Complex Life Cycle Of Parasite Research Articles

Ontological representation, modeling, and analysis of parasite vaccines

BackgroundPathogenic parasites are responsible for multiple diseases, such as malaria and Chagas disease, in humans and livestock. Traditionally, pathogenic parasites have been largely an evasive topic for vaccine design, with most successful vaccines only emerging recently. To aid vaccine design, the VIOLIN vaccine knowledgebase has collected vaccines from all sources to serve as a comprehensive vaccine knowledgebase. VIOLIN utilizes the Vaccine Ontology (VO) to standardize the modeling of vaccine data. VO did not model complex life cycles as seen in parasites. With the inclusion of successful parasite vaccines, an update in parasite vaccine modeling was needed.ResultsVIOLIN was expanded to include 258 parasite vaccines against 23 protozoan species, and 607 new parasite vaccine-related terms were added to VO since 2022. The updated VO design for parasite vaccines accounts for parasite life stages and for transmission-blocking vaccines. A total of 356 terms from the Ontology of Parasite Lifecycle (OPL) were imported to VO to help represent the effect of different parasite life stages. A new VO class term, ‘transmission-blocking vaccine,’ was added to represent vaccines able to block infectious transmission, and one new VO object property, ‘blocks transmission of pathogen via vaccine,’ was added to link vaccine and pathogen in which the vaccine blocks the transmission of the pathogen. Additionally, our Gene Set Enrichment Analysis (GSEA) of 140 parasite antigens used in the parasitic vaccines identified enriched features. For example, significant patterns, such as signal, plasma membrane, and entry into host, were found in the antigens of the vaccines against two parasite species: Plasmodium falciparum and Toxoplasma gondii. The analysis found 18 out of the 140 parasite antigens involved with the malaria disease process. Moreover, a majority (15 out of 54) of P. falciparum parasite antigens are localized in the cell membrane. T. gondii antigens, in contrast, have a majority (19/24) of their proteins related to signaling pathways. The antigen-enriched patterns align with the life cycle stage patterns identified in our ontological parasite vaccine modeling.ConclusionsThe updated VO modeling and GSEA analysis capture the influence of the complex parasite life cycles and their associated antigens on vaccine development.

Comparative analysis of metacyclogenesis and infection curves in different discrete typing units of Trypanosoma cruzi

Chagas disease (CD), caused by the complex life cycle parasite Trypanosoma cruzi, is a global health concern and impacts millions globally. T. cruzi’s genetic variability is categorized into discrete typing units (DTUs). Despite their widespread presence in the Americas, a comprehensive understanding of their impact on CD is lacking. This study aims to analyze life cycle traits across life cycle stages, unraveling DTU dynamics. Metacyclogenesis curves were generated, inducing nutritional stress in epimastigotes of five DTUs (TcI (MG), TcI (DA), TcII(Y), TcIII, TcIV, and TcVI), resulting in metacyclic trypomastigotes. Infection dynamics in Vero cells from various DTUs were evaluated, exploring factors like amastigotes per cell, cell-derived trypomastigotes, and infection percentage. Statistical analyses, including ANOVA tests, identified significant differences. Varying onset times for metacyclogenesis converged on the 7th day. TcI (MG) exhibited the highest metacyclogenesis potential. TcI (DA) stood out, infecting 80% of cells within 24 h. TcI demonstrated the highest potential in both metacyclogenesis and infection among the strains assessed. Intra-DTU diversity was evident among TcI strains, contributing to a comprehensive understanding of Trypanosoma cruzi dynamics and genetic diversity.

