Zoonotic diseases: who gets sick, and why? Explorations from Africa

Countering Zoonotic Diseases: Current Scenario and Advances in Diagnostics, Monitoring, Prophylaxis and Therapeutic Strategies

Human life and health have interacted reciprocally with the surrounding environment and animal fauna for ages. This relationship is evident in developing nations, where human life depends more on the animal population for food, transportation, clothing, draft power, and fuel sources, among others. This inseparable link is a potent source of public health issues, especially in outbreaks of zoonotic diseases transmitted from animals to humans. Zoonotic diseases are referred to as diseases that are naturally transmitted between vertebrate animals and humans. Among the globally emerging diseases in the last decade, 75% are of animal origin, most of which are life-threatening. Since most of them are caused by potent new pathogens capable of long-distance transmission, the impact is widespread and has serious public health and economic consequences. Various other factors also contribute to the transmission, spread, and outbreak of zoonotic diseases, among which industrialization-led globalization followed by ecological disruption and climate change play a critical role. In this regard, all the possible strategies, including advances in rapid and confirmatory disease diagnosis and surveillance/monitoring, immunization/vaccination, therapeutic approaches, appropriate prevention and control measures to be adapted, and awareness programs, need to be adopted collaboratively among different health sectors in medical, veterinary, and concerned departments to implement the necessary interventions for the effective restriction, minimization, and timely control of zoonotic threats. The present review focuses on the current scenario of zoonotic diseases and their counteracting approaches to safeguard their health impact on humans.

Understanding the roles of economy and society in the relative risks of zoonosis emergence from livestock

The emergence of zoonotic infections that can develop into pathogens of pandemic potential is a major concern for public health. The risks of emergence and transmission relate to multiple factors that range from land use to human-non-human animal contacts. Livestock agriculture plays a potentially significant role in those risks, shaping landscapes and providing hosts that can act as the source or amplifiers of emergent pathogens. The relative risks will be contingent upon the nature of those systems, with comparisons often made between intensive, indoor, biosecure systems and more extensive, outdoor, insecure systems. Microbiological, ecological and veterinary sciences provide useful entry points in specifying and modelling some of the relative risks. Yet, they often do so with little regard for social science inputs and by making assumptions about social and economic conditions. In this article, we respond to recent analyses of relative risks by raising the importance of social and economic drivers of risk. We chart social science insights and research that materially alter the zoonotic risks associated with livestock production. Our purpose is to emphasize the requirement for full appreciation of the social, economic and political components of zoonotic and pandemic risk.

It Was Not the Perfect Storm: The Social History of the HIV-2 Virus in Guinea-Bissau

The perfect storm model that was elaborated for the HIV-1M pandemic has also been used to explain the emergence of HIV-2, a second human immunodeficiency virus-acquired immunodeficiency syndrome (HIV-AIDS) that became an epidemic in Guinea-Bissau, West Africa. The use of this model creates epidemiological generalizations, ecological oversimplifications and historical misunderstandings as its assumptions-an urban center with explosive population growth, a high level of commercial sex and a surge in STDs, a network of mechanical transport and country-wide, en masse mobile campaigns-are absent from the historical record. This model fails to explain how the HIV-2 epidemic actually came about. This is the first study to conduct an exhaustive examination of sociohistorical contextual developments and align them with environmental, virological and epidemiological data. The interdisciplinary dialogue indicates that the emergence of the HIV-2 epidemic piggybacked on local sociopolitical transformations. The war's indirect effects on ecological relations, mobility and sociability were acute in rural areas and are a key to the HIV-2 epidemic. This setting had the natural host of the virus, the population numbers, the mobility trends and the use of technology on a scale needed to foster viral adaptation and amplification. The present analysis suggests new reflections on the processes of zoonotic spillovers and disease emergence.

