EID prevention and control strategies require a One Health approach
One Health is a holistic approach that emphasizes, but is not restricted to, the need to understand and regulate the environmental context (human-animal-ecosystem interface) of disease emergence and expression [
21]. EIDs are characterized by their complexity and uncertainty as to their causes, consequences and likely solutions [
22]. In broad terms, the occurrence and cross-species transmissibility of many emerging pathogens, like Ebolavirus (EBOV) and H7N9, arise from human activities such as changes in land use, growth in global trade and travel and intensification of animal husbandry practices [
23‐
25]. The speed with which our understanding of the biology and epidemiology of H7N9 has developed demonstrates how much our ability to respond to new EID threats has improved over the last few decades. Yet despite advances in immunobiology and genomics that have contributed to diagnostics, therapeutics, and vaccine development, the threat of EIDs to human health and community wellbeing persists.
Part of the reason why EID threats remain in spite of scientific advances, are that EID events are not simply about pathogens jumping species barriers. The threats posed by EIDs are comprised of complex and contingent sets of relations that involve socioeconomic and socio-political drivers and consequences, with the latter extending beyond the impact of the disease. The social, cultural and economic impacts of zoonoses are significant. The examples contained in Tables
1 and
2 demonstrate the difficult balance between the human health risks and socioeconomic and cultural costs of EID control [
26,
27]. Policy decisions should be based on sound evidence – but it is often the case in dealing with EIDs that the evidence required is absent or fluid. EID events are often dynamic situations that are characterised by uncertainty. As events unfold new evidence is created. Consequently decisions made on the basis of present data can be seen as wrong in the future, as more evidence and a better understanding emerges.
Table 1
EIDs of immediate importance to Australasia
Hendra virus infection is endemic among at least two species of flying fox in Australia and causes rare, but catastrophic, human infection [ 85]. Loss of habitat has led to increasingly intense incursions of flying foxes into populated rural and peri-urban areas and promoted the ‘spill-over’ of Hendra virus into horses and then to people [ 86]. Hundreds of people have been directly exposed to Hendra virus, with seven confirmed human infections and four deaths since 1994. With over one hundred dead horses and persistent risk, the emergence of Hendra has had significant impact on equine and tourist industries in north eastern Australia, diverted major research resources and caused significant distress and controversy in the broader community [ 31, 87]. |
Nipah virus, a close relative of Hendra, is endemic in East Asian flying fox populations. In 1999, after a program of deforestation and agricultural development in Eastern Malaysia it spread to pigs then humans and other animals, causing respiratory disease and severe encephalitis [ 88]. It subsequently was reported in India and Bangladesh. Humans can be infected directly from bats, by ingestion of contaminated food and from other humans. Among 522 confirmed human cases, the overall mortality was greater than 50 % [ 89]. Nipah control programs devastated Malaysia’s pig industry and caused high unemployment and dislocation of rural populations, at a cost of more than US$1 billion to the national economy [ 90]. Nipah virus has been identified by WHO as a likely cause of future pandemics. |
Rabies virus infects the central nervous systems of people, wildlife and domestic mammals. The disease is transmitted by bites from infected animals and once it becomes symptomatic, it is virtually always fatal. 55,000 people die and 7.5 million receive post exposure prophylaxis annually, costing $124 billion [ 91]. Rabies is endemic in much of South East Asia but its range is expanding. Focusing on Australia, the continent is free from Rabies, but the current expansion of the disease in Indonesia [ 92] is a genuine threat to northern regions. Although likely controllable in domestic dog populations [ 93], if Rabies were to become endemic amongst wild or feral animals in this setting, current modelling indicates it would be almost impossible to eradicate [ 94]. |
Table 2
Significant historical (i.e. effectively eradicated) EIDs
Severe acute respiratory syndrome ( SARS) is a human respiratory infection, caused by a coronavirus isolated from Chinese horseshoe bats [ 95]. It was first reported in Asia in 2003 and, within a few months, spread to thirty seven countries in the Americas, Europe and Asia. It affected more than 8000 people and caused 774 deaths, before being successfully eliminated by concerted international efforts. The outbreak and fear that another pandemic could occur are estimated to have cost Canadian and east Asian economies US$200 billion [ 27]. |
Bovine spongiform encephalitis/variant Creutzfeldt Jacob disease ( BSE/vCJD) is a rare but fatal human neurodegenerative condition, caused by consumption of bovine products contaminated with the prions that cause BSE. Since vCJD was first identified in 1996, 175 cases have been reported in the UK and forty nine elsewhere. The World Bank estimates that the direct costs of vCJD/BSE to date exceed more than US $11 billion. Infected herds and the control measure imposed to prevent further infections devastated agricultural communities. The impacts of the emergence of a new zoonotic disease amongst the British public were far broader than agriculture, including the cessation of UK plasma production because of potential iatrogenic infection. With an estimated one in 4000 UK residents carrying vCJD, the burdens will continue well into this century [ 96]. |
Official reviews of canonical EID events such SARS [
17] and BSE/vCJD [
28] share two key findings: (i) that actions to reduce risk should not be predicated on scientific certainty; and (ii) that policies to deal with the risks and effects of an EID need to be founded on widely held values, so that people understand, in advance, the kinds of choices that will have to be made. This suggests that the One Health approach needs more than inter-sectoral collaboration and robust health legislation, as
the unique nature of EIDs critically limits the effectiveness of scientific, top-down and technocratic approaches to governance [
29].
