The spatial ecology of host parasite communities


Shaun Keegan

Email: Shaun.Keegan@liverpool.ac.uk

Start Year: 2015, 2nd cohort

Host University: The University of Liverpool

Department: Institute of Integrative Biology

Supervisors: Prof Andy Fenton (University of Liverpool); Prof Mike Begon (University of Liverpool); Dr Amy Pedersen (University of Edinburgh) Prof Owen Petchey (University of Zurich)

Twitter:@SP_Keegan

Shaun Keegan

Academic profile

Education:

BSc (Hons) in Zoology; The University of Glasgow, 2012 – 2015
BSc (Hons) in Parasitology; The University of Glasgow, 2004 – 2008

Skills and relevant qualifications: 

Programming with R, Statistical analysis

ACCE Ph.D. Research topic

The spatial ecology of host-parasite communities

Parasite transmission occurs through contacts between susceptible individuals and the infective stages of parasites. Standard models of the epidemiological spread of infections typically assume random mixing of these contacts (the ‘mass action’ assumption) typical of density-dependent transmission, which assumes contacts and transmission simply increase with the density of infected individuals in the total population (McCallum et al 2001; Begon et al 2002; Fenton et al 2002). In reality, however, these contacts are likely to show varying degrees of non-random structure, arising from the spatial arrangement of individuals, environmental heterogeneity and social or behavioural constraints that restrict individual movement.

Obviously, the mode of transmission of a parasite will affect its spatial dynamics of transmission. Many parasites transmit either via long-lived infective stages in the environment (e.g., many parasitic helminths) or via vectors (typically biting arthropods). Furthermore, although vector-borne diseases are often grouped as one method of transmission, this is perhaps a poor approach to addressing the broader questions relating to transmission mode and space. Some vectors fly (e.g., biting flies such as mosquitoes), some vectors sit and wait for a host to pass (e.g., ticks), and some vectors make their home in the nests of their hosts and only periodically predate on the host when they need to feed (e.g., fleas). In this sense, the traditional grouping of “vector-borne” diseases may not be as ubiquitous a group as other infections in relation to their spread through space. Overall these differences in transmission mode are clearly going to affect how transmission relates to the spatial arrangement and movement of hosts.

We have 6 years of longitudinal data (individuals caught multiple times throughout their lives) of rodent hosts (wood mice and bank voles) and around 30 of their parasites (viral, bacterial, protozoan, worm and ectoparasite), collected in the North West of England from 2009-2014. These data were collected at fine temporal scales and is spatially hierarchical. With over 30 parasite species, several different transmission modes are represented. This allows a comprehensive investigation into how transmission mode influences the spatial and spatiotemporal ecology of parasites. For example, is there a relationship between presence and intensity of infection, and the location in space? If so, what might explain these spatial heterogeneities? Are some sites more spatially heterogeneous than others, in that they have distinct hot and cold spots of infection? To what extent does an individual’s risk of infection depend on the number and infection status of its neighbours? Finally, for all the above questions, how do the patterns seen vary across parasites with different transmission modes – do they show different degrees of spatial heterogeneity? Do they overlap in space? How wide, and over what temporal scales, does the infection status of an individual’s ‘neighbourhood’ influence its infection risk?