Infective Stage Of Parasite Research Articles

Assessment of enteric helminth parasites in bushmeat in Ghana

Anthropogenic activities, such as hunting wild animals for food, increase the risk of zoonotic transmission of infective stages of parasites to humans. The handling, processing and consumption of wild animal meat, popularly known as ‘bushmeat’, as well as exposure to wildlife habitats, can pose a significant risk to human health through the transfer of parasitic infective stages. This study sought to assess the enteric helminth parasite burden and potentially zoonotic helminths in fresh, wild animal carcasses being processed for food. Parasitological analysis of samples of rectal and intestinal contents collected from a total of fifty (50) wild animal carcasses belonging to eight (8) different species at the Atwemonom Bushmeat Market in Kumasi showed nine (9) genera of enteric helminth parasites with an overall prevalence of 71.0%. Individual parasite species prevalence was assessed, with Ascaris sp. showing 25% and 87.5% by coprological and molecular assessment, respectively. Molecular analysis showed a higher parasite species prevalence in all samples analyzed. Species-specific analysis indicated the presence of two potentially zoonotic parasites, Strongyloides stercoralis and Trichuris trichiura, in wild animals, indicating the need to intensify one health approach in wild animal parasitic infections. Data from this study suggest that wild animals in addition to being natural hosts, may also serve as reservoirs for numerous parasites of medical and veterinary importance.

When does a parasite become a disease? eDNA unravels complex host-pathogen dynamics across environmental stress gradients in wild salmonid populations

Infectious diseases stem from disrupted interactions among hosts, parasites, and the environment. Both abiotic and biotic factors can influence infection outcomes by shaping the abundance of a parasite's infective stages, as well as the host's ability to fight infection. However, disentangling these mechanisms within natural ecosystems remains challenging. Here, combining environmental DNA analysis and niche modelling at a regional scale, we uncovered the biotic and abiotic drivers of an infectious disease of salmonid fish, triggered by the parasite Tetracapsuloides bryosalmonae. We found that the occurrence and abundance of the parasite in the water—i.e., the propagule pressure— were mainly correlated to the abundances of its two primary hosts, the bryozoan Fredericella sultana and the fish Salmo trutta, but poorly to local abiotic environmental stressors. In contrast, the occurrence and abundance of parasites within fish hosts—i.e., proxies for disease emergence—were closely linked to environmental stressors (water temperature, agricultural activities, dams), and to a lesser extent to parasite propagule pressure. These results suggest that pathogen distribution alone cannot predict the risk of disease in wildlife, and that local anthropogenic stressors may play a pivotal role in disease emergence among wild host populations, likely by modulating the hosts' immune response. Our study sheds light on the intricate interplay between biotic and abiotic factors in shaping pathogen distribution and raises concerns about the effects of global change on pathogen emergence.

Understanding How Parasites from Farmed Fish May Influence Wild Fish Declines Using Epidemiological Modelling

Beside various fields of its applications, in this study epidemiological modelling was used to understand how parasites from farmed fish may cause wild fish declines. Two separate strategic models were constructed addressing the transmission of micro-parasites and macro-parasites between farmed and wild fish: A SIR (Susceptible-Infective-Removed) model for micro-parasite infections and a compartmental density-dependent model for macro-parasite infestations. The results indicated that parasites originated in wild fish populations, after infecting farmed fish can cause epizootics. Subsequently, these parasites can be transmitted from farmed to wild fish and might have negative impact on the dynamics of wild fish populations. Sensitivity analysis of the basic model parameters in both models showed that model parameters, which are influenced by abiotic factors and allow passive manipulation, such as pathogen specific transmission rate (β), pathogen specific transmission rate between infected farmed and susceptible wild fish (δ), the rate of production of infective stages by an adult parasite (λ) and transmission rate between host and parasite infective stages (β) are more sensitive compared to model parameters which encompass chemical control and fallowing. This emphasizes the importance of the preventive medicine rather than intervention procedures in aquaculture aiming at eradicating epizootics caused by parasites and protecting wild fish stocks.

