Complex life cycle helminths use their intermediate hosts as both a source of nutrients and as transportation. There is an assumed trade-off between these functions in that parasite growth may reduce host survival and thus transmission. The virulence of larval helminths can be assessed by experimentally increasing infection intensities and recording how parasite biomass and host mortality scale with intensity. I summarize the literature on these relationships in larval helminths and I provide an empirical example using the nematode Camallanus lacustris in its copepod first host. In all species studied thus far, including C. lacustris, overall parasite volume increases with intensity. Although a few studies observed host survival to decrease predictably with intensity, several studies found no intensity-dependent mortality or elevated mortality only at extreme intensities. For instance, no intensity-dependent mortality was observed in male copepods infected with C. lacustris, whereas female survival was reduced only at high intensities (>3) and only after worms were fully developed. These observations suggest that at low, natural intensity levels parasites do not exploit intermediate hosts as much as they presumably could and that increased growth would not obviously entail survival costs.

The ability of animals to cope with an increasing parasite load, in terms of resilience and resistance, may be affected by both nutrient supply and demand. Here, we hypothesized that host nutrition and growth potential interact and influence the ability of mice to cope with different parasite doses. Mice selected for high (ROH) or low (ROL) body weight were fed a low (40 g/kg; LP) or high (230 g/kg; HP) protein diet and infected with 0, 50, 100, 150, 200 or 250 L3 infective Heligmosomoides bakeri larvae. ROH-LP mice grew less at doses of 150 L3 and above, whilst growth of ROH-HP and of ROL mice was not affected by infection pressure. Total worm burdens reached a plateau at doses of 150L3, whilst ROH mice excreted fewer worm eggs than ROL mice. Serum antibodies increased with infection dose and ROH mice were found to have higher parasite-specific IgG1 titres than ROL mice. In contrast, ROL had higher total IgE titres than ROH mice, only on HP diets. The interaction between host nutrition and growth potential appears to differentially affect resilience and resistance in mice. However, the results support the view that parasitism penalises performance in animals selected for higher growth.

Acanthochondria cornuta (Copepoda: Chondracanthidae) (N=4841; prevalence: 80·0%; mean±s.d. [range] intensity: 28·8±24·0 [1–110] parasites) infected the branchial chambers of the European flounder, Platichthys flesus (L.), (N=210) according to an established spatial pattern. This was independent of host size. Higher intensities resulted, most frequently, in higher numbers of infection sites, probably due to increased intraspecific competition. Preferential infection of the ocular side was supported by the recorded abundance data and reflected, probably, the fish's bottom-dwelling behaviour. As the parasite develops from one stage into another, it seems to migrate towards different sites: the copepodites and pre-adult females occurred, mainly, in the holobranchs; the adults preferred the internal wall (non-gravid/post-gravid females; adult males) or the pseudobranchs (gravid females). The ventilating water current along with the blood supply are suggested as 2 major factors in determining parasite spatial distribution within the chamber. Parasite crowding in a restricted and narrow space of the posterior region of the internal wall was recorded frequently and resembled that previously reported for the plaice. Differences to other host-parasite systems previously studied should relate with the anatomy of the respiratory apparatus. Bigamous females are reported for the first time.

We have explored a large body of novel data focusing on small-scale temporal and spatial patterns in the composition and structure of larval trematode communities in Lymnaea stagnalis (L.) from a typical Central European agricultural landscape. The 5 eutrophic fishponds studied provide excellent environments for the development of species-rich and abundant trematode communities. Nine prevalent species were consistently present in component communities, but had differential contribution to the parasite flow in the 5 ponds resulting in significant contrasting patterns of community similarity and the prevalence of the 3 major transmission guilds driving this similarity. Component communities split into 2 groups: (i) those from the large pond dominated by anatid and larid generalists with active miracidial transmission; and (ii) those from the smaller ponds dominated by 2 plagiorchioideans infecting snails via egg ingestion. We put forward 3 hypotheses for the remarkable differences in larval trematode flow in the similar and closely located eutrophic ponds: (i) species-specific differences in parasite colonization potential displayed by an ‘active-passive’ dichotomy in miracidial transmission strategies of the species; (ii) top-down effects of pond context on transmission pathways of the trematodes; and (iii) competition as an important mechanism in eutrophic environments with a bottom-up effect on component community structure.

