Helminth parasites of the wood mouse, Apodemus sylvaticus (n = 440), were surveyed in five localities, comprising woodland and grassland sites, in Southern England. Seven species of helminths were identified, among which Heligmosomoides polygyrus and Syphacia stroma were dominant (prevalence = 79.1% and 54.1%, respectively). Less common species were the trematode Corrigia vitta (14.8%), cestodes Catenotaenia pusilla (8.4%), Hydatigera taeniaeformis (4.1%) and Microsomacanthus crenata (3.4%) and the nematode Aonchotheca murissylvatici (0.2%). Differences in prevalences between localities were found for H. polygyrus, H. taeniaeformis and M. crenata and in abundances of H. polygyrus, S. stroma and C. vitta. Age-dependent increases in both parameters were identified among species and for helminth species richness. The only species to show significant host sex bias was S. stroma with prevalence values being higher in male mice. A number of different methods for exploiting raw data, and data corrected for significant confounding factors, were used to determine whether there were significant associations (prevalence) between species or quantitative interactions (abundance). The strongest evidence for a positive association was shown in concurrent infections with the trematode C. vitta and the cestode C. pusilla (significant in the whole dataset and evident in each locality, both sexes and both age classes). The abundance of C. pusilla was also higher in mice with C. vitta and vice versa. Overall, however, there was little support for associations or quantitative interactions between species, especially after data had been corrected for significant extrinsic/intrinsic factors, and we conclude that the helminths of wood mice in these communities are largely non-interactive and hence, perhaps better referred to as assemblages.

The distributions of the nematode parasites Heligmosomoides polygyrus and Syphacia stroma were quantified in three equal-length sections along the intestine of wood mice (Apodemus sylvaticus) trapped in three different locations in the south of England. The distribution of H. polygyrus did not change in the presence of S. stroma, this species being largely confined to the anterior third of the intestine, whether S. stroma was or was not present. However, while in single infections with S. stroma, worms were equally distributed in the anterior and middle sections of the intestine, in the presence of H. polygyrus, a higher percentage of worms was located in the middle section. This was a dose-dependent response by S. stroma to increasing worm burdens with H. polygyrus, and even relatively low intensities of infection with H. polygyrus (e.g. ≤10 worms) were sufficient to cause a posterior redistribution of S. stroma into the middle section. A similar posterior shift in the percentage distribution of S. stroma in the intestine was evident in juvenile and mature mice of both sexes, and in mice from all three study sites. The ecological significance of these results is discussed.

Syphacia stroma (von Linstow, 1884) Morgan, 1932 and Syphacia frederici Roman, 1945 are oxyurid nematodes that parasitize two murid rodents, Apodemus sylvaticus and Apodemus flavicollis, on the European mainland. Only S. stroma has been recorded previously in Apodemus spp. from the British Isles. Despite the paucity of earlier reports, we identified S. frederici in four disparate British sites, two in Nottinghamshire, one each in Berkshire and Anglesey, Wales. Identification was based on their site in the host (caecum and not small intestine), on key morphological criteria that differentiate this species from S. stroma (in particular the tail of female worms) and by sequencing two genetic loci (cytochrome C oxidase 1 gene and a section of ribosomal DNA). Sequences derived from both genetic loci of putative British S. frederici isolates formed a tight clade with sequences from continental worms known to be S. frederici, clearly distinguishing these isolates from S. stroma which formed a tight clade of its own, distinct from clades representative of Syphacia obvelata from Mus and S. muris from Rattus. The data in this paper therefore constitute the first record of S. frederici from British wood mice, and confirm the status of this species as distinct from both S. obvelata and S. stroma.

It is becoming increasingly evident that biological invasions result in altered disease dynamics in invaded ecosystems, with knock-on effects for native host communities. We investigated disease dynamics in an invaded ecosystem, using the helminth communities of the native wood mouse (Apodemus sylvaticus) in the presence and absence of the invasive bank vole (Myodes glareolus) in Ireland. Native wood mice were collected over 2 years from four sites to assess the impact of the presence of the bank vole on wood mouse helminth community dynamics both at the component and infracommunity level. We found evidence for dilution (Syphacia stroma), spill-back (Aonchotheca murissylvatici) and spill-over (Taenia martis) in native wood mice due to the presence of the bank vole. Site of capture was the most important factor affecting helminth community structure of wood mice, along with year of capture and host-age and the interactions between them.

