If the relationship between climate and animal disease could be described as a journey: it would be a long and arduous one filled with unexpected twists and turns. Global climate change is one such twist that has the potential to totally alter our existing frames of understanding. Diseases are emerging in geographies where they were previously unknown – other diseases are re-emerging among populations where they were long ago extant. Historical geographic divisions between tropic and temperate diseases have in some cases become so diffuse as to be irrelevant.
Disease, however, is not a static entity and change is implicit to its very nature. However, it is apparent that the animal health landscape is dramatically and, some would argue, irreversibly altering. It is largely agreed that such alterations are not because of random variation or the presence of existing drivers alone: climate change is now considered a key accelerant. However, therein the problem lies. Climate is only one variable among many that are known to alter disease states. Indeed, emerging and re-emerging diseases have been linked to land use change, urbanization, deforestation and human, livestock and wildlife migration. The rapid globalization of the livestock trade driven by the demands of a vast and emerging population of consumers is frequently pointed to as the underlying reason for the global rise in livestock production and subsequently disease, including zoonoses. From the outset, we know that all drivers are not equal with regard to emerging and re-emerging diseases. However, crucially we are less clear of the exact role and impact of climate change across this dynamic.
The OECD predicts that with a ‘business as usual’ scenario for the global economy the average global temperature will raise by 3–6 °C by 2050. Clearly such a shift will accelerate the spread and intensity of some animal health threats while decreasing the spread and intensity of others. However, the core problem at the moment is the general disagreement over which diseases will fall into which camp. On a wider level, when faced with such shifting sands the question remains: will we cling to existing paradigms approaches and solutions or will we forge a ‘new normal’?
Therefore, in the following special issue, eight global experts have been asked to provide their opinion on research gaps across a range of issues important to the animal health sector. The initial focus was on those diseases with generally agreed climate effects: arboviral, parasitic and tick-borne diseases. Authors were given a free rein to discuss those issues they believed were of most importance to the wider debate and to identify or argue for those areas of research or practice they deemed most critical.
What emerged from this exercise is eight polemics exploring a wide range of issues from the need for better data to the expansion of One Health to a new paradigmatic framework to the better application of surveillance tools and gaps regarding future approaches/methodologies.
However, across the articles a number of common themes emerged. First, our level of certainty, or in this case uncertainty, regarding the impacts of climate change on disease should be the starting, rather than the end-point of analysis. Thus, we need to move past the polemical debate on causality. Second, solutions are required. As such, change must be embraced and practical tools created. But in answering the increasingly clarion call for urgent action, we must guard against easy answers, thereby allowing analytical and critical rigor to be left on the doorstep. Finally, while the devil is in the detail, such detail should disaggregate inter-relationships at the biological, agro-ecological, management and societal levels.
The issue begins with an article by Kock, which sets the macro-level scene for the interface between infectious disease and human behavior. Kock argues that the global food system based on free markets and globalization has opened Pandora's Box with regard to pathogen expansion on a global scale. He treats climate change as the penultimate insult to a global agro-ecological system in crisis and calls for the adoption of a wider and more integrated One Health socio-political agenda.
Alternately, Randolph notes that the wide-scale adoption of the ‘climate change’ meme as a key driver of infectious disease is obfuscating reality. On a wider level, she cautions that the loss of scientific scepticism will ultimately lead us down the road to bias. Randolph argues for a balanced view of climate change and disease via the lens of tick-borne diseases. However, she opens the possibility for a more nuanced understanding of disease dynamics, which makes a distinction between causal factors that expand distribution versus those which increase the incidence of a disease.
Conversely, Morgan, in relation to parasitic disease, begins from the supposition of the importance of climate change to disease emergence but drills down to the interplay between biology, management and the creation of decision-support tools. Morgan explores the gap between scientific expertise, research agendas and the low priority often accorded to the creation of practical control tools. On a wider level, he argues that current research metrics are biased toward quantitative, rather than applied inquiries, which will ultimately impact our ability to address emerging and re-emerging health threats.
In relation to arboviral disease, Baylis utilizes bluetongue as an example and explores a range of research gaps at the vector and host levels. Baylis argues that the paucity of data regarding vectors and the distribution of hosts will greatly impact our ability to correctly predict the risk of bluetongue and other vector-borne diseases. Baylis points out that our methods for predicting vector numbers are also problematic in accurately modeling disease emergence. The author proffers that a fundamental overhaul of arboviral disease research in which better cooperation or sharing of data is required. Equally, the increased training of taxonomists and greater investment in basic biological research on vectors would aid in addressing key gaps.
Addressing more downstream constraints in relation to animal health and climate change, Salman describes the range of issues currently impacting surveillance systems. Salman frames the article via the crucial distinction between surveillance versus monitoring. He argues that existing tools, which integrate climate and livestock disease data, can be better applied to underpin a more accurate epidemiological knowledge base. Broadening traditional surveillance to include climate data will ultimately aid mitigation and adaptation strategies.
Conversely, Heffernan describes a new approach to better understand the role and impact of climate change on animal health: climate change syndemics. In a call for a paradigm shift, she argues for a more integrated as opposed to holistic approach. Any such shift must begin from the premise that our confusion over the role of climate change on animal health is at its core, derived from a lack of knowledge regarding the inter-relationships and synergies between both causal factors and disease states themselves. In this manner, our reliance on existing approaches needs to be challenged and recalibrated in the context of climate change.
Gillette, in an exploration of the sustainability of pastoralist and subsistence farming systems, argues that sustainable agro-ecosystems bring direct and quantifiable benefits to public health. However, she notes that, under conditions of climate change, the savings derived from disease prevention at the ecosystems level are largely under-valued. Gillette explores the challenges involved in quantifying health savings and wider benefits of disease prevention from a sustainability and agro-ecosystems perspective.
In the final article, Wilkinson returns to the global food system and explores the interplay between food production, health and animal disease from the perspective of the field of Futures studies. Wilkinson recaptures the theme of critical assessment in the application of the modern Futures toolkit from foresight exercises to scenarios. As discourse is often the best predictor of action, she argues that it will be our world view or the narrative framing food, health and disease that will ultimately undermine or support our ability to confront future challenges.
As the editor of this special issue, the above contributors have made my job an easy one and I am grateful for the authors' insights and time.
