This grant will support a three-day workshop to take a broad overview of the field of infectious disease ecology and assess where the field will be headed in the next 5 to 10 years. The field of infectious disease ecology is relatively young. Although there is identifiable research that extends back at least several decades, it is only in the past 10 to 15 years that there has been a surge in interest with new journals being established and a large increase in research. Now is an appropriate time for such an overview assessment. Issues to be explored include: methodological developments over the past 10 years, limitations in accomplishments over that time, what new tools and disciplines are needed, and how these might allow greater insights into disease dynamics and control in a changing world.
Improving our knowledge of infectious disease ecology has important implications for public health, agro-economics, and the management of wildlife and natural systems. The workshop will assess previous successes in these issues and identify novel approaches and interdisciplinary insights that could build on our understanding of disease dynamics and be improved means of predicting, preventing and intervening with disease outbreaks.
Frontiers in Infectious Disease Ecology: This grant provided funds to run a small meeting in Washington DC to consider the state of research in infectious disease in the context of an ecological approach. The plan was to review the current state of the field and see ways that the ecological approach could assist our understanding and control of new and emerging infections. Historically, the study of Infectious diseases has been considered a clinical discipline, the purview of medical and veterinary sciences with the major academic societies and Universities having their infectious disease Departments embedded within their Medical School. This has resulted in clinically orientated studies that focus on the treatment of an individual’s disease symptoms rather than considering the issues of disease spread and control. The fresh approach that ecology brings to the discipline and the driving need to make this more interdisciplinary has helped greatly although there is still much more that can be done. There were particular concerns that host taxonomy has determined too much of the approach and a move to bridge these disciplinary and taxonomic gaps could lead to novel insights and important synergistic advances in the control of infectious disease. A comparative approach, agnostic to the origin of the host, that focused attention on the fundamental ecological and evolutionary processes that are inherent to a pathogenic lifestyle, e.g. transmission, host immune defenses, the role of virulence, community interactions, would provide promising new conceptual and technical insights. The ecological approach to studying the dynamics of infectious disease arose from a synthesis of population dynamics and the biology of infection. The objective was to capture the important biological features of the host-pathogen interaction, particularly the non-linear dynamics that shape the spatio-temporal spread of infection and then to identify the most effective intervention techniques. The intriguing aspect of the parasite-host interactions are that they are intimate such that changes in one have consequences for the other. When an infectious host develops immunity the host effectively becomes dead habitat for further infection colonization although the host continues to produce offspring, which of course provide new susceptible habitat for the infection to invade. Ecologically the dynamics are akin to a predator-prey system where the infectious hosts effectively hunt down the susceptible hosts so generating instability and producing the classical epidemiological outbreak scenario. Critical within this is the fact that not all hosts are the same - there is increasing evidence of very large variation between hosts in their susceptibility and infectiousness that can have dramatic influences on the likelihood of an infection becoming established and spreading. Early studies on HIV identified that variation in sexual partner exchange and HIV transmission explained the rapid rise of HIV in sub Saharan Africa. In a similar way the spread of SARS in the populations of Hong Kong and Singapore was influenced by a very small proportion of individuals, essentially responsible for the majority of transmission events. For the future we need to understand more about what determines the role of the individual host in these processes and targeting of intervention mechanisms could help greatly. So while a basic ecological concept has become fundamental to epidemiology and has helped us quantify the impact of various control measures, it is apparent that this is an integral of the birth and death processes of infection. If we wish to obtain a better understanding of disease dynamics we need to deconstruct the processes of transmission and get to grips with the drivers of heterogeneity. There are other aspects of ecology that have an intriguing bearing on our understanding of infectious disease biology. Ecology is not just about the distribution and abundance of species but also about their biotic and abiotic interactions and how any one species is embedded within that community structure. One intriguing question that has arisen over the past 20 years is how the structure of the community and in particular the diversity of species available for a host species can reduce the risk of spillover from a wild host species to humans? Overall there is evidence to suppose that high biodiversity results in reduced transmission of infection to humans, particularly with vector borne infections because the vectors tend to be catholic in their tastes and will bite hosts that do not amplify the viruses and in so doing these are considered "wasted bites" and the biodiversity acts to reduce the likelihood of onward transmission. In reality the presence or absence of a specific species can make all the difference.
