Apodemus sylvaticus infected with Heligmosomoides polygyrus (Nematoda) in an arable ecosystem: epidemiology and effects of infection on the movements of male mice

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Abstract

We studied the epidemiology of Heligmosomoides polygyrus (Nematodd) in the wood mouse (Apodemus sylvaticus) in an arable ecosystem, and investigated any association between infection and the movement patterns of male mice by manipulating worm burdens. Methods included the live-trapping of mice, estimation of worm burdens by faecal analysis, administration of either an anthelminthic or water (as a control) and the radio-tracking of selected animals.

Heligmosomoides polygyrus showed an overdispersed distribution pattern, with prevalence tending to be higher in males and heavier mice. Prevalence and intensity peaked in spring and declined in autumn both in the entire population and in adults. This seasonality in the arable ecosystem in comparison to woodland may arise due to the direct and indirect impact of agricultural practice.

To investigate the link between infection and movements, radio-tracked mice were classed as either‘Uninfected’or‘Infected’; mice were also classed as either‘Control’or‘Dosed’. There were no significant differences in movement parameters between‘Infected/Dosed’and‘Infected/Control’, possibly because treatment was not administered sufficiently frequently. Both‘Infected’classes of mice moved significantly faster than‘Uninfected’ones, and‘Infected/Dosed’mice moved significantly further than‘Uninfected’ones. The percentage of time spent moving was also greater, and the home range area was larger, for‘Infected/Dosed’and‘Infected/Control’than for‘Uninfected’mice. The observed differences in movement may have been the result of either the behaviour of mice influencing their parasite load or the parasite manipulating its host.

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