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Trends in Parasitology May 2021Protozoan parasites acquire essential ions, nutrients, and other solutes from their insect and vertebrate hosts by transmembrane uptake. For intracellular stages, these... (Review)
Review
Protozoan parasites acquire essential ions, nutrients, and other solutes from their insect and vertebrate hosts by transmembrane uptake. For intracellular stages, these solutes must cross additional membranous barriers. At each step, ion channels and transporters mediate not only this uptake but also the removal of waste products. These transport proteins are best isolated and studied with patch-clamp, but these methods remain accessible to only a few parasitologists due to specialized instrumentation and the required training in both theory and practice. Here, we provide an overview of patch-clamp, describing the advantages and limitations of the technology and highlighting issues that may lead to incorrect conclusions. We aim to help non-experts understand and critically assess patch-clamp data in basic research studies.
Topics: Animals; Biological Transport; Cell Membrane; Eukaryota; Parasites; Parasitology; Patch-Clamp Techniques
PubMed: 33640269
DOI: 10.1016/j.pt.2021.02.002 -
Parasitology Jun 2013Many studies have identified various host behavioural and ecological traits that are associated with parasite infection, including host gregariousness. By use of... (Meta-Analysis)
Meta-Analysis Review
Many studies have identified various host behavioural and ecological traits that are associated with parasite infection, including host gregariousness. By use of meta-analyses, we investigated to what degree parasite prevalence, intensity and species richness are correlated with group size in gregarious species. We predicted that larger groups would have more parasites and higher parasite species richness. We analysed a total of 70 correlations on parasite prevalence, intensity and species richness across different host group sizes. Parasite intensity and prevalence both increased positively with group size, as expected. No significant relationships were found between host group size and parasite species richness, suggesting that larger groups do not harbour more rare or novel parasite species than smaller groups. We further predicted that the mobility of the host (mobile, sedentary) and the mode of parasite transmission (direct, indirect, mobile) would be important predictors of the effects of group sizes on parasite infection. It was found that group size was positively correlated with the prevalence and intensity of directly and indirectly transmitted parasites. However, a negative relationship was observed between group size and mobile parasite intensity, with larger groups having lower parasite intensities. Further, intensities of parasites did not increase with group size of mobile hosts, suggesting that host mobility may negate parasite infection risk. The implications for the evolution and maintenance of sociality in host species are discussed, and future research directions are highlighted.
Topics: Animals; Host-Parasite Interactions; Humans; Parasites; Parasitic Diseases
PubMed: 23425516
DOI: 10.1017/S0031182012002259 -
Parasitology Sep 2019The investigation of the glycan repertoire of several organisms has revealed a wide variation in terms of structures and abundance of glycan moieties. Among the... (Review)
Review
The investigation of the glycan repertoire of several organisms has revealed a wide variation in terms of structures and abundance of glycan moieties. Among the parasites, it is possible to observe different sets of glycoconjugates across taxa and developmental stages within a species. The presence of distinct glycoconjugates throughout the life cycle of a parasite could relate to the ability of that organism to adapt and survive in different hosts and environments. Carbohydrates on the surface, and in excretory-secretory products of parasites, play essential roles in host-parasite interactions. Carbohydrate portions of complex molecules of parasites stimulate and modulate host immune responses, mainly through interactions with specific receptors on the surface of dendritic cells, leading to the generation of a pattern of response that may benefit parasite survival. Available data reviewed here also show the frequent aspect of parasite immunomodulation of mammalian responses through specific glycan interactions, which ultimately makes these molecules promising in the fields of diagnostics and vaccinology.
Topics: Animals; Diagnostic Tests, Routine; Glycoconjugates; Host-Parasite Interactions; Life Cycle Stages; Parasites; Parasitic Diseases; Vaccines
PubMed: 31057132
DOI: 10.1017/S0031182019000465 -
Trends in Parasitology Dec 2015Inter-specific interactions between parasites impact on parasite intra-host dynamics, host health, and disease management. Identifying and understanding interaction... (Review)
Review
Inter-specific interactions between parasites impact on parasite intra-host dynamics, host health, and disease management. Identifying and understanding interaction mechanisms in the wild is crucial for wildlife disease management. It is however complex because several scales are interlaced. Parasite-parasite interactions are likely to occur via mechanisms at the within-host level, but also at upper levels (host population and community). Furthermore, interactions occurring at one level of organization spread to upper levels through cascade effects. Even if cascade effects are important confounding factors, we argue that we can also benefit from them because upper scales often provide a way to survey a wider range of parasites at lower cost. New protocols and theoretical studies (especially across scales) are necessary to take advantage of this opportunity.
