Strengthening a One Health approach to emerging zoonoses

The first cases of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were described in humans in late 2019. Rapid global spread ensued and the World Health Organization (WHO) declared a global pandemic on 11 March 2020 (WHO 2020). Two years later, by March 2022, SARS-CoV-2 had been reported to have infected over 470 million people and has led to over 6 million deaths globally (WHO 2022). Many people infected with SARS-CoV-2 also continue to suffer from post-COVID-19 conditions (Davido et al. 2020). In addition to significant impacts on individual health and healthcare systems, there have been direct and profound social and economic impacts (Bonotti and Zech 2021).

SARS-CoV-2-related viruses have been well-described in bat populations, suggesting that SARS-CoV-2 originated in bats before spilling over into humans (Hul et al. 2021; Wacharapluesadee et al. 2021; Zhou et al. 2021). The setting (forest, farm, live animal market, or other) for spillover and the potential role of an intermediate host remain unknown. Shortly after the pandemic was declared, several non-human animal² species were reported to be susceptible to SARS-CoV-2 infection (Hobbs and Reid 2021; OIE 2021). These included captive and companion animals, as well as wildlife, raising the possibility of a secondary animal reservoir for the virus.

The massive global burden of SARS-CoV-2 in humans has resulted in spillover to naïve animal species (e.g., mink, cats, dogs, deer) (Dhama et al. 2020; Kuchipudi et al. 2022) and to the environment, where viral RNA has been detected in wastewater (Giacobbo et al. 2021). In addition to infecting a broad range of animal species through spillover from humans, variants of concern (VOCs) are broadening the susceptible species range for SARS-CoV-2. For example, the Alpha variant harbouring the N501Y mutation in the viral Spike protein is capable of infecting Mus musculus (the house mouse) (Shuai et al. 2021), whereas the parental viral strain is restricted to Cricetidae species of rodents, such as hamsters and deer mice. The genomic plasticity of the virus permits rapid and impactful adaptations that are critical to understand; peri-domestic wildlife with host viral receptors most closely resembling the human angiotensin converting enzyme 2 receptor may be at highest risk, meriting surveillance particularly in areas with high rates of human SARS-CoV-2 infection.

The implications of one or more animal reservoirs for SARS-CoV-2 are significant. A secondary wildlife reservoir introduces the risk of novel coronaviruses re-emerging after adaptation though mutations or recombination with other SARS-CoV-2 or endogenous animal coronaviruses, and may undermine the efficacy of medical countermeasures, including vaccines and antivirals. It is imperative that we understand the fundamental biology of potentially pandemic viruses, considering that the severity of clinical disease, population-level transmission, and social impact are a result of virological determinants (Kirlin 2020). For example, the Alpha VOC drove wave 3 of the pandemic in Canada, resulting in high rates of hospitalizations and further public health measures, and the genomic changes in the Delta variant translated into a 64% increase in household transmission (secondary attack rate) relative to the Alpha VOC, and is associated with increased severity of disease and risk of reinfection. Also, changes in the Delta variant genome contributed to immune escape and reduced efficacy of monoclonal antibody therapy (Allen et al. 2021; Public Health Ontario 2021). The Omicron variant (and sub-lineages) is highly diverged from other SARS-CoV-2 and has been clearly associated with reduced vaccine efficacy against infection, escape from monoclonal antibody therapy, and enhanced transmission (Accorsi et al. 2022; Escalera et al. 2022; Tatham et al. 2022). It is also speculated to have an animal origin, although no Omicron-like virus has been identified in animals prior to emergence in humans. Regardless, the emergence of Omicron and its subsequent impact highlights the significant potential for harm from new VOCs that could spillover from animal populations.

White-tailed deer in Canada and the United States have been screened for SARS-CoV-2 viral RNA and antibodies to establish evidence of infection and exposure. There are high rates of positivity (up to 82.5% by PCR or viral detection) among deer in the United States, and non-VOC, Alpha, Delta, and Omicron viruses have all been reported in this species (Vandegrift et al. 2022; Kuchipudi et al. 2022; Hale et al. 2022; Marques et al. 2022; Kotwa et al. 2022; Pickering et al. in press). Based upon the genomic epidemiology, multiple human-to-deer transmission events have occurred, but the route(s) of transmission remain unknown. Viral RNA has been detected in hunter-harvested Canadian deer as well, raising important questions around wildlife health, country foods, and the potential evolutionary trajectory of SARS-CoV-2 (Kotwa et al. 2022). The highly divergent SARS-CoV-2 variant detected in Ontario deer is unrelated to any other existing SARS-CoV-2 circulating among humans, and there are data supporting deer-to-human spillover in at least one instance (Pickering et al. in press). This is the first evidence of independent, parallel evolution of SARS-CoV-2 in another species, and of deer-to-human transmission.