Using of Nanoparticles in treating of Hydatid Disease in Domestic Animals

The parasite Echinococcus granulosus is the cause of unilocular hydatid disease, which is a serious health risk to people and domestic animals worldwide. Livestock with hydatid disease suffers substantial financial losses due to the slaughterhouse's disapproval of the diseased animal parts, productivity losses (such as lowered live weight gain, milk yield, reproductive rates, and hide and skin value), and expenses related to caring for both humans and animals. Because of the parasite's complex life cycle and the difficulties associated with traditional treatment techniques, new strategies are needed to handle this crippling illness more successfully. In the treatment of hydatid illness, nanomedicine and nanoparticles have shown great promise, providing new approaches to medication distribution, focused therapy, diagnosis, and control measures. The possible roles and applications of nanomedicine and nanoparticles in treating hydatid illness in domestic animals are reviewed in this article. Owing to their distinct physicochemical characteristics at the nanoscale, nanoparticles enable tailored medication administration, enhancing anthelmintic agent potency while reducing systemic side effects. Therapeutic drugs like praziquantel or albendazole can be encapsulated in these nanoparticles, allowing for improved permeability and retention at the location of the parasite cysts. Additionally, imaging agents and diagnostic instruments at the nanoscale enable. Additionally, nanotechnology offers avenues for developing innovative control measures, including environmental disinfection and targeted delivery of parasiticides. Collaborative efforts between researchers, veterinarians, and experts in nanotechnology are crucial to harnessing the full potential of nanoparticles and nanomedicine in effectively managing the infection in domestic animals.

Merging socioecological variables to predict risk of Chagas disease

How far are we from predicting the occurrence of zoonotic diseases? In this paper we have made use of both socioecological and ecological variables to predict Chagas disease occurrence. Chagas disease involves, Trypanosoma cruzi, a complex life-cycle parasite which requires two hosts: blood-feeding triatomine insects and vertebrate hosts including humans. We have used a common risk assessment method combined with datasets that imply critical environmental and socioeconomic drivers of Chagas dynamics to predict the occurrence of this disease. We also carried out a network analysis to assess the interactions among triatomines and mammal host species given their human contact via whether hunted, domesticated or associated with anthropogenic landscapes in Mexico. We found that social backwardness variation, lack of health services and altitude had the largest relative influence Chagas events. Triatoma pallidipennis made use of the largest host diversity. Host species shared by the highest number of different triatomines were a woodrat, the highly appreciated bushmeat, and racoon. These results indicate both the predominance of socio-economic factors over ecological ones, and how close we are from predicting zoonotic diseases.

Deconstructing dams and disease: predictions for salmon disease risk following Klamath River dam removals

The health of fish populations and the river systems they inhabit have broad ecological, cultural, recreational, and economic relevance. This is exemplified by the iconic anadromous salmonid fishes native to the West Coast of North America. Salmon populations have been constrained since the mid nineteenth century by dam construction and water reallocation. In the Klamath River (Oregon and California, USA), a series of dams built in the early-mid 20th century cut the basin in two and blocked anadromous fish access to more than 600 river kilometers. This dramatic loss of habitat, coupled with infectious diseases and resulting epizootics, have impacted the wellbeing of these salmonid populations. In 2023-2024, the Klamath River will undergo the largest river restoration project in US history. Removal of the four lowermost dams will cause profound physical changes to the river, including flow, water temperature, and channel geomorphology. The dam removals will reconnect the lower and upper portions of the basin, and provide fish passage after a century of segregation. Reestablishment of upstream and downstream fish movements will also alter the occupancy and abundance of the salmonid hosts and their pathogens. The increased habitat availability and longer migration routes will increase duration of pathogen exposure and potential impacts on juvenile survival and adult pre-spawn mortality. However, restoration of more natural flow and sediment regimes will decrease overall fish disease risk by disrupting complex parasite life cycles. To better understand these multifarious, competing factors, we review the salmonid species in the Klamath River, and provide an overview of their historical pathogen challenges and associated diseases and use this as a framework to predict the effects of dam removals on disease dynamics. Our review and predictions are a synthesis of expertise from tribal biologists, fish health specialists and fish biologists, many of whom have lived and worked on the Klamath River for decades. We conclude with recommendations for expansion of current pathogen monitoring and research efforts to measure changes in host-pathogen dynamics basin-wide.

