A recent article published by researchers from the University of Cambridge and the University of Leeds highlights the risks of emerging infectious diseases (EID) associated with extensive (low-yield) farming and intensive (high-yielding or factory) farming.
The link between EID and factory farming or factory farming is well established. A 2020 United Nations Environment Report makes a direct link between the emergence of new zoonotic pandemics and rising meat consumption, unsustainable agricultural intensification and increased use and exploitation of wildlife. However, the EID risk of extensive or low-yield livestock farming is not as well studied.
In contrast to factory farming, extensive animal husbandry often involves keeping livestock on large tracts of land. Although it provides lower yields per unit of production, the practice is considered by some farmers to be more labor efficient as it promises higher yields and better animal welfare. But sprawling farms often encroach on natural habitats, creating opportunities for increased human and livestock interaction with wildlife populations.
The study argues that extensive animal husbandry also comes with its own pandemic risks. First, because animals spend most of their time outdoors and roam freely in large, remote areas, sprawling farms often require more labor than factory farms, increasing the number of potential hosts for EID. Second, higher human-livestock contact rates and poorer biosecurity measures lead to “different, but not necessarily lower, EID risks than higher-yielding systems that produce the same amount of food,” the authors write.
“Low- and high-yield farming systems carry different risks for the emergence of infectious diseases,” says Hannah Bartlett, lead author of the study published in The Royal Society of Open Science.
The authors further acknowledge that due to significant knowledge gaps, they cannot conclude whether more intensive systems with lower or higher yields are better at limiting the risk of future pandemics. However, the study points to some of the risks associated with low-yield livestock farming that have not previously been addressed.
“Biosecurity is critical in both intensive and low-yield farming systems,” says Bartlett.
But surveillance presents a unique set of obstacles to either approach. On factory farms, the crowded, filthy facilities weaken the farm animals’ immune systems and provide an ideal environment for the emergence and spread of zoonoses. Farm animals often come into contact with diseased wild animals, quickly spreading the infection to the rest of the farm. Animal waste, often used as fertilizer on land, is another potential source of livestock-to-wildlife transmission and water pollution. The lack of proper ventilation also throws pathogens into the air, increasing the risk of transmission to communities living near factory farms.
On low-yield farms, the sheer amount of land the farm uses increases the risk of exposure and subsequent spread of a zoonotic disease. Their size creates more opportunities for direct and indirect contact between infected wild and farm animals. In this new cycle of disease transmission, farm animals and their handlers are becoming intermediate hosts for novel pathogens. And while the researchers weren’t able to determine the exact variance in biosecurity risks between the two different farming styles, it’s clear that humans and animals on both high- and low-yield farms have the ability to spread disease off the farm transferred to.
Establishing standardized biosecurity practices for high and low yield farms has proven to be a challenge. Producers are not always willing to make the necessary changes. In addition, monitoring the daily activities that contribute to hygiene on farms, such as washing hands, changing clothes and disinfecting livestock transport vehicles, is costly and time-consuming.
Researchers say preventing global spillover events from wild habitats will largely depend on local authorities to control the consequences of factors contributing to reduced biosecurity, such as illegal deforestation and illegal wildlife trade. And while the COVID-19 pandemic had led to a general awareness of the risks of zoonotic diseases, most high-level efforts have focused on responding to the pandemic rather than prevention.
“The recent wave of HPAI [avian flu] Outbreaks in Europe, and France in particular, have shown that optimal biosecurity standards are difficult to achieve,” says Dr. Guillaume Fournié, Senior Research Fellow at the Royal Veterinary College, University of London. Fournié is also studying the impact of intensifying chicken production on the risk of zoonosis.
“At high operating density, this can lead to large outbreaks,” he says.
The solution is not easy. Widespread conversion to non-intensive systems without a significant change in diet would require a significant expansion of farmland, Bartlett says. The associated loss of habitat would further increase the risk of zoonosis.
However, the authors of the study do not foresee any significant reduction in global meat consumption anytime soon, and most experts agree. “Meat consumption per person is starting to fall in some countries but is rising rapidly elsewhere,” says Dr. Andrew Balmford, Professor of Conservation Sciences at the University of Cambridge and senior author of the study. “Therefore, it seems reasonable to think about how to limit the risk of novel zoonotic diseases in a world where we continue to keep large numbers of livestock.”
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Devatha P.Nair
Devatha is a vegan freelance writer and materials scientist based in Denver, Colorado.
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