The role of social vulnerability in improving interventions for neglected zoonotic diseases: The example of Kyasanur Forest Disease in India

Forest-based communities manage many risks to health and socio-economic welfare including the increasing threat of emerging zoonoses that are expected to disproportionately affect poor and marginalised groups, and further impair their precarious livelihoods, particularly in Low-and-Middle Income (LMIC) settings. Yet, there is a relative dearth of empirical research on the vulnerability and adaptation pathways of poor and marginalised groups facing emerging zoonoses. Drawing on a survey of 229 households and a series of key-informant interviews in the Western Ghats, we examine the factors affecting vulnerability of smallholder and tribal households to Kyasanur Forest Disease (KFD), an often-fatal tick-borne viral haemorrhagic fever endemic in south India. Specifically, we investigate how different socio-demographic and institutional factors interact to shape KFD vulnerability and the strategies employed by households to adapt to disease consequences. Although surveyed households generally perceived KFD as an important health issue in the study region, there was variability in concern about contracting the disease. Overall results showed that poor access to land (AOR = 0.373, 95% CI: 0.152-0.916), being at or below the poverty line (AOR = 0.253, 95% CI: 0.094-0.685) and being headed by an older person (AOR = 1.038, 95% CI: 1.006-1.071) were all significant determinants of perceived KFD vulnerability. Furthermore, KFD vulnerability is also modulated by important extra-household factors including proximity to private hospitals (AOR = 3.281, 95% CI: 1.220-8.820), main roads (AOR = 2.144, 95% CI: 1.215-3.783) and study location (AOR = 0.226, 95% CI: 0.690-0.743). Our findings highlight how homogenous characterisation of smallholder and tribal communities and the 'techno-oriented' approach of existing interventions may further marginalise the most vulnerable and exacerbate existing inequalities. These findings are important for designing context-specific and appropriate health interventions (including the prioritisation of awareness raising, knowledge networks, livelihood diversification) that enhances the resilience of at-risk social groups within the KFD context. More broadly, our findings highlight how a focus on social vulnerability can help national and international health planners improve health interventions and prioritise among diseases with respect to neglected endemic zoonoses.

Understanding Factors that Shape Exposure to Zoonotic and Food-Borne Diseases Across Wild Meat Trade Chains

The rise of zoonotic disease-related public health crises has sparked calls for policy action, including calls to close wildlife markets. Yet, these calls often reflect limited understanding of where, precisely, exposure to risk occurs along wildlife and wild meat trade chains. They also threaten to negatively impact food security and livelihoods. From a public health perspective, it is important to understand the practices that shape food safety all along the trade chain, resulting in meat that is either safe to eat or managed as a potential vector of pathogens. This article uses ethnographic methods to examine the steps that lead a wild animal from the forest to the plate of an urban consumer in Yangambi and Kisangani in the Democratic Republic of Congo (DRC). Focusing on hunters, village-level consumers, transporters, market traders and urban consumers, we highlight specific practices that expose different actors involved in the trade chain to wild meat related health risks, including exposure to food borne illnesses from contaminated meat and zoonotic pathogens through direct contact with wild animals, and the local practices in place to reduce the same. We discuss interventions that could help prevent and mitigate zoonotic and food borne disease risks associated with wild meat trade chains.

Is There Always a Negative Causality between Human Health and Environmental Degradation? Current Evidence from Rural China

This study explores the incidence and trend of zoonoses in China and its relationship with environmental health and proposes suggestions for promoting the long-term sustainable development of human, animal, and environmental systems. The incidence of malaria was selected as the dependent variable, and the consumption of agricultural diesel oil and pesticides and investment in lavatory sanitation improvement in rural areas were selected as independent variables according to the characteristics of nonpoint source pollution and domestic pollution in China's rural areas. By employing a fixed effects regression model, the results indicated that the use of pesticides was negatively associated with the incidence of malaria, continuous investment in rural toilet improvement, and an increase in economic income can play a positive role in the prevention and control of malaria incidence. Guided by the theory of One Health, this study verifies human, animal, and environmental health as a combination of mutual restriction and influence, discusses the complex causal relationship among the three, and provides evidence for sustainable development and integrated governance.

Vulnerability and One Health assessment approaches for infectious threats from a social science perspective: a systematic scoping review

Vulnerability assessments identify vulnerable groups and can promote effective community engagement in responding to and mitigating destabilising events. This scoping review maps assessments for local-level vulnerabilities in the context of infectious threats. We searched various databases for articles written between 1978 and 2019. Eligible documents assessed local-level vulnerability, focusing on infectious threats and antimicrobial resistance. Since few studies provided this dual focus, we included tools from climate change and disaster risk reduction literature that engaged the community in the assessment. We considered studies using a One Health approach as essential for identifying vulnerability risk factors for zoonotic disease affecting humans. Of the 5390 records, we selected 36 articles for review. This scoping review fills a gap regarding vulnerability assessments by combining insights from various approaches: local-level understandings of vulnerability involving community perspectives; studies of social and ecological factors relevant to exposure; and integrated quantitative and qualitative methods that make generalisations based on direct observation. The findings inform the development of new tools to identify vulnerabilities and their relation to social and natural environments.