Implementing a One Health approach faces socio-political, ethical and legal challenges
The success of One Health depends on more than scientific knowledge and technical achievement because some of the issues that arise in addressing EID risks are so-called ‘wicked problems’ [
30]. When a new EID threat emerges there are rarely ready-made solutions and health policymakers and practitioners are often forced to make tragic choices that may contravene widely held values. Considerations must include the need to protect public health and the wider social, economic and environmental impacts of proposed interventions. Economic and political interests can complicate the decision-makers’ motives and decision-maker uncertainty is compounded by policy decisions becoming entangled in political, ethical and legal considerations [
31‐
33]. As events surrounding the EBOV outbreak in West Africa illustrate, the importance placed on a specific EID threat at any one time also depends on who is setting the agenda [
34]. Therefore to be successfully implemented, the One Health approach must address a range of socio-political, ethical and legal challenges that arise as a consequence of the spread of infection within and between species. Most of these challenges are not unique to One Health, but are shared by any approach to addressing EIDs. However these challenges frequently go unrecognized. In the following section we will clarify the nature of these issues so they can be addressed later in the paper.
(1)
Socio-political challenges
A focus on individualism, perceptions, short term solutions, populism and avoiding controversy are features of political life, which can prove challenging for EID policy and work against developing effective strategies for addressing EIDs.
Policy responses to EID events such as Nipah and Hendra virus infections (outlined in Box 1) tend to focus on necessary and proximal causes (what individuals do to put themselves at direct risk from an infectious pathogen) because the science about other aspects of EIDs is often complex, uncertain and lacking a clear narrative. Compounding this, our moral psychologies have evolved to respond to direct harms – not indirect distal causal stories. Many people in liberal democracies believe that they are entitled to rights and freedoms that cannot be sacrificed merely for the marginal gains of others. As the discourse surrounding climate change and other wicked problems illustrates, this promotes technological solutions because they do not require substantive changes in human behaviours and underlying values systems. [
35] The net result is that the policy focus for EID prevention and control tends to remain on individual behaviours rather than the structural drivers of emergence and transmission – a case example being the focus on vaccine development and the husbandry practices of horse owners in response to the zoonotic risks of Hendra virus [
31,
36]..
The political impetus for action in response to many EIDs is not necessarily scientific evidence but societal perceptions. Indeed, in the face of scientific uncertainty and ethical ambiguity, ideological perspectives and short-term political considerations often supplant efforts to devise effective long-term interventions [
28,
37].
Political imperatives to avoid, or at least minimise, public concern whilst dealing with EIDs can also prove challenging. In the case of BSE, powerful interests dominated early government responses, leading policymakers to make decisions that avoided public controversy, but had major economic consequences. As the crisis unfolded, expertise became politicized leading to conflict between agencies and policy inconsistency between health communication strategies and the measures being taken to minimize the risks to human health [
38]. Even when the link between BSE and vCJD became clear, existing feed bans were poorly enforced and risk communication was dominated by fear of public panic [
39]; even as the decision was made to remove all potential sources of human infection from the UK food supply, messages were confused and policy implementation impeded by poor co-ordination between agencies [
28].
A common but problematic response to EID threats has been to invoke the precautionary principle. Roughly speaking, the precautionary principle can be applied in situations where human activities create a scientifically plausible, but uncertain, risk of significant harm. In response the principle advocates that actions ought to be taken to avoid or reduce the harm, and that these actions need to be proportionate to the seriousness of the potential harm. In other word, in the absence of evidence take a conservative approach.