The environment has also been implicated in the SARS-CoV-2 pandemic, with substantial spillover of viral RNA from humans into wastewater. Environmental monitoring through wastewater surveillance has been an essential public health tool. Although it is unknown whether animal or human exposure to wastewater leads to infection, given the widespread detection of environmental SARS-CoV-2 viral RNA, this possibility must be investigated, particularly considering that the range of host species susceptible to SARS-CoV-2 may be expanding due to VOCs.

Despite heralding events such as the emergence of SARS-CoV in the early 2000s, and the ongoing circulation of Middle East respiratory syndrome coronavirus (MERS-CoV), we were blindsided by the pandemic spread of SARS-CoV-2. Regardless of the clear and present danger posed by high-consequence coronaviruses, we failed to prepare for this coronavirus pandemic. No coronavirus surveillance was in place, research on coronavirus virology and medical countermeasures was scant, and most importantly, limited efforts had been made to mitigate spillover and spread of another highly pathogenic coronavirus in the years since SARS-CoV and MERS-CoV emerged. These failures resulted from a limited understanding of viral biology and the drivers of emergence, on the one hand, and from lack of political will, on the other. It is abundantly clear that the existing pandemic planning was insufficient to address one of the most significant health threats of this century.

Thus, there is a pressing need for a deeper understanding of the interface where all animals, including humans, interact in their shared environments, and the intersecting biological, ecological, and socioecological factors contributing to the emergence, spread, and impact of zoonotic diseases. This is essential to enhance resilience at all scales, gain insights into the connections between animal and land health, and to better understand how human actions are impacting this relationship.

Because of the interdependence of human, other animal, and ecosystem health, the decisions humans make have consequences beyond human society. National and international travel and trade played important roles in the rapid global spread of SARS-CoV-2, and urbanization, food insecurity, and trade of wild and domestic animals are contributing factors to the emergence of several other high consequence pathogens.

As the human population grows and our cities expand, we encroach further into natural areas and clear land to produce more food for burgeoning populations of people and domestic animals. This expansion not only reduces natural areas providing critical habitat for wild plants and animals, but also creates new intersection points where humans, vectors, domestic animals, and wildlife come into contact. These changes increase opportunities for new pathogens to adapt (emergence) and infect non-traditional hosts (spillover). Environmental factors, such as climate, seasonality, and habitat availability determine the lifecycles and geographic range of different host species, vectors, and microorganisms, thus affecting where and how zoonoses emerge, spillover, and survive. It has been predicted that as the pace of change of these environmental factors becomes even greater, there will be more spillover events and increased incidence of emerging infectious disease (Jones et al. 2008).

Along with the impacts on health and healthcare systems, COVID-19 has worsened many pre-existing inequities associated with poverty, race, ethnicity, and gender, both regionally and internationally. Throughout the pandemic, marginalized populations have been the most heavily burdened by both viral infection and policies put in place to prevent the spread of COVID-19 (WHO 2021; Cronin and Evans 2022). The large social and economic costs associated with the control of and response to the COVID-19 pandemic provide a strong and inarguable case for substantial investments in reducing inequities by addressing the structural drivers of inequities. One approach to reduce the interconnectedness of inequities would be to enact Canada’s commitment to implement gender-based analysis plus (GBA+) and the Calls to Action of the Truth and Reconciliation Commission.

The COVID-19 pandemic has highlighted existing societal inequities and continues to degrade health, healthcare, social, and economic well-being. Our shared experience with COVID-19 is sharpening the focus on the urgent need for new ways of tackling and preventing future pandemics in this time of pressing environmental threats.

At its core, One Health is about recognizing the connections between all living things and our shared spaces. Others call this concept by different names (e.g., public health, Ecohealth, and traditional ecological knowledge) (Lerner and Berg 2017). One Health is often portrayed as three pillars (or circles): Human health, animal health, and environmental health (World Organisation for Animal Health, n.d.; Centers for Disease Control and Prevention 2021; Destoumieux-Garzón et al. 2018). By recognizing the shared determinants of health (or disease) and interdependencies among these pillars, we highlight the foundational importance of the intrinsic value of all species and generations, and the importance of reciprocal care for each other (as people), animals, and the spaces we all share (Stephen and Gallagher 2021). The importance of equity, value, and reciprocal care are well-described in EcoHealth (Charron 2012). These three critical elements are needed to address sustainability and to build more resilient and equitable systems able to withstand many complex and growing health threats.