Non-linear effects of non-host diversity on the removal of free-living infective stages of parasites

Among the ecological functions and services of biodiversity is the potential buffering of diseases through dilution effects where increased biodiversity results in a reduction in disease risk for humans and wildlife hosts. Whether such effects are a universal phenomenon is still under intense debate and diversity effects are little studied in cases when non-host organisms remove free-living parasite stages during their transmission from one host to the next by consumption or physical obstruction. Here, we investigated non-host diversity effects on the removal of cercarial stages of trematodes, ubiquitous parasites in aquatic ecosystems. In laboratory experiments using response surface designs, varying both diversity and density at same time, we compared three combinations of two non-hosts at four density levels: predatory crabs that actively remove cercariae from the water column via their mouth parts and gills, filter feeding oysters that passively filter cercariae from the water column while not becoming infected themselves, and seaweed which physically obstructs cercariae. The addition of a second non-host did not generally result in increased parasite removal but neutralised, amplified or reduced the parasite removal exerted by the first non-host, depending on the density and non-host combination. These non-linear non-host diversity effects were probably driven by intra- and interspecific interactions and suggest the need to integrate non-host diversity effects in understanding the links between community diversity and infection risk.

Consumption of trematode parasite infectious stages: from conceptual synthesis to future research agenda.

Given their sheer cumulative biomass and ubiquitous presence, parasites are increasingly recognized as essential components of most food webs. Beyond their influence as consumers of host tissue, many parasites also have free-living infectious stages that may be ingested by non-host organisms, with implications for energy and nutrient transfer, as well as for pathogen transmission and infectious disease dynamics. This has been particularly well-documented for the cercaria free-living stage of digenean trematode parasites within the Phylum Platyhelminthes. Here, we aim to synthesize the current state of knowledge regarding cercariae consumption by examining: (a) approaches for studying cercariae consumption; (b) the range of consumers and trematode prey documented thus far; (c) factors influencing the likelihood of cercariae consumption; (d) consequences of cercariae consumption for individual predators (e.g. their viability as a food source); and (e) implications of cercariae consumption for entire communities and ecosystems (e.g. transmission, nutrient cycling and influences on other prey). We detected 121 unique consumer-by-cercaria combinations that spanned 60 species of consumer and 35 trematode species. Meaningful reductions in transmission were seen for 31 of 36 combinations that considered this; however, separate studies with the same cercaria and consumer sometimes showed different results. Along with addressing knowledge gaps and suggesting future research directions, we highlight how the conceptual and empirical approaches discussed here for consumption of cercariae are relevant for the infectious stages of other parasites and pathogens, illustrating the use of cercariae as a model system to help advance our knowledge regarding the general importance of parasite consumption.

Low-temperature exposure has immediate and lasting effects on the stress tolerance, chemotaxis and proteome of entomopathogenic nematodes.

Temperature is one of the most important factors affecting soil organisms, including the infective stages of parasites and entomopathogenic nematodes, which are important biological control agents. We investigated the response of 2 species of entomopathogenic nematodes to different storage regimes: cold (9°C), culture temperature (20°C) and temperature swapped from 9 to 20°C. For Steinernema carpocapsae, cold storage had profound effects on chemotaxis, stress tolerance and protein expression that were retained in temperature-swapped individuals. These effects included reversal of chemotactic response for 3 (prenol, methyl salicylate and hexanol) of the 4 chemicals tested, and enhanced tolerance to freezing (−10°C) and desiccation (75% RH). Label-free quantitative proteomics showed that cold storage induced widespread changes in S. carpocapsae, including an increase in heat-shock proteins and late embryogenesis abundant proteins. For Heterorhabditis megidis, cold storage had a less dramatic effect on chemotaxis (as previously shown for proteomic expression) and changes were not maintained on return to 20°C. Thus, cold temperature exposure has significant effects on entomopathogenic nematodes, but the nature of the change depends on the species. Steinernema carpocapsae, in particular, displays significant plasticity, and its behaviour and stress tolerance may be manipulated by brief exposure to low temperatures, with implications for its use as a biological control agent.