Topics: Animals; Animals, Wild; Ecosystem; Host-Parasite Interactions; Humans; Parasites; Parasitic Diseases, Animal; Parasitology
PubMed: 26440785
DOI: 10.1016/j.pt.2015.07.005 -
International Journal For Parasitology Aug 2014Although parasites are widely touted as representing a large fraction of the Earth's total biodiversity, several questions remain about the magnitude of parasite... (Review)
Review
Although parasites are widely touted as representing a large fraction of the Earth's total biodiversity, several questions remain about the magnitude of parasite diversity, our ability to discover it all and how it varies among host taxa or areas of the world. This review addresses four topical issues about parasite diversity. First, we cannot currently estimate how many parasite species there are on Earth with any accuracy, either in relative or absolute terms. Species discovery rates show no sign of slowing down and cryptic parasite species complicate matters further, rendering extrapolation methods useless. Further, expert opinion, which is also used as a means to estimate parasite diversity, is shown here to be prone to serious biases. Second, it seems likely that we may soon not have enough parasite taxonomists to keep up with the description of new species, as taxonomic expertise appears to be limited to a few individuals in the latter stages of their career. Third, we have made great strides toward explaining variation in parasite species richness among host species, by identifying basic host properties that are universal predictors of parasite richness, whatever the type of hosts or parasites. Fourth, in a geographical context, the main driver of variation in parasite species richness across different areas is simply local host species richness; as a consequence, patterns in the spatial variation of parasite species richness tend to match those already well-documented for free-living species. The real value of obtaining good estimates of global parasite diversity is questionable. Instead, our efforts should be focused on ensuring that we maintain sufficient taxonomic resources to keep up with species discovery, and apply what we know of the variation in parasite species richness among host species or across geographical areas to contribute to areas of concern in the ecology of health and in conservation biology.
Topics: Animals; Biodiversity; Host-Parasite Interactions; Parasites; Parasitic Diseases; Species Specificity
PubMed: 24607559
DOI: 10.1016/j.ijpara.2014.02.003 -
Parasitology Dec 2012SUMMARY Molecular phylogeography has revolutionised our ability to infer past biogeographic events from cross-sectional data on current parasite populations. In... (Review)
Review
SUMMARY Molecular phylogeography has revolutionised our ability to infer past biogeographic events from cross-sectional data on current parasite populations. In ecological parasitology, this approach has been used to address fundamental questions concerning host-parasite co-evolution and geographic patterns of spread, and has raised many technical issues and problems of interpretation. For applied parasitologists, the added complexity inherent in adding population genetic structure to perceived parasite distributions can sometimes seem to cloud rather than clarify approaches to control. In this paper, we use case studies firstly to illustrate the potential extent of cryptic diversity in parasite and parasitoid populations, secondly to consider how anthropogenic influences including movement of domestic animals affect the geographic distribution and host associations of parasite genotypes, and thirdly to explore the applied relevance of these processes to parasites of socio-economic importance. The contribution of phylogeographic approaches to deeper understanding of parasite biology in these cases is assessed. Thus, molecular data on the emerging parasites Angiostrongylus vasorum in dogs and wild canids, and the myiasis-causing flies Lucilia spp. in sheep and Cochliomyia hominovorax in humans, lead to clear implications for control efforts to limit global spread. Broader applications of molecular phylogeography to understanding parasite distributions in an era of rapid global change are also discussed.
