Animal agriculture is in the spotlight as commentators and researchers assess its contribution to greenhouse gas emissions, emerging infectious disease, environmental degradation, non-communicable food-related diseases and inadequate animal welfare. To date, however, research has largely failed to explore the significant differences between livestock species and the range of production systems under which they are raised. There is an absence of validated classification systems that are based on ontological processes. In many areas of the world, traditional livestock raising practices have survived for thousands of years and continue to date, yet they are under pressure with human population pressure, land and water use. In the 20th century, intensive livestock production systems were hailed as economic successes with environmental externalities largely ignored. Moving forward what constitutes ‘tolerable’ animal agriculture in a changing world facing multiple existential threats? Do the limits vary across geographies, production systems and cultures? If they do, how can these differences be measured? How might these limits contribute to defining associated sustainable and circular bioeconomies?

To help setting boundaries to infectious disease aspects of One Health science, there is a need to define clearly meanings for terms commonly used to describe aspects of the science. The One Health High-Level Expert Panel, convened by the International Health Agencies, has now defined One Health https://doi.org/10.1371/journal.ppat.1010537 providing a basis for examining ontology of key terms frequently used in the subject area, in the past and in the future. For example, when describing pathogens of concern to humans, originating from animals, narratives in use are extremely loose and unspecific. This can lead to confusion on the role of animals in human infections (from genetic origins through to contemporary infection sources), and this can lead to inappropriate response or interventions, as well as mislead research priorities. From an ethical and welfare standpoint, misunderstanding of the role or significance of animal origins can also cause unnecessary persecution or destruction of animals, justified by perceived benefits of these actions to human health security. In this context, there has been a trend to emphasise the role of wildlife species as a source of human pathogens based seemingly on myth, speculation or assumption. The key terms for consideration for the question are as follows: emerging infection disease (of humans), zoonotic origin pathogens, zoonosis and zooanthroponosis. These terms have been more commonly in use since the last decades of the 20th Century, coincident with an apparent rise in novel human infectious viral diseases, such as HIV AIDs, Ebola Virus, human and zoonotic influenzas (H1N1, H5N1) and the coronaviruses. Language is fundamental in providing a logical framework for understanding and knowledge. For the new Science of One Health, this is the first step to ensuring clear research directions. We invite authors to explore the historic use of these terms and their ontologies and examine if they provide sufficient specificity to enable clear understanding and interpretation of disease origins and/or are adequate to communicate and scientifically describe the epidemiological role of animals in human disease occurrence. Examining how the evolution of language in science and communication might influence prioritisation for research on as well as prevention and response to infectious diseases will be a core element in answering this question.

The bulk of One Heath’s investment and research focuses on how animal or environmental threats impact human health or well-being. One Health has been less attentive to how human and environmental dimensions interact to impact animal health or on the environmental implications of health management at the human-animal interface. There has also been comparatively little investigation on how to create One Health programmes that promote reciprocal care that is neither human first, nor animal first nor environment first, but rather concurrently protects the health of all three. With this question, we invite authors to explore if or how current policies, practices and perspectives have shaped the primacy of human health as a benefactor of One Health and examine what changes need to be made, if any, to broaden the application of One Health approaches and perspectives. We encourage the use of implementation science methods and strategies to develop evidence-based policies and practice and to promote their regular use by researchers, practitioners and policymakers.

Decision makers want more information on the presence, distribution, movement, and impacts of pathogens in wild animals to anticipate or assess the risk of pathogen spillover from wildlife to people or domestic animals or to better understand the conservation implications of contagious diseases in wildlife. There are many impediments to designing and implementing a wildlife health surveillance system that fulfils all the expectations for ‘good’ surveillance. There are well-known pragmatic limitations such as the inability to sample targeted populations consistently and regularly in a representative manner, lack of validated tests, and funding limitations that restrict surveillance to periodic surveys. The nature and impact of the biases on data collection, generation, management, quality, analysis, interpretations, and information sharing are poorly studied. We invite authors to address the question in the title.

The looming challenges of pandemic recovery, climate change emergencies, species extinction, and growing food insecurity are driving calls for more One Health to “do more.” To address these calls, it is reasonable to anticipate an explosion in One Health training programs. Many One Health educational efforts were originally designed in response to emerging zoonotic diseases. As the scope of practice of One Health grows, the breadth of knowledge, skills, and attitudes to be cultivated through education and training also grows. Many One Health programs created in the early days of One Health could not benefit from the experiences of years of applying One Health in practice that exist today. Few One Health programs have been systematically evaluated to see if or how their structure or curriculum empowers learners to be effective One Health researchers or practitioners. We invite authors to provide evidence-based assessments of the impacts of different means, methods, and targets for training and/or systematic assessments of educational theory to help answer the Question, “is there an ideal curriculum and pedagogy to achieve an optimal One Health practitioner capable of contributing to the growing expectations for One Health?”

