Scientists are unsure where the novel coronavirus SARS-Cov-2 came from, but evidence suggests the COVID-19 outbreak could be traced to live animal markets common across Asia and that most likely the virus came from a bat, not a lab. As the world continues to battle the ongoing COVID-19 pandemic, the importance of public health studies and more specifically, those focusing on global health, are more relevant than ever. This is where animal scientists come in.
The American Society of Animal Science (ASAS) defines this field of study as “concerned with the science and business of producing domestic livestock species, including but not limited to beef cattle, dairy cattle, horses, poultry, sheep, and swine” Furthermore, “an animal scientist applies principles of the biological, physical, and social sciences to the problems associated with livestock production and management.” Animal scientists are thus, not only responsible for understanding the science of the how and why, but also must help educate and communicate effectively the importance of proper management practices through many cultural and socio economic backgrounds.
What is a zoonotic disease?
A zoonosis is defined by the World Health Organization (WHO) as “any disease or infection that is naturally transmissible from vertebrate animals to humans.” These infections may be of bacterial, viral, or parasitic origin and many of them could have an adverse effect on both human and animal health and subsequently in animal production. Animal to human transmission of zoonotic diseases occurs through three main pathways: contact, consumption and vectors. Transmission can occur either through direct contact or indirect contact with active lesions, bodily fluids or waste such as ringworm (which is actually a fungal infection!) or endoparasites like roundworms or hookworms. Another route of transmission could be in the case of contaminated food or water, such as is the case of infection with trichinella and Bovine Spongiform Encephalopathy (BSE) commonly known as Mad Cow Disease after the 1980s outbreaks in the United Kingdom. BSE is different from a virus or bacterial disease though as it is caused by a prion and occurs from consuming infected beef, resulting in neurodegenerative disease. The problem with prions is that they cannot only survive on surfaces and flooring for long periods of time but they remain active even when heated during cooking. Animals that are even suspected of infection of BSE are not used for human consumption or for animal feed and are removed from the slaughterhouse.
Lastly, and one of the most common routes of transmission, are those spread by vectors. According to the WHO, “Vector-borne diseases account for more than 17% of all infectious diseases, causing more than 700,000 deaths annually.” Some examples of vector-borne diseases you might have heard of are viral diseases such as Dengue, Malaria, Chikungunya and Zika which are transmitted by mosquito species in tropical regions (Aedes aegypti) or Rocky Mountain Spotted Fever, caused by the bacteria Rickettsia rickettsii which can be transmitted by ticks in more temperate regions. You might be wondering, what exactly is the difference between a vector and a host? Well vectors transmit or carry the infectious disease, while hosts are organisms that harbor other organisms, either in a parasitic or symbiotic relationship. In the case of COVID-19, for example, humans are the host while the accused bat is the vector.
Animal-human pathogenic interactions are an incredibly essential field of study as the world’s meat consumption has moved food and animal production to reach a larger and larger scale every year. These large production farms and live animal markets, if not managed properly, could provide the perfect environment for the mutation and propagation of these zoonotic diseases in what is known as “spillover”. We’ve already seen it happen with the 1918 Avian Flu Pandemic, as well as the SARS (2003) and MERS (2012) epidemics and we’re currently living it real-time with the COVID-19 pandemic that began late 2019.
Spillover occurs in scenarios where animals are housed in close proximity and in close contact with humans such as farms, slaughter-houses, and live markets. These scenarios are particularly beneficial for the pathogen when there are multiple species together. With such a large quantity of possible hosts, a virus has more opportunity to replicate and mutate until eventually gaining the ability to infect humans. Infection in a human will only be considered successful if the virus mutates and in the process develops the ability to attach and replicate itself in human cells. Additionally, in order for it to propagate amongst humans, it must also adapt to be transmissible without killing the human host. In animal production, species such as poultry and pigs are often considered original hosts for these pathogens, going so far as sometimes referring to pigs as “mixing vessels” for these diseases. However, these original hosts tend to show some immunity to them but it’s not transferred to humans or other species. Identification and source tracing for these viruses, such as the case of influenza traced back to poultry farms, or SARS-Cov-2 traced to bats in live animal markets can help animal scientists and epidemiologists predict tendencies and propose changes to legislation accordingly while respecting cultural and socioeconomic differences globally.
Prevention! Prevention! Prevention!
As far as our farms go, is there anything we can do to prevent these outbreaks in our own “backyard”? Yes! First, we can strive for better and more strict measures of biosecurity when in close contact with animals. Biosecurity in an animal-human interaction scenario refers to the set of protocols and controls that help protect both the health of the animals and humans by preventing the spread of pathogens and illness on the farm and across farms. These measures include keeping good records, practicing good hygiene including clothing, shoes, and vehicles, work-flows from cleanest to dirtiest, cleaning, and disinfecting work surfaces often while using the appropriate products are among many other small changes that can make a big difference in terms of health safety. We can also move towards a smaller scale farming model so that animals aren’t housed as closely together, keep animals from different species separate from each other and also educate personnel that work with these animals about the role they play in disseminating these pathogens at the workplace and home. Remember, preventing a disease will always be preferable over treating a disease!
One Health and what it means for agriculture
With an ever growing population and a food production system based on large scale farming, we can’t speak of public health without including the animal food industry in the conversation. Which is why careers in animal science within the public health spectrum can be very broad! An animal scientist can pursue careers as a DVM, many universities offering a DVM/MPH program, such as those under the OneHealth initiative; as well as careers in research areas such as Pathology, Epidemiology, Immunology, Food Science, Genetics, Molecular Biology and more! OneHealth thrives on the idea that through cooperation across disciplines we can protect each other and the earth.
When speaking of health, and specifically public health policy, it becomes easier to make the right choices within the food industry and animal-based research as we begin to see animal health and human health as an ongoing relationship instead of two completely separate areas of study. We, as humans, not only shape the well being of these animals but we shape our own in the process as we become more conscious of the animal products we produce and consume. By moving towards a smaller, more sustainable farming model we can positively influence our communities, while taking care of our planet and each other in our mission to prevent future outbreaks while achieving food security for all.
References:
Boni, M.F., Lemey, P., Jiang, X. et al. Evolutionary origins of the SARS-CoV-2 sarbecovirus lineage responsible for the COVID-19 pandemic. Nat Microbiol (2020). https://doi.org/10.1038/s41564-020-0771-4
Spickler, Anna Rovid. 2016. Bovine Spongiform Encephalopathy. Retrieved from http://www.cfsph.iastate.edu/DiseaseInfo/factsheets.php.
Pluhar, E. (2009). Meat and Morality: Alternatives to Factory Farming.Journal Of Agricultural And Environmental Ethics,23(5), 455-468. https://doi.org/10.1007/s10806-009-9226-x
Collins, J. D., & Wall, P. G. (2004). Food safety and animal production systems: controlling zoonoses at farm level.Revue Scientifique et Technique-Office International des Épizooties,23(2), 685-700.