Upcoming talk

“Livestock-dense habitat functions as an ecological trap for vampire bats: immunological evidence”
Daniel Becker
4 January 2016
Society for Integrative & Comparative Biology Annual Meeting
Oregon Convention Center
Portland, Oregon, USA

Urbanization and agriculture cause declines for many wildlife, but some species benefit from human-provided food. The abundance and predictability of these provisioned resources can affect wildlife behavior and physiology and in turn alter infectious disease dynamics. Specifically, host condition and immune defense responses to resource shifts are key to understanding whether provisioning amplifies or dampens pathogen transmission. We here tested relationships between provisioning, host condition, and immunity through a cross-sectional study of vampire bats (Desmodus rotundus) in Peru and Belize. This hematophagous species has potentially benefited from intensification of livestock rearing, which could reduce starvation stress and energy spent during foraging, allowing bats to invest more in immunity. We predicted that bats captured in sites of high livestock density would be in better body condition, display less chronic stress and inflammation, and have higher investment in humoral immunity. Contrary to this prediction, we found increasing livestock density was associated with poorer condition, greater levels of stress and inflammation, and lower IgG, and that these negative health impacts were more severe in reproductively active bats. We also found that although livestock intensification was associated with impaired bat health, capture success increased with livestock density. Together these results suggest livestock-dense habitats could function as ecological traps by producing source populations of immunologically impaired vampire bats. Increasing the relative abundance of such habitat could have profound impacts on bat susceptibility to zoonotic pathogens and the spatial spread of infections.



New paper

Are All Hosts Created Equal? Partitioning Host Species Contributions to Parasite Persistence in Multihost Communities

Building on our previous paper studying the different mechanisms through which different host species can arise as “key hosts” for parasite transmission, this new paper with Andy Fenton, Owen Petchy and Amy Pedersen creates a quantitative framework for partitioning R0 among many host species. This is a really exciting advance because we’re able to assess how robust estimates are to uncertainty in rates of cross-species versus within-species transmission and everything is estimated from fairly standard parasitological data. Applying this framework to my undergraduate dataset on gut parasites in small mammals confirms the existence of key hosts even for outwardly multi-host parasites (cryptic specialization) and shows in a hypothetical way, how different control measures could be more or less effective when targeting based on species specific values of R0.


Data for the paper are available here: http://dx.doi.org/10.5061/dryad.972mv

Abstract: Many parasites circulate endemically within communities of multiple host species. To understand disease persistence within these communities, it is essential to know the contribution each host species makes to parasite transmission and maintenance. However, quantifying those contributions is challenging. We present a conceptual framework for classifying multihost sharing, based on key thresholds for parasite persistence. We then develop a generalized technique to quantify each species’ contribution to parasite persistence, allowing natural systems to be located within the framework. We illustrate this approach using data on gastrointestinal parasites circulating within rodent communities and show that, although many parasites infect several host species, parasite persistence is often driven by just one host species. In some cases, however, parasites require multiple host species for maintenance. Our approach provides a quantitative method for differentiating these cases using minimal reliance on system-specific parameters, enabling informed decisions about parasite management within poorly understood multihost communities.  

Upcoming talks

“Impact of human-provided food resources on infectious disease dynamics”
Daniel Becker
8 July 2015
International Association of Landscape Ecology World Congress
Portland Hilton
Portland, Oregon, USA

“Heterogeneity in patch quality buffers metapopulations from pathogen impacts”
Daniel Becker
13 August 2015
Ecological Society of America Annual Meeting
Baltimore Convention Center
Baltimore, Maryland, USA

New paper

Complex effects of dietary provisioning on wildlife disease dynamics 

reacBecker, D., Streicker, D.G., & Altizer (2015) Linking anthropogenic resources to wildlife-pathogen dynamics: a review and meta-analysis. Ecology Letters. doi: 10.1111/ele.12428

Abstract: Urbanisation and agriculture cause declines for many wildlife, but some species benefit from novel resources, especially food, provided in human-dominated habitats. Resulting shifts in wildlife ecology can alter infectious disease dynamics and create opportunities for cross-species transmission, yet predicting host–pathogen responses to resource provisioning is challenging. Factors enhancing transmission, such as increased aggregation, could be offset by better host immunity due to improved nutrition. Here, we conduct a review and meta-analysis to show that food provisioning results in highly heterogeneous infection outcomes that depend on pathogen type and anthropogenic food source. We also find empirical support for behavioural and immune mechanisms through which human-provided resources alter host exposure and tolerance to pathogens. A review of recent theoretical models of resource provisioning and infection dynamics shows that changes in host contact rates and immunity produce strong non-linear responses in pathogen invasion and prevalence. By integrating results of our meta-analysis back into a theoretical framework, we find provisioning amplifies pathogen invasion under increased host aggregation and tolerance, but reduces transmission if provisioned food decreases dietary exposure to parasites. These results carry implications for wildlife disease management and highlight areas for future work, such as how resource shifts might affect virulence evolution.

Table 1. Representative study systems and evidence for different mechanisms that might drive relationships between food and disease.

New arrival!

Welcome to Victoria Estacio! Vicky has a BSc from Queen Mary University in London and worked previously at the Instituto Nacional de Salud in Lima, Peru. She will be helping with data management and sample processing for serology and sequencing

New arrivals!

Welcome to Julio Benavides! Julio is a new postdoc who will be working on viral dynamics at the interface of bats and livestock in Peru and will be thinking a lot about inferring meaningful epidemiological processes from messy, perhaps observation-biased, data. He may also slowly convince everyone that we should be working on gorillas in Congo instead. Very glad to have you on board!

Also a belated welcome to John Claxton, who started as International Projects Manager in December and is making fantastic progress towards overcoming the hurdles of international research coordination and legal agreements. John joins us from the European Commission.

Upcoming talks

“Too much of a good thing: supplemental feeding alters infectious disease dynamics in urban-foraging wildlife”

Daniel Becker
5 January 2015
Society for Integrative and Comparative Biology Annual Meeting
Palm Beach Convention Center
West Palm Beach, Florida, USA

“Heterogeneity in patch quality buffers metapopulations from pathogen impacts”

Daniel Becker
17 January 2015
Graduate Student Symposium
Odum School of Ecology
Athens, Georgia, USA