From bats to humans: the social, ecological and biological dynamics of pathogen spillover

Newly-emerging infectious diseases pose a great challenge to human and animal health. Most new diseases, such as SARS and HIV-AIDS, originate from wild animals and it is predicted that many more new diseases will emerge from wildlife in the future. In particular, a series of highly virulent RNA (or ribonucleic acid) virus diseases of humans and domestic animals has emerged in the last 15 years from bats. These include SARS, Hendra virus and Nipah virus. Also, Ebola and Marburg fatal haemorrhagic fevers are now known to be caused by RNA viruses from bats.
It is not yet understood why so many new and important diseases of humans have their origins in
bats or how these diseases ?spill over? from bats into people, but there are many potential opportunities for these disease spillover events to occur. Examples include people sharing food sources with bats, the hunting and eating of bats and bats living in close proximity with people, either within the structures of houses or as massive populations roosting in cities. Also, indirect transmission can occur, whereby bat viruses infect other animals which, in turn, then infect people. In this Catalyst Grant Proposal, we aim to build relationships between researchers to understand the complex interactions between RNA viruses, their bat hosts and humans, in order to find out what causes bat viruses to spill over into people and how this can be prevented. We also aim to understand how people perceive bats and the diseases caught from them and how these diseases are diagnosed by the medical profession in different countries. This improved knowledge and diagnosis will reduce the public health risks.
This catalyst proposal will be used to create an interdisciplinary team of international experts to investigate virus transmission between bats and humans. We will review current discipline-specific literature and plan a comprehensive, holistic programme of research that addresses the complex and interwoven facets of virus spillover from bats to humans. Reviews will be written on the factors underlying infection spillover, incorporating ecological, medical, social and environmental perspectives and how changing environments and livelihoods lead to new kinds of bat-human interactions. A final workshop will be used to develop a structure for a research consortium proposal: the specific research questions and the scientific approaches needed to explore bat-to-human viral transmission will be decided and practical details, such as management structure, communication strategies and user engagement, will be addressed.

Bats are increasingly being recognised as reservoir hosts for significant human pathogens: within the past 15 years, bats have been identified as the source of Hendra, Nipah, SARS, Ebola and Marburg viruses, amongst others, all of which are RNA viruses and all of which cause incurable diseases in humans with high case fatality rates. Bats also are the reservoir hosts of lyssaviruses, the rabies family of viruses, which are also zoonotic RNA viruses. In addition to being responsible for sporadic, but frequent, fatal human disease outbreaks on an annual or semi-annual basis, there is some evidence of bat RNA virus adaptations to the human host; in particular, henipaviruses have been highlighted as a possible future pandemic threat to public health. Although progress has been made on diagnostic techniques and on identifying the source wildlife species and populations of these viruses, the factors driving or facilitating zoonotic emergence, including bat to human transmission, are little understood. These factors are likely to be multiple, interrelated and complex, involving aspects of pathogen biology, host ecology and human behaviour. The catalyst grant will explore this multifaceted complexity through four key questions: the transmission dynamics of RNA viruses in identified bat populations; the population dynamics and behaviours of these bats; the dynamics of infection spillover from bats to humans and the dynamics of medical diagnosis and response. This investigation is necessarily multi-disciplinary and is divided into two phases. The first involves a review of the literature and the identification of missing disciplines and collaborators needed to build an integrative conceptual framework linking environmental and social dimensions with the modelling of infection dynamics. The second phase involves jointly-written literature reviews and critiques, preparatory work on new theoretical research questions and consultations with end-users in order to develop a comprehensive and holistic research consortium proposal. We will, therefore, use this catalyst grant to build a world-class multidisciplinary consortium of scientists, integrating pre-existing and new research activities in West Africa, South Asia and Australia, to develop a strong interdisciplinary research programme to investigate bat-human pathogen dynamics. This newly-formed consortium will be well positioned to advance the intellectual boundaries of current thinking on wildlife-to-human virus transmission by asking new theoretical, multi-disciplinary questions that more closely address social, environmental and medical interrelationships and complex realities.