The application of the FLOTAC technique for detection of helminth eggs of medical and veterinary importance in soil samples

The FLOTAC technique was initially developed to detected infective stages of parasites in animal and human feces. Recently, its applicability has been extended by the use in pastures and vegetables for human consumption. However, its use for the detection of parasites in the soil has never been investigated. In this study, we assessed the performance of the FLOTAC and compared with centrifugal flotation (CFT) and spontaneous sedimentation (SST) techniques. A total of 50 soil samples were collected from the Metropolitan region of Recife, Northeastern Brazil. Initially, samples were standardized, and then assessed in duplicate by the FLOTAC, CFT and SST. Cohen's kappa coefficient, sensitivity, specificity, positive and negative predictive values, and accuracy of the FLOTAC, CFT and SST were assessed using the results of the combination of all three techniques as gold standard. Out of all analyses performed, in 96% (48/50), helminth eggs of parasites were detected. In particular, 96% (48/50) of samples analysed through the FLOTAC technique, 76% (38/50) for CFT and 28% (14/50) for SST were positive. Nematode eggs of the Ancylostomatidae and Ascarididae families were those mostly detected in this study. Overall, the FLOTAC presented high values of sensitivity, demonstrating that this method may also be employed for detection of parasites in soil samples. This study opens new possibilities for the use of the FLOTAC technique, highlighting its role as a potential tool for detecting environmental contamination by parasites of medical and veterinary importance.

Temporal and seasonal variation of metazoan parasites in Pimelodus ornatus (Siluriformes: Pimelodidae) from the Amazon River, Brazil.

This study investigated the influence of temporal and seasonal (i.e., rainy and dry seasons) in communities and infracommunities of metazoan parasites in Pimelodus ornatus, a Siluriformes from the Amazon River in the state of Amapá, in northern Brazil. A total of 144 fish were collected during 2020 and 2021. In 2020, five species of parasites were found (1 Monogenea, 3 Nematoda, and 1 Cestoda), and in 2021, seven species of parasites were found (1 Monogenea, 3 Nematoda, 1 Cestoda, 1 Digenea, and 1 Crustacea). In 2020, Spirocamallanus inopinatus was dominant, while in 2021, Contracaecum sp. was dominant. Brillouin diversity, species richness, and evenness were higher in 2021. There were differences for some parasite infracommunities between years and between seasonal periods. Brillouin diversity and species richness were higher in the rainy season, but there were no differences in evenness and Berger-Parker dominance between the seasonal periods. Temporal and seasonal variations were mainly influenced by rainfall levels, oxygen levels, and environmental temperature and, later, by the availability of infective stages of parasites in the environment and the size of the hosts. Lastly, the influence of the temporal and seasonal variations on the structure of communities and infracommunities of parasites was weaker than expected due to the low infection rates of the majority of parasites found.

Random Forest Model Predictions Afford Dual-Stage Antimalarial Agents.

The need for novel antimalarials is apparent given the continuing disease burden worldwide, despite significant drug discovery advances from the bench to the bedside. In particular, small-molecule agents with potent efficacy against both the liver and blood stages of Plasmodium parasite infection are critical for clinical settings as they would simultaneously prevent and treat malaria with a reduced selection pressure for resistance. While experimental screens for such dual-stage inhibitors have been conducted, the time and cost of these efforts limit their scope. Here, we have focused on leveraging machine learning approaches to discover novel antimalarials with such properties. A random forest modeling approach was taken to predict small molecules with in vitro efficacy versus liver-stage Plasmodium berghei parasites and a lack of human liver cell cytotoxicity. Empirical validation of the model was achieved with the realization of hits with liver-stage efficacy after prospective scoring of a commercial diversity library and consideration of structural diversity. A subset of these hits also demonstrated promising blood-stage Plasmodium falciparum efficacy. These 18 validated dual-stage antimalarials represent novel starting points for drug discovery and mechanism of action studies with significant potential for seeding a new generation of therapies.