Toxoplasma gondii is a globally distributed parasite infecting humans and warm-blooded animals. Although many surveys have been conducted for T. gondii infection in mammals, little is known about the detailed distribution in localized natural populations. In this study, host genotype and spatial location were investigated in relation to T. gondii infection. Wood mice (Apodemus sylvaticus) were collected from 4 sampling sites within a localized peri-aquatic woodland ecosystem. Mice were genotyped using standard A. sylvaticus microsatellite markers and T. gondii was detected using 4 specific PCR-based markers: SAG1, SAG2, SAG3 and GRA6 directly from infected tissue. Of 126 wood mice collected, 44 samples were positive giving an infection rate of 34·92% (95% CI: 27·14–43·59%). Juvenile, young adults and adults were infected at a similar prevalence, respectively, 7/17 (41·18%), 27/65 (41·54%) and 10/44 (22·72%) with no significant age-prevalence effect (P = 0·23). Results of genetic analysis of the mice showed that the collection consists of 4 genetically distinct populations. There was a significant difference in T. gondii prevalence in the different genotypically derived mouse populations (P = 0·035) but not between geographically defined populations (P = 0·29). These data point to either a host genetic/family influence on parasite infection or to parasite vertical transmission.

The protozoan parasite Toxoplasma gondii is prevalent worldwide and can infect a remarkably wide range of hosts despite felids being the only definitive host. As cats play a major role in transmission to secondary mammalian hosts, the interaction between cats and these hosts should be a major factor determining final prevalence in the secondary host. This study investigates the prevalence of T. gondii in a natural population of Apodemus sylvaticus collected from an area with low cat density (<2·5 cats/km2). A surprisingly high prevalence of 40·78% (95% CI: 34·07%–47·79%) was observed despite this. A comparable level of prevalence was observed in a previously published study using the same approaches where a prevalence of 59% (95% CI: 50·13%–67·87%) was observed in a natural population of Mus domesticus from an area with high cat density (>500 cats/km2). Detection of infected foetuses from pregnant dams in both populations suggests that congenital transmission may enable persistence of infection in the absence of cats. The prevalences of the related parasite, Neospora caninum were found to be low in both populations (A. sylvaticus: 3·39% (95% CI: 0·12%–6·66%); M. domesticus: 3·08% (95% CI: 0·11%–6·05%)). These results suggest that cat density may have a lower than expected effect on final prevalence in these ecosystems.

Two populations of Apodemus sylvaticus, one in deciduous woodland and another in coniferous forest in Co. Down, Northern Ireland, were trapped at monthly intervals over 33 months. The dynamics, reproduction and age structure of the mouse populations differed between years with over a 40 fold range of population size. Nine species of helminths were recovered from the alimentary tract and associated organs of the mice. The prevalence and mean worm burden of the cestodes, Catenotaenia lobata, Hymenolepis hibernia and Taenia taeniaeformis varied erratically. The trematodes, Corrigia vitta and to a lesser degree Brachylaima recurva, had seasonal changes in abundance. The nematodes Capillaria murissylvatici and Nematospiroides dubius had strongly seasonal cycles of abundance associated with the onset of host reproduction. Trichuris muris was the rarest helminth. Despite protracted periods of absence this species maintained a seasonal increase in mean worm burden in late winter. The nematode, Syphacia stroma, had a weakly seasonal pattern of dynamics. The bases of these cyclical and non-cyclical dynamics of the helminths of A. sylvaticus are discussed.

We analysed 3 independently collected datasets of fully censused helminth burdens in wood mice, Apodemus sylvaticus, testing the a priori hypothesis of Behnke et al. (2005) that the presence of the intestinal nematode Heligmosomoides polygyrus predisposes wood mice to carrying other species of helminths. In Portugal, mice carrying H. polygyrus showed a higher prevalence of other helminths but the magnitude of the effect was seasonal. In Egham, mice with H. polygyrus showed a higher prevalence of other helminth species, not confounded by other factors. In Malham Tarn, mice carrying H. polygyrus were more likely to be infected with other species, but only among older mice. Allowing for other factors, heavy residual H. polygyrus infections carried more species of other helminths in both the Portugal and Egham data; species richness in Malham was too low to conduct a similar analysis, but as H. polygyrus worm burdens increased, so the prevalence of other helminths also increased. Our results support those of Behnke et al. (2005), providing firm evidence that at the level of species richness a highly predictable element of co-infections in wood mice has now been defined: infection with H. polygyrus has detectable consequences for the susceptibility of wood mice to other intestinal helminth species.