One Health encompasses synergies described as One Medicine by Calvin Schwabe (1984) over 40 years ago. Broader concepts of health and the critical consideration of interrelatedness between health and the environment are embodied in the Ottawa Charter for Health Promotion (World Health Organization 1986), which advances the notion of reciprocal care and pledges to “counteract the pressures towards harmful products, resource depletion, unhealthy living conditions, and environments.” Caring, holism, and ecology are deemed necessary for health promotion, and the Ottawa Charter called for international action to achieve Health for All by the year 2000. In 2004, the Wildlife Conservation Society hosted a symposium in New York, where the Manhattan Principles underpinning the concept of One World One Health (OWOH) were established (Wildlife Conservation Society 2004). These principles were advanced through a series of consultations on influenza in Beijing (2005), Bamako (2006), New Delhi (2007), and Sharm el-Sheikh, Egypt (2008), as well as International Ministerial Conferences on avian and pandemic influenza. The Beijing Principles were outlined early in this process, and ultimately the OWOH approach was formally adopted by the WHO, the Food and Agriculture Organization (FAO), the World Organisation for Animal Health (OIE), the United Nations Children’s Fund, the United Nations System Influenza Coordination, and the World Bank, based on recommendations made at these meetings.

The OWOH approach is summarized in the report entitled Contributing to One World, One Health: A Strategic Framework for Reducing Risks of Infectious Diseases at the Animal-Human-Ecosystems Interface (2008) (Food and Agriculture Organization of the United Nations et al. 2008). This foundational document was sparked by outbreaks and the pandemic threat of the highly pathogenic avian influenza virus (HPAI) H5N1, which was causing widespread outbreaks by 2003 (after its initial detection in 1996 in Hong Kong) (Sonnberg et al. 2013). This virus is resurging globally now, with unprecedented levels of activity in Canada. The emergence and spread of HPAI H5N1 virus at that time highlighted an urgent need to understand the drivers of emergence, transmission, and persistence of emerging infectious diseases at the interface where humans interact with other animals and ecosystems. National authorities were encouraged to consider key priorities for surveillance; public health responses; and strategic research through collaboration, multidisciplinary, cross-sectoral partnerships; integration of governance; and technical and sociocultural aspects of implementation. The current H5N1 situation is an acute reminder of the importance of these key activities.

The OWOH Strategic Framework encouraged decision-makers to reinforce existing mandates, institutions, and programs, and to include all levels of government. Emphasis on technical leadership in surveillance and data sharing, risk assessment, and capacity building helped strengthen national laboratory testing and reporting systems, highlighting gaps in communication and coordination. This focus on improvements included acknowledging the importance of integrating wildlife and ecosystems into surveillance and control programs and the need to establish effective financing frameworks. Key research areas were identified in the OWOH Strategic Framework, including understanding zoonotic pathogen emergence, spread, and persistence; pathogen biology; diagnostics and prevention; sociocultural determinants; and implementation. A range of specific initiatives emerged from an unprecedented orchestration of efforts, stemming from the control of the HPAI H5N1 virus. Building upon the pre-existing Global Framework for the Progressive Control of Transboundary Animal Diseases (2022), these initiatives included FAO’s Emergency Centre for Transboundary Animal Diseases (2022), the joint FAO/OIE/WHO Global Early Warning System (GLEWS) (2022), and the Network of Expertise on Avian Influenza (Edwards 2006).

In November of 2012, the World Veterinary and World Medical Associations signed a collaborative Memorandum of Understanding in Bangkok, Thailand (Wilson 2012). The scope of this memorandum included joint educational efforts, cross-species surveillance, the responsible use of antimicrobials, and collaborative research. More recently, the original Manhattan Principles, released in 2005, were updated as the Berlin Principles in 2021 (Gruetzmacher et al. 2021).

Presently, there are a myriad of definitions and descriptions of One Health, but all share common features (Gruetzmacher et al. 2021; Centers for Disease Control and Prevention 2018; One Health Commission 2022; World Organization for Animal Health 2022). First, One Health is about health—the health of people, animals, plants, and ecosystems. It is about how health is the result of the interdependence between species living in shared environments, over time, and across space. One Health is also about collaboration, trust, and sharing of responsibility. By recognizing health interdependencies, One Health calls for more and better inter-, multi-, and transdisciplinary efforts to break down silos and work together to preserve and promote health gains. The UN Sustainable Development Goals (United Nations 2015) are a key example of how upstream drivers can have far-reaching consequences. Building health, promoting resilience, striving for equity, and ensuring capacity to cope and adapt are all hallmarks of holistic health approaches, be they One Health, EcoHealth, Planetary Health, or other.