However applying the precautionary principle to EIDs in an attempt to protect the public can result in what, in retrospect, amounts to an excessive response. This occurred with attempts to control Nipah infection, where significant damage was inflicted on industry, livelihoods and the economy. Similarly, experience with highly pathogenic avian influenza (HPAI) H5N1 in China and SE-Asia showed that overzealous policy responses can destroy livelihoods and threaten food supplies [
40,
41]. In Vietnam alone, almost 40 million birds were culled in 2004 in an attempt to eradicate HPAI. Although many birds were owned by large commercial operations, others were kept by ‘backyard’ farmers and villagers. Mass culling of poultry appears decisive, but places excessive burdens on vulnerable populations, is ineffective in the context of extensive ‘backyard’ poultry farming and can, in fact, promote the spread of disease [
42]. A similar scenario is currently playing out with Rabies control in Bali.
Unfortunately, the precautionary principle and analytic tools and concepts appealed to in this domain, fail to deliver what is required at times of EID outbreaks since they do not advance public engagement or help resolve disagreements in times of uncertainty [
43,
44]. Philosophical critiques of the precautionary principle applied to EIDs have also shown its limitations, including that defining criteria by which to judge a threat as
plausible and a response
proportionate, often will only substitute one uncertainty for two others [
45].
The effectiveness of an EID control policy will depend on the context of its implementation and particularly its alignment with stakeholder and public values [
17,
46]. In modern liberal democracies at least some consensus over what is in the public interest and an understanding of the values which support it, is therefore required for the successful implementation of EID responses. Yet this is precisely what has been lacking in outbreaks where fracture lines, differences and value conflicts have become apparent. When the stakes are high, evidence and the implications of actions are uncertain, the situation is complex and resources may be limited but where decisions need to be made, differences are exposed. Such differences could be around beliefs about how to deal with ecological and environmental issues, which may conflict with the importance people attach to public goods, protection of individual autonomy and animal welfare [
47]. These conditions of crisis and division are conducive to undesirable consequences including public fear, mistrust, misinformation and non-compliance with public health directives. For example in Canada during the SARS crisis, leaders were unprepared for the range of ethical conflicts that arose, including those over: individual freedom versus the common good; healthcare workers’ safety versus their duty to care for the sick; and economic costs versus the need for containment [
48]. As indicated in Box 2, both the outbreak itself and fear that another outbreak could occur had significant economic consequences.
Any approach which hopes to successfully respond to EID threats, including a One Health approach, needs to address the ethical concerns articulated above. To this end, potentially conflicting values and logic must be negotiated to realise effective, sustainable and just solutions. Prioritisation and resource allocation require political processes based on fundamental ethical questions about what is valuable, what is to be protected and, ultimately, what is dispensable. To be effective, public policy must be consistent with the values of citizens to whom it is applied, otherwise it can become mired in controversy about whose values should prevail [
31,
37,
49]. Therefore, one of the first and most important tasks of policy work is to establish how the public interest is best defined.
The legal environment in which EID policy is made and in which responses to outbreaks occur, presents its own set of challenges. The law surrounding EID responses in most jurisdictions is diffuse, complicated and often subject to re-interpretation on the basis of whose interests are given primacy at the time decisions are made. Moreover, in many countries different approaches by State/Provincial and local authorities, overlaid by Federal/National powers, complicate regulation so much that ‘hard law’ is often replaced by resort to ‘soft law’ of executive and administrative powers and international instruments, such as the International Health Regulations (IHR) [
50]. This may add complexity and confusion to the EID regulatory structures, rather than facilitating public health responses to a new threat. Such confusion provides a salient reminder that even in ‘global law’ approaches to EIDs, the sovereign state remains the institution responsible for regulation and control [
51].
Public health law responses to EIDs tend to be oriented towards controlling cross-border pathogen transfer and community outbreaks rather than the underlying deficiencies and structural conditions from which the threats emerge. Other laws, such as environmental law, may be more useful in addressing structural conditions for emergence. Changes in land use and agricultural intensification in developing societies are major drivers of EID. However, the cost of laws that restrict development may be greater global health inequities, with consequential effects for health outcomes. In order to clarify EID-related legal tensions between economic development and health security, a more explicit recognition is needed of who are the primary beneficiaries and who bears the costs of a One Health approach to EIDs [
52].
Legal clarity around the frameworks designed to protect populations from EIDs is critical to providing an enabling infrastructure to co-ordinate and support the One Health-based work of policymakers, development planners, human and animal health-workers and biosecurity agencies.