Paleoecological Implications of Trematode-Induced Pit Size in Chamelea Gallina from the Adriatic Sea, Italy

Gymnophallid trematodes are complex life cycle parasites that induce characteristic pits in their bivalve intermediate hosts, which serve as their sole fossil record. Previous work demonstrated that trematode prevalence increases with rising sea levels, but little has been done to investigate patterns of trematode pit size in relation to Holocene sea-level and environmental changes. Here we focus on trematode pits preserved in the bivalve Chamelea gallina from five late Holocene core samples (2510-3140 y BP) and eight modern death assemblages from the Po-Adriatic system (northern Italy). Using ImageJ, we measured 838 total pits, with 715 from the core samples and 123 from the death assemblages. The geometric mean of the primary and secondary axis was used as a proxy for trace size, which ranges from 0.117 mm to 1.708 mm. The median size of Holocene pits (0.497 mm) is significantly larger (pWilcoxon = 1.73e-05) than the median size of modern pits (0.396 mm), indicating a decrease in trematode metacercariae body size over this time. There was no significant relationship between trematode pit size and host bivalve body size and only whole, well-preserved Holocene valves were analyzed to minimize the influence of taphonomy. We interpret a change in C. gallina-trematode parasite-host interactions over the last 3 ky, which could be the result of several scenarios. Modern pits could be created by different taxa, which have smaller body sizes, or the pits could be formed by the same parasitic taxa which now may have a decreased body size, perhaps due to stress. These results, coupled with a survey of modern metacercariae sizes, suggest that the trematode pit size record can provide relevant information on parasite paleoecology and, perhaps, identity. Such information will enable more nuanced analyses of parasite-host response to environmental change in the past with an eye to the future.

Modelling the epidemiology of zoonotic parasites transmitted through a predator-prey system in urban landscapes: The Calgary Echinococcus multilocularis Coyote Agent-based model (CEmCA)

Traditional epidemiological models for managing disease risk face serious hurdles when applied to complex life-cycle parasites that involve several host species. Echinococcus multilocularis (Em) is such a parasite and the aetiological agent of a serious zoonosis, Alveolar Echinococcosis, affecting thousands of people every year worldwide. The parasite is transmitted through predation of infectious intermediate hosts (rodents) by definitive hosts (foxes, coyotes). Definitive hosts are usually territorial with individual home ranges in spatially heterogeneous urban landscapes, where they carry very diverse parasite load, thus creating a highly heterogeneous distribution of the parasite in the urban environment. To incorporate individual differences and spatial heterogeneity into an epidemiological model, we developed Calgary Echinococcus multilocularis Coyote Agent-based model (CEmCA).The CEmCA was developed to understand the processes and mechanisms that produces the heterogeneity in the transmission of Em. The model simulates behaviors of individual coyotes inhabiting the City of Calgary as agents, reproducing behavioral patterns such as their home ranges, where and which prey species they hunt, where they defecate, and how they transmit Em. The agents perform all its behaviors in a simulation landscape that represent an actual Calgary landscape that includes maps of natural habitats and small mammal assemblages.The CEmCA proved to be highly sensitive to unobservable epidemiological parameters, and although not fully matching the observed patterns it provided useful insights into the epidemiological processes of Em. Moreover, our experimental simulations supported the hypothesis that distribution of intermediate hosts and separation of habitats were the main causes of spatial heterogeneity in infection.By integrating individual differences and spatial heterogeneity this study contributed to the understanding of the epidemiology of trophically transmitted parasite with complex life-cycles. Notwithstanding requiring further work, this approach holds many promises for further applications in preventative management of infectious diseases in urban landscapes.

Dihydroartemesinin and Curcumin Based Self-Microemulsifying Drug Delivery System for Antimalarial Activity.