When might host heterogeneity drive the evolution of asymptomatic, pandemic coronaviruses?

Controlling many infectious diseases, including SARS-Coronavirus-2 (SARS-CoV-2), requires surveillance followed by isolation, contact-tracing and quarantining. These interventions often begin by identifying symptomatic individuals. However, actively removing pathogen strains causing symptomatic infections may inadvertently select for strains less likely to cause symptomatic infections. Moreover, a pathogen's fitness landscape is structured around a heterogeneous host pool; uneven surveillance efforts and distinct transmission risks across host classes can meaningfully alter selection pressures. Here, we explore this interplay between evolution caused by disease control efforts and the evolutionary consequences of host heterogeneity. Using an evolutionary epidemiology model parameterized for coronaviruses, we show that intense symptoms-driven disease control selects for asymptomatic strains, particularly when these efforts are applied unevenly across host groups. Under these conditions, increasing quarantine efforts have diverging effects. If isolation alone cannot eradicate, intensive quarantine efforts combined with uneven detections of asymptomatic infections (e.g., via neglect of some host classes) can favor the evolution of asymptomatic strains. We further show how, when intervention intensity depends on the prevalence of symptomatic infections, higher removal efforts (and isolating symptomatic cases in particular) more readily select for asymptomatic strains than when these efforts do not depend on prevalence. The selection pressures on pathogens caused by isolation and quarantining likely lie between the extremes of no intervention and thoroughly successful eradication. Thus, analyzing how different public health responses can select for asymptomatic pathogen strains is critical for identifying disease suppression efforts that can effectively manage emerging infectious diseases.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11071-022-07548-7.

Social insights on the implementation of One Health in zoonosis prevention and control: a scoping review

Background

The One Health (OH) concept has been promoted widely around the globe. OH framework is expected to be applied as an integrated approach to support addressing zoonotic diseases as a significant global health issue and to improve the efficiency and effectiveness of zoonosis prevention and control. This review is intended to overview the social impact of the implementation of OH on zoonosis prevention and control.

Methods

A scoping review of studies in the past 10 years was performed to overview the integration feature of OH in zoonosis prevention and control and the social impacts of OH. PubMed and Web of Science were searched for studies published in English between January 2011 and June 2021. The included studies were selected based on predefined criteria.

Results

Thirty-two studies were included in this review, and most of them adopted qualitative and semi-qualitative methods. More than 50% of the studies focused on zoonosis prevention and control. Most studies were conducted in low- and middle-income countries in Africa and Asia. Applying OH approach in diseases control integrates policymakers, stakeholders, and academics from various backgrounds. The impact of OH on economic is estimated that it may alleviate the burden of diseases and poverty in the long term, even though more financial support might be needed at the initial stage of OH implementation. OH implementation considers social and ecological factors related to zoonosis transmission and provides comprehensive strategies to assess and address related risks in different communities according to regions and customs.

Conclusions

Based on reviewed literature, although there seems to be a lack of guidelines for assessing and visualizing the outcomes of OH implementation, which may limit the large-scale adoption of it, evidence on the contributions of implementing OH concepts on zoonosis prevention and control indicates long-term benefits to society, including a better integration of politics, stakeholders and academics to improve their cooperation, a potential to address economic issues caused by zoonosis, and a comprehensive consideration on social determinants of health during zoonosis prevention and control.

