Parasite Communities Research Articles

Long-term temporal variation in the parasite community structure of metazoans of Pimelodus blochii (Pimelodidae), a catfish from the Brazilian Amazon.

The Amazon represents one of the most complex biomes in the world; however, the temporal variations in parasite community structure of fishes inhabiting this region remain poorly understood. Therefore, processes generating such variations are still unknown. The present study evaluated the long-term temporal variation of communitystructure of metazoan parasites of Pimelodus blochii collected in Iaco River, State of Acre (Southwestern Brazilian Amazon). A total of 196 parasites were collected over a 6-year period (2012-2017). Twenty-four different taxa of parasites were found, of which 5 Monogenea, 11 Nematoda, 3 Digenea, 1 Acanthocephala, 1 Cestoda, and 3 Crustacea. The overall species richness ranged from 4 in 2012 to 17 in 2016, in which nematodes (larvae and adults) showed higher numerical dominance, diversity, and species richness. However, the annual species richness was similar between the study years, except in 2016, where it showed a distinctly higher value. The overall parasite diversity was also different in 2012 and 2016, whereas the overall abundance differed in 2013 and 2017. The prevalence and abundance of some infracommunities of parasites varied over time. The temporal changes in the parasite community structure of P. blochii are probably related to variations in host-related features, i.e., body size and shift in diet composition as well as to the occurrence of parasites with distinct life history and biology (mainly monogeneans, digeneans, and nematodes). This is the first evaluation of a long-term temporal variation in the structure of the parasite community in fish from the Amazon.

An inverse latitudinal gradient in infection probability and phylogenetic diversity for Leucocytozoon blood parasites in New World birds.

Geographic variation in environmental conditions as well as host traits that promote parasite transmission may impact infection rates and community assembly of vector-transmitted parasites. Identifying the ecological, environmental and historical determinants of parasite distributions and diversity is therefore necessary to understand disease outbreaks under changing environments. Here, we identified the predictors and contributions of infection probability and phylogenetic diversity of Leucocytozoon (an avian blood parasite) at site and species levels across the New World. To explore spatial patterns in infection probability and lineage diversity for Leucocytozoon parasites, we surveyed 69 bird communities from Alaska to Patagonia. Using phylogenetic Bayesian hierarchical models and high-resolution satellite remote-sensing data, we determined the relative influence of climate, landscape, geography and host phylogeny on regional parasite community assembly. Infection rates and parasite diversity exhibited considerable variation across regions in the Americas. In opposition to the latitudinal gradient hypothesis, both the diversity and prevalence of Leucocytozoon parasites decreased towards the equator. Host relatedness and traits known to promote vector exposure neither predicted infection probability nor parasite diversity. Instead, the probability of a bird being infected with Leucocytozoon increased with increasing vegetation cover (NDVI) and moisture levels (NDWI), whereas the diversity of parasite lineages decreased with increasing NDVI. Infection rates and parasite diversity also tended to be higher in cooler regions and higher latitudes. Whereas temperature partially constrains Leucocytozoon diversity and infection rates, landscape features, such as vegetation cover and water body availability, play a significant role in modulating the probability of a bird being infected. This suggests that, for Leucocytozoon, the barriers to host shifting and parasite host range expansion are jointly determined by environmental filtering and landscape, but not by host phylogeny. Our results show that integrating host traits, host ancestry, bioclimatic data and microhabitat characteristics that are important for vector reproduction are imperative to understand and predict infection prevalence and diversity of vector-transmitted parasites. Unlike other vector-transmitted diseases, our results show that Leucocytozoon diversity and prevalence will likely decrease with warming temperatures.

Gastrointestinal investigation of parasites and Enterobacteriaceae in loggerhead sea turtles from Italian coasts