Preliminary Survey of Soil Transmitted Helminths in Some Selected Primary Schools in Okitipupa Local Government Area, Ondo State, South West Nigeria

Soil transmitted helminths are nematodes commonly known as intestinal worms; characterized by high prevalence in regions exhibiting warm and moist climates, lacking adequate sanitation and proper hygiene. In this study, the prevalence and distribution of soil transmitted helminths (STHs) in five randomly selected Primary schools in Okitipupa Local Government Area, Ondo State, Nigeria was examined. The study involved soil examination for infective stages of helminth parasites. To determine the type and number of infective helminth ova, topsoil samples were collected from ecologically important sites; the playgrounds, front of classrooms, back of classrooms, around the toilet and the entrance of each selected schools. Of the 75 soil samples examined, 36 were infected showing a total prevalence of 48%. Accordingly, Ascaris lumbricoides (26 ova), Trichiuris trichuira (9 ova), Strongyloides stercoralis (6 ova/larva) and hookworm (15 ova) were the STHs parasites recorded in sampled soils. Ascaris was the most distributed parasite 26 ova (46.1%) across sites; and specifically most abundant in Ikoya 8 (30.8%), while Ayeka 9 (16.1%) reportedly had the least total parasite distribution. The total parasite prevalence in this study was 46.7%.

Sponges (Porifera: Spongillida) as ecological indicators for parasitic protozoans Cryptosporidium and Giardia infective stages in freshwater ecosystems

Sponges filter large volumes of water by actively pumping it through their bodies to acquire nutrients, while Cryptosporidium and Giardia are aquatic ecosystems' primary faecal parasitic pollutants. Five aquatic matrices each of surface water (SW), water sediments (WS), substrate-associated biofilms (SAB), as well as five sponges collected from Lake Buhi were investigated for the presence of parasitic protozoan (oo) cysts. Modified Kinyoun's acid-fast stain (MK) was used to detect Cryptosporidium, while immunofluorescence (IFT) staining was employed to detect both Cryptosporidium and Giardia. Scanning Electron Microscopy (SEM) was used to visualize the skeletal sponge structures and simulated contamination with C. parvum oocysts. Aquatic matrices of WS and SAB demonstrated a 20% (3/15) positivity for Cryptosporidium spp. oocysts with MK and IFT. Overall, the study site prevalence of Cryptosporidium spp. oocysts in aquatic matrices were 60% (3/5). Freshwater sponges demonstrated 100% (5/5) Cryptosporidium and 20% (1/5) Giardia (oo) cysts positivity through IFT. Sponges were ascribed to Radiospongilla cfr. philippinensis (Annandale, 1909) based on diagnostic morphotraits of the siliceous skeleton, i.e., megascleres and gemmuloscleres identified under light microscopy (LM) and SEM. Sponges spiked with Cryptosporidium parvum oocysts simulated parasitic protozoan contamination and demonstrated that oocysts could fit through and be trapped within the sponge aquiferous canals. The presence of Cryptosporidium spp. oocysts in aquatic matrices and Cryptosporidium and Giardia spp. (oo) cysts in Radiospongilla cfr. philippinensis demonstrated the contamination of Porifera with infective stages of both parasites. This study submits a promising perspective on the role of freshwater sponges as ecological indicators, i.e. reservoirs and potential biomonitors for the contamination of infective stages of waterborne parasitic protozoans in aquatic ecosystems.

Specific Recognition of β-Galactofuranose-Containing Glycans of Synthetic Neoglycoproteins by Sera of Chronic Chagas Disease Patients.

