Food Animal Production, Zoonotic Disease, and Global Security
The rapid replacement of traditional food animal production schemes with industrialized systems throughout much of the developing world has serious implications for global health.
The domestication of animal populations helped shape human civilization. However, our success and ingenuity carries significant costs that are escalating with globalization.
Since humans first began domesticating animals, we have shared not only communities, but infectious disease threats. Approximately 60% of all human infectious diseases and 75% of emerging infectious diseases are zoonoses, diseases that originate in animals. In recent years, highly pathogenic H5N1 avian influenza outbreaks and the H1N1 pandemic illustrated the potential social and economic impact of emerging zoonotic disease outbreaks. Many zoonotic threats can be traced to the globalized, industrialized production of meat.
The world population is expected to reach 10 billion by 2050, and population growth means more pressure on food supplies. Increased per capita income and urbanization have also helped drive a sharp increase in the demand for animal protein (meat, poultry, dairy products, and eggs) among the emerging economies of East, Southeast, and South Asia. Industrial food animal production (IFAP) is increasingly replacing traditional systems as a means to maximize production and efficiency, particularly throughout Asia and South America.
While SARS and H5N1 (or bird flu) focused international attention on "wet markets" and backyard farms, IFAP may ultimately represent a greater animal and public health risk. For example, the odds of H5N1 infections and outbreaks among poultry in Thailand during the 2004 outbreak were significantly higher in large-scale commercial poultry operations as compared with backyard flocks. IFAP builds in biological risks by reducing genetic diversity in animals, creating more uniform susceptibility to disease. Antibiotic regimens that promote livestock growth increase the danger that animal diseases that cross into humans may resist treatment. Animal stress due to crowding and transport can suppress animals' immune systems, facilitating animal-human and animal-animal disease transmission.
The Salmonella outbreak that sickened over 1,500 people in the US this summer highlights another threat of IFAP: expansive supply chains can rapidly disseminate dangerous products from a single source, leading to more illness and expensive recalls.
Our understanding of the ecology of intensive agriculture systems with respect to disease emergence and transmission is surprisingly limited, but the existing evidence points to real vulnerabilities. Animal wastes often contaminate the outside environment. Integrated livestock management systems may cross borders, exposing people and other animals. Rapid transport of live poultry contributed to the spread of simultaneous H5N1 outbreaks across eight Southeast Asian countries in 2004. Interactions between animals like pigs and poultry at various points throughout IFAP can also facilitate the re-assortment of influenza viruses, as animals may act as "mixing vessels" in which novel pathogens can be created and then transmitted to people. Although bird flu has been overshadowed by an H1N1 pandemic that proved less severe than worst case scenarios, H5N1 could still recombine or change in one of these animal "vessels" to become more transmissible among humans while remaining just as deadly.
Industrial food animal production (IFAP) ecology varies widely in different parts of the world and may lead to unique disease threats. IFAP in many developing countries takes place on the fringes of megacities in order to minimize cost and time of animal product transport, displacing small-scale farmers. This means unpredictable changes to the continuum of animal-human interactions, with the possibility of quick dissemination among densely crowded populations should a disease emerge.
Animal populations in Asia are likely to continue to grow, and IFAP is unlikely to fall out of favor as a way to keep meat, dairy, and eggs relatively cheap. The most practical defense would be to strengthen systems capable of detecting and containing zoonotic outbreaks before they cross into human populations.
Regrettably, veterinary services throughout most of the world are inadequate to address the needs of production animal health, zoonoses, and population health. Despite recent efforts in many countries, disease surveillance communication between veterinary and medical sectors still falls short. This gap is most evident in developing countries, which are rapidly transitioning to industrial agriculture.
The first challenge is finding ways to strengthen veterinary regulatory processes, technology and human capacities, areas rarely at the center of development agendas. A multi-faceted level of engagement should include
- Continued technical and financial assistance to help strengthen basic and advanced veterinary public health training (including in production animal health and zoonotic diseases), and dissolve barriers between human and animal health institutions.
- Engagement with IFAP owners and operators to understand how they might help control disease transmission and explain their roles in local, national and global disease ecologies.
- Regulation of IFAP sanitation to promote best practices and swift reporting mechanisms to retailers, other producers, the FDA and human and health services.
- Surveillance and coordination in animal populations that integrates both public health and traditional forms of animal study and surveillance.
Only an approach that integrates knowledge of production networks and disease ecology will be effective and mitigating the impacts of large scale animal farming. The One Health Initiative, endorsed by veterinary and medical leaders, recognizes the relationship between human, animal, and ecological health and aims to increase collaboration across these sectors, including in the context of development assistance. An integrated approach can be instrumental in reducing security threats from food animal zoonoses, but much work remains before this ideal materializes. While helping partner nations develop their capacities to detect and contain animal disease outbreaks in "factory farms" may not be glamorous, it could be one of our best hopes of averting a future global health catastrophe.
Photo credit: rrodrickbeiler via iStockphoto #1402299