Larval helminths exploit the physiology of their intermediate hosts: first, as a resource for energy and space and second by altering the immune system activity to ensure their survival. Whereas the growth pattern under parasite competition has been investigated, the effect of multiple infections on the level of parasite-induced immunodepression in a trophically transmitted helminth has been neglected. In this study, amphipods Gammarus pulex were infected in the laboratory by the acanthocephalan Pomphorhynchus laevis to investigate how parasite density in the intermediate host affected (i) cystacanth growth and (ii) the level of parasite-induced alterations of the host immune defences, two traits strongly linked to host exploitation. The study highlights that sharing a host is costly. As parasite intensity increases, competition for resources translates into a reduction in cystacanth volume. Immune manipulation is also modulated by density. Interestingly, immunodepression is higher in double-infected hosts compared to hosts with a single infection, suggesting an opportunity for cooperative immune manipulation. However, in higher multiple infections, parasites do not further down-regulate the host immune response, possibly to avoid additional costs that may outweigh the benefits of immunodepression.

One of the major threats to biodiversity involves biological invasions with direct consequences on the stability of ecosystems. In this context, the role of parasites is not negligible as it may enhance the success of invaders. The red-eared slider, Trachemys scripta elegans, has been globally considered among the worst invasive species. Since its introduction through the pet trade, T. s. elegans is now widespread and represents a threat for indigenous species. Because T. s. elegans coexists with Emys orbicularis and Mauremys leprosa in Europe, it has been suggested it may compete with the native turtle species and transmit pathogens. We examined parasite transfer from American captive to the two native species that co-exist in artificial pools of a Turtle Farm in France. As model parasite species we used platyhelminth worms of the family Polystomatidae (Monogenea) because polystomes have been described from American turtles in their native range. Phylogenetic relationships among polystomes parasitizing chelonian host species that are geographically widespread show patterns of diversification more complex than expected. Using DNA barcoding to identify species from adult and/or polystome eggs, several cases of host switching from exotic to indigenous individuals were illustrated, corroborating that parasite transmission is important when considering the pet trade and in reintroduction programmes to reinforce wild populations of indigenous species.

Introduction. Palaeozoic calcareous sponges (stromatoporoids) are common bio-constructing fossils; they are sometimes found in association with helicoidal structures of unknown biological affinities. The interaction between the tube-forming organisms has usually been classified as commensalism. Methods. About 260 stromatoporoid skeletons from the Middle Devonian (Givetian) of the Mont d'Haurs section near Givet (Champagne-Ardenne, France) were thin-sectioned and analysed under transmitted light. Results. Approximately 10% of the examined stromatoporoids (mainly belonging to the genera Actinostroma, Stromatopora and Stromatoporella) contain tubes classified as Torquaysalpinx sp. The Torquaysalpinx organisms penetrated the skeletons of stromatoporoids in vivo (as evidenced by skeletal overgrowths); around the infesting organisms, growth bands are bent down. Conclusion. Diminished growth rates around the infesting organism demonstrate a negative influence on the host, similar to that seen in the modern demosponge–polychaete association of Verongia–Haplosyllis. This is demonstrated by changes in growth bands. As in the above-mentioned association, the endosymbiont might have been feeding directly upon the tissues of the host. The Torquaysalpinx organisms were gaining habitat and possibly also food resources – for them this interaction was clearly positive. This long-term association can therefore be classified as parasitism. This is the first evidence for parasitism in Palaeozoic sponges.

Phylogenetic analyses of SSU rDNA sequences have previously revealed the existence of 2 Ichthyobodo species able to infect Atlantic salmon (Salmo salar L.). Ichthyobodo necator sensu stricto (s.s.) is assumed to be a freshwater parasite, while a genetically distinct but undescribed species, Ichthyobodo sp. II sensu Todal et al. (2004) have been detected on Atlantic salmon in both fresh- and seawater. In the present study a morphological description of Ichthyobodo sp. II from the gills of salmon reared in fresh-, brackish- and seawater is presented, using both light- and electron microscopy. Comparative morphometry show that Ichthyobodo sp. II from both freshwater and seawater displays a different cell shape, and is significantly smaller than I. necator s.s. Also, ultrastructural characteristics distinguish these two species, notably differences in the attachment region and the presence of spine-like surface projections in Ichthyobodo sp. II. Based on both unique SSU rDNA sequences and morphological characteristics, we conclude that Ichthyobodo sp. II. represents a novel species for which we propose the name Ichthyobodo salmonis sp. n.