Co-production of knowledge as part of a OneHealth approach to better control zoonotic diseases

There is increased global and national attention on the need for effective strategies to control zoonotic diseases. Quick, effective action is, however, hampered by poor evidence-bases and limited coordination between stakeholders from relevant sectors such as public and animal health, wildlife and forestry sectors at different scales, who may not usually work together. The OneHealth approach recognises the value of cross-sectoral evaluation of human, animal and environmental health questions in an integrated, holistic and transdisciplinary manner to reduce disease impacts and/or mitigate risks. Co-production of knowledge is also widely advocated to improve the quality and acceptability of decision-making across sectors and may be particularly important when it comes to zoonoses. This paper brings together OneHealth and knowledge co-production and reflects on lessons learned for future OneHealth co-production processes by describing a process implemented to understand spill-over and identify disease control and mitigation strategies for a zoonotic disease in Southern India (Kyasanur Forest Disease). The co-production process aimed to develop a joint decision-support tool with stakeholders, and we complemented our approach with a simple retrospective theory of change on researcher expectations of the system-level outcomes of the co-production process. Our results highlight that while co-production in OneHealth is a difficult and resource intensive process, requiring regular iterative adjustments and flexibility, the beneficial outcomes justify its adoption. A key future aim should be to improve and evaluate the degree of inter-sectoral collaboration required to achieve the aims of OneHealth. We conclude by providing guidelines based on our experience to help funders and decision-makers support future co-production processes.

Using Intersectionality to Identify Gendered Barriers to Health-Seeking for Febrile Illness in Agro-Pastoralist Settings in Tanzania

Background

Research has shown that gender is a significant determinant of health-seeking behavior around the world. Gender power relations and lay etiologies of illness can influence the distribution of household resources, including for healthcare. In some rural settings in Africa, gender intersects with multiple forms of health inequities, from proximal socio-cultural factors to more “upstream” or distal health system determinants which can amplify barriers to health-seeking for specific groups in specific contexts.

Aim

We used an intersectionality approach to determine how women in particular, experience gendered barriers to accessing healthcare among Maa and non-Maa speaking agro-pastoralists in northern Tanzania. We also explored lay etiologies of febrile illness, perceptions of health providers and rural health-seeking behavior in order to identify the most common barriers to accessing healthcare in these settings.

Methods

Mixed method ethnographic approaches were used to collect data between 2016 and 2018 from four Maa-speaking and two Swahili-speaking agro-pastoralist villages in northern Tanzania. Maa-speaking villages were based in Naiti, Monduli district while non-Maa speaking villages were selected from Msitu in Babati district. Data on health seeking behaviors was collected through semi-structured questionnaires, in-depth interviews, focus group discussions, and home and facility-based participant observation.

Findings

The results primarily focus on the qualitative outcomes of both studies. We found that febrile illness was locally categorized across a spectrum of severity ranging from normal and expected illness to serious illness that required hospital treatment. Remedial actions taken to treat febrile illness included attending local health facilities, obtaining medicines from drug sellers and use of herbal remedies. We found barriers to health-seeking played out at different scales, from the health system, community (inter-household decision making) and household (intra-household decision making). Gender-based barriers at the household had a profound effect on health-seeking. Younger married women delayed seeking healthcare the most, as they often had to negotiate health-seeking with husbands and extended family members, including co-wives and mothers-in-law who make the majority of health-related decisions.

Conclusion

An intersectional approach enabled us to gain a nuanced understanding of determinants of health-seeking behavior beyond the commonly assumed barriers such lack of public health infrastructure. We propose tapping into the potential of senior older women involved in local therapy-management groups, to explore gender-transformative approaches to health-seeking, including tackling gender-based barriers at the community level. While these social factors are important, ultimately, improving the public health infrastructure in these settings is a first step toward addressing structural determinants of treatment-seeking.

One Health Perspectives on New Emerging Viral Diseases in African Wild Great Apes

The most recent emerging infectious diseases originated in animals, mainly in wildlife reservoirs. Mutations and recombination events mediate pathogen jumps between host species. The close phylogenetic relationship between humans and non-human primates allows the transmission of pathogens between these species. These pathogens cause severe impacts on public health and impair the conservation of habituated or non-habituated wild-living apes. Constant exposure of great apes to human actions such as hunting, deforestation, the opening of roads, and tourism, for example, contributes to increased interaction between humans and great apes. In spite of several studies emphasizing the risks of pathogen transmission between animals and humans, outbreaks of the reverse transmission of infectious agents threatening wildlife still occur on the African continent. In this context, measures to prevent the emergence of new diseases and conservation of primate species must be based on the One Health concept; that is, they must also ensure the monitoring of the environment and involve political and social aspects. In this article, we review and discuss the anthropological aspects of the transmission of diseases between people and wild primates and discuss new anthropozoonotic diseases in great apes in Africa from studies published between 2016 and 2020. We conclude that the health of great apes also depends on monitoring the health of human populations that interact with these individuals.

