The Streicker Group
1. Spatial epidemiology, ecology and control of vampire bat rabies
Interventions to control infectious diseases of wildlife that affect human or domestic animal health often seek to control or eliminate the pathogen from its wildlife reservoir using culling or vaccination. While such efforts are intuitive in theory and offer the seductive possibility of a permanent solution, implementation is notoriously difficult and controversial. Poor understanding of what drives pathogen transmission in wildlife can even lead such interventions to be counterproductive for disease control.
In Latin America, vampire bat–transmitted rabies virus represents a key example of how such uncertainty can impede efforts to prevent cross-species transmission. Despite decades of bat culling programs, agricultural and human health losses remain surprisingly high. These limitations seem to arise from the more general problem of how to design control strategies for pathogens that persist through spatial processes in wild or free-ranging animal populations. In projects funded by the Wellcome Trust and Royal Society, we are combining longitudinal surveillance of vampire bat colonies, bat population genetics, viral genomics and epidemiological time series data to improve anticipation of outbreaks and develop a scientific basis for interventions.
This work has revealed key findings of relevance to control programs.
- Rabies exposures in bats are independent of colony sizes (Streicker et al. 2012 Proc Roy Soc B)
- Culling bats appears either ineffective or counter productive for rabies control (Streicker et al. 2012 Proc Roy Soc B)
- Persistence relies on high rates of bat dispersal and frequent immunizing infections (Blackwood et al. 2013 PNAS)
- For culling to have a chance at being effective, it must be spatially coordinated across large geographic scales (Blackwood et al. 2013 PNAS)
2. Metagenomic tracking of viral emergence between bats and livestock
Vampire bats are an unusually well connected species since they bite to feed on other mammals nightly and often live in large aggregations with other bat species. Thus they may serve as an ecological conduit for human and domestic animal infection by diverse viruses. Our work within the MRC Centre for Virus Research will test the hypothesis that vampire bats accumulate viruses from other species, making them potential conduits to emergence in livestock and humans. We will use metagenomic characterization of viral diversity (a.k.a. ‘viromes’) to test how bat species richness affects viral diversity in vampire bats and to identify shared pathogens between vampire bats and their livestock prey. By sampling other bat species, we will further test how ecological similarity, phylogenetic relatedness and geographic range overlap affect patterns of viral sharing between species. Finally, sentinel livestock are being installed to experimentally track rates of cross-species transmission.
3. Bat influenza
H17 and H18 influenza viruses were recently discovered in American bats; however, little is known of their geographic or host species distribution or their epidemiological or evolutionary dynamics. In Peru, we are combining serological analyses of samples collected over the past 7 years with phylogenetic analyses of contemporary samples collected from bats and bat caves (photo) to characterize basic epidemiological dynamics of influenzaviruses in Peruvian bats with particular interest in determining which host species may contribute to persistence within the bat community and using this as a model system to quantify cross-species transmission.
4. Vampire bat population genetics
Different genomes can provide different information depending on patterns of inheritance and rates of evolution. With colleagues at the University of Georgia (Dara Satterfield) and the Czech Academy of Sciences (Jamie Winternitz), we are taking a tri-genomic approach to uncovering how sex biased animal movement patterns can shape the geographic distribution and spatiotemporal dynamics of their directly transmitted pathogens. Applying this to a large dataset of hosts (bats) and their pathogen (rabies virus), we have shown that male biased dispersal seeds rabies outbreaks in genetically isolated female colonies. This allows viral persistence on the landscape level and therefore the risk of cross-species transmission to humans and livestock.
5. Virome networks as a tool for anticipating pathogen spread
Pathogens in wildlife often persist through spatial processes such as metapopulation dynamics or traveling waves of spread. Anticipating how emerging or endemic pathogens will spread through a network of hosts relies on understanding how subpopulations of hosts are connected on landscapes. Field approaches such as GPS tagging, mark-recapture and radiotelemetry are labor intensive and still cannot be used effectively in many host species. Genetics have also been used, but host markers suffer from lack of resolution, particularly for characterizing contemporary population structure. We are analyzing whether comparisons of viral genetic diversity inferred from metagenomic sequencing can provide a high-resolution host network that may predict the spread of important pathogens like rabies using samples from a series of vampire bat colonies in southern Peru.
- Managing viral emergence at the interface of bats and livestock, Wellcome Trust, £951,380 (2014-2019)
- Managing viral emergence at the interface of bats and livestock, Wellcome Trust, £25,000 (2014-2019)