Imagine 40,000 people living next to each other in a shed for six weeks. Your intuition would rightly consider this a public health problem. It’s no surprise then that commercial broilers, chickens raised for their meat under such conditions, are particularly susceptible to pathogens spreading quickly through their ranks.
Bacteria that cause food poisoning, such as Campylobacter And salmonella, have been consistently recorded in flocks over the past decades, but the past three years have seen the highest ever outbreaks of another pathogen: bird flu. Most alarming of all, in 2024, H5N1 bird flu made the unprecedented jump to cows, with the U.S. dairy industry reporting more and more outbreaks every week. This alarming jump between species means there has never been a more important time to suppress bird flu rates within our chicken populations before it can make the leap to humans.
Once the first case of “bird flu” occurs in a birdhouse, the nature of its breeding means that it is only a matter of days before the infection spreads through the entire flock of thousands, in some cases killing almost every bird. Having 40,000 infected birds in a house then creates a colossal reservoir for disease – 40,000 opportunities for the disease to spread into the wider environment, or even to the farmers who handle it.
These spillovers are rare, and human-to-human transmission is highly unlikely – after all, bird flu is a virus that evolved to be optimized in birds. But every time a human infection occurs, we run the risk of the virus mutating into one that excels at person-to-person transmission.
This is how many global pandemics started. Between 2003 and 2022, there have been 868 reported cases of human infection with the particularly nasty H5N1 variant (the variant currently sweeping through the US dairy industry). 456 of these cases were fatal – a mortality rate of 53 percent. That alarming statistic serves as good motivation for the argument that something must be done, but it must be done precisely What is not that simple.
“Why don’t we just reduce herd size?”
Britain slaughters more than a billion broilers every year – that’s more than thirty chickens every second. This demand has grown year after year, creating a market that needs these large cohorts. Herds that can be fed, watered and processed at the same time are crucial to meeting that absurd-sounding demand.
“Why don’t we give them more space?”
The logical argument is that if people are further apart, you are less likely to infect your neighbor. UK legislation currently limits the density of chicken coops to a maximum of 39kg/m22 – which is about the same as an A4 sheet of paper per bird. My PhD research simulated the spread of bacterial diseases in a broiler flock and theorized that we would need at least 20 times as much space until you power are starting to see a marked reduction in transmission rates, and much more to have any chance of birds being slaughtered uncolonized.
This means we either have to build stables the size of Windsor Castle, or we have to raise them mainly outdoors. Although outdoor rearing is a great benefit to the well-being of the birds themselves, we increase the risk of an outbreak of bird flu – as most primary infections are caused by wild birds flying overhead. For this reason, broiler farms in the UK have endured the brunt of strict ‘bird lockdown’ regulations over the past three years – requiring all poultry to be raised entirely indoors.
‘Why don’t we increase biosecurity?’
We already have Aside from the fairly unique new bird lockdown rules, numerous improved biosecurity measures have been implemented on farms over the past decade. These include chemical shoe dip to prevent farmers from bringing in pathogens on their shoes, while the Red Tractor standards label requires further disinfection of vehicles entering the site and the use of personal protective equipment. These efforts have had only limited success in reducing existing pathogens, such as food poisoning bacteria. To be honest, we still don’t understand exactly how and when pathogens get into a herd in the first place.
“Why don’t we just clean up all the infected animals?”
We are already doing this in some circumstances, with millions of birds being culled every year in the UK, and those are just the outbreaks we are aware of. There is also a risk that if culling practices are made even stricter, with more birds from neighboring farms being pre-emptively culled or facilities being forced to remain empty for a while, farms will eventually feel incentivized to keep quiet about infections out of fear. lose large parts of the business community.
This effect is currently visible in the US dairy industry. Despite the government’s offer of free testing to help farms test their milk production for the rampant H5N1 variant, no company has yet taken up the offer for fear of losing their business. In disease control, having as much information as possible is critical, and losing that information risks making things even more dangerous.
“Why don’t we reduce demand?”
Governments have previously curbed consumer demand for products they consider a public health risk, such as cigarettes and alcohol, through the use of retail excise taxes. Just as you might point out the collateral consequences of passive smoking or drunk driving, too could be argue that the danger of a global pandemic is a public health risk caused by those who choose to eat chicken meat.
However, in the midst of a cost-of-living crisis, it’s hard to imagine a less popular policy choice than raising the price of one of the country’s most important sources of protein. If you’re trying to reduce the consumption of something, you should also have a specific target amount in mind: exactly how much chicken should we eat to reduce the risk by x percent? This is a scientific question that we do not yet have an answer to. It also shifts the burden of responsibility to the very end of the food chain, in response to a risk that ultimately arises from the movements of wild bird populations.
There will be many discussions over the next century about the challenges posed by meat demand – land use, climate impact, subsidy requirements, to name a few. It will be a generations-long and hard-fought battle to rid humanity of meat. It is a wide-ranging issue that is beyond the scope of this specific challenge and is not a viable solution to this very urgent problem.
‘So can we do?’
The answer is to identify the nail before wondering which hammer to use. Unlike human populations, the movements and interactions of the poultry population are well recorded and documented, but we have not yet used this data to investigate how infections and pathogens can move and persist in the complex network of hatcheries, stables, farms and vehicles.
While bacteria like it Campylobacter are unfortunately widespread throughout the system, this means that we can use this organism to start this work immediately, without having to wait for new outbreaks of bird flu. We then need to understand how wild bird populations move and interact across Britain so we can create better predictive maps of where outbreaks are likely to occur, so we know where and when we may need to be extra vigilant. Research into this is currently seriously lacking.
There are several vaccine candidates currently in development that could serve as valuable tools in preventing outbreaks through herd vaccination. However, it would be extremely expensive to put a billion lampreys in a billion wings every year. By better understanding when certain locations are at risk, or which facilities have the most industrial impact, we can instead target specific areas with vaccines.
Different countries appear to have different disease burdens within their poultry flocks. We have spent much of the last twenty years trying to copy the way the Nordic countries raise their chickens (as they seem to have significantly lower levels of pathogens in their flocks) with varying degrees of success. By conducting the above work in multiple countries, we can build a stronger sense of which ideas or protocols work, and which are just noise in the signal.
Finally, for those inspired to get involved themselves, we can all educate ourselves more about what exactly the stickers on chicken carcasses mean. Generally speaking, more stickers mean a more expensive chicken, but labels like “RSPCA Assured”, “Red Tractor Enhanced Welfare” and “Soil Association Organic” indicate a greater level of monitoring of bird health during raising. As consumers become willing to pay for those higher costs, more suppliers will adopt them.
These above steps will take time and investment to build and deliver results. It’s best we start now, to minimize the number of times we continue to gamble on another pandemic.
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