On the Eastern Tibetan Plateau region (Sichuan province, China) dogs are regarded as important definitive hosts of Echinococcus multilocularis. We studied dog spatial behaviour in 4 Tibetan villages in order to determine the role of dogs in environmental contamination and their potential interactions with small mammal intermediate hosts. We identified definitive host species and Echinococcus spp. infection status of feces collected in the field by PCR methods and analysed the spatial distribution of canid feces. Nocturnal space utilization of GPS collared dogs in and around villages was also undertaken. E. multilocularis DNA was amplified in 23% of dog feces (n=142) and in 15% of fox feces (n=13) but this difference was not significant. However, dog feces were more frequently observed (78% of collected feces) than fox feces and are therefore assumed to largely contribute to human environment contamination. Feces were mainly distributed around houses of dog owners (0–200 m) where collared dogs spent the majority of their time. Inside villages, the contamination was aggregated in some micro-foci where groups of dogs defecated preferentially. Finally, small mammal densities increased from the dog core areas to grasslands at the periphery of villages occasionally used by dogs; male dogs moving significantly farther than females. This study constitutes a first attempt to quantify in a spatially explicit way the role of dogs in E. multilocularis peri-domestic cycles and to identify behavioural parameters required to model E. multilocularis transmission in this region.

Corridor disease is an acute, fatal disease of cattle caused by buffalo-adapted Theileria parva. This is a nationally controlled disease in South Africa and strict control measures apply for the movement of buffalo, which includes mandatory testing for the presence of T. parva and other controlled diseases. Accurate diagnosis of the T. parva carrier state in buffalo using the official real-time hybridization PCR assay (Sibeko et al.2008), has been shown to be affected by concurrent infection with T. sp. (buffalo)-like parasites. We describe the Hybrid II assay, a real-time hybridization PCR method, which compares well with the official hybridization assay in terms of specificity and sensitivity. It is, however, not influenced by mixed infections of T. sp. (buffalo)-like parasites and is as such a significant improvement on the current hybridization assay.

Fish parasites are used to monitor long-term change in finfish grouper mariculture in Indonesia. A total of 210 Epinephelus fuscoguttatus were sampled in six consecutive years between 2003/04 and 2008/09 and examined for parasites. The fish were obtained from floating net cages of a commercially run mariculture facility that opened in 2001. The fauna was species rich, consisting of ten ecto- and 18 endoparasite species. The ectoparasite diversity and composition was relatively stable, with the monogeneans Pseudorhabdosynochus spp. (83–100% prevalence, Berger-Parker Index of 0·82–0·97) being the predominant taxon. Tetraphyllidean larvae Scolex pleuronectis and the nematodes Terranova sp. and Raphidascaris sp. 1 were highly abundant in 2003/04–2005/06 (max. prevalence S. pleuronectis 40%, Terranova sp. 57%, Raphidascaris sp. 1 100%), and drastically reduced until 2008/09. These parasites together with the prevalence of Trichodina spp., ecto-/endoparasite ratio and endoparasite diversity illustrate a significant change in holding conditions over the years. This can be either referred to a definite change in management methods such as feed use and fish treatment, or a possible transition of a relatively undisturbed marine environment into a more affected habitat. By visualizing all parameters within a single diagram, we demonstrate that fish parasites are useful bioindicators to monitor long-term change in Indonesian grouper mariculture. This also indicates that groupers can be used to monitor environmental change in the wild. Further taxonomic and systematic efforts in less sampled regions significantly contributes to this new application, supporting fish culture and environmental impact monitoring also in other tropical marine habitats.

Risk factors related to herd and farmer status, farm and pasture management, and environmental factors derived by satellite data were examined for their association with the prevalence of F. hepatica in sheep and goat farms in Thessaly, Greece. Twelve farms (16·2%) and 58 farms (78·4%) of 74 had evidence of infection using coproantigen and serology respectively. The average normalized difference vegetation index (NDVI) of farm location for 12 months before sampling was the most significant environmental risk factor for F. hepatica infection based on high seropositivity. The risk of infection increased by 1% when the value of NDVI increased by 0·01 degree. A geospatial map was constructed to show the relative risk (RR) of Fasciola infection in sheep and goat farms in Thessaly. In addition, geospatial maps of the model-based predicted RR for the presence of Fasciola infection in farms in Thessaly and the entire area of Greece were constructed from the developed model based on NDVI. In conclusion, this study demonstrated that Thessaly should be regarded as an endemic region for Fasciola infection and it represents the first prediction model of Fasciola infection in small ruminants in the Mediterranean basin.