BackgroundCaretta caretta is the most abundant sea turtle species in the Mediterranean, and studies on this species have vastly expanded during recent years, including those investigating gut bacterial and parasitic communities. Members of these communities have been reported with variable prevalence and pathogenicity, mainly depending on their host and environment (e.g. lifespan, distribution, habitat, diet, health status and stressors). Indeed, many species commonly inhabiting the sea turtle gastrointestinal tract exhibit an opportunistic behaviour.This study aimed to provide baseline data on enterobacterial and parasitic composition, through bacteriological culture-based methods and the FLOTAC parasitological technique, in cloacal and faecal samples of 30 live Caretta caretta, examined upon their arrival at the Marine Turtle Research Centre (Portici, Italy).ResultsEnterobacteriaceae were isolated in 18/23 cloacal samples (78.3%), with Citrobacter and Morganella as the most common genera, followed by Proteus, Enterobacter, Providencia, and Hafnia. Parasitic elements were detected in 11/30 faecal samples (36.7%), with Enodiotrema, Rhytidodes, and Eimeria as most common genera, followed by Pachypsolus and Cymatocarpus. Additionally, Angiodyctium is reported for the first time in this host. The majority (47.8%) of sea turtles hosted exclusively Enterobacteriaceae, whereas 30.4% hosted both parasites and Enterobacteriaceae; the remaining 21.8% hosted neither of the agents.ConclusionsBacteria and parasites evaluated in the present study are common in Mediterranean loggerhead sea turtles, with slight differences between the western and eastern basin. Although naturally present in the gastrointestinal system of free-living sea turtles, their relationship with these hosts might range from mutualism to parasitism. Indeed, members of the gut community might express their pathogenic potential in immune-compromised animals, such as those in rehabilitation facilities. Therefore, it is advisable to include in the standard work-up of rescued sea turtles a screening procedure for such opportunistic agents, in order to better evaluate the animal’s health status and achieve timely intervention with appropriate treatment, thus improving rehabilitation. Furthermore, data collected from free-living sea turtles represent a starting point for investigating wild populations. However, further studies are needed to clarify the differences between sea turtle’s normal gut microbiome and pathobiome.

Effects of River Hydrology and Physicochemistry on Anchovy Abundance and Cymothoid Isopod Parasitism

The flow regime of a river is an important driver of many ecosystem components. However, few studies explore how differences in flow rates and water chemistry can influence communities of parasites and their hosts. Here, we investigate the impact of dissolved oxygen, pH, salinity, water temperature, and river flow on the abundance and prevalence of cymothoid isopod parasitism (Lironeca ovalis) of the Bay Anchovy (Anchoa mitchilli) in the Alafia and Hillsborough rivers of Tampa Bay (Florida). We also explore seasonality by comparing monthly samples preserved throughout 2005-2007. Although both the Alafia and Hillsborough rivers had similar average water temperatures and salinity, and similar wet and dry season cycles, the upstream damming of the Hillsborough River had numerous negative effects on water flow rate, dissolved oxygen content, and acidity. This disruption in water quality corresponded with a lower abundance of anchovy hosts, fewer free-swimming cymothoids, and low prevalence of anchovy parasitism. Anchovies were much more abundant in the Alafia River, but flow negatively affected abundance-a negative effect that could be mitigated by positive changes in water temperature, salinity, and pH. Flow rates also negatively affected free-swimming cymothoid abundance; however, water flow was less important in predicting their parasitism of anchovies. In Alafia, fewer anchovies were parasitized when dissolved oxygen was high and water acidity was low, but more were parasitized during the wet season. These findings corroborate predictions that flow can moderate habitat stability and complexity which, in turn, can impact opportunities for parasitism of host communities.

Detecting parasite associations within multi-species host and parasite communities.

Understanding the role of biotic interactions in shaping natural communities is a long-standing challenge in ecology. It is particularly pertinent to parasite communities sharing the same host communities and individuals, as the interactions among parasites-both competition and facilitation-may have far-reaching implications for parasite transmission and evolution. Aggregated parasite burdens may suggest that infected host individuals are either more prone to infection, or that infection by a parasite species facilitates another, leading to a positive parasite-parasite interaction. However, parasite species may also compete for host resources, leading to the prediction that parasite-parasite associations would be generally negative, especially when parasite species infect the same host tissue, competing for both resources and space. We examine the presence and strength of parasite associations using hierarchical joint species distribution models fitted to data on resident parasite communities sampled on over 1300 small mammal individuals across 22 species and their resident parasite communities. On average, we detected more positive associations between infecting parasite species than negative, with the most negative associations occurring when two parasite species infected the same host tissue, suggesting that parasite species associations may be quantifiable from observational data. Overall, our findings suggest that parasite community prediction at the level of the individual host is possible, and that parasite species associations may be detectable in complex multi-species communities, generating many hypotheses concerning the effect of host community changes on parasite community composition, parasite competition within infected hosts, and the drivers of parasite community assembly and structure.

