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Trends in Parasitology Dec 2017Expanding 'omics' datasets for parasitic nematodes have accelerated the identification of putative drug targets derived from the nematode nervous system. However, novel... (Review)
Review
Expanding 'omics' datasets for parasitic nematodes have accelerated the identification of putative drug targets derived from the nematode nervous system. However, novel drug target validation is hampered by the absence of adequate localisation, functional characterisation, and receptor deorphanisation tools in key nematode pathogens. Reverse genetics techniques have advanced to encompass transgenic, targeted mutagenesis, gene silencing (RNA interference), and genome editing (CRISPR/Cas9) approaches in Caenorhabditis elegans. Unfortunately the translation to nematode pathogens has been slow, such that parasite-focused toolbox development and optimisation is critical. Here we review the discovery, localisation, and functional characterisation toolkit available for parasitic nematode neuropeptide research, and assess the scope and limitations of the tools and techniques for novel nematicide discovery.
Topics: Animals; Caenorhabditis elegans; Nematoda; Neuropeptides; Parasites; Parasitology
PubMed: 28986106
DOI: 10.1016/j.pt.2017.08.009 -
Trends in Ecology & Evolution Mar 2007In natural systems, individuals are often co-infected by many species of parasites. However, the significance of interactions between species and the processes that... (Review)
Review
In natural systems, individuals are often co-infected by many species of parasites. However, the significance of interactions between species and the processes that shape within-host parasite communities remain unclear. Studies of parasite community ecology are often descriptive, focusing on patterns of parasite abundance across host populations rather than on the mechanisms that underlie interactions within a host. These within-host interactions are crucial for determining the fitness and transmissibility of co-infecting parasite species. Here, we highlight how techniques from community ecology can be used to restructure the approaches used to study parasite communities. We discuss insights offered by this mechanistic approach that will be crucial for predicting the impact on wildlife and human health of disease control measures, climate change or novel parasite species introductions.
Topics: Animals; Animals, Wild; Biodiversity; Climate; Ecology; Host-Parasite Interactions; Humans; Life Cycle Stages; Parasites; Parasitic Diseases, Animal; Population Dynamics; Residence Characteristics; Species Specificity
PubMed: 17137676
DOI: 10.1016/j.tree.2006.11.005 -
Future Microbiology Jan 2012Preventing disease is a major goal of applied bioscience and explaining variation in the harm caused by parasites, and their infectiousness, are major goals of... (Review)
Review
Preventing disease is a major goal of applied bioscience and explaining variation in the harm caused by parasites, and their infectiousness, are major goals of evolutionary biology. The emerging field of evolutionary medicine integrates these two ambitions to inform the development of control strategies that retard or withstand unfavorable parasite evolution. However, as parasites live in hostile and changeable environments - the bodies of other organisms - the success of integrating evolutionary biology with medicine requires a better understanding of how natural selection has solved the problems parasites face. There is increasing appreciation that natural selection shapes parasite strategies to survive in the host and transmit between hosts through facultative (plastic) shifts in parasite traits expressed during infections and in different hosts. This article describes how integrating parasite plasticity into biomedical thinking is central to explaining disease outcomes and transmission patterns, as well as predicting the success of control measures.
Topics: Animals; Biological Evolution; Ecology; Ecosystem; Host-Parasite Interactions; Humans; Parasites; Parasitic Diseases; Phenotype
PubMed: 22191443
DOI: 10.2217/fmb.11.134 -
Current Opinion in Microbiology Dec 2020
Topics: Animals; Host-Parasite Interactions; Humans; Immunity; Parasites; Parasitic Diseases
PubMed: 33328088
DOI: 10.1016/j.mib.2020.11.008 -
Journal of Helminthology Jan 2019In recent decades, parasite community ecology has produced hundreds of studies on an ever-growing number of host species, and developed into an active sub-discipline of... (Review)
Review
In recent decades, parasite community ecology has produced hundreds of studies on an ever-growing number of host species, and developed into an active sub-discipline of parasitology. However, this growth has been characterized by a lack of standards in the practices used by researchers, with many common approaches being flawed, unjustified or misleading. Here, in the hope of promoting advances in the study of parasite community ecology, I identify some of the most common errors or weaknesses in past studies, and propose ten simple rules for best practice in the field. They cover issues including, among others, taxonomic resolution, proper and justifiable analytical methods, higher-level replication, controlling for sampling effort or species richness, accounting for spatial distances, using experimental approaches, and placing raw data in the public domain. While knowledge of parasite communities has expanded in breadth, with more and more host species being studied, true progress has been very limited with respect to our understanding of fundamental general processes shaping these communities. It is hoped that the guidelines presented here can direct researchers away from the entrenched use of certain approaches flawed in design, analysis or interpretation, by offering a more rigorous and standardized set of practices, and, hopefully, a way forward.