The infectivity of wild and laboratory strains of Heligmosomoides polygyrus (Nematospiroides dubius) in laboratory mice and in three species of wild British rodent was compared. Wild strains, of the subspecies H. p. polygyrus, were isolated from wild caught Apodemus sylvaticus. Only very low-level infections of the wild strains became established in laboratory mice. Similar worm burdens of the laboratory strain became established in laboratory mice and A. sylvaticus, although infections in A. sylvaticus were more short lived. Cortisone treatment of hosts increased the establishment and survival of the heterologous worm strain to that of the homologous strain. In contrast, neither strain of parasite established in Clethrionomys glareolus or Microtus agrestis, and cortisone treatment of C. glareolus did not increase establishment. Infection of laboratory mice with the wild-strain parasite induced significant immunity to a challenge infection with the laboratory strain.

Transfer of Eimeria apionodes from wood mice directly into untreated laboratory mice was unsuccessful but transfer into corticosteroid-treated animals produced an oocyst output, about 1000 times less than that observed from wood mice after a similar inoculum. Repeated passage through corticosteroid-treated laboratory mice resulted in a line adapted to survival in untreated animals. This line was compared with the parent strain maintained in wood mice and some features of the oocyst output patterns, notably the pre-patent period, appeared to be controlled by the host species. The oocyst production of each population was higher in the host species to which it was adapted than in the other host species (P > 0·001). Once adapted to laboratory mice, the line produced insignificantly different levels of oocysts in corticosteroid-treated and untreated animals (P > 0·05).

Characteristics of four species of Eimeria isolated from Apodemus sylvaticus are described. From oocyst morphology, three are identified as E. apionodes, E. hungaryensis and E. uptoni, the fourth being unnamed. Cloning demonstrated that oocysts of E. hungaryensis were polymorphic. Previous literature relating to the taxonomy is discussed and discrepancies outlined. Species isolated from A. sylvaticus were not transmissible to Clethrionomys glareolus, but both E. hungaryensis and E. apionodes have been passaged through immunosuppressed laboratory mice, the former species more than 16 times. In both A. sylvaticus and immunosuppressed laboratory mice, endogenous development of E. hungaryensis occurred mainly in enterocytes near the tips of the villi in the first half of the small intestine, with a few parasites in the rest of the small intestine and into the large intestine. The pre-patent period was 2 days in both hosts but oocyst output was higher in the natural hosts. E. apionodes parasitized enterocytes on the sides or at the base of the villi, mainly in the last 90% of the small intestine with a few parasites in the large intestine. The pre-patent period was 7 days. Parasites, probably E. hungaryensis and E. apionodes, were also isolated from A. flavicollis.

Few data are available and little is known about spatial variation in post-dispersal seed removal at different levels throughout the geographic range of a plant species. Here, we compare post-dispersal seed removal by rodents within and among sites in two distinct regions, the south-eastern Spanish Mediterranean highlands and the Swiss Jura. Seed removal was assessed experimentally for four fleshy-fruited species (Berberis vulgaris, Crataegus monogyna, Rosa spp. and Taxus baccata) in heterogeneous sites with distinct microhabitats. A factorial general linear model (GLM) analysis was used to evaluate the relative influence of species-specific seed traits on removal at three spatial levels (microhabitat, site and region). In both highland ecosystems, live trapping revealed that rodents were the main seed removers: Apodemus sylvaticus was observed in both regions, whereas A. flavicollis and Clethrionomys glareolus occurred only at the Swiss sites. There was a significant difference in seed removal between regions, and the preferences of the rodents varied among plant species and microhabitats. Variation in rodent presence explained some differences in seed removal between regions and among microhabitats. Finally, the effect of rodent presence on seed removal differs due to both regional and microhabitat effects.