The underlying mechanism of predisposition to Ascaris infection is not yet understood but host genetics are thought to play a fundamental role. We investigated the association between the Intelectin-2 gene and resistance in F2 mice derived from mouse strains known to be susceptible and resistant to infection. Ascaris larvae were isolated from murine lungs and the number of copies of the Intelectin-2 gene was determined in F2 mice. Intelectin-2 gene copy number was not significantly linked to larval burden. In a pilot experiment, the response to infection in parental mice of both sexes was observed in order to address the suitablity of female F2 mice. No overall significant sex effect was detected. However, a divergence in resistance/susceptibility status was observed between male and, female hybrid offspring. The responsiveness to Ascaris in mice is likely to be controlled by multiple genes and, despite a unique absence from the susceptible C57BL/6j strain, the Intelectin-2 gene does not play a significant role in resistance. The observed intra-strain variation in larval burden requires further investigation but we hypothesize that it stems from social/dominance hierarchies created by the presence of female mice and possibly subsequent hormonal perturbations that modify the intensity of the immune response.

There is a gap in our understanding of the relative and interactive effects of different parasite species on the same host population. Here we examine the effects of the acanthocephalan Acanthocephalus galaxii, an unidentified cyclophyllidean cestode, and the trematodes Coitocaecum parvum and Microphallus sp. on several fitness components of the amphipod Paracalliope fluviatilis, using a combination of infection surveys and both survival and behavioural trials. In addition to significant relationships between specific parasites and measures of amphipod survival, maturity, mating success and behaviour, interactions between parasite species with respect to amphipod photophilia were also significant. While infection by either A. galaxii or C. parvum was associated with increased photophilia, such increases were negated by co-infection with Microphallus sp. We hypothesize that this is due to the more subtle manipulative effect of A. galaxii and C. parvum being impaired by Microphallus sp. We conclude that the low frequency at which such double infections occur in our sampled population means that such interactions are unlikely to be important beyond the scale of the host individual. Whether or not this is generally true, implying that parasitological models and theory based on single parasite species studies do generally hold, requires cross-species meta-analytical studies.

Lymphatic filariasis (LF), a common parasitic infection in tropical countries, causes lymphoedema of limbs, hydrocele and acute attacks of dermato-lymphangio-adenitis. Recent advances in diagnosis have helped to recognize that LF infection is often acquired in childhood. Newly available diagnostic techniques like sensitive antigen and antibody assays, Doppler ultrasonography and lymphoscintigraphy have helped to understand the subclinical pathology caused by this infection, which was hitherto generally believed to be irreversible. Recent studies indicate that drugs used in the mass drug administration (MDA) programme under GPELF are capable of reversing the sub-clinical lymphatic damage in children and provide benefits other than interruption of transmission. Albendazole and ivermectin used in MDA are effective against soil-transmitted helminthic infections common in children in LF endemic areas. Thus MDA had other ‘beyond LF’ benefits in treated children including increased appetite, weight gain, greater learning ability and concentration, better school attendance and prevention of anaemia. MDA should no longer be viewed as a measure for interrupting transmission alone. Recent findings of reversibility of early lymphatic pathology in treated children indicate that both MDA and ‘foot-hygiene’ measures are effective strategies in preventing and managing morbidity. Programme managers should effectively utilize this information to strengthen their advocacy efforts to achieve high and sustainable coverage in MDA.

Manipulative parasites with complex life cycles are known to induce behavioural and physiological changes in their intermediate hosts. Cyathocephalus truncatus is a manipulative parasite which infects Gammarus pulex as intermediate host. G. pulex males display pre-copulatory mate guarding as a response to male-male competition for access to receptive females. In this paper, we tested the influence that C. truncatus-infection might have on male G. pulex sperm number and pairing success. We considered 3 classes of G. pulex males in our experiments: (i) uninfected males found paired in the field, (ii) uninfected males found unpaired in the field, or (iii) infected males found unpaired in the field. Both infected males and uninfected unpaired males paired less with a new female than uninfected paired males did. Furthermore, infected males appear to be at a strong disadvantage when directly competing for females with a healthy rival male, and had fewer sperm in their testes. We discuss the potential effect of male and female mating strategies on such male host mating alteration.