Chagas disease (CD) can be accurately diagnosed by detecting Trypanosoma cruzi in patients’ blood using polymerase chain reaction (PCR). However, parasite-derived biomarkers are of great interest for the serological diagnosis and early evaluation of chemotherapeutic efficacy when PCR may fail, owing to a blood parasite load below the method’s limit of detection. Previously, we focused on the detection of specific anti-α-galactopyranosyl (α-Gal) antibodies in chronic CD (CCD) patients elicited by α-Gal glycotopes copiously expressed on insect-derived and mammal-dwelling infective parasite stages. Nevertheless, these stages also abundantly express cell surface glycosylphosphatidylinositol (GPI)-anchored glycoproteins and glycoinositolphospholipids (GIPLs) bearing nonreducing terminal β-galactofuranosyl (β-Galf) residues, which are equally foreign to humans and, therefore, highly immunogenic. Here we report that CCD patients’ sera react specifically with synthetic β-Galf-containing glycans. We took a reversed immunoglycomics approach that entailed: (a) Synthesis of T. cruzi GIPL-derived Galfβ1,3Manpα-(CH2)3SH (glycan G29SH) and Galfβ1,3Manpα1,2-[Galfβ1,3]Manpα-(CH2)3SH (glycan G32SH); and (b) preparation of neoglycoproteins NGP29b and NGP32b, and their evaluation in a chemiluminescent immunoassay. Receiver-operating characteristic analysis revealed that NGP32b can distinguish CCD sera from sera of healthy individuals with 85.3% sensitivity and 100% specificity. This suggests that Galfβ1,3Manpα1,2-[Galfβ1,3]Manpα is an immunodominant glycotope and that NGP32b could potentially be used as a novel CCD biomarker.

The enemy of my enemy is my friend: Consumption of parasite infectious stages benefits hosts and predators depending on transmission mode.

Research Highlight: Hobart, B. K., Moss, W. E., McDevitt-Galles, T., Stewart Merrill, T. E., Johnson, P. T. J. (2021). It's a worm-eat-worm world: Consumption of parasite free-living stages protects hosts and benefits predators. Journal of Animal Ecology, https://doi.org/10.1111/1365-2656.13591 Many parasites and pathogens have infectious stages that are vulnerable to consumption by non-host organisms. This consumption can benefit both the predators that consume this unusual food resource and the hosts which are less likely to encounter infectious propagules. Yet the importance of these benefits may also depend on parasite transmission, which can influence consumer opportunities to feed upon free-living infectious stages. Hobart et al. (2021) report that freshwater snails with high densities of symbiotic oligochaetes are less likely to be parasitized by trematodes (Platyhelminthes) with an 'active' versus 'passive' (motile or stationary, respectively) mode of transmission, supporting a protective effect via oligochaete predation upon infectious propagules. However, these predators benefit from snails harbouring passively acquired infections, and likely achieve their higher abundance from easy access to prey in the form of a second infectious stage emerging from these hosts. Consumption of free-living infectious stages is thus beneficial to hosts and predators, but varies with parasite life history and ecology.

Detection of Plasmodium Sporozoites in Anopheles Mosquitoes using an Enzyme-linked Immunosorbent Assay.

Plasmodium sporozoites are the infective stage of malaria parasites that infect humans. The sporozoites residing in the salivary glands of female Anopheles mosquitoes are transmitted to humans via mosquito bites during blood feeding. The presence of sporozoites in the mosquito salivary glands thus defines mosquito infectiousness. To determine whether an Anopheles mosquito carries Plasmodium sporozoites, the enzyme-linked immunosorbent assay (ELISA) method has been the standard tool to detect the Plasmodium circumsporozoite protein (CSP), the major surface protein of the sporozoites. In this method, the head along with the thorax of each mosquito is separated from the abdomen, homogenized, and subjected to a sandwich ELISA to detect the presence of CSP specific to Plasmodium falciparum and each of the two subtypes, VK210 and VK247, of Plasmodium vivax.This method has been used to study malaria transmission, including the seasonal dynamics of mosquito infection and the species of the major malaria vectors in the study sites.

Geospatial Modelling and Univariate Analysis of Commensal Rodent-Borne Cestodoses: The Case of Invasive spp. of Rattus and Indigenous Mastomys coucha From South Africa.