Divergent evolutionary trajectories following speciation in two ectoparasitic honey bee mites

Multispecies host-parasite evolution is common, but how parasites evolve after speciating remains poorly understood. Shared evolutionary history and physiology may propel species along similar evolutionary trajectories whereas pursuing different strategies can reduce competition. We test these scenarios in the economically important association between honey bees and ectoparasitic mites by sequencing the genomes of the sister mite species Varroa destructor and Varroa jacobsoni. These genomes were closely related, with 99.7% sequence identity. Among the 9,628 orthologous genes, 4.8% showed signs of positive selection in at least one species. Divergent selective trajectories were discovered in conserved chemosensory gene families (IGR, SNMP), and Halloween genes (CYP) involved in moulting and reproduction. However, there was little overlap in these gene sets and associated GO terms, indicating different selective regimes operating on each of the parasites. Based on our findings, we suggest that species-specific strategies may be needed to combat evolving parasite communities.

Metazoan parasites, condition factor and hepato-somatic index of amphibians from oil-producing communities in Rivers State, Nigeria

Amphibians were collected from six locations in Rivers State, Nigeria, using search and capture techniques, and purchases from local markets. The locations were Okwale and Teka Sogho in Ogoniland, Akabuka in Omoku, Omofo in Ndele, Rumuche in Emohua and Ikata in Ahoada East. Amphibians were euthanized; body mass, liver mass, and snout-vent length of each specimen were taken after which they were examined for helminth endoparasites in the gastrointestinal tract, lungs, liver, urinary bladder and body cavity. Prevalence and mean intensity of parasite infections were computed; body condition factor and hepato somatic index of amphibians were also computed. Amphibian species encountered included Sclerophrys spp., Hoplobatrachus occipitalis, Silurana tropicalis, Hymenochirus sp., and Ptychadena species. Parasite species recovered were trematodes (Prosotocus exovitellosus, Ganeo africana, Diplodiscus fischthalicus, Metahaematoloechus exoterorchis, Mesocoelium monodi, Mesocoelium sp.), cestodes (Baerietta jaegerskioeldii), acanthocephalan cysthacanths, pentastomids (Raillietiella sp.), monogeneans (Polystoma aeschlimanni, P. baeri and P. pricei), and nematodes (Amplicaecum africanum, Ascaridida larva, Batracocamallanus siluranae, Chabaudus leberrei, Cosmocerca ornata, Oswaldocruzia hoepplii, Rhabdias africanus, Rhabdias sp. 1 and 2. Hymenochirus sp. is reported as a new host for C. leberrei. Parasite community structure closely followed that of the hosts. Parasites were generally less prevalent in hosts from Ogoni and Omoku. Condition factor of all amphibians examined were greater than 1. Higher HSI values were recorded in Hymenochirus sp. from Akabuka Omoku indicating higher stress level in that location.Keywords: Helminth; health status; petroleum industry; anthropogenic change; habitat alteration.

How parasite interaction strategies alter virulence evolution in multi-parasite communities.

The majority of organisms host multiple parasite species, each of which can interact with hosts and competitors through a diverse range of direct and indirect mechanisms. These within-host interactions can directly alter the mortality rate of coinfected hosts and alter the evolution of virulence (parasite-induced host mortality). Yet we still know little about how within-host interactions affect the evolution of parasite virulence in multi-parasite communities. Here, we modeled the virulence evolution of two coinfecting parasites in a host population in which parasites interacted through cross immunity, immune suppression, immunopathology, or spite. We show (1) that these within-host interactions have different effects on virulence evolution when all parasites interact with each other in the same way versus when coinfecting parasites have unique interaction strategies, (2) that these interactions cause the evolution of lower virulence in some hosts, and higher virulence in other hosts, depending on the hosts infection status, and (3) that for cross immunity and spite, whether parasites increase or decrease the evolutionarily stable virulence in coinfected hosts depended on interaction strength. These results improve our understanding of virulence evolution in complex parasite communities, and show that virulence evolution must be understood at the community scale.

Mini-FLOTAC as an alternative, non-invasive diagnostic tool for Schistosoma mansoni and other trematode infections in wildlife reservoirs

