Animal’s social behaviour affects epidemics

When a virus or another parasite infects humans or animals, their behaviour influences whether and how an epidemic develops. But how does behaviour influence the emergence and evolution of epidemics? Jessica Stephenson at Stockholm University studies the dynamics between guppy fish and their parasites.

This year, eight prominent researchers who are appointed Wallenberg Academy Fellows were nominated by Stockholm University.

Jessica Stephenson, can you tell us more about your research?

– Host behaviour is the biggest gap in our understanding of infectious disease dynamics. The spread of parasites that cause infectious diseases depends on host behaviour, but how host social behaviour affects the size and structure of parasite populations is not well understood. This limits our ability to predict how host behaviour may drive parasite rapid evolution, which can change the course of epidemics dramatically. In particular, more social hosts theoretically drive the evolution of more ‘virulent’ parasites: those that kill hosts at a higher rate. However, during an outbreak, animals often ‘socially distance’, probably reducing parasite spread, and affecting parasite population size and structure. The magnitude of this host behavioural change may depend on parasite virulence (though this is untested). Host social behaviour and parasite virulence therefore likely interact via multiple pathways throughout epidemics.

– My research group aims to provide integrated theoretical and empirical tests of the dynamic interactions between host social behaviour, parasite transmission, and virulence evolution. Using a small fish – the guppy – and its parasites, we run experimental epidemics in host populations that differ in their social behaviour. Phenotypic and genomic data from these typically large-scale experiments, along with cutting-edge mathematical models, generate refined theoretical predictions that we test in natural Trinidadian stream communities. Using our experiment, model, and field sampling, we test how host social behaviour: 1) shapes the size and structure of parasite populations; 2) drives parasite virulence evolution; 3) responds to an outbreak to slow its spread.

What do you hope to attain?

– Thanks to COVID-19, we have all just lived through a crash course in epidemiology. One of the key lessons to me was that it’s amazing how much we still don’t know, and how much of what we think we know is based on assumptions or theory alone. My planned research represents the first experimental tests of several long-held assumptions. It is also the first empirical consideration of how ecological context may affect virulence evolution. Given that spillover from wildlife is a key route for emerging infectious diseases in humans (see the current concern about bird flu!), and predation is ubiquitous in nature – this is an urgent knowledge gap.

In general, we hope to identify and evaluate general ecological and evolutionary mechanisms by which host social behaviour and parasite virulence interact across systems. If we are able to achieve this goal, our work will have substantial relevance for infectious disease management.

Which challenges do you face?

– My research is highly integrative, which requires a lot of collaboration with people across disciplines. Sometimes this brings communication challenges. Our experiments are large scale, long running, and very intense, which can put additional pressure on interpersonal relationships. We also have been recently struggling with the computational load of the videos of fish interacting, and processing them in a timely manner. But – too much data is a good problem to have!

What does receiving the Wallenberg Academy Fellows mean for you and your research?

– It is very exciting that we have the opportunity, thanks to the WAF program, to move to Sweden. While the move itself will be challenging – especially with two small children and hundreds of fish – we are excited about the new research environment, with more focus on ecology and evolutionary biology.

Why did you choose Sweden, Stockholm and Stockholm University?

– The facilities and intellectual environment make the Department of Zoology and Stockholm University the ideal place for me to develop a world-leading research program. I have appreciated being part of a large, interdisciplinary faculty at the University of Pittsburgh, but am ready for the change! In Stockholm, my research group will benefit from daily interactions with others working at the interface of evolutionary and behavioural ecology, especially those already using the guppy, Poecilia reticulata, system to address related questions. It also seems like a really exciting time for Swedish research, particularly in Stockholm, with the SciLifeLab and Data Driven Life Sciences programmes – particularly the focus on epidemiology.

What advantages are there of being a researcher at Stockholm University?

– My research explores questions at the interface of ecology, evolution and behaviour. I will therefore synthesize and be supported by the three main research strengths of the Department of Zoology. My work on experimental evolution and guppy behaviour clearly complements, and will benefit hugely from, current work in the Department using this system, and my expertise in disease evolutionary ecology, specifically in fish, brings exciting extra dimensions to the research of many existing faculty. Indeed, I am already actively collaborating within the department (with Prof. Niclas Kolm), investigating how host traits affect disease parameters and impact epidemics. Other themes of my research would benefit from collaboration with other researchers in the department, such as: how the evolution of host sexual traits affects within-host responses to parasites, and between-host transmission-relevant behavior; the effect of parasite hybridization on within-host evolution and between-host transmission; and how host behavior structures parasite population genetics. As well as within the Department of Zoology, I can see potential for other synergistic collaborations in the Biology section more broadly.

To the website >>