Poor socio-economic and unsanitary conditions are conducive to commensal rodent infestations, and these conditions are widespread in South Africa. Cestode species of zoonotic interest are highly prevalent in commensal rodents, such as invasive Rattus norvegicus, Rattus rattus, Rattus tanezumi, and indigenous Mastomys coucha, and have been frequently recovered from human stool samples. These cestode species have similar transmission dynamics to traditional soil-transmitted helminths (STHs), which ties them to infections associated with poverty and poor sanitation. Univariate analysis was used in the present study to determine the association between rodent-related factors and cestode prevalence, while ecological niche modelling was used to infer the potential distribution of the cestode species in South Africa. Cestode prevalence was found to be associated with older rodents, but it was not significantly associated with sex, and ectoparasite presence. The predicted occurrence for rodent-borne cestodes predominantly coincided with large human settlements, typically associated with significant anthropogenic changes. In addition, cestode parasite occurrence was predicted to include areas both inland and along the coast. This is possibly related to the commensal behaviour of the rodent hosts. The study highlights the rodent-related factors associated with the prevalence of parasites in the host community, as well as the environmental variables associated with parasite infective stages that influence host exposure. The application of geospatial modelling together with univariate analysis to predict and explain rodent-borne parasite prevalence may be useful to inform management strategies for targeted interventions.

Acanthocephaliasis And Sparganosis Occurrence in An Asian Vine Snake (Ahaetulla prasina): A Perspective of Neglected Zoonotic Disease

Ahaetulla prasina commonly known as asian vine snake frequently kept as exotic pet in Indonesia. Snake also susceptible to various parasitic disease and one of them have zoonotic potential such as sparganosis and acanthocephaliasis. Sparganosis is an infection of humans and animals especially reptiles caused by tapeworms which belonging to the genus Spirometra. Sparganosis and acanthocephaliasis has been reported sporadically in reptiles around the world, with higher cases occurs in several Asian countries including Indonesia even though this disease categorized as neglected zoonotic disease. To our knowledge, sparganosis and acanthocephaliasis infection case has not been reported in this snake species. Therefore, this study aims to report sparganosis and acanthocephaliasis infection in asian vine snake which kept as an exotic pet and moreover provide scientific foundation for preventing sparganosis which include in zoonotic disease among animals and humans. A sudden death snake collected as sample from pet owner which suspected with parasites infection. Necropsy method was performed to investigate the distribution of parasites inside the snake body cavity. Identification of parasite infective stages using Carmine staining and examination under light microscope with a magnification of 40x and 100x. The results of this study found that Ahaetulla prasina was infected with Spirometra and Acanthocephalan parasites. The parasites located within subcutaneous tissues, muscular tissues, and coelom cavity of snake. The muscular tissues had highest intensity of parasites infection compared with subcutaneous tissues and coelom cavity sites. Present report of this finding can potentially contributes not only diagnosing parasitic disease in exotic animals but also proposing prevention program for zoonotic disease in humans worldwide. Moreover, education about neglected parasitic disease with zoonotic potential should take into consideration above this fndings and reports.

Animal migrations and parasitism: reciprocal effects within a unified framework.

Migrations, i.e. the recurring, roundtrip movement of animals between distant and distinct habitats, occur among diverse metazoan taxa. Although traditionally linked to avoidance of food shortages, predators or harsh abiotic conditions, there is increasing evidence that parasites may have played a role in the evolution of migration. On the one hand, selective pressures from parasites can favour migratory strategies that allow either avoidance of infections or recovery from them. On the other hand, infected animals incur physiological costs that may limit their migratory abilities, affecting their speed, the timing of their departure or arrival, and/or their condition upon reaching their destination. During migration, reduced immunocompetence as well as exposure to different external conditions and parasite infective stages can influence infection dynamics. Here, we first explore whether parasites represent extra costs for their hosts during migration. We then review how infection dynamics and infection risk are affected by host migration, thereby considering parasites as both causes and consequences of migration. We also evaluate the comparative evidence testing the hypothesis that migratory species harbour a richer parasite fauna than their closest free-living relatives, finding general support for the hypothesis. Then we consider the implications of host migratory behaviour for parasite ecology and evolution, which have received much less attention. Parasites of migratory hosts may achieve much greater spatial dispersal than those of non-migratory hosts, expanding their geographical range, and providing more opportunities for host-switching. Exploiting migratory hosts also exerts pressures on the parasite to adapt its phenology and life-cycle duration, including the timing of major developmental, reproduction and transmission events. Natural selection may even favour parasites that manipulate their host's migratory strategy in ways that can enhance parasite transmission. Finally, we propose a simple integrated framework based on eco-evolutionary feedbacks to consider the reciprocal selection pressures acting on migratory hosts and their parasites. Host migratory strategies and parasite traits evolve in tandem, each acting on the other along two-way causal paths and feedback loops. Their likely adjustments to predicted climate change will be understood best from this coevolutionary perspective.

