Understanding interactions between animals and humans is critical in preventing outbreaks of zoonotic disease. This is particularly important for avian influenza. Food animal production has been transformed since the 1918 influenza pandemic. Poultry and swine production have changed from small-scale methods to industrial-scale operations. There is substantial evidence of pathogen movement between and among these industrial facilities, release to the external environment and exposure to farm workers which challenges the assumption that modern poultry production is more bio secure and bio contained as compared with backyard or small holder operations in preventing introduction and release of pathogens. An analysis of data from Thai government investigation in 2004 indicates that the odds of H5N1 outbreaks and infections were significantly higher in large-scale commercial poultry operations as compared with backyard flocks. These data suggest that successful strategies to prevent or mitigate the emergence of pandemic avian influenza must consider risk factors specific to modern industrialized food animal production.
The emergence and spread of avian influenza viruses are complex and incompletely understood. While preparation for pandemic disease is a critically important public health task, understanding risk factors for disease transmission at the animal –human interface may identify opportunities for disease prevention and outbreak containment. Since 1918, much has changed in the relationship between human populations and domesticated food animals, including poultry and swine. It is often assumed that modern method of intensive food animal production provide increased biosecurity and bio containment and thus reduced risks for transfer of zoonotic disease to humans but these assumptions need to be critically examined. Over the past 70 years, food animal production in much of the world has been transformed from traditional small-scale methods and entrepreneurial organization to industrial-scale operations and vertically integrated management in which most if not all aspects of production( breeding, supply of young animals, feeds, animal husbandry) are controlled by a single entity. Both of these characteristics are relevant to understanding the current nature of the animal-human interface. Industrial or large scale food animal production (IFAP) involves high throughput animal husbandry in which thousands of animals of one breed and for one purpose (i.e. pigs, layer hens, broiler chickens, ducks, turkeys, beef or dairy cattle, tin fish or crustacean) are raised with short-generation intervals at single conditions, often in confined housing with defined feeds replacing access to forage crops. These method for facilitate the uniform and reliable production of consumer products through streamlined organizational and production structure, improvement in breeding and animal husbandry increased veterinary oversight and specially formulated diets, including the addition of antibiotics to promote feed conversion efficiency and growth rates.
These new modes of poultry and swine production have changed the nature of animal-human interface in both agriculture and the surrounding environment with important implications for zoonotic disease and biosecurity more generally. Biosecurity is defined as any practice or system that prevents the spread of infectious agents from infected to susceptible animals or prevents the introduction of infected animals into a herd, region or country in which the infection has not yet occurred. The high throughput and confinement of highly concentrated animal populations increases the intensity of microbial exposure for farmers, their families, farm workers, veterinarians and others in contact with these operations. Scientists, including those from the University of Sheffield in the UK, said overuse of antibiotics, high animal numbers and low genetic diversity caused by intensive farming techniques increase the likelihood of these pathogens becoming a major public health risk. According to a study, intensive farming techniques have led to a common antibiotic-resistant pathogen to become capable of infecting both cattle and human which suggests the need to check agriculture practices for such outbreaks. Scientists from the University of Sheffield, UK investigated the evolution of Campylobacter jejuni, a bacterium carried by chickens and cattle and a leading cause of food poisoning. Based on their finding, the bacterium is able to infect more than one species because of its ability to transfer genes and adapt quickly to new host environments.
These bacteria are often resistant to antibiotics, due to use of drugs in farming and can be transferred to people when they eat undercooked meat and poultry. When they assessed the genetic evolution of the pathogen, the researchers found that cattle-specific strains of the bacterium emerged at the same time as a dramatic rise in cattle numbers in the 20th century. The Scientists suggests that changes in cattle diet, anatomy and physiology triggered the transferred of genes between general and cattle-specific strains of pathogen. They noted that this helped the bacterium to cross the species barrier and infect humans, triggering a major public health problem. Human pathogens carried in animals are an increasing threat and the findings highlight how their adaptability can allow them to switch hosts and exploit intensive farming practices. Human activities have had profound effect on the Earth’s ecosystem and biodiversity, particularly among livestock species, such as cattle. Escalating livestock numbers and global trade have been linked with the emergence of zoonotic diseases that pose a significant threat to both animal and human health, with the current COVID-19 pandemic being the most dramatic and serious example to date. There are an estimated 1.5 billion cattle on Earth, each producing 30kgs of manure each day. If roughly 20% of these are carrying Campylobacter that amounts to a huge potential public health. The finding is a wake-up call to be more responsible about farming methods. So we can reduce the risk of outbreaks of problematic pathogens in the future. Combine this with the increased movement of animals globally, intensive farming practices have provided the perfect environment in which to spread globally through trade networks. Over the past few decades, there have been several viruses and pathogenic bacteria that have switched species from wild animals to human: HIV started in monkeys; H5N1 came from birds; now Covid-19 is suspected to have come from bats. The finding shows that environmental change and increased contact with farm animals has caused bacterial infections to cross over to humans too.
