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)
Main collaborators: Julio Benavides (Glasgow), William Valderrama (RENACE), Carlos Shiva (UPCH), Nestor Falcon (UPCH), Katie Hampson (Glasgow)
Funding from: Wellcome Trust, Royal Society
2. Metagenomic tracking of pathogen transmission 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 pathogens. Work in collaboration with the MRC Centre for Virus Research is testing the hypothesis that vampire bats accumulate pathogens 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. We are also studying patterns of bacterial transmission between species, with a particular interest in how antimicrobial resistance moves between wildlife, domestic animals and humans.
Main collaborators: Laura Bergner (Glasgow), Richard Orton (Glasgow), Roman Biek (Glasgow), Pablo Murcia (Glasgow), Julio Benavides (Glasgow), Carlos Shiva (UPCH), Nestor Falcon (UPCH)
Funding from: Wellcome Trust, Royal Society, CONCYTEC
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.
Main collaborators: Mafalda Viana (Glasgow), Kader Behdenna (Glasgow), Vicky Estacio (Glasgow), Dan Becker (University of Georgia)
Funding from: Wellcome Trust, Royal Society, Leverhulme trust
4. Intervention strategies for vampire bat rabies
We want to understand how to improve control of vampire bat rabies within the bat reservoir. This means understanding why existing control efforts like culling have limited success for preventing rabies and considering whether alternatives such as oral vaccination could be more effective. Ongoing research on this topic is evaluating how large scale culling programs affect bat population dynamics, frequency of spillover infections to livestock and the spatial spread of rabies within vampire bats. Another project is using field experiments with biomarkers and mathematical models to evaluate how topically transmitted oral rabies vaccines could spread among bats by grooming and whether the herd immunity achieved would be enough to stop rabies outbreaks in bats, thereby protecting people.
Main collaborators: Julio Benavides (Glasgow), William Valderrama (RENACE), Kevin Bakker (University of Michigan), Tonie Rocke (USGS), Jorge Osorio (University of Wisconsin), Regional Government of Apurimac
Funding from: Royal Society Challenge Grants
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.
Main collaborators: Laura Bergner (Glasgow), Richard Orton (Glasgow), Roman Biek (Glasgow), Pablo Murcia (Glasgow)
Funding from: Wellcome Trust, Royal Society