Post-pandemic transformations: How and why COVID-19 requires us to rethink development

COVID-19 is proving to be the long awaited 'big one': a pandemic capable of bringing societies and economies to their knees. There is an urgent need to examine how COVID-19 - as a health and development crisis - unfolded the way it did it and to consider possibilities for post-pandemic transformations and for rethinking development more broadly. Drawing on over a decade of research on epidemics, we argue that the origins, unfolding and effects of the COVID-19 pandemic require analysis that addresses both structural political-economic conditions alongside far less ordered, 'unruly' processes reflecting complexity, uncertainty, contingency and context-specificity. This structural-unruly duality in the conditions and processes of pandemic emergence, progression and impact provides a lens to view three key challenge areas. The first is how scientific advice and evidence are used in policy, when conditions are rigidly 'locked in' to established power relations and yet so uncertain. Second is how economies function, with the COVID-19 crisis having revealed the limits of a conventional model of economic growth. The third concerns how new forms of politics can become the basis of reshaped citizen-state relations in confronting a pandemic, such as those around mutual solidarity and care. COVID-19 demonstrates that we face an uncertain future, where anticipation of and resilience to major shocks must become the core problematic of development studies and practice. Where mainstream approaches to development have been top down, rigid and orientated towards narrowly-defined economic goals, post-COVID-19 development must have a radically transformative, egalitarian and inclusive knowledge and politics at its core.

Distinct Molecular Mechanisms of Host Immune Response Modulation by Arenavirus NP and Z Proteins

Endemic to West Africa and South America, mammalian arenaviruses can cross the species barrier from their natural rodent hosts to humans, resulting in illnesses ranging from mild flu-like syndromes to severe and fatal haemorrhagic zoonoses. The increased frequency of outbreaks and associated high fatality rates of the most prevalent arenavirus, Lassa, in West African countries, highlights the significant risk to public health and to the socio-economic development of affected countries. The devastating impact of these viruses is further exacerbated by the lack of approved vaccines and effective treatments. Differential immune responses to arenavirus infections that can lead to either clearance or rapid, widespread and uncontrolled viral dissemination are modulated by the arenavirus multifunctional proteins, NP and Z. These two proteins control the antiviral response to infection by targeting multiple cellular pathways; and thus, represent attractive targets for antiviral development to counteract infection. The interplay between the host immune responses and viral replication is a key determinant of virus pathogenicity and disease outcome. In this review, we examine the current understanding of host immune defenses against arenavirus infections and summarise the host protein interactions of NP and Z and the mechanisms that govern immune evasion strategies.

Power, participation and their problems: A consideration of power dynamics in the use of participatory epidemiology for one health and zoonoses research

The use of Participatory Epidemiology in veterinary research intends to include livestock keepers and other local stakeholders in research processes and the development of solutions to animal health problems, including potentially zoonotic diseases. It can also be an attempt to bring some of the methods and insights of social science into a discipline largely shaped by natural science methods and ways of seeing the world. The introduction of participatory methodologies to veterinary epidemiology and disease surveillance follows a wider movement in development thinking, questioning the top-down nature of much post-second world war development efforts directed from the Global North towards the Global South. In the best cases, participatory methods can help to empower the poor and marginalised to participate in and have some control over research and interventions which affect them. Compiled from experience in multi-disciplinary One Health projects, this paper briefly traces the rise of participatory epidemiology before examining some of the limitations observed in its implementation and steps that might be taken to alleviate the problems observed. The three areas in which the operationalisation of Participatory Epidemiology in veterinary and One Health research could be improved are identified as: broadening the focus of engagement with communities beyond quantitative data extraction; taking note of the wider power structures in which research takes place, and questioning who speaks for a community when participatory methods are used. In particular, the focus falls on how researchers from different disciplines, including veterinary medicine and the social sciences, can work together to ensure that participatory epidemiology is employed in such a way that it improves the quality of life of both people and animals around the world.

