Control H5N1 Bird Flu
Neither Theory nor Practice Really Supports It

Culling

     The tamest meaning of the word, "cull", is "the selection and removal of a group of individuals from a given population." But make no mistake: "cull" means "kill", where the removal process is for the purpose of controlling disease outbreaks and spread. Zohar Lederman et al. attempt to review this practice from the perspective of a one-health approach, which involves looking at the health of entire ecosystems, rather than at the health of a limited part of such systems:

Lederman Z, Magalhães-Sant'Ana M, Voo TC (2021). Stamping Out Animal Culling: From Anthropocentrism to One Health Ethics, Journal of Agricultural and Environmental Ethics, 34(5):27. doi: 10.1007/s10806-021-09868-x. Epub 2021 Aug 29. PMID: 34483696; PMCID: PMC8403469.

Culling is used in traditional public health policies to control animal populations. These policies aim primarily to protect human interests but often fail to provide scientific evidence of effectiveness.

... we argue that public health policies primarily based on culling fail to adequately consider the interests of those involved other than humans and that we need to move from an anthropocentric approach to disease control towards a One Health ethics.

 ... killing animals for food is one thing, killing them because we think it might control disease outbreaks is another. The latter requires strong evidence, which does not exist. Worst, some culling practices aim at killing animals that are not at increased risk of disease, for the sole purpose of testing preparedness to react in the event of an outbreak. While pandemic preparedness is important, it does not justify the killing of otherwise healthy animals.

     While the phrase, "one health", appears (in this context) to describe a desirable, expanded view of "health", the phrase, unfortunately has been hijacked by groups such as the World Health Organization (WHO) to erroneously align ecosystem health with the false narrative of human-caused climate change. This perversion of focus forces illegitimate science to dictate ill-conceived public health policy. I do not, therefore, consider the Lederman et al. use of the term the same as the WHO use of the term. The more sensible use of the term simply serves to expand our consciousness of health beyond human-focused, virus-centric, mass culling (i.e., mass killing) that protects short-term human interests. The least-perverted sense of the term also incorporates legitimate, evidence-based science, rather than politically charged doom narratives that scare people into accepting excessive control of their lives.

Alternatives

     Chris Degeling et al. discuss the idea of alternatives to culling:

Degeling C, Lederman Z, Rock M (2016). Culling and the Common Good: Re-evaluating Harms and Benefits Under the One Health Paradigm, Public Health Ethics, 9(3):244-254. doi: 10.1093/phe/phw019. Epub 2016 May 3. PMID: 27790290; PMCID: PMC5081039.

These authors generally mention altering "configurations" of industrial farms and altering "interactions" between humans and animals, but they never pinpoint precisely, with concrete statements, exactly how we might go about doing this. They never clarify exactly what they are talking about, which results in their article's being of little use in guiding real-world efforts. They do, however, provide an important perspective, pointing out that culling remains the major strategy used to control emergent disease events in animal populations:

The aim of culling is to eradicate a host species, to prevent the pathogen entering and contaminating new individuals and populations. It is commonly believed that culling eliminates or reduces the size of reservoir populations, either halting or decreasing the frequency of pathogen transmission to new hosts. However, evidence as to the epidemiological efficacy and cost-effectiveness of culling as a sustainable solution to many zoonotic and epizootic risks remains inconclusive ....

     The authors emphasize that humans and animals live together in ecological systems where infectious pathogens are key parts of these systems. Further, they insist that humans need ... "to learn to work with, rather than against, complex microbial environments." Again, this is a general statement without any functional pathway into the real world. I can only guess what they might be suggesting, based on the following sparse commentary in other parts of their article:

The ecosystems created by large-scale poultry production are providing ideal conditions for rapid evolution and replication of low pathogenic avian influenza (LPAI) into more virulent strains of virus. LPAI viruses are endemic in wild waterfowl where they tend to cause mild respiratory symptoms.

... suggest that the persistence of the virus in domestic poultry flocks is a function of farm size, and that current production systems are increasingly configured in ways that can sustain the pathogen indefinitely.