Western notions of One Health were long preceded by traditional forms of knowledge, including Indigenous ways of knowing. Indigenous knowledge recognizes and respects the interconnectedness among all things and is a distinct approach from the Western concept of One Health, using a different set of assumptions than those advanced through Western thought. In Indigenous knowledge systems, the process is often more important than the endpoint itself, and there is no single path or approach for a given process. Based on common principles, Indigenous knowledge differs among Nations and communities. Although Western focus is shifting toward more collaborative, comprehensive, and interdisciplinary approaches through broader incorporation of concepts of land stewardship and health, important gaps remain in listening to Indigenous perspectives and leadership (WHO 2017b; Hillier et al. 2021).

It is also important to recognize the Indigenous context for health and to address the disparities that exist due to colonization and institutional and systemic barriers to good health. First Nations, Inuit, and Métis peoples living both on and off reserve experience clear disparities in health and wellness (McGregor 2009; Statistics Canada 2015). We cannot consider applying Indigenous models of One Health, on the one hand, while disregarding these inequities, on the other. Good health and clean water are basic human rights and must be ensured for Indigenous Peoples, recognizing Indigenous Peoples’ rights to individual, community, and land health. The right to a self-determined future for land, animal, and human health must be recognized in an active, enabling way.

A rapid decline in land health due to human exploitation and climate change also merits focused attention. Cultural genocide and colonialism have coalesced with these anthropogenic drivers, leading to environmental dispossession through direct disruption of land health or the rupture of Indigenous Peoples’ relationships with the land. Connection with the land is considered one of the key determinants of health for Indigenous Peoples (Government of Canada 2018). Thus, environmental dispossession has a profound impact on ways of knowing, ways of life, and spiritual, physical, and mental health (Big-Canoe and Richmond 2014; Jones 2019; Mashford-Pringle et al. 2021; Tobias and Richmond 2014). Also, as land health erodes, so does landscape immunity (Ruscio et al. 2015), increasing the risk of zoonoses for those closest to the land and adding to the disproportionate burden of disease incurred by Indigenous Peoples. This issue has been underscored during the pandemic and goes beyond baseline health and severe outcomes associated with COVID-19 and includes hunting and gathering and other key practices for sustenance and wellness, which were severely affected by individual exposure/quarantine or illness, population-level states of emergency and other regional measures (Tobias and Richmond 2014).

The Convention on Biological Diversity clearly underscores the importance of Indigenous knowledge systems in resource management (Plowright et al. 2021). This knowledge is diverse, participatory, and experiential, and not readily defined using static Western frameworks. Supporting Indigenous concepts of One Health includes respecting natural laws and implementing earth-based solutions through land pedagogy (Convention on Biological Diversity n.d.; Learning the Land n.d.). A key element of some Indigenous knowledge systems is using different ways of knowing through collaboration, including Two-Eyed Seeing or Etuaptmumk in Mi’kmaq knowledge systems (Bartlett et al. 2012). Incorporation of Indigenous knowledge systems ensures Indigenous leadership and self-determination in One Health solutions to specific challenges; it also increases the impact by applying culturally and environmentally relevant knowledge that is absent or sparse in more Eurocentric approaches to One Health.

One Indigenous approach to One Health, outlined by Joe Copper Jack, has been applied to key activities in land planning, culture, and education in Yukon (One Health Concept Box 1). It is essential that these activities begin with (1) relationship building and (2) the implementation of traditional knowledge protocols—processes that must be respected. Extracting Indigenous knowledge and using it out of context for convenience or other purposes is harmful and unacceptable. While Western knowledge strives for endpoints independent of relationships, Indigenous knowledge systems revolve around relationships. Relationship building and protocols allow trust and understanding to be established and to evolve over time.

Zoonotic disease emergence in humans is driven by human activities and behaviour that change human, other animal, and (or) vector interactions. Addressing how humans interact with other animals, including wildlife, is a key component of EID risk management and response (Watsa 2020). Decreased habitat availability, pollution, and climate change impact the health of wildlife and other animals, including humans (One Health Concept Box 2). Over the past 50 years, wild animal populations around the globe have declined by 60% on average (Grooten and Almond 2018) and 28% of assessed species are threatened with extinction (IUCN 2021). Ecosystems have been degraded, changing how different species interact and increasing the risk of exposure to novel pathogens. Prevention of EIDs will require us to tackle these underlying factors, including climate change, ecosystem degradation, and land-use change.

We know that ecosystem and land-use change can have dramatic impacts on pathogen transmission patterns. For example, in Malaysia, the development of large-scale swine production facilities near mango orchards where fruit bats roosted is believed to be a driver of Nipah virus transmission from fruit bat reservoirs to pigs, with spillover into humans (Pulliam et al. 2012). Although there are many cases in which land-use change is associated with increased disease transmission, this is not always clear, leading Gottdenker et al. (2014) to suggest that “there is still uncertainty regarding the direction, magnitude, and mechanisms of anthropogenic disturbances on infectious disease transmission and persistence.” More research is required to fully understand the impacts of changing landscapes on disease emergence; however, land-use change should be considered as a key risk factor.

