Improving projections for the future of bluetongue and its vectors under scenarios of climate and environmental change

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Bluetongue (BT) is a vector-borne disease of ruminants which, since 1998, has caused the deaths of millions of head of livestock in Europe. BT's emergence has been linked to climate change: first, by demonstrating overlap between the disease and regions of greatest warming; and second, by driving a model of BT's basic reproduction number (a measure of outbreak risk following viral introduction) with observed climate and successfully capturing many aspects of the disease's emergence.

While climate change is implicated in BT's past, we lack a framework for investigating the disease's future. The aim of this project is to integrate a newly developed BT transmission model (which is spatially explicit, has infection spread by recorded animal movements and vector dispersal, incorporates control measures and is climate-sensitive) with state-of-the-art climate-model projections of the future. We will then investigate disease dynamics in future years (to 2050), and the efficacy of control measures under conditions of future climate.

Non-climate drivers (environmental, demographic, husbandry etc) may also impact on BT over similar timescales. We will solicit expert opinion about these drivers and how they may change in future, and we will then consider future scenarios for non-climate drivers within our modelling system.

Models of the future are always uncertain. We will address the question of whether the larger uncertainty in our model arises from uncertainty in the disease model or from the uncertainty about our future climate.

Finally, we will reduce uncertainty in our disease model by field study of key aspects of vector biology. We will trap vectors at 144 farms across England and Wales in order to map them; develop climate-driven models for their density; and undertake detailed studies on a subset of farms to record data on vector biting rates, mortality rates and feeding preferences.

The future impact of climate change on health is of major interest to certain Government departments and national and international organisations, given their roles in horizon scanning and policy development for adaptation/mitigation of climate change impacts. BT does not affect directly human health but it is a threat to food security, and it is perceived as a prime example of how climate change might affect vector-borne diseases, both human and animal, in the future. Hence, interest in our work is not limited to veterinary and farming professionals. This is exemplified by some of the organisations which in recent years have commissioned inputs from us on BT, on climate change and disease, or on the spread of vector-borne diseases: the UK government's Foresight programme (2005), the UK's Health Protection Agency (2010), the World Bank (2011) and the US Department of Defense (2011) as well as non-governmental organisations (the Smith School of Enterprise and the Environment, Catholic Overseas Development Agency, Humanitarian Futures Programme). We have also recently (September 2011) received funding from industry (Horse Race Betting Levy Board, £130,000 over 4 years) to train a veterinary resident in the epidemiology of a closely related disease to BT called African horse sickness (AHS), including adaptation of our basic farm-to-farm transmission model for this disease.
These or equivalent organisations will benefit from the proposed work, as per academics, in terms of understanding, methods and application. Understanding - by adding to the evidence-base that climate change and non-climate drivers can affect diseases. Methods - by providing a tool for quantitative assessment of climate change's future impact on a vector-borne disease, as well as the role of non-climate disease drivers. Application - by providing projections for the future of BT, along with the uncertainty surrounding the projections, under future conditions of climate and environment, and with the ability to investigate control options.
We therefore envisage the outputs of the proposal to be useful to a range of organisations in terms of preparedness for future vector-borne disease incidence and control. Hence, we intend that it will contribute in terms of enhancing the effectiveness of policy formulation, and to enhancing quality of life.