Malaria is a significant global problem which still persists despite the development of various effective antimalarial drugs. It is challenging to treat this disease due to the parasite's complex life cycle and high recrudensce of antimalarial drugs. A new self-micro emulsifying drug delivery system has been developed to improve the solubility of dihydroartemisinin and curcumin. The prepared formulation contained Dihydroartemesinin, curcumin, Groundnut Oil, Cremephor RH, and Tween 80. Self-micro emulsification time, zeta potential, droplet size, polydispersity index, transmission electron microscopy, drug release, and in-vivo studies were performed for characterization. The globule size was found to be 25.59±0.40 nm and the zeta potential was-5.75±0.18 mV. The globules prepared were spherical in shape. The in-vitro dissolution performance of formulation of dihydroartemisinin and curcumin self emulsifying drug delivery system showed significantly (p<0.05, Origin Pro 8.5) higher release as compared to the pure drugs. The results of the study suggested that the prepared self emulsifying drug delivery system combination of Dihydroartemesinin and curcumin has a better potential to cure parasitemia as compared to the individual drug.

A conserved malaria parasite protein required for maintenance of sporozoite cell shape and transmission.

Malaria parasites are transmitted by mosquitoes and a substantial part of the parasite's complex life cycle takes place inside the insect. Parasite transmission starts with the uptake of parasite stages called gametocytes from the vertebrate host with the blood meal of a female vector mosquito, completing several weeks later with the injection of parasite stages called sporozoites into the vertebrate host by mosquito bite. The sporozoites form in their thousands inside ookinete-derived oocysts situated on the abluminal side of the mosquito midgut epithelium by a process of cell division known as sporogony. After their formation, sporozoites egress from the oocyst into the haemolymph, invade the salivary glands and mature to become infective to the vertebrate. This MicroCommentary reviews recent reports describing a conserved plasma membrane-associated protein of Plasmodium berghei, PBANKA_1422900, and its role in maintaining the shape and structural integrity of sporozoites in salivary glands and during inoculation into the vertebrate host. Combined results from three separate studies provide mechanistic insights into how this protein achieves structural maintenance of the sporozoite, and how in turn this promotes the sporozoite's ability to overcome several physical obstacles and allow it to establish infection in the vertebrate.

Life history mediates the association between parasite abundance and geographic features.

Although parasites are ubiquitous in marine ecosystems, predicting the abundance of parasites present within marine ecosystems has proven challenging due to the unknown effects of multiple interacting environmental gradients and stressors. Furthermore, parasites often are considered as a uniform group within ecosystems despite their significant diversity. We aim to determine the potential importance of multiple predictors of parasite abundance in coral reef ecosystems, including reef area, island area, human population density, chlorophyll-a, host diversity, coral cover, host abundance and island isolation. Using a model selection approach within a database of more than 1,200 individual fish hosts and their parasites from 11 islands within the Pacific Line Islands archipelago, we reveal that geographic gradients, including island area and island isolation, emerged as the best predictors of parasite abundance. Life history moderated the relationship; parasites with complex life cycles increased in abundance with increasing island isolation, while parasites with direct life cycles decreased with increasing isolation. Direct life cycle parasites increased in abundance with increasing island area, although complex life cycle parasite abundance was not associated with island area. This novel analysis of a unique dataset indicates that parasite abundance in marine systems cannot be predicted precisely without accounting for the independent and interactive effects of each parasite's life history and environmental conditions.

Affinity-purified Plasmodium tubulin provides a key reagent for antimalarial drug development

Hirst et al. used a TOG-domain-based affinity-purification approach to reconstitute and define the in vitro dynamics of blood-stage Plasmodium falciparum αβ-tubulin. This provides a key reagent for defining parasite microtubule (MT) dynamics and for evaluating the efficacy of anti-MT drugs throughout the complex parasite life cycle.