The wildlife trade also provides opportunities for disease transmission that may affect the health of humans, domestic animals, wildlife, and ecosystems (Karesh et al. 2005). For example, monkeypox emerged in the United States as a consequence of the wildlife pet trade in 2003. Human exposure resulting in 47 confirmed or probable cases in six states was traced to contact with pet prairie dogs that had been co-housed with monkeypox virus-infected rodents imported from Ghana (Prevention 2003). Currently, a global outbreak of monkeypox is being sustained through human-to-human transmission. This serves as a stark reminder of the critical importance of supporting regional efforts for control in endemic regions, and of investing in global health and security. The wildlife trade has been investigated as one of the key factors leading to the emergence of SARS in 2003 and SARS-CoV-2 in 2019 (Mallapaty 2020; World Animal Protection n.d.). International regulation of the legal wildlife trade falls under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Data from imports and exports falling under this agreement reveal that the legal wildlife trade is in the range of 11.5 million wild animals from 1,316 species over a five-year period (2012–16). The United States is the greatest consumer of legal wildlife (Can Ö et al. 2019). The disease risks and conservation concerns associated with the wildlife trade (both legal and illegal) have been well-documented and the COVID-19 pandemic has renewed calls to ban the global wildlife trade (Karesh et al. 2005; Roe and Lee 2021). However, some researchers have been urging caution as wildlife trade bans may have substantial unintended consequences, including socioeconomic impacts on local communities and an increase in the illegal wildlife trade (Roe and Lee 2021; Federal Provincial and Territorial Governments of Canada and Canadian Wildlife Health Cooperative 2018). These issues need to be considered from a One Health perspective, including the assessment of potential unintended consequences such as health impacts on animals from displacement and infectious diseases.

There is a pressing need for an action-oriented, comprehensive plan for One Health surveillance in Canada and for surveillance to be adaptable enough to respond to changes when needed. Key to accomplishing a suitable plan for surveillance is identifying some of the major gaps in current surveillance systems and recognizing the challenges inherent in establishing an ideal One Health surveillance system.

To address emerging zoonoses, One Health surveillance systems need to operate across a range of jurisdictions, and Canada participates in numerous international, national, provincial/territorial, regional, and sector-specific surveillance efforts. However, when one considers that One Health surveillance requires detailed information about diverse human, other animal, and environmental sources, the need for multifaceted and integrated surveillance is apparent. Despite some excellent surveillance efforts and programs (e.g., Canadian Integrated Program for Antimicrobial Resistance Surveillance and the Canadian Wildlife Health Cooperative) (Public Health Agency of Canada 2007), the scope, depth, and connectivity of surveillance efforts in Canada across the One Health spectrum is suboptimal. Optimal surveillance should be standardized, goal-oriented, transparent, comprehensive, adaptable, sustainable, have adequate surge capacity and be integrated within and across human, other animal, and environmental health sectors. It should also be informed by existing knowledge of biological determinants of transmission and disease. For example, surveillance for novel coronaviruses among animals would include advanced genomic sequencing methods and computational biology to examine key determinants of spillover risk and pathogenicity (Mercer and Salit 2021) and biological characterization to assess risk to health.

Data are only useful if they are used. Inadequate effort or ability to access and translate data into action, particularly in real time, can hinder surveillance systems. Some degree of delay is inherent in the surveillance process as time is required to gather, analyze, and transfer information, but when dealing with emerging issues, time lags diminish the value of surveillance as an early identification or intervention tool.

A One Health approach to surveillance necessarily involves integrating the surveillance activities of diverse specialists and stakeholders (One Health Case Study 2). In Canada, surveillance is performed by a wide range of individuals and groups, including governments (Indigenous, federal, provincial, territorial, and local), academic institutions, healthcare facilities for humans and other animals, professional networks, and private diagnostic laboratories. Within government, surveillance is often performed across multiple departments. This intersectionality highlights the complexity of the issues surveillance tries to address and the importance of intersectoral and interdisciplinary work, but it also creates potential barriers (e.g., timely and comprehensive information exchange), inefficiencies, duplications, and gaps.

Communication of surveillance activities is key and should be multidirectional and ongoing. Stakeholders and rights holders need to be included early in surveillance initiatives to ensure that needs are met, to identify resources to support surveillance, to identify potential synergies, and to facilitate rapid and effective use of surveillance data. Communication between people involved in surveillance and stakeholders must continue throughout, to ensure that surveillance data are properly used and that emerging issues are identified and acted upon.

How and when surveillance data are communicated is also important. Surveillance reporting should be as granular and timely as possible, but it is limited in some surveillance programs, as the time from data collection to release of results can be many years. This delay reduces or negates the applied use of surveillance data.