Qualitative Research for One Health: From Methodological Principles to Impactful Applications

The One Health concept has inspired a rich vein of applied research and scholarly reflection over the past decade, yet with little influence from qualitative methodologists. With this overview, we describe the underpinning assumptions, purposes, and potential pitfalls of data collection techniques and methods of data analysis in key qualitative research methodologies. Our aim is to enhance One Health collaborations involving qualitative researchers, veterinary epidemiologists, and veterinary economists. There exist several distinct traditions of qualitative research, from which we draw selectively for illustrative purposes. Notwithstanding important distinctions, we emphasize commonalities and the potential for collaborative impact. The most important commonality is a shared focus on contextualizing human behavior and experience–culturally, economically, historically, and socially. We demonstrate that in-depth attention to context can assist veterinary economists and epidemiologists in drawing lessons from the implementation of policies and programs. In other words, qualitative researchers can assist One Health teams in distilling insights from “success stories,” but also from adverse events and unintended consequences. As a result, qualitative researchers can contribute to One Health research and policy discussions by formulating more accurate and contextually-relevant parameters for future quantitative studies. When performed well, qualitative methodologies can help veterinary economists and epidemiologists to develop impactful research questions, to create more accurate and contextually-relevant parameters for quantitative studies, and to develop policy recommendations and interventions that are attuned to the political and socio-cultural context of their implementation. In sketching out the properties and features of influential methodologies, we underscore the value of working with seasoned qualitative researchers to incorporate questions about “what,” “how,” and “why” in mixed-methods research designs.

EcoHealth and One Health: A theory-focused review in response to calls for convergence

BACKGROUND

EcoHealth and One Health are two major approaches broadly aimed at understanding the links between human, animal, and environment health. There have been increasing calls for convergence between the two. If convergence is desired, greater clarity regarding the underlying theoretical assumptions of both approaches is required. This would also support integrated research to effectively address complex health issues at the human, animal and environment interface. To better understand the areas of overlap and alignment, we systematically compared and contrasted the theoretical assumptions of both approaches.

OBJECTIVES

We aimed to gain a more in-depth understanding of the ontological, epistemological and methodological underpinnings of EcoHealth and One Health in order to identify areas of difference and overlap, and consider the extent to which closer convergence between the two may be possible.

METHODS

We undertook a scoping review of literature about the ontological, epistemological and methodological positions of EcoHealth and One Health, and analyzed these according to Lincoln, Lynham and Guba's paradigm framework.

RESULTS

EcoHealth and One Health are both collaborative, systems-focused approaches at the human, animal, and ecosystem health interface. EcoHealth typically leans towards constructivist-leaning assumptions. Many consider this a necessary aspiration for One Health. However, in practice One Health remains dominated by the veterinary and medical disciplines that emphasize positivist-leaning assumptions.

DISCUSSION

The aspirations of EcoHealth and One Health appear to overlap at the conceptual level, and may well warrant closer convergence. However, further shared discussions about their epistemological and ontological assumptions are needed to reconcile important theoretical differences, and to better guide scopes of practice. Critical realism may be a crucial theoretical meeting point. Systems thinking methods (with critical realist underpinnings), such as system dynamics modelling, are potentially useful methodologies for supporting convergent practice.

Vector-borne disease and climate change adaptation in African dryland social-ecological systems

BACKGROUND

Drylands, which are among the biosphere's most naturally limiting and environmentally variable ecosystems, constitute three-quarters of the African continent. As a result, environmental sustainability and human development along with vector-borne disease (VBD) control historically have been especially challenging in Africa, particularly in the sub-Saharan and Sahelian drylands. Here, the VBD burden, food insecurity, environmental degradation, and social vulnerability are particularly severe. Changing climate can exacerbate the legion of environmental health threats in Africa, the social dimensions of which are now part of the international development agenda. Accordingly, the need to better understand the dynamics and complex coupling of populations and environments as exemplified by drylands is increasingly recognized as critical to the design of more sustainable interventions.