Heat sensitivity of first host and cercariae may restrict parasite transmission in a warming sea

To predict global warming impacts on parasitism, we should describe the thermal tolerance of all players in host–parasite systems. Complex life-cycle parasites such as trematodes are of particular interest since they can drive complex ecological changes. This study evaluates the net response to temperature of the infective larval stage of Himasthla elongata, a parasite inhabiting the southwestern Baltic Sea. The thermal sensitivity of (i) the infected and uninfected first intermediate host (Littorina littorea) and (ii) the cercarial emergence, survival, self-propelling, encystment, and infection capacity to the second intermediate host (Mytilus edulis sensu lato) were examined. We found that infection by the trematode rendered the gastropod more susceptible to elevated temperatures representing warm summer events in the region. At 22 °C, cercarial emergence and infectivity were at their optimum while cercarial survival was shortened, narrowing the time window for successful mussel infection. Faster out-of-host encystment occurred at increasing temperatures. After correcting the cercarial emergence and infectivity for the temperature-specific gastropod survival, we found that warming induces net adverse effects on the trematode transmission to the bivalve host. The findings suggest that gastropod and cercariae mortality, as a tradeoff for the emergence and infectivity, will hamper the possibility for trematodes to flourish in a warming ocean.

Temporal effects and changes in the parasitic community ofProchilodus lineatus(Valenciennes, 1837) (Characiformes: Prochilodontidae) in a floodplain

The construction of dams causes several impacts on aquatic environments, altering the flow of rivers, environmental variables, and all biota present, including parasites. Little is known about how the parasitic community can be influenced in the long term by environmental changes. In this study, it was expected that the impacts caused by environmental disturbances will be directly reflected by the composition of the parasite populations. We evaluated the change in the structure of the Prochilodus lineatus endoparasite community between two periods sampled 15 years apart in the upper Paraná River floodplain. There was a significant difference in the weight-length relationship of P. lineatus between these periods and a total of 15 species of parasites were found: 11 species in Period 1 and nine species in Period 2 and five species occurred in both periods. The species richness and diversity were higher in Period 1, and we observed that the correlation of descriptors (richness, diversity and evenness) increased with fish length in this period. In both periods, digeneans numerically dominated the parasitic community, and we verified changes in the composition of parasites between periods. Both the host and the parasites were possibly affected by the environmental impacts resulting from the construction of dams over time, and it is noteworthy that complex life cycle parasites such as Digenea and Acanthocephala require intermediate hosts to complete their life cycle, and the population responds to fluctuations in the face of modified environments.

Habitat fragmentation and vegetation structure impact gastrointestinal parasites of small mammalian hosts in Madagascar.

Deleterious effects of habitat loss and fragmentation on biodiversity have been demonstrated in numerous taxa. Although parasites represent a large part of worldwide biodiversity, they are mostly neglected in this context. We investigated the effects of various anthropogenic environmental changes on gastrointestinal parasite infections in four small mammal hosts inhabiting two landscapes of fragmented dry forest in northwestern Madagascar. Coproscopical examinations were performed on 1,418 fecal samples from 903 individuals of two mouse lemur species, Microcebus murinus (n = 199) and M. ravelobensis (n = 421), and two rodent species, the native Eliurus myoxinus (n = 102) and the invasive Rattus rattus (n = 181). Overall, sixteen parasite morphotypes were detected and significant prevalence differences between host species regarding the most common five parasites may be explained by parasite–host specificity or host behavior, diet, and socioecology. Ten host‐ and habitat‐related ecological variables were evaluated by generalized linear mixed modeling for significant impacts on the prevalence of the most abundant gastrointestinal parasites and on gastrointestinal parasite species richness (GPSR). Forest maturation affected homoxenous parasites (direct life cycle) by increasing Lemuricola, but decreasing Enterobiinae gen. sp. prevalence, while habitat fragmentation and vegetation clearance negatively affected the prevalence of parasites with heterogenic environment (i.e., Strongyloides spp.) or heteroxenous (indirect cycle with intermediate host) cycles, and consequently reduced GPSR. Forest edges and forest degradation likely change abiotic conditions which may reduce habitat suitability for soil‐transmitted helminths or required intermediate hosts. The fragility of complex parasite life cycles suggests understudied and potentially severe effects of decreasing habitat quality by fragmentation and degradation on hidden ecological networks that involve parasites. Since parasites can provide indispensable ecological services and ensure stability of ecosystems by modulating animal population dynamics and nutrient pathways, our study underlines the importance of habitat quality and integrity as key aspects of conservation.