Good surveillance is designed to provide an appropriate reflection of the broader population. However, for reasons such as expense, logistics, or lack of knowledge, many surveillance systems collect data that are, in fact, based on specific sub-populations and do not generalize to broader populations. This introduces bias, which limits interpretation and conclusions (Lipsitch et al. 2015). For example, relying on case fatality rate (proportion of deaths among confirmed cases) data obtained from hospitals may lead to an overestimate of the overall case fatality rate of a disease that has a range of presentations, if only severe cases are hospitalized (Lipsitch et al. 2015). These biases can be overcome if they are recognized.

Animal health surveillance in Canada has largely focused on diseases that negatively impact agricultural production and create food safety issues, with less direct attention to broader animal health and welfare issues. Although foodborne and production-limiting diseases are of significant concern, they do not fully encompass all the risks to animals (especially companion and working animals) and non-foodborne zoonotic diseases. Improved integration of human and other animal clinical and diagnostic data could help to move animal health surveillance toward a One Health system.

Detection of naturally occurring diseases in humans and other animals through routine clinical and diagnostic activities may be the most effective and efficient early response to some threats; however, there are significant gaps in effective use of clinical diagnostic data. One example is Echinococcus in dogs (One Health Case Study 3).

At the transection of human and other animal health, pathogens with a wide range of hosts cause many major diseases of public health importance, introducing complex transmission dynamics. This complexity may pose considerable challenges in understanding certain pathogen systems, but a One Health approach provides opportunities to use a wide range of species for potential surveillance purposes.

Implementing a One Health surveillance system is undoubtedly a complex and costly endeavor and would require adequate long-term funding to cover surveillance of human health (acute care, community care), other animal health (wildlife, food animals, companion animals), and the environment (air, soil, water). Funding would also be necessary to integrate these surveillance data into a One Health system and to develop the necessary expertise, infrastructure, and coordination. Although expensive, investing in effective and sustainable One Health surveillance programs would be less costly than responding to future disease emergences (see Section 5).

Social inequity is rooted in the dominance of one group over another. Social inequities—including gender, ethnic, territorial, and economic inequities—lead to marked inequities in health and well-being across populations. Gender inequity is ubiquitous but not uniform as it combines with other health inequities such as homelessness, poverty, or structural racism (Abrams and Szefler 2020; Bailey et al. 2017; Craig 2020; van Daalen et al. 2020; Yaya et al. 2020). This interaction has been variously termed and analyzed: Matrix of oppression (Hill Collins 1990), co-constitution (Bilge 2015), co-substantiality (Kergoat 1982) and intersectionality (Cho et al. 2013; Crenshaw 1989; Crenshaw 2019). Attention to this can illustrate how people’s experiences of hazards differ across multiple intersections such as location, ethnicity, gender, and age and how these differences are influenced by broader social structures and power relationships, such as histories of colonization and gendered norms and expectations (Walker et al. 2021). In Canada, the economic repercussions of social inequities highlight the vulnerability with which certain populations, including women, youth, recent immigrants, and racialized people, live (Bastien et al. 2020).

The societal roles attributed to genders and the life experiences of individuals, marked by their differing economic, social, and physical conditions, bring people into contact with their environment, including zoonosis, differently. For example, in many parts of the world, girls and women are responsible for raising household livestock, shopping at wet markets, and preparing animal-derived food for household consumption. This proximity to animals can put them at greater risk of exposure to zoonosis (Bagnol et al. 2015). Further, as primary food providers, girls and women can be disproportionately affected by food insecurity. They must care for malnourished family members and work extra hours to make up the shortfall. For example, depending on the region, women farmers are responsible for a substantial proportion of all food production in developing countries. Due to climate change, traditional food sources are increasingly difficult to predict, making it a challenge for women to feed and provide for their families. In situations like this, some people are at higher risk for various diseases, and by seeking non-traditional food sources, they may be more likely to contract zoonoses (Keatts et al. 2021).

The challenges of human, other animal, and ecosystem health are complex and increasingly interrelated. Issues related to zoonotic pathogens, antimicrobial resistance, and climate change do not respect species or geopolitical divides. Professionals across the diverse disciplines related to animal and human health need a firm academic grounding beyond narrow professional constructs, including an understanding of the interface among their disciplines and with areas of ecology, social science, and Indigenous knowledge.

To achieve this holistic knowledge base, programs in veterinary, medical, and other health professional education should include core competencies related to One Health in their curricula. Already used by leading medical and veterinary education organizations, existing frameworks can become the basis to establish education programs using accreditation standards within their respective jurisdictions. Establishing One Health education programs within accreditation standards will assure consistent and more universal adoption of One Health curricula.