MAIN BODY

This scoping review examines the challenge of vector-borne disease control in drylands with a focus on Africa, and the dramatic, ongoing environmental and social changes taking place. Dryland societies persisted and even flourished in the past despite changing climates, extreme and unpredictable weather, and marginal conditions for agriculture. Yet intrusive forces largely out of the control of traditional dryland societies, along with the negative impacts of globalization, have contributed to the erosion of dryland's cultural and natural resources. This has led to the loss of resilience underlying the adaptive capacity formerly widely exhibited among dryland societies. A growing body of evidence from studies of environmental and natural resource management demonstrates how, in light of dryland system's inherent complexity, these factors and top-down interventions can impede sustainable development and vector-borne disease control. Strengthening adaptive capacity through community-based, participatory methods that build on local knowledge and are tailored to local ecological conditions, hold the best promise of reversing current trends.

CONCLUSIONS

A significant opportunity exists to simultaneously address the increasing threat of vector-borne diseases and climate change through methods aimed at strengthening adaptive capacity. The integrative framework and methods based on social-ecological systems and resilience theory offers a novel set of tools that allow multiple threats and sources of vulnerability to be addressed in combination. Integration of recent advances in vector borne disease ecology and wider deployment of these tools could help reverse the negative social and environmental trends currently seen in African drylands.

Hemorrhagic Fever-Causing Arenaviruses: Lethal Pathogens and Potent Immune Suppressors

Hemorrhagic fevers (HF) resulting from pathogenic arenaviral infections have traditionally been neglected as tropical diseases primarily affecting African and South American regions. There are currently no FDA-approved vaccines for arenaviruses, and treatments have been limited to supportive therapy and use of non-specific nucleoside analogs, such as Ribavirin. Outbreaks of arenaviral infections have been limited to certain geographic areas that are endemic but known cases of exportation of arenaviruses from endemic regions and socioeconomic challenges for local control of rodent reservoirs raise serious concerns about the potential for larger outbreaks in the future. This review synthesizes current knowledge about arenaviral evolution, ecology, transmission patterns, life cycle, modulation of host immunity, disease pathogenesis, as well as discusses recent development of preventative and therapeutic pursuits against this group of deadly viral pathogens.

Local disease-ecosystem-livelihood dynamics: reflections from comparative case studies in Africa

This article explores the implications for human health of local interactions between disease, ecosystems and livelihoods. Five interdisciplinary case studies addressed zoonotic diseases in African settings: Rift Valley fever (RVF) in Kenya, human African trypanosomiasis in Zambia and Zimbabwe, Lassa fever in Sierra Leone and henipaviruses in Ghana. Each explored how ecological changes and human–ecosystem interactions affect pathogen dynamics and hence the likelihood of zoonotic spillover and transmission, and how socially differentiated peoples’ interactions with ecosystems and animals affect their exposure to disease. Cross-case analysis highlights how these dynamics vary by ecosystem type, across a range from humid forest to semi-arid savannah; the significance of interacting temporal and spatial scales; and the importance of mosaic and patch dynamics. Ecosystem interactions and services central to different people's livelihoods and well-being include pastoralism and agro-pastoralism, commercial and subsistence crop farming, hunting, collecting food, fuelwood and medicines, and cultural practices. There are synergies, but also tensions and trade-offs, between ecosystem changes that benefit livelihoods and affect disease. Understanding these can inform ‘One Health’ approaches towards managing ecosystems in ways that reduce disease risks and burdens.

This article is part of the themed issue ‘One Health for a changing world: zoonoses, ecosystems and human well-being’.

One Health for a changing world: new perspectives from Africa

The concept of One Health, which aims to drive improvements in human, animal and ecological health through an holistic approach, has been gaining increasing support and attention in recent years. While this concept has much appeal, there are few examples where it has been successfully put into practice. This Special Issue explores the challenges in African contexts, with papers looking at the complex interactions between ecosystems, diseases and poverty dynamics; at underlying social and political dimensions; at the potentials for integrative modelling; and at the changes in policy and practice required to realise a One Health approach. This introductory paper offers an overview of the 11 papers, coming from diverse disciplinary perspectives, that each explore how a One Health approach can work in a world of social, economic and environmental change.