BackgroundSchistosomiasis and food-borne trematodiases are not only of major public health concern, but can also have profound implications for livestock production and wildlife conservation. The zoonotic, multi-host nature of many digenean trematodes is a significant challenge for disease control programmes in endemic areas. However, our understanding of the epidemiological role that animal reservoirs, particularly wild hosts, may play in the transmission of zoonotic trematodiases suffers a dearth of information, with few, if any, standardised, reliable diagnostic tests available. We combined qualitative and quantitative data derived from post-mortem examinations, coprological analyses using the Mini-FLOTAC technique, and molecular tools to assess parasite community composition and the validity of non-invasive methods to detect trematode infections in 89 wild Hubert’s multimammate mice (Mastomys huberti) from northern Senegal.ResultsParasites isolated at post-mortem examination were identified as Plagiorchis sp., Anchitrema sp., Echinostoma caproni, Schistosoma mansoni, and a hybrid between Schistosoma haematobium and Schistosoma bovis. The reports of E. caproni and Anchitrema sp. represent the first molecularly confirmed identifications for these trematodes in definitive hosts of sub-Saharan Africa. Comparison of prevalence estimates derived from parasitological analysis at post-mortem examination and Mini-FLOTAC analysis showed non-significant differences indicating comparable results between the two techniques (P = 1.00 for S. mansoni; P = 0.85 for E. caproni; P = 0.83 for Plagiorchis sp.). A Bayesian model, applied to estimate the sensitivities of the two tests for the diagnosis of Schistosoma infections, indicated similar median posterior probabilities of 83.1% for Mini-FLOTAC technique and 82.9% for post-mortem examination (95% Bayesian credible intervals of 64.0–94.6% and 63.7–94.7%, respectively).ConclusionsOur results showed that the Mini-FLOTAC could be applied as an alternative diagnostic technique for the detection of the zoonotic S. mansoni and other trematodes in rodent reservoirs. The implementation of non-invasive diagnostics in wildlife would offer numerous advantages over lethal sampling methodologies, with potential impact on control strategies of zoonotic helminthiases in endemic areas of sub-Saharan Africa and on fostering a framework of animal use reduction in scientific practice.

Evolutionary lability of host associations promotes phylogenetic overdispersion of co-infecting blood parasites.

Co-infections with multiple parasite taxa are ubiquitous in nature and have the potential to impact the co-evolutionary dynamics between host and parasite, though patterns of phylogenetic community structure of co-infecting parasites and the processes that generate these patterns have rarely been studied across diverse host-parasite communities. Here, we tested for the roles of host and parasite evolutionary history as well as environmental variables as drivers of phylogenetic community structure among co-infecting haemosporidian (malaria) parasites and their avian hosts in the North American boreal forest, a region characterized by an extraordinarily high blood parasite co-infection rate. We used multiple methods to identify non-random patterns of co-infection among parasite species and determined whether these patterns were influenced more by co-evolutionary host associations or environmental variables. We used model-based approaches to test whether parasites that occurred together in a single host individual exhibited phylogenetic clustering or overdispersion. Lastly, we tested whether the observed phylogenetic community structure could be explained by parasites having convergently evolved similar patterns of host associations. We found that haemosporidian parasite co-infections occurred at a high frequency in the boreal forest system and that parasite taxa co-occurred in significantly non-random patterns within host individuals and among host species. Parasite taxa that occurred in co-infections tended to be phylogenetically overdispersed. We show that this pattern of phylogenetic overdispersion can be attributed largely to the effect of evolutionarily labile, convergent host associations that have resulted in the pool of parasites that have the potential to infect a given host consisting nearly exclusively of distantly related lineages. Our findings illustrate that environmental filtering of convergent traits can produce phylogenetically overdispersed communities, even at the level of co-infecting parasites within an individual host organism. Broadly, this analysis illustrates how co-evolutionary history can have a strong influence on the modern phylogenetic community assembly of diverse host-symbiont communities.

Seasonal and depth related variation of parasite communities of Notacanthus bonaparte Risso, 1840 (Notacanthiformes: Notacanthidae) over the northwest Mediterranean slope

In the last decades fishing activities have spread from coastal to deeper waters with serious effects on the deep-sea ecosystems and its fauna, which are considered to be highly susceptible to these impacts. The implementation of protection measures is necessary, but the knowledge on this biome is scant, and often limited to species of commercial value. To the best of our knowledge, this study is the first survey to describe and analyse parasite infracommunities of the deep-sea fish Notacanthus bonaparte sampled from three bathymetric strata between the upper and lower slope in the western Mediterranean Sea (Balearic Sea, Spain). The aim of this work was to assess the effect of host specific parameters as well as environmental conditions and spatial and temporal variation on the composition and structure of the parasite communities. We have found poor parasite infracommunities, usually described rather for bathypelagic fishes than observed in fishes with benthic feeding habits such as N. bonaparte, in which two out of five species are considered as accidental infections. The infracommunity composition is determined by the factors, depth and maturity status (size). The dominating taxon, cucullanid larvae, seem to be accumulated throughout the life of the host showing higher abundances in larger fish in deeper waters on the middle and lower slope. The prevalence and abundance of this parasite could be linked to increased water turbidity and it is supposed that these larvae are free-living in the sediment being ingested by N. bonaparte when feeding on benthic organisms. The results suggest that N. bonaparte acts as important intermediate host for this taxon though, the final host is still unknown. The single monogenean species Tinrovia mamaevi was mainly recorded in the upper slope and its higher prevalence in this depth range could be related to higher host densities observed in these depths. The prevalence and abundance of this parasite species could be linked to temperature and salinity, and although measured variations for these parameters were marginal it is supposed that these and probably further additional abiotic factors may influence its distribution pattern. Considering previously published diet data this study indicates potential pathways other than those expected for parasites transmitted via the food web using N. bonaparte as intermediate and definitive host.