Because we now live in a globalized world, new influenza viruses can spread across populations and continents in ways that outpace current vaccine-making technologies.

In Vietnam alone, almost 40 million birds were culled in 2004 in an unsuccessful attempt to ‘stamp out’ H5N1 HPAI.

     Degeling et al., thus, seem to be alluding to reduction of crowding in commercial flocks, reduction of animal population-density per housing unit, stricter cleaning of housing units, stricter monitoring of farm perimeters to guard against entry by migratory birds, plus greater willingness to observe outbreaks of illness, determine severity of illness and allow animals that survive infection to recover and develop future generations into a more resistant breed. In other words, they seem to be suggesting that industrial animal farmers wait and see, instead of instantly annihilating entire animal populations, when an uncertain PCR test merely detects traces of a pathogen's genetic material in apparently healthy animals.

Consequences of Culling

     Eunha Shim and Alison P. Galvani discuss the epidemiological consequences of mass culling:

Shim E, Galvani AP (2009). Evolutionary Repercussions of Avian Culling on Host Resistance and Influenza Virulence, PLoS One, 4(5):e5503. doi:10.1371/journal.pone.0005503. Epub 2009 May 11. PMID: 19430529; PMCID:PMC2675103.

Our findings indicate that culling impedes the evolution of avian host resistance against influenza. On the pathogen side of the coevolutionary race between pathogen and host, culling selects for heightened virulence and transmissibility of influenza.

Mass culling achieves a short-term benefit at the expense of long-term detriments: a more genetically susceptible host population, ultimately greater mortality, and elevated influenza virulence.

Our analysis also indicates that an avian population that evolves genetic resistance in the absence of culling will be resistant to influenza re-emergence, whereas a population that evolves less resistance will require repeated culling. Indeed, despite the mass cullings that have occurred since 1997, H5N1 continues to re-emerge in bird populations. 

On the host side of the coevolutionary race, culling is found to stunt the evolution of resistance. On the pathogen side, culling selects for heightened virulence. These results suggest that the implementation of mass culling may play a role in the increasingly frequent outbreaks of pathogenic H5N1, H7N3, H9N2 and H7N7 influenza subtypes among poultry. Likewise, H5N1 isolates from domestic birds in China collected between 1999 and 2003 have revealed a pattern of increasing virulence, which is consistent with these results. Furthermore, epidemiological studies suggest that the evolution of H5N1 has resulted in mounting transmissibility among humans, apparently as H5N1 adapts towards its optimal transmissibility and hence virulence.

Even though Shim and Galvani describe problems with mass culling, these authors fall short of committing to clearly-stated, prescriptive alternatives. Once again, as with Degeling et al., there are hints that commercial farms should increase space between animals and between groups of animals to help thwart the emergence and spread of H5N1.

Vaccinating Instead of Culling?

     Declan Butler draws attention to the possibility of vaccinating animals as an alternative to culling:

Butler, D (2005). Vaccination Will Work Better Than Culling, Say Bird Flu Experts, Nature, 434:810. https://doi.org/10.1038/4344810a

The shift [to a mindset that considers vaccination as an alternative to culling] was driven by a realization that the lethal H5N1 strain is widespread in wild and domestic bird populations, such as ducks. This means that no matter how often affected poultry flocks are culled, the virus is likely to reappear.

     Mass culling appears to have become a knee-jerk reaction to the mere detection of a potential pathogen, driven by reasoning that validates killing one vulnerable population only to replace it with another equally vulnerable population. The virus itself — the source of disease — remains untouched, because migratory birds transport it freely into whatever setting supports available hosts. Killing one region's entire population merely eliminates that particular population of hosts. Replacing the killed population with another population seems more akin to a coin toss, where the hope is that chance favors survival of the replacement population. A vaccine aimed at the virus itself would seem to be an attractive (and more reasonable) alternative, shifting the destructive focus to the source of disease, rather than maintaining the destructive focus on the host that a disease attacks.