Antimicrobial resistance (AMR) is a global health threat to humanity, animals, plants and the wider environment. The intrinsic complexity and interconnectivity of human, animal and environmental factors has now been globally acknowledged and warrants a One Health approach. International communities launched guidelines to support the development and implementation of comprehensive national One Health (OH) AMR strategies with a particular concern for threatened antibiotics. Yet, AMR National Action Plans have proven difficult to implement because of social and structural obstacles/barriers, which are well-known as OH challenges (Keune, Payyappallimana, Morand and Rüegg 2022) such as overcoming inter-sectorial and interdisciplinary barriers, taking into account structural societal dynamics, implementing transdisciplinary system’s approaches. To enhance necessary transformative system changes, it is vital to operationalize and contextualize One Health AMR approaches for the design, implementation and evaluation of community-based AMR interventions, tailored to the local circumstances.

The healthcare sector has proven to be supportive in stimulating health through contact with nature (Robinson and Breed, 2019; Kondo et al., 2020). Despite the positive practice examples, we see several challenges. There is no clear consensus or common understanding on quality assurance and health impact assessment of green care: there still is a wide range of approaches within different health expert communities and contexts, either with or without some form of qualified support such as coaching. As there is no ‘one size’ prescription fit for all, green care needs to be tailored to individual characteristics and circumstances, both of which are dynamic, e.g., in an environmental sense due to climate change, or related to socio-cultural dynamics (Beute et al., 2020a,b; Superior Health Council Belgium 2021). Sustainable health-related nature contact is not always easy to achieve especially when there is no follow-up with either healthcare professionals or other supporting organizations through social prescription. Accessibility of natural areas is often quite unequally distributed, with the more vulnerable often benefitting least, especially in urbanized areas. Another challenge is to achieve a reciprocal health relationship with nature: a stronger connection with nature and caring for nature helps to sustain a positive healthy relationship (O’Brien et al., 2010; Kurt et al., 2018), which may also contribute to nature conservation in a One Health perspective. As such, the healthcare sector can act as ambassadors for ‘One Healthy’ natural environments.

Achieving sustainable development is one of the greatest challenges for humanity. This includes producing food in a way that enhances ecosystem, animal and human health, at the farm level and more broadly. To measure the enhancement brought about by animal production systems, producers, livestock industries and governments need a deeper understanding of the nutrient distribution across the edible parts of the animal. This case study examined the nutrient distribution across food products (carcase and co-products (edible offal and slaughter fat)) derived from a typical Australian lamb, using modelling with secondary data. Due to data gaps, some edible offal products were not able to be incorporated into the model (blood, trachea, omasum, abomasum, intestines, feet/tendons and head meat). Co-products accounted for approximately 24% of total edible product (i.e., carcase and co-product) by weight, 18% of the total protein and 37% of the total fat. With regards to micronutrients, the co-products contained 42% of the total iron content and the liver had more vitamin A, folate and vitamin B12 than the carcase and other co-products combined. This case study highlighted the nutritional value of co-products, especially liver, in the context of the whole animal and, the importance of including co-products in assessments of animal production systems.

The One Health concept explicitly acknowledges that the well-being of humans, animals and environments are linked. These relationships are complex and dynamic, evolving through time. Temporal perspectives also frame biological evolution and contextualise changes in our knowledge base and disease mitigation measures.

Socio-economic, environmental and ecological factors have repeatedly been shown to drive emerging infectious disease risk. However, these factors remain largely excluded from surveillance, warning and response systems. Similarly, even though hazards’ impacts are vastly interconnected (e.g. climate change, flooding, droughts, tropical cyclones, heatwaves, water-borne and vector-borne diseases), warning systems tend to act and work in silos. The disconnect among sectors, disaster risk reduction and health preparedness leads to reactive systems that wait for a disaster to occur before issuing a response.

There are multiple challenges concerning food security and sustainability that a One Health perspective can help tackle. We propose that the community focus on the following three shared by the 100 questions initiative (https://the100questions.org/) which they kindly proposed we publish on their behalf:

In the aftermath of the SARS-CoV-2 pandemic, and in due course for a full recovery to reduce the health burden and complications of the disease, the public discussion has moved from a pandemic slowdown to a more monitoring-based approach in public health. Stay-at-home rules, quarantine requirements for the infected ones, along with local lockdowns and social distancing measures around the planet have shown how vulnerable could be the ties between one’s demographic origins, morbidity and mortality.

Tick-borne pathogens are a growing threat with increasing negative impact on species diversity, food security and human health. Ticks, as a group, are second only to mosquitoes as vectors of pathogens to humans and are the primary vector for pathogens of livestock, companion animals, and wildlife (Mansfield et al., 2017). There are many tick species in Europe that carry human pathogens, and there are many more in North and South America and Asia. Changes in climate and land usage are leading to changes in the tick populations and therefore pathogen spread (Gandy et al., 2023).1 To mitigate the impact of these tick-borne pathogens, we need to better understand the complex relationships between vector, pathogen and host. Disease management approaches (including preventative measures and treatment protocols) vary significantly from country to country, partly due to resource challenges, but also due to knowledge siloes. Testing and treatment protocols for many tick-borne diseases are an acknowledged area of research need, and there is a growing patient, political and clinical voice calling for improvement. Effective multidisciplinary and international collaboration has the potential to yield significant improvements in scientific understanding, disease management and treatment strategies.