The gastro-intestinal (GI) nematode Heligmosomoides polygyrus is an important experimental model in laboratory mice and a well-studied parasite of wood mice in the field. Despite an extensive literature, the taxonomy of this parasite in different hosts is confused, and it is unclear whether laboratory and field systems represent the same or different Operational Taxonomic Units (OTUs). Molecular analyses reveal high sequence divergence between H. p. bakeri (laboratory) and H. p. polygyrus (field); 3% difference in the ribosomal DNA Internal Transcribed Spacers (ITS) and 8·6% variation in the more rapidly evolving mitochondrial cytochrome c oxidase I (COI) gene. The COI sequence of U.K. H. p. polygyrus is more similar to H. glareoli from voles than to H. p. bakeri, while a single isolate of H. p. polygyrus from Guernsey confirms the extent of genetic variation between H. p. polygyrus populations. Analysis of molecular variance demonstrated that mtCOI sequence variation is associated primarily with groups with distinct ITS2 sequences, and with host identity, but is not partitioned significantly with a single combined taxon H. polygyrus incorporating European and North American isolates. We conclude therefore that the laboratory OTU should be raised to the level of a distinct species, as H. bakeri from the laboratory mouse Mus musculus, and we reject the hypothesis that H. bakeri has diverged from H. polygyrus in the recent past following introduction into America. However, we are unable to reject the hypothesis that H. polygyrus and H. bakeri are sister taxa, and it may be that H. polygyrus is polyphyletic or paraphyletic.

Sexual transmission occurs commonly in microparasites such as viruses and bacteria, but this is an unusual transmission route for macroparasites. Here we present evidence which suggests that a nematode parasite of Wood Mice (Apodemus sylvaticus) may be sexually transmitted and we have classified the nematode using molecular data. Wood Mice were collected annually in the course of work on their reproductive physiology. Larval nematodes were found in the epididymides of 19·6% of males. It seems likely that they would be transmitted to females at ejaculation. To identify these larval nematodes, which we were unable to do using morphological features, we sequenced the 18S rDNA. Sequence comparisons with the molecular phylogeny of Blaxter et al. (1998) demonstrated that they were bursate nematodes (Order Strongylida). The relationships between strongylid taxa were poorly resolved by 18S rDNA. However, both distance and parsimony analyses grouped the nematode with the superfamily Metastrongylidea in a clade containing Filaroides and Angiostrongylus sp. Importantly, the sequences were distinct from those of Heligmosomoides polygyrus and Angiostrongylus dujardini, two common strongylid nematodes of Apodemus. We were therefore unable positively to identify these worms by matching their sequences with those from morphologically identifiable adult strongylid nematodes infecting Apodemus. These results demonstrate that an as yet unidentified strongylid is quite commonly found in large numbers in the male reproductive tract of Wood Mice. Further work is required to understand the biology and transmission dynamics of this interesting system.

Wood mice Apodemus sylvaticus are potentially useful indicators of change in arable ecosystems. Here we focus on changes resulting from removal of land from arable production under the set-aside scheme. Wood mice were radio-tracked to compare: (a) their use of set-aside, crop and hedgerow before and after harvest; (b) set-aside configured as margins and as a 3 ha block; (c) cut and uncut 20-m wide set-aside margins. Males had larger home ranges, and were more mobile than females. Ranges were larger, and animals more mobile, before harvest than afterwards. There were no differences in range sizes of breeding and non-breeding animals after harvest, suggesting that changes in habitat use were not a function of cessation of breeding. Before harvest, wood mice used habitats within their ranges at random, and their ranges contained a high proportion of cropped area. After harvest they preferred hedgerow and avoided margin set-aside within their ranges, but did not similarly avoid the set-aside block. The proportion of cropped area within their ranges decreased after harvest, and the proportion of margin increased. Our evidence suggests wood mice avoided using the area adjacent to the hedgerow, perhaps to avoid predators. Uncut set-aside patches were favoured and cut patches avoided, possibly in response to differences in food availability and levels of protection from predators. These results confirm that wood mice are useful indicators of change in arable landscapes.