Structural drivers of vulnerability to zoonotic disease in Africa

This paper argues that addressing the underlying structural drivers of disease vulnerability is essential for a ‘One Health’ approach to tackling zoonotic diseases in Africa. Through three case studies—trypanosomiasis in Zimbabwe, Ebola and Lassa fever in Sierra Leone and Rift Valley fever in Kenya—we show how political interests, commercial investments and conflict and securitization all generate patterns of vulnerability, reshaping the political ecology of disease landscapes, influencing traditional coping mechanisms and affecting health service provision and outbreak responses. A historical, political economy approach reveals patterns of ‘structural violence’ that reinforce inequalities and marginalization of certain groups, increasing disease risks. Addressing the politics of One Health requires analysing trade-offs and conflicts between interests and visions of the future. For all zoonotic diseases economic and political dimensions are ultimately critical and One Health approaches must engage with these factors, and not just end with an ‘anti-political’ focus on institutional and disciplinary collaboration.

This article is part of the themed issue ‘One Health for a changing world: zoonoses, ecosystems and human well-being’.

People, Patches, and Parasites: The Case of Trypanosomiasis in Zimbabwe

Understanding the socio-ecology of disease requires careful attention to the role of patches within disease landscapes. Such patches, and the interfaces between different socio-epidemiological systems, we argue, have important implications for disease control. We conducted an interdisciplinary study over three years to investigate the spatial dynamics of human and animal trypanosomiasis in the Zambezi valley, Zimbabwe. We used a habitat niche model to identify changes in suitable habitat for tsetse fly vectors over time, and this is related to local villagers' understandings of where flies are found. Fly trapping and blood DNA analysis of livestock highlighted the patchy distribution of both flies and trypanosome parasites. Through livelihoods analysis we explored who makes use of what areas of the landscape and when, identifying the social groups most at risk. We conclude with a discussion of the practical implications, including the need for an integrated 'One Health' approach involving targeted approaches to both vector control and surveillance.

One Health contributions towards more effective and equitable approaches to health in low- and middle-income countries

Emerging zoonoses with pandemic potential are a stated priority for the global health security agenda, but endemic zoonoses also have a major societal impact in low-resource settings. Although many endemic zoonoses can be treated, timely diagnosis and appropriate clinical management of human cases is often challenging. Preventive 'One Health' interventions, e.g. interventions in animal populations that generate human health benefits, may provide a useful approach to overcoming some of these challenges. Effective strategies, such as animal vaccination, already exist for the prevention, control and elimination of many endemic zoonoses, including rabies, and several livestock zoonoses (e.g. brucellosis, leptospirosis, Q fever) that are important causes of human febrile illness and livestock productivity losses in low- and middle-income countries. We make the case that, for these diseases, One Health interventions have the potential to be more effective and generate more equitable benefits for human health and livelihoods, particularly in rural areas, than approaches that rely exclusively on treatment of human cases. We hypothesize that applying One Health interventions to tackle these health challenges will help to build trust, community engagement and cross-sectoral collaboration, which will in turn strengthen the capacity of fragile health systems to respond to the threat of emerging zoonoses and other future health challenges. One Health interventions thus have the potential to align the ongoing needs of disadvantaged communities with the concerns of the broader global community, providing a pragmatic and equitable approach to meeting the global goals for sustainable development and supporting the global health security agenda.This article is part of the themed issue 'One Health for a changing world: zoonoses, ecosystems and human well-being'.

Integrative modelling for One Health: pattern, process and participation

This paper argues for an integrative modelling approach for understanding zoonoses disease dynamics, combining process, pattern and participatory models. Each type of modelling provides important insights, but all are limited. Combining these in a '3P' approach offers the opportunity for a productive conversation between modelling efforts, contributing to a 'One Health' agenda. The aim is not to come up with a composite model, but seek synergies between perspectives, encouraging cross-disciplinary interactions. We illustrate our argument with cases from Africa, and in particular from our work on Ebola virus and Lassa fever virus. Combining process-based compartmental models with macroecological data offers a spatial perspective on potential disease impacts. However, without insights from the ground, the 'black box' of transmission dynamics, so crucial to model assumptions, may not be fully understood. We show how participatory modelling and ethnographic research of Ebola and Lassa fever can reveal social roles, unsafe practices, mobility and movement and temporal changes in livelihoods. Together with longer-term dynamics of change in societies and ecologies, all can be important in explaining disease transmission, and provide important complementary insights to other modelling efforts. An integrative modelling approach therefore can offer help to improve disease control efforts and public health responses.This article is part of the themed issue 'One Health for a changing world: zoonoses, ecosystems and human well-being'.