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Parasite life cycles in changing environments: experimental and modelling approaches

  • Full or part time
    Dr Barber
  • Application Deadline
    Applications accepted all year round
  • Awaiting Funding Decision/Possible External Funding
    Awaiting Funding Decision/Possible External Funding

Project Description

Introduction: Environmental change has great potential to impact host-parasite interactions (HPIs), but we know remarkably little about how changing temperatures affect the prevalence of infections, or the ‘infection phenotypes’ of parasitized individuals. Developing a better and more predictive understanding of the consequences of environmental change for HPIs therefore represents a critically important challenge (Altizer et al. 2013 Science 341, 514-519). We recently showed that elevated temperatures dramatically change the HPIs of stickleback fish and their parasite Schistocephalus solidus, with larval parasites benefiting significantly in terms of growth and reproductive potential at the expense of hosts (Macnab & Barber 2012 Global Change Biology 18, 1540–48). However, since the lifecycle of S. solidus involves multiple hosts and developmental stages, extrapolating this finding to population level processes is not possible using lab experiments or field observations alone. Mathematical modelling presents a powerful and convenient tool for investigating such questions, permitting wide-ranging exploration of HP systems without unfeasible, large-scale field studies. In particular, mathematical models of stickleback-Schistocephalus HPIs – constructed using results from small-scale lab and mesocosm experiments – would allow us to explore population level responses (e.g. disease prevalence) in response to gradual temperature change. The model predictions could be further verified using existing field data on infection dynamics in natural stickleback populations.

Aims and objectives: The broad aim of the project is to develop understanding of the implications of climate change for patterns of disease in host populations. Specific objectives of the project are:
(1) To determine the temperature sensitivity of relevant life stages and processes in both parasites and host fish, using controlled experimental infection carried out in the laboratory.
(2) To use data from experiments, and the published literature, to develop a set of increasingly complex mathematical models to make both short- and long term predictions about the consequences of altered thermal regimes for HPIs, transmission dynamics, host and parasite population sizes and infection prevalence.
(3) To use larger-scale mesocosm studies to test model predictions about transmission rates in populations of freely interacting hosts and parasites.
(4) To compare obtained model predictions with available field observations in natural lakes, using the data from existing literature as well as from new observations.

Methods and project specific training: The project will involve both experimental parasitological and mathematical modelling studies with the aim that each informs the development of the other. The student will undertake carefully controlled lab experiments to study the effects of a range of thermal regimes on all developmental stages of the parasite, and their interaction with the full range of hosts in the life cycle. The student will receive specialist training in the lab maintenance of hosts (sticklebacks / copepods) and the in vivo and in vitro culture of parasite developmental stages. The student will also be trained to quantify HPIs and infection phenotypes, host immune responses, behavioural effects of infection and important correlates of host and parasite fitness.
The mathematical approach will involve the construction of stage-structured models of increasing complexity for the dynamics of parasite and host, as well as their interactions. The model parameters will be considered to be temperature-dependent. Both spatially explicit and mean-field models will be investigated. Lab and mesocosm experiments will inform key mechanisms required for model construction (e.g. transmission rates, behaviour changes etc.) and for further model validation. The student will receive intensive general training in model building for theoretical population ecology and epidemiology. The student will also learn basic analytical techniques to explore mathematical properties of the model (e.g. bifurcation analysis) and receive intensive training in numerical simulation of models using a modern computer language.

Supervisors: Dr Iain Barber has 20 years of experience with the stickleback-Schistocephalus system; published >60 peer-reviewed articles on fish parasitology and behaviour; supervised 5 PhD students to completion; runs a small but dynamic research group of 2 PhD students, a postdoc and a technician. Dr Andrey Morozov (Maths, Leicester) has15 years of experience in mathematical modelling in population ecology, eco-epidemiology and evolution; published >40 peer-reviewed papers. Professor Sergei Petrovskii (Maths, Leicester) has broad research experience in complex systems and in the application of mathematics to ecology; published >80 papers in peer-reviewed journals; Editor-in-chief of Ecological Complexity, a journal of mathematical ecology.

We are an equal opportunities employer and particularly welcome applications for Ph.D. places from women, minority ethnic and other under-represented groups.

Funding Notes

This project is proposed as one of the NERC CENTA projects due to start in October 2014 (see View Website for details). This project exploits complementary expertise in experimental parasitology and mathematical modelling to iteratively develop and test models examining the consequences of environmental change for the prevalence of infectious diseases. One major aim of the project is to train a PhD student in the mathematical and biological study of host-parasite interactions, which is recognised as a major area for future research and one that is lacking suitably qualified expertise.


Barber, I. (2013) Sticklebacks as model hosts in ecological and evolutionary parasitology. Trends in Parasitology 29, 556-566
Macnab V & Barber I (2012) Some (worms) like it hot: fish parasites grow faster in warmer water, and alter host thermal preferences. Global Change Biology 18, 1540–1548
Barber I & Scharsack JP (2010) The three-spined stickleback - Schistocephalus solidus system: an experimental model for investigating host-parasite interactions. Parasitology 137, 411-424.
Morozov A. Yu., Pasternak AF, Arashkevich EG (2013) Revisiting the role of individual variability in population persistence and stability. PLoS ONE 8: e70576
Morozov A. Yu., Adamson M.W. (2011). Evolution of virulence driven by predator-prey interaction: possible consequences for population dynamics. Journal of Theoretical Biology, 276, 181-191
Petrovskii, S.V., Petrovskaya, N.B. (2012) Computational ecology as an emerging science. Interface Focus 2, 241-254.
Petrovskii, S.V., Blackshaw, R.P., & Li, B.-L. (2008) Persistence of structured populations with and without the Allee effect under adverse environmental conditions. Bulletin of Mathematical Biology 70, 412-437.
Iain Barber website http://www2.le.ac.uk/departments/biology/research/evolutionary/lab

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