     In the human world, killing a population of people in order to prevent a virus from infecting it would be absurd. Simply replacing the dead population with a different population, thinking that the same virus would somehow act differently, would be beyond any moral bounds by which humans live. While the idea of a vaccine seems supremely reasonable and more humane, unfortunately, there are problems here too.

Imperfect or "Leaky" Vaccines

     The problems with vaccinating are clearly summarized by Andrew F. Read et al. in a paper published in 2015:

Read A F, Baigent S J, Powers C, Kgosana L B, Blackwell L, Smith LP et al. (2015). Imperfect Vaccination Can Enhance the Transmission of Highly Virulent Pathogens, PLoS Biology 13(7): e1002198. doi:10.1371/journal.pbio.1002198

Abstract

     Conventional wisdom is that natural selection will remove highly lethal pathogens if host death greatly reduces transmission. Vaccines that keep hosts alive but still allow transmission could thus allow very virulent strains to circulate in a population. Here we show experimentally that immunization of chickens against Marek's disease virus enhances the fitness of more virulent strains, making it possible for hyperpathogenic strains to transmit. Immunity elicited by direct vaccination or by maternal vaccination prolongs host survival but does not prevent infection, viral replication or transmission, thus extending the infectious periods of strains otherwise too lethal to persist. Our data show that anti-disease vaccines that do not prevent transmission can create conditions that promote the emergence of pathogen strains that cause more severe disease in unvaccinated hosts.

     Andrew Read (co-author of the above article) also co-authored a book-chapter on this same subject in 2008, where he and Margaret J. Mackinnon went into greater detail: 

Read, A F & Mackinnon, M J (2008). Pathogen Evolution in a Vaccinated World, Chapter 11 in Evolution in Health and Disease by Stearns, S C & Koella, J, 2nd ed., pp. 139-152, Oxford University Press.

This chapter gives pause to consider that critical understanding of vaccines has been lost in the name of profit and career advancement. As a result, evolving public health policies have become facades that serve these interests.

     James J. Bull and Rustom Antia try very diligently to discount the seriousness of the findings by Read et al., as they suggest that chance does not favor the evolution of virulent strains resulting from vaccination. Their analysis seems like a blend of uncertain mathematical modeling supported by hope-for-the-best, as they continually acknowledge the very real possibility that Read et al. clearly exposed, using real-world observations. Interestingly, they make a point to state the imperfect vaccine theory in a way that strengthens the theory, rather than detracting from its serious implications:

Bull J J, and R Antia (2022). Which 'Imperfect Vaccines' Encourage the Evolution of Higher Virulence?, Evolution, Medicine, and Public Health, 10(1):202-213. doi: 10.1093/emph/eoac015. PMID: 35539897; PMCID: PMC9081871.

     A somewhat recent and unexpected discovery, one with potentially profound public health ramifications, is that the vaccine given to defend against symptoms of Marek’s disease virus (MDV), administered on a global scale to billions of chickens in the poultry industry, has resulted in the evolution of a highly virulent wild-type virus. Not only did the evolved virus evade vaccine-immunity and cause disease in vaccinated birds, but it also killed unvaccinated birds far faster and with more certainty than did the original strain. If this evolutionary process were to repeat itself for any widely-used human vaccine, it could ultimately limit the efficacy of the vaccine, ‘addict’ civilization to the vaccine, potentially causing severe disease in unvaccinated individuals.

If Not Culling or Vaccinating, Then What?

     If neither culling nor vaccinating appear to properly address the problem of bird flu, then where are we to turn for solutions? An important clue to the answer lies in a paper by C. Andrew Aligne MD, MPH:

Aligne, CA (2022). Lost Lessons of the 1918 Influenza: The 1920s Working Hypothesis, the Public Health Paradigm, and the Prevention of Deadly Pandemics, American Journal of Public Health, 112(10), 1454-1464. 

Taken together, the findings presented here from history, public health, military medicine, veterinary science, molecular genetics, virology, immunology, and epidemiology are consistent with a virus that was immunologically similar throughout the World War I pandemic but varied intensely in virulence in response to war-related environmental factors such as industrial-scale, prolonged, extreme overcrowding.