Long-term change in the parasite burden of shore crabs (Hemigrapsus oregonensis and Hemigrapsus nudus) on the northwestern Pacific coast of North America.

The abundances of free-living species have changed dramatically in recent decades, but little is known about change in the abundance of parasitic species. We investigated whether populations of several parasites have shifted over time in two shore crab hosts, Hemigrapsus oregonensis and Hemigrapsus nudus, by comparing the prevalence and abundance of three parasite taxa in a historical dataset (1969-1970) to contemporary parasite abundance (2018-2020) for hosts collected from 11 intertidal sites located from Oregon, USA, to British Columbia, Canada. Our data suggest that the abundance of the parasitic isopod Portunion conformis has varied around a stable mean for the past 50 years. No change over time was observed for larval acanthocephalans. However, larval microphallid trematodes increased in prevalence over time among H. oregonensis hosts, from a mean of 8.4-61.8% between the historical and contemporary time points. The substantial increase in the prevalence of larval microphallid trematodes could be owing to increased abundances of their bird final hosts, increased production of parasite infective stages by snail intermediate hosts or both. Our study highlights the variability among parasite species in their temporal trajectories of change.

Metabolites as predictive biomarkers for Trypanosoma cruzi exposure in triatomine bugs

Trypanosoma cruzi, the causative agent of Chagas disease (American trypanosomiasis), colonizes the intestinal tract of triatomines. Triatomine bugs act as vectors in the life cycle of the parasite and transmit infective parasite stages to animals and humans. Contact of the vector with T.cruzi alters its intestinal microbial composition, which may also affect the associated metabolic patterns of the insect. Earlier studies suggest that the complexity of the triatomine fecal metabolome may play a role in vector competence for different T. cruzi strains. Using high-resolution mass spectrometry and supervised machine learning, we aimed to detect differences in the intestinal metabolome of the triatomine Rhodnius prolixus and predict whether the insect had been exposed to T. cruzi or not based solely upon their metabolic profile. We were able to predict the exposure status of R. prolixus to T. cruzi with accuracies of 93.6%, 94.2% and 91.8% using logistic regression, a random forest classifier and a gradient boosting machine model, respectively. We extracted the most important features in producing the models and identified the major metabolites which assist in positive classification. This work highlights the complex interactions between triatomine vector and parasite including effects on the metabolic signature of the insect.

Mussel Shutdown: Does the Fear of Trematodes Regulate the Functioning of Filter Feeders in Coastal Ecosystems?

Parasite infections have negative impacts on their hosts. Accordingly, many organisms try to detect and avoid infective parasite stages, leading to changes in host behaviour or physiology. Such non-consumptive effects on host traits can have cascading impacts on whole ecosystems but remain largely overlooked. Here, we discuss the potential impacts of the presence of free-living trematode stages on blue mussels Mytilus edulis, an important ecosystem engineer in coastal habitats, and highlight the ecological implications of these interactions. Specifically, we discuss how parasite avoidance behaviour can regulate the filtration activity of these bivalves in coastal ecosystems and show how even moderate changes in mussel behaviour can lead to far-reaching shifts in energy flow. Such processes might be further amplified under future climate change developments, since both parasite abundance and biotic productivity are highly temperature dependent. Overall, we hypothesize that, in addition to their more evident consumptive impacts, trematodes act as cryptic ecosystem engineers by shaping bivalve filtration processes via non-consumptive effects. Due to our still very limited understanding of these parasite-mediated processes, we outline key questions for future research directions. We hope this perspective will help encourage new efforts to empirically investigate these fascinating processes that can be crucial regulatory forces in complex ecological systems.