Topics: Animals; Genetic Variation; Host-Parasite Interactions; Humans; Parasites; Parasitic Diseases; Phylogeography; Population Dynamics; Species Specificity
PubMed: 22917112
DOI: 10.1017/S0031182012001060 -
Parasite (Paris, France) Sep 2008Mathematical modelling of parasite transmission systems can provide useful information about host parasite interactions and biology and parasite population dynamics. In... (Review)
Review
Mathematical modelling of parasite transmission systems can provide useful information about host parasite interactions and biology and parasite population dynamics. In addition good predictive models may assist in designing control programmes to reduce the burden of human and animal disease. Model building is only the first part of the process. These models then need to be confronted with data to obtain parameter estimates and the accuracy of these estimates has to be evaluated. Estimation of parasite densities is central to this. Parasite density estimates can include the proportion of hosts infected with parasites (prevalence) or estimates of the parasite biomass within the host population (abundance or intensity estimates). Parasite density estimation is often complicated by highly aggregated distributions of parasites within the hosts. This causes additional challenges when calculating transmission parameters. Using Echinococcus spp. as a model organism, this manuscript gives a brief overview of the types of descriptors of parasite densities, how to estimate them and on the use of these estimates in a transmission model.
Topics: Animals; Demography; Echinococcosis; Echinococcus; Host-Parasite Interactions; Humans; Mathematics; Models, Biological; Parasites; Parasitic Diseases; Population Density; Population Dynamics; Population Growth
PubMed: 18814726
DOI: 10.1051/parasite/2008153477 -
Evolution; International Journal of... Dec 2023Hyperparasites (species which parasitize other parasites) are common in natural populations, affecting many parasitic taxa, including: eukaryotic parasites; bacterial...
Hyperparasites (species which parasitize other parasites) are common in natural populations, affecting many parasitic taxa, including: eukaryotic parasites; bacterial and fungal pathogens. Hyperparasitism is therefore likely to shape the ecology and evolution of many host-parasite systems, representing a promising method for biocontrol (e.g., treating antimicrobial resistant infections). However, the eco-evolutionary consequences of hyperparasitism have received little attention. We use a host-parasite-hyperparasite model to explore how introducing a hyperparasite drives the evolution of parasite virulence, and what impact this has on the host population. We show when the introduction of a hyperparasite selects for higher or lower parasite virulence, and the changes in virulence experienced by the host population. Crucially, we show that variation in the direct effects of hyperparasites on virulence and transmission, and the probability of cotransmission, can lead to a previously unseen hysteresis effect, whereby small shifts in hyperparasite characteristics can lead to sudden shifts in parasite virulence. We also show that hyperparasites can induce diversification in parasite virulence, leading to the coexistence of high and low virulence strains. Our results show hyperparasites can have dramatic effects on the evolution of parasite virulence, and that the use of hyperparasites in biocontrol should be approached with caution.
Topics: Animals; Parasites; Virulence; Ecology; Biological Evolution; Host-Parasite Interactions
PubMed: 37778003
DOI: 10.1093/evolut/qpad178 -
Parasite (Paris, France) Sep 2008
Topics: Animals; Genetic Variation; Host-Parasite Interactions; Humans; Parasites; Phylogeny
PubMed: 18814679
DOI: 10.1051/parasite/2008153185 -
Parasitology 1997Recent developments in parasite immune evasion and exploitation are reviewed with special reference to the papers presented in this volume. Parasites, broadly defined,... (Review)
Review
Recent developments in parasite immune evasion and exploitation are reviewed with special reference to the papers presented in this volume. Parasites, broadly defined, of animals with good immune responses have evolved many strategies that adapt them to survive and reproduce. These strategies may be passive, or may involve active intervention with host immune regulation, and can be categorized as immune evasion, immune exploitation and molecular piracy. The concept of immune evasion began with Paul Ehrlich's demonstration of antigenic variation in African trypanosomes and was reinforced by later ideas on molecular mimicry. Molecular mimicry is updated in the light of recent discoveries about degeneracy and plasticity of TCR/MHC-peptide recognition. Possible connections between two of its postulated consequences, evasion and autoimmunity, are discussed. Another putative consequence of molecular mimicry, host antigenic polymorphism, is also updated. The concept of exploitation of host immune responses by parasites has been reinforced by new data on its first known examples, especially the immune dependence of schistosome egg excretion. Newer examples include use of host cytokines as parasite growth factors, virokines, viroreceptors and helminth pseudocytokines. Finally, questions of host gene capture by viruses and possible horizontal gene transfer between host and parasite mediated by retroviruses are examined. The latter is compared with molecular conservation as a source of molecular mimicry and other aspects of host--parasite coevolution.
Topics: Animals; Autoimmunity; Biological Evolution; Host-Parasite Interactions; Humans; Molecular Mimicry; Parasites; Parasitic Diseases
PubMed: 9571701
DOI: 10.1017/s0031182097002357