     The 1918 influenza pandemic, of course, was a human pandemic, but notice the role of crowding that enabled the disease to be so devastating. Now remember references to crowding by previously mentioned authors, who pointed to this factor as a critical cause of animal pandemics on industrial farms, where crowding is extraordinarily excessive.

     Just how excessive is crowding on industrial farms? A report by Ann Linder et al. provides the answer. While the authors' apparent allegiance to the human-caused climate-change narrative is misguided, their statistics on animal crowding and culling are eyeopening :

Ann Linder et al. (2023). Animal Markets and Zoonotic Disease in the United States, Publisher: Harvard Law School and New York University. 

Over 98% of U.S.-produced livestock comes from 21,000 highly concentrated factory farms. A single facility can contain more than five million animals, a headcount greater than the human population of 27 of the 50 states.

In 2015, for example, 50 million laying hens were killed to contain the spread of highly pathogenic avian influenza, costing taxpayers one billion dollars. In 2022, a similar strain moved through commercial flocks in the United States, reaching 46 states and resulting in the death of over 57 million birds.

Facilities can stretch more than a mile long and contain millions of animals, some with populations larger than the City of Los Angeles.

Safe management and disposal of animal carcasses and animal waste have proved challenging as both processes can spread pathogens. For example, in North Carolina, the state’s 9 million swine produce over 62 million pounds of manure each day and 10 billion gallons of waste each year. A single swine facility can produce more sewage than all but a small handful of the largest cities in the United States.

Many of the same qualities that make these facilities frequent targets of criticism by animal welfare groups also make them susceptible to zoonotic disease: poor sanitation, limited air flow, excess waste, overcrowded conditions, poor animal health and welfare, and a lack of veterinary oversight.

     The fundamental source of the bird-flu problem, then, seems to lie in how industrialized societies have grown highly dependent on a faulty method of producing and supplying animal products to an immensely vast and demanding consumer market. The problem is the paradigm. The paradigm is deeply ingrained and growing ever more embedded in our way of life. Treating live animals that we rely on for food the same way we treat non-living commodities simply has been the wrong mindset from the outset.

     This point of view, in no way, advocates for the elimination of meat from our diets. Rather, it suggests that there is a better way to raise animals for human sustenance — a way that reduces over-crowding, a way that enables some semblance of a normal life for animals before slaughter, and a way that reduces disease outbreaks that either devastate animal populations or threaten human populations dependent on them.

     Microsoft's Copilot AI answered the following question posed on 2 August 2024:

Theoretically, could family farms meet current consumer demands for meat, if the entire philosophy of meat production shifted to this philosophy?

Copilot AI answered as follows:

In theory, yes! If the entire philosophy of meat production shifted from factory farms to family farms, it’s possible to meet current consumer demand for meat. Here’s how:

1. Efficiency and Scale: Family farms can be efficient and productive if they adopt modern practices. While they may not match the scale of large factory farms, they can still produce substantial amounts of meat.

2. Diverse Livestock: Family farms often raise a variety of livestock, including chickens, pigs, and cattle. By diversifying, they can meet different consumer preferences for meat.

3. Local and Sustainable: Family farms are often more localized, reducing transportation costs and environmental impact. Sustainable practices can also be prioritized, such as rotational grazing and organic feed.

4. Quality Over Quantity: Family farms can focus on quality rather than sheer volume. Consumers increasingly value ethically raised, high-quality meat, which family farms can provide.

5. Education and Awareness: Shifting consumer preferences toward supporting family farms would require education and awareness campaigns. If consumers actively choose these products, demand can shift. 

     Remember, this transition would take time, and adjustments would be needed to ensure supply meets demand. But theoretically, family farms could play a significant role in sustainable meat production.

     In order for such a major shift to occur in the United States, government expenditures and subsidies would have to be revamped. The amount of money that the U. S. government gives to other countries is astounding, and so a case could be made for re-directing this money to programs that improve our own domestic well-being, certainly re-directing this money to programs that would upgrade our own food supply.

# # #

.pdf copy of this article