Parasitism and host behavior in the context of a changing environment: The Holocene record of the commercially important bivalve Chamelea gallina, northern Italy.

Rapid warming and sea-level rise are predicted to be major driving forces in shaping coastal ecosystems and their services in the next century. Though forecasts of the multiple and complex effects of temperature and sea-level rise on ecological interactions suggest negative impacts on parasite diversity, the effect of long term climate change on parasite dynamics is complex and unresolved. Digenean trematodes are complex life cycle parasites that can induce characteristic traces on their bivalve hosts and hold potential to infer parasite host-dynamics through time and space. Previous work has demonstrated a consistent association between sea level rise and increasing prevalence of trematode traces, but a number of fundamental questions remain unanswered about this paleoecological proxy. Here we examine the relationships of host size, shape, and functional morphology with parasite prevalence and abundance, how parasites are distributed across hosts, and how all of these relationships vary through time, using the bivalve Chamelea gallina from a Holocene shallow marine succession in the Po coastal plain. Trematode prevalence increased and decreased in association with the transition from a wave-influenced estuarine system to a wave-dominated deltaic setting. Prevalence and abundance of trematode pits are associated with large host body size, reflecting ontogenetic accumulation of parasites, but temporal trends in median host size do not explain prevalence trends. Ongoing work will test the roles of temperature, salinity, and nutrient availability on trematode parasitism. Parasitized bivalves in one sample were shallower burrowers than their non-parasitized counterparts, suggesting that hosts of trematodes can be more susceptible to their predators, though the effect is ephemeral. Like in living parasite-host systems, trematode-induced malformations are strongly aggregated among hosts, wherein most host individuals harbor very few parasites while a few hosts have many. We interpret trace aggregation to support the assumption that traces are a reliable proxy for trematode parasitism in the fossil record.

Acquisition and decay of IgM and IgG responses to merozoite antigens after Plasmodium falciparum malaria in Ghanaian children.

Developing a vaccine against Plasmodium falciparum malaria has been challenging, primarily due to high levels of antigen polymorphism and a complex parasite lifecycle. Immunization with the P. falciparum merozoite antigens PfMSRP5, PfSERA9, PfRAMA, PfCyRPA and PfRH5 has been shown to give rise to growth inhibitory and synergistic antisera. Therefore, these five merozoite proteins are considered to be promising candidates for a second-generation multivalent malaria vaccine. Nevertheless, little is known about IgG and IgM responses to these antigens in populations that are naturally exposed to P. falciparum. In this study, serum samples from clinically immune adults and malaria exposed children from Ghana were studied to compare levels of IgG and IgM specific for PfMSRP5, PfSERA9, PfRAMA, PfCyRPA and PfRH5. All five antigens were found to be specifically recognized by both IgM and IgG in serum from clinically immune adults and from children with malaria. Longitudinal analysis of the latter group showed an early, transient IgM response that was followed by IgG, which peaked 14 days after the initial diagnosis. IgG levels and parasitemia did not correlate, whereas parasitemia was weakly positively correlated with IgM levels. These findings show that IgG and IgM specific for merozoite antigens PfMSRP5, PfSERA9, PfRAMA, PfCyRPA and PfRH5 are high in children during P. falciparum malaria, but that the IgM induction and decline occurs earlier in infection than that of IgG.