Topics: Animals; Biodiversity; Biota; Ecology; Host Specificity; Host-Parasite Interactions; Parasites; Parasitology
PubMed: 30141383
DOI: 10.1017/S0022149X18000767 -
Advances in Parasitology 2013Co-infection of individual hosts by multiple parasite species is a pattern that is very commonly observed in natural populations. Understanding the processes that... (Review)
Review
Co-infection of individual hosts by multiple parasite species is a pattern that is very commonly observed in natural populations. Understanding the processes that generate these patterns poses a challenge. For example, it is difficult to discern the relative roles of exposure and susceptibility in generating the mixture and density of parasites within hosts. Yet discern them we must, if we are to design and deliver successful medical interventions for co-infected populations. Here, we synthesise an emergent understanding of how processes operate and interact to generate patterns of co-infection. We consider within-host communities (or infracommunities) generally, that is including not only classical parasites but also the microbiota that are so abundant on mucosal surfaces and which are increasingly understood to be so influential on host biology. We focus on communities that include a helminth, but we expect similar inferences to pertain to other taxa. We suggest that, thanks to recent research at both the within-host (e.g. immunological) and between-host (e.g. epidemiological) scales, researchers are poised to reveal the processes that generate the observed distribution of parasite communities among hosts. Progress will be facilitated by using new technologies as well as statistical and experimental tools to test competing hypotheses about processes that might generate patterns in co-infection data. By understanding the multiple interactions that underlie patterns of co-infection, we will be able to understand and intelligently predict how a suite of co-infections (and thus the host that bears them) will together respond to medical interventions as well as other environmental changes. The challenge for us all is to become scholars of co-infections.
Topics: Animals; Coinfection; Humans; Parasites; Parasitic Diseases
PubMed: 23548088
DOI: 10.1016/B978-0-12-407706-5.00005-8 -
Parasitology 1994Parasite-induced modifications of host behaviour are known from a wide range of host-parasite associations. In many cases, these behavioural changes are thought to be... (Review)
Review
Parasite-induced modifications of host behaviour are known from a wide range of host-parasite associations. In many cases, these behavioural changes are thought to be adaptive and benefit the parasite by increasing its probability of successful transmission. However, in many cases, energy spent on host manipulation will not be available for other functions, such as growth. These trade-offs suggest that in the absence of other constraints, natural selection will optimize, and not maximize, the influence of parasites on host behaviour. This argument is developed and expanded into theoretical considerations of the evolution of host behaviour manipulation by parasites. Among populations of the same parasite species or among closely-related species, the optimal investment into manipulation, or optimal manipulative effort (ME*), of individual parasites is predicted to increase as (1) typical infrapopulation size decreases, (2) prevalence increases, (3) the longevity of the infected host, or of the parasite in its host, decreases, (4) passive transmission rates decrease, and (5) parasite fecundity decreases. This evolutionary analysis indicates that ecological and life history variables may have played an important role in the evolution of manipulation of host behaviour by parasites.
Topics: Adaptation, Physiological; Animals; Behavior, Animal; Host-Parasite Interactions; Parasites; Parasitic Diseases
PubMed: 7854845
DOI: 10.1017/s0031182000085127 -
Behavioural Processes Mar 2005
Review
Topics: Adaptation, Physiological; Animals; Behavior Control; Behavior, Animal; Ecosystem; Host-Parasite Interactions; Parasites; Parasitic Diseases, Animal; Sick Role; Virulence
PubMed: 15792696
DOI: 10.1016/j.beproc.2004.07.010 -
Parasitology 1997We examine the evolution of microparasites in response to the immune system of vertebrate hosts. We first describe a simple model for an acute infection. This model... (Review)
Review
We examine the evolution of microparasites in response to the immune system of vertebrate hosts. We first describe a simple model for an acute infection. This model suggests that the within-host dynamics of the microparasite will be a 'race' between parasite multiplication and a clonally expanding response by the host immune system, resulting either in immune-mediated clearance or host death. In this very simple model, in which there is only a single parasite and host genotype, maximum transmission is obtained by parasites with intermediate rates of growth (and virulence). We examine how these predictions depend on key assumptions about the parasite and the host, and consider how this model may be expanded to incorporate the effect of additional complexities such as host-parasite co-evolution, host polymorphism, and multiple infections.
Topics: Animals; Biological Evolution; Host-Parasite Interactions; Mathematics; Models, Biological; Parasites; Parasitic Diseases; Virulence
PubMed: 9571700
DOI: 10.1017/s003118209700200x -
Current Opinion in Microbiology Aug 2015Plasmodium parasites belong to the Apicomplexan phylum, which consists mostly of obligate intracellular pathogens that vary dramatically in host cell tropism. Plasmodium... (Review)
Review
Plasmodium parasites belong to the Apicomplexan phylum, which consists mostly of obligate intracellular pathogens that vary dramatically in host cell tropism. Plasmodium sporozoites are highly hepatophilic. The specific molecular mechanisms, which facilitate sporozoite selection and successful infection of hepatocytes, remain poorly defined. Here, we discuss the parasite and host factors which are critical to hepatocyte infection. We derive a model where sporozoites initially select host cells that constitute a permissive environment and then further refine the chosen hepatocyte during liver stage development, ensuring life cycle progression. While many unknowns of pre-erythrocytic infection remain, advancing models and technologies that enable analysis of human malaria parasites and of single infected cells will catalyze a comprehensive understanding of the interaction between the malaria parasite and its hepatocyte host.
Topics: Animals; Disease Models, Animal; Hepatocytes; Host-Pathogen Interactions; Humans; Models, Biological; Parasitology; Plasmodium
PubMed: 26102161
DOI: 10.1016/j.mib.2015.05.013