To successfully tackle the complex and urgent health and environmental challenges of the 21st century, a strong workforce of skilled individuals and leaders is needed. Critical knowledge and skills are required to apply integrated and collaborative approaches, foster knowledge and resource sharing across disciplines, knowledge traditions and communities, and maximize the likelihood of creating proactive, effective, and sustainable solutions (Barrett et al. 2019; Cleaveland et al. 2017; Parkes et al. 2020; Togami et al. 2018; Whitmee et al. 2015).

To meet this growing need, institutions across the world have been developing One Health training programs, however, only recently have efforts been made to develop shared competencies and learning outcomes for One Health to help ensure consistent and robust training across institutions. Competency-based education has been used for decades, including in, but not limited to, human and veterinary medicine and public health (AAVMC Working Group on Competency-Based Veterinary Education et al. 2018), ensuring that, regardless of the institution, students leave their respective programs with the specific skills, attributes, and knowledge needed for successful practice (Public Health Agency of Canada 2021). Following the establishment of competencies, specific learning outcomes are identified that provide a scaffold for students to ultimately achieve the desired competency (Albanese et al. 2008; Hooper et al. 2014). Efforts are underway in Canada to develop core competencies for One Health, which will likely include competency in health knowledge and understanding, problem solving and critical thinking, leadership and collaboration, communication, and professional and ethical behaviour.

Because of the complexity of the research questions at hand and the interdisciplinarity essential to research programs focused on One Health, it may be challenging to finitely define what constitutes One Health research. Here we consider research examining multiple (but not necessarily all) facets of health, including that of ecosystems, humans, and other animals to be applying a One Health approach. In this policy report we focus on zoonotic disease research, but evidently there is an expanse of research beyond this area that merits deeper consideration, including equally pressing questions around health and climate change, pollution, forest degradation, biodiversity, social and political ecology, socioeconomics, geopolitics, food security, and armed conflict, among others.

One Health zoonotic disease research is expansive and may include hypothesis-driven research, translational research and development, implementation, and evaluative sciences (One Health Case Study 5). For example, examining the effect of artificial light on bird immunity and susceptibility to infection by West Nile virus is as much a One Health project as is looking at the impact of pasteurization of water buffalo milk on Brucella control and farmer health and livelihood. Both examine health from more than one perspective and stand to improve it.

Clear challenges exist with a One Health approach to research. Fragmented, ineffective research outcomes may be secondary to persistent silos, competition (for financial support or recognition), conflicting priorities, poor planning and coordination, differing values, short-term and limited support, and a myriad of other impediments. Mutual goal and scope-setting at the outset is helpful. Starting conditions, including investigator experience, the research context, and relational dynamics between researchers can set the tone for process and influence outcomes; one study examining health events (97% related to infectious diseases) found several determinants of productive One Health research collaborations, including education and training, prior experience and existing relationships, organizational structures, organizational culture, human resources, communication, network structures and relationships, leadership, management, available and accessible resources, and the political environment (Errecaborde et al. 2019).

COVID-19 has inarguably revealed the interconnectedness between key domains of human and other animal health, with strong links to habitat and ecosystem health through possible knock-on, if not causative, effects. Thus, the Chairs of the Lancet One Health Commission have called for a One Health research coalition for COVID-19 (Amuasi et al. 2020). Unfortunately, research efforts remain loosely coordinated where they exist, with vast lacunae where they are absent. These gaps are present within the conventional framework of One Health research encompassing all animals, including humans, and ecosystems. They also exist across disciplines, where biological (virology, bacteriology, mycology, parasitology, immunology, computational biology), epidemiological (disease ecology, modelling, and clinical epidemiology), environmental (ecosystems, climate, landscape immunity), and social (human populations structures, cultures, economics, geopolitics, and governance) research suffers from important omissions in substance and collaboration. Finally, ensuring that public health and academia engage with each other is essential to high quality, relevant, and immediately actionable research to guide decision-making; while some examples exist, there were many missed opportunities over the course of the pandemic in Canada.

Substantial challenges exist with One Health research funding in Canada. Tri-Agency—Canadian Institutes for Health Research (CIHR), Natural Sciences and Engineering Research Council (NSERC), and Social Sciences and Humanities Research Council (SSHRC) funding has occasionally supported projects with One Health aspects. However, there are scant sustained and truly multidisciplinary funding schemes focusing on One Health approaches to emerging pathogens and zoonoses or other aspects of One Health. CIHR’s Institute of Infection and Immunity (III) has supported zoonotic disease research networks, but these remain narrow in pathogen scope (e.g., Lyme Disease Network, antimicrobial resistance). The recently released Institute of Infection and Immunity Strategic Plan, identified priorities, including global infectious disease threats, climate change-related zoonoses, and One Health approaches for antimicrobial resistance. These represent welcome progress provided there are substantial and sustained commitments to building the expertise, networks, workforce, and infrastructure (both physical and regulatory) required to execute this and broader work.

