researchEvolution and virulence
- Overview
- Characterizing evolution
- Identifying gene function and expression
- Investigating coevolution
- Next step phylodynamics
Overview
We study the evolution of parasites and pathogens (including those which jump to novel host species, causing emerging disease), and how this affects their pathogenicity and virulence. We are also investigating coevolution between hosts and disease agents, and between interacting parasites and pathogens of different strains and species. Findings are relevant to disease surveillance and control policies.
Characterizing evolution
CIDD researchers are:
- Conducting large-scale genomic analyses to detect patterns of parasite and pathogen evolution.
- Modeling evolutionary processes to gain insights about evolutionary mechanisms and reconstruct evolutionary histories.
We mostly focus on:
- RNA viruses, which demonstrate particularly high rates of genetic change.
- Pathogenic bacteria and related strains and species that are less pathogenic. For example, the subspecies Bordetella pertussis and B. parapertussis are both human pathogens but appear to have evolved independently: they are more closely related to B. bronchiseptica (infects mice and other animals) than to each other.
» CIDD Bordetella Workshop, 2005 - A few DNA viruses. For instance, Cattadori et al. are currently investigating evolution of virulence in the myxoma virus in natural populations of European rabbits (Oryctolagus cuniculus) in the U.K. We are addressing questions like: how fast did myxoma evolve from high to low virulence? Was the pattern similar in different parts of the U.K.? What may we expect to see happening in the future?
Identifying gene function and expression
Once genetic differences between related microorganisms have been identified, we are looking in more detail at some of them to investigate the function and expression of particular genes. This can enable us to identify the genes involved in virulence and the circumstances under which they are expressed. For instance, Schuster and colleagues are investigating the bacterium Wolinella succinogenes which is non-pathogenic to its bovine host, but contains genes identified as virulence factors in related species (e.g. Campylobacter jejuni).
Investigating coevolution
Hosts and pathogens can exert powerful selective pressures on each other. CIDD researchers are investigating coevolution of hosts and disease agents in a variety of systems. For example:
- Luis is examining a hypothesis that hibernation patterns have evolved to reduce parasite burdens.
- Holmes, Grenfell and colleagues are investigating how genetic change in RNA viruses can result from gene swapping between different viral strains, and how the nature and rate of viral evolution depends on characteristics of host populations — such as heterogeneities in immune status and transmission through social networks.
Next step phylodynamics
Information about patterns, mechanisms and causes of evolution is at the core of the emerging discipline of phylodynamics, which is being pioneered by CIDD researchers.