Schistocephalus parasite infection alters sticklebacks\u2019 movement ability and thereby shapes social interactions

Parasitism is ubiquitous in the animal kingdom. Although many fundamental aspects of host-parasite relationships have been unravelled, few studies have systematically investigated how parasites affect organismal movement. Here we combine behavioural experiments of Schistocephalus solidus infected sticklebacks with individual-based simulations to understand how parasitism affects individual movement ability and thereby shapes social interaction patterns. High-resolution tracking revealed that infected fish swam, accelerated, and turned more slowly than did non-infected fish, and tended to be more predictable in their movements. Importantly, the strength of these effects increased with increasing parasite load (proportion of body weight), with more heavily infected fish showing larger changes and impairments in behaviour. When grouped, pairs of infected fish moved more slowly, were less cohesive, less aligned, and less temporally coordinated than non-infected pairs, and mixed pairs were primarily led by the non-infected fish. These social patterns also emerged in simulations of self-organised groups composed of individuals differing similarly in speed and turning tendency, suggesting infection-induced changes in mobility and manoeuvrability may drive collective outcomes. Together, our results demonstrate how infection with a complex life-cycle parasite affects the movement ability of individuals and how this in turn shapes social interaction patterns, providing important mechanistic insights into the effects of parasites on host movement dynamics.

Behavioral changes in host foraging: Experiments with Clinostomum (Trematoda, Digenea) parasitizing Loricariichthys platymetopon (Loricariidae)

Complex life cycle parasites can manipulate the behavior of intermediate hosts in order to reduce their fitness and increase the chance of completing life cycle. In order to understand the effects of the trematode parasites of the genus Clinostomum on host fish Loricariichthys platymetopon, a filmed experiment was carried out to quantify the foraging activity of hosts with different intensities of infection. The results suggest that hosts with higher parasite intensities reduced foraging activity early in the morning when compared to hosts with low intensities. This period may be critical for hosts since birds, the target hosts of such trematodes, forage intensively at dawn.

Pomphorhynchus laevis manipulates Gammarus pulex behaviour despite salt pollution

Abstract Salt pollution of freshwater ecosystems represents a major threat to biodiversity, and particularly to interactions between free‐living species and their associated parasites. Acanthocephalan parasites are able to alter their intermediate host's phenotype to reach final hosts, but this process could be affected by salt pollution, thereby compromising survival of the parasite. We experimentally assessed the impact of salt on the extended phenotype of the parasite Pomphorhynchus laevis in their intermediate host, the amphipod Gammarus pulex, based on three amphipod behaviours: distance covered in flowing water, phototaxis, and geotaxis. We hypothesised that: (1) salt pollution negatively affected the behaviour of uninfected gammarids, and (2) that P. laevis could maintain their capacity to manipulate their host despite this pollution. All three amphipod behaviours were altered by P. laevis: infected G. pulex covered a greater distance, were less photophobic and were more attracted to the water surface than uninfected amphipods, in control or salt‐polluted water. However, salinity reduced distance covered in flowing water and increased attraction to the water surface of uninfected and infected G. pulex. For the phototaxis behaviour, P. laevis enhanced this capacity of manipulation in salt‐polluted water compared to control water. Pomphorhynchus laevis can still manipulate the behaviour of their intermediate host in salt‐polluted water. Acanthocephalan parasites have not been known to be able to manipulate their intermediate host when under pollution stress. Trophic interactions, but not the chances of parasite transmission to their definitive host, appear to be affected by salt pollution. Our study indicates that behavioural modifications induced by complex lifecycle parasites should be more considered in the context of growing concentrations of chemical pollutants in some freshwater ecosystems. Interspecific interactions, and particularly host–parasite relationships, are a key component of ecosystem stability and their alteration could result in major changes in energy flow.

The Role of MicroRNAs in Parasitology.

MicroRNAs (miRNAs), as epigenetic regulators, are small non-coding RNAs regulating gene expression in eukaryotes at the post-transcriptional level to control biological functions. MicroRNAs play a role in development, physiology, infection, immunity and the complex life cycles of parasites. Also, parasite infection can alter host miRNA expression that might result in either parasite clearance or infection. Over the past 20 years, thousands of miRNAs have been identified in the nematode Caenorhabditis elegans and other parasites. Thus, miRNA pathways are potential targets for the diagnostic and therapeutic control of parasitic diseases. Here, we review the current status and potential functions of miRNAs related to protozoans, helminths, and arthropods.