To date, there have been few, if any, panels with the combined expertise to consider One Health-related proposals. Because most One Health proposals overlap with multiple funding agencies, these tend to fall in between agency priorities for funding, and are left unfunded. The Canadian Safety and Security Program (Defence Research and Development Canada) and the Public Health Agency of Canada’s Infectious Diseases and Climate Change fund have supported One Health-oriented projects, which have catalyzed several regional and national initiatives. However, without long-term prospects for support, there are high opportunity costs due to unsustainability, and One Health research does not lend itself to one- to two- year timeframes. The lack of pre-existing intramural and other executive research bodies (e.g., equivalents of the National Institute of Allergy and Infectious Diseases Laboratory of Virology; Rocky Mountain Laboratories, Montana; Centers for Research in Emerging Infectious Diseases; National Biocontainment Laboratories and Fogarty International Center) put Canada at a clear disadvantage, both domestically and internationally during the pandemic. It was also not immediately evident with whom partnerships were possible, with public health and academic research at arm’s length from each other and many government scientists seconded to operational tasks, particularly early in the pandemic. Canada has also not invested in programs to tackle zoonotic diseases in the same manner as other leading initiatives, such as the EcoHealth Alliance in the United States or the Friedrich Loeffler Institute in Europe.

There have been some regional initiatives, such as Quebec’s Multi-Party Observatory on Zoonoses and Adaptation to Climate Change, part of the Government of Quebec’s 2020 Climate Action Plan supported by the Green Fund (Germain et al. 2019). However, there are no national observatories to support research prioritization. In addition, regional initiatives cannot be conducted effectively or meaningfully in Canada unless they involve Indigenous scholars, health organizations, knowledge holders, and governments, particularly in areas around Arctic One Health, wildlife surveillance, and Indigenous Peoples’ health. The Institute of Indigenous Peoples’ Health at CIHR has funded several Indigenous COVID-19 rapid-response grants, but like so much other catalyst COVID-19 funding, there are no clear plans to leverage these investments for long-term projects around zoonotic disease and Indigenous health.

In addition, limited investment has been made in international One Health research. Meaningful participation by Canadian scientists is essential to (1) contribute to global efforts to combat infectious diseases (most importantly) and (2) enable efforts to protect Canadians from transboundary novel and emerging pathogens. Initiatives such as the Global Governance Research Network on Infectious Disease (GGRID) are commendable but limited and require further investment and expansion. It is critical to also support international One Health research integrating natural sciences. Without foundational knowledge of non-endemic etiologic agents, we will continue to have too few experienced scientists able to competently work on special pathogens. There is also limited coordination among high level (3 and 4) containment laboratories in Canada—each function as a silo and has limited capacity to collaborate nationally, let alone internationally, and there is an excess of both overlap and gaps in emerging zoonoses projects. Also, few academic centres have the capacity to focus on zoonotic diseases for animal health (e.g., there is limited work on pathogens such as Brucella canis). Finally, from an ecological perspective, without understanding the drivers of pathogen emergence outside our borders, we cannot anticipate predisposing conditions within.

Knowing where to begin with One Health-related research will require thoughtful prioritization over both short- and long-term time scales across national and international domains. There are both urgent needs that potentially overlap with public and animal health mandates and longer-term, systems-based questions that merit attention. Work in the United States indicates that several wildlife species are susceptible to SARS-CoV-2, but we have a very limited line of sight on this in Canada since this research falls between academic research and public health and between natural sciences and health, meaning it has limited support from public health current peer-reviewed funding mechanisms. Fortunately, Defence Research and Development Canada, the Public Health Agency of Canada, Environment and Climate Change Canada, the Canadian Food Inspection Agency and provinces (ministries of natural resources) have stepped in to temporarily and partially address this important gap with short-term, modest targeted investments for limited surveillance (leading to the detection of SARS-CoV-2 in Canadian wildlife; Kotwa et al. 2022; Pickering et al. in press), but fulsome research programs are not currently in view.

In summary, there are currently no robust, sustained funding streams for One Health research in Canada. Past investment in emerging zoonoses is either limited or virtually nonexistent, compared to other areas of health, and there are few established mechanisms to access funding for rapid, effective collaborative research in times of acute need for those with existing expertise and capacity. These become urgent and critical challenges as new threats such as highly pathogenic avian influenza virus rapidly emerge. This, at least in part, may be attributed to the absence of a national One Health Action Plan. In the same fashion that climate change policy and planning has been driven by science, so must One Health-related policy and decision-making be supported by robust data, which at the moment, are very sparse in Canada.