The first long-term (27 month) survey of single species of Eimeria occurring in a population of Apodemus sylvaticus in the UK showed that Eimeria apionodes, E. hungaryensis and E. uptoni occurred throughout the period whilst E. sp. E. was only found during 4 months. In first-captured animals, overall prevalence of Eimeria spp. was 73%: a figure higher than previously published, but possibly an underestimate. Multiple infections (2 or 3 species) occurred in 34% of first-capture infected animals, but without significant associations. There were no significant differences of prevalence rates between the sexes, nor between adults and juveniles, except for E. uptoni which was more common in juveniles than in adults. E. hungaryensis and E. uptoni probably occurred as near-continuous infections whilst E. apionodes occurred more intermittently but with no long-term total immunity. Monthly prevalence data indicated ongoing trends over the 27 months. Prevalences of E. apionodes indicated an annual cycle, lowest in January–May and with a peak in October–November, correlating positively with both the number of animals and the percentage of juveniles in the host population and also with the environmental relative humidity. There was no consistent pattern for E. uptoni and an annual cycle for E. hungaryensis was not apparent.

We investigated the effects of crop type on numbers and movements of wood mice Apodemus sylvaticus in field edges and in arable fields containing either winter wheat, winter barley or oil-seed rape, grown on a 3-year rotation. We also investigated the effect of habitat (field centre vs edge), and of season and year. This was done at the individual level using radio-tracking, and at the population level using live-trapping. Wood mouse population size (estimated as minimum number alive) was significantly affected by season. Wood mouse numbers also differed between crop types. Rape field centres and edges had significantly lower numbers than did barley or wheat field centres and edges. Populations were largest from April to July, when the crop was tall. In winter, significantly more mice were found in field edges compared with field centres. The patterns of movement of individual mice also showed differences between habitats and between seasons. Mice were found to move more quickly when they were tracked through rape compared with the other crops. When the crop was growing, they moved faster through field edges bordered with hedgerow than they did through wood. This pattern was reversed later in the year when the crop was tall. The distances moved during a session of tracking showed differences which paralleled those for speed of movement. Also, males tended to move faster than females. Differences between the sexes in movement patterns were affected by season; when the crop was down (in winter) females moved further than males during a session of tracking, but when the crop was growing and tall, this was reversed.

Forty-eight wood mice Apodemus sylvaticus were radio-tracked over an estimated 1500 h yielding 9000 fixes. The mice were living in three contiguous arable fields, and showed that they respond to weedy microhabitat patches within superficially homogeneous crops. Plant species' abundance and the composition of the seed bank were assessed in quadrats taken in areas in which (a) mice foraged, (b) through which mice travelled, or (c) at random within each home range. Wood mice avoided foraging in areas with a high abundance of bare earth, and selected areas with a high abundance of Alopecurus myosuroides, Stellaria media, Avena fatua, Galium aparine or Bromus sterilis. The food plants apparently selected by wood mice differed markedly between months and between sexes. This may relate to the energetic and nutritional demands incurred by the contrasting reproductive tactics of male and female wood mice. There were no differences between seed bank samples taken from quadrats where the mice foraged, travelled through, or which were selected at random. Our study, the first large-scale analysis of wood mouse microhabitat preference using radio-tracking, reveals that whereas the mice do not react to heterogeneity on the scale of the mosaic of crop fields, they are greatly influenced by the dispersion of food plants within the superficially homogeneous crop itself.

Wood mice Apodemus sylvaticus were radio-tracked in an area covering three cereal fields, which was notionally divided into 5×5 m squares; each of these squares was classified to one of four habitat types (hedgerow, wheat, barley and oil-seed rape). From a sample of 79 radio-tracked wood mice, yielding 8500 fixes, we defined home-range boundaries and estimated for two seasons: (a) the extent to which each habitat was present in each individual's home range relative to its overall availability in the surrounding landscape; (b) the extent to which each habitat was used by the mice relative to its abundance within a home range. Hedgerow ranked highest in preference (as distinct from use) for all comparisons made in both winter and summer. In winter, home ranges contained significantly more hedgerow than barley and wheat, and significantly more rape than wheat. Animals also used the habitats within their home ranges non-randomly, with a significant preference for hedgerow. In summer, home ranges contained significantly less rape than other habitats. Habitats within home ranges were used at random. Seasonal patterns in habitat use appeared to be largely a response to seasonal disturbance and the availability of cover in the fields.