Sexual and age characteristics of the parasitofauna of Abramis brama (Cypriniformes, Cyprinidae) of the Lower Irtysh (Russia)

In the present study, an evaluation was made of the dependence between infections by various types of parasites and the sex and age of the host. The parasitic community of Abramis brama includes 24 species of parasites. We assessed the degree of infestation by parasites in groups of male, female and juvenile specimens. It was established that only male bream were infested with Zschokkella nova (Klokacewa, 1914), Hysteromorpha triloba (Rudolphi, 1819), Allocreadium isoporum (Looss, 1894), Ichthyocotylurus platycephalus (Сrерlin, 1852). The ciliates of Trichodina nigra (Lom, 1960) were noted on the gills and fins of all the examined fish, the extensiveness of infection in the group of juveniles exceeded that of the groups of females and males. Specimens of Myxobolus rotundus (Nemeczek, 1911) were found on the gills and in the kidneys, and M. parviformis only on the gills of the fish. The level of infection in males was three times the EI in females and juvenile fish. The infestation on the fins by the metacercaria of Rhipidocotyle campanula (Dujardin, 1845) in male bream was more than 6 times higher than infection in females and juveniles. An increase in the extensiveness of infection in males by the nematode Philometra ovata (Zeder, 1803) was also noted in comparison with groups of females and juvenile fish. Species-specific monogeneans: Dactylogyrus falcatus (Wedl, 1857), D. wunderi (Bychowsky, 1931), D. zandti (Bychowsky, 1933), Gyrodactylus elegans (Nordmann, 1832); the trematodes Sphaerostomа bramae (Müller, 1776) and Diplostomum chromatophorum (Brown, 1931) infested all individuals of bream in approximately the same proportion, whereas an increase in the EI of the Caryophyllaeus laticeps (Pallas, 1781) cestode in males was observed. Infection with metacercariae Metorchis sp. in males exceeded that in females and juvenile fish. At the same time, only females and juvenile bream were infected by Chilodonella sp., metacercariae Opisthorchis felineus (Rivolta, 1884) and glochidia Unionidae gen. sp. During the studies in females, the following species of parasite were observed singly : Proteocephalus sp., Azygia lucii (Miiller, 1776), Ergasilus sieboldi (Nordmann, 1832). Parasitization by Raphidascaris acus (Bloch, 1779) was recorded only in males and juveniles, whereas in females this parasite was not observed. The dominant parasite in males was G. elegans, in females – the representatives of the genus Dactylogyrus, in the juvenile individuals the trematode S. bramae dominated. Analysis of the parasite fauna in various age groups allowed us to establish that at the age of 5+–6+ bream were infected by 20 species of parasites, in age group 3+–4+ there were 15 species, at the age of 7+–8+ the fish were infected only with 11 parasitic species. The fish in all three groups were infected by T. nigra, Dactylogyrus spp., G. elegans, D. chromatophorum, S. bramae, R. acus almost at the same level and had no sharp differences in extensiveness and abundance of infection. Unionidae gen. sp. were observed only in group 3+–4+. Parasitization by Proteocephalus sp., metacercariae H. triloba and I. platycephalus, A. isoporum, and A. lucii was found in bream of age group 5+–6+, the species did not occur in bream at other ages. Nematode P. ovata and crustacean E. sieboldi infested the fish in age groups 3+–4+ and 5+–6+ with a slight increase in the extensiveness of infection at low abundance rates. The same age groups were observed to have decrease in the extensiveness of infection with Chilodonella sp. and metacercariae O. felineus. Myxozoan Z. nova parasitized in age group 5+–6+ and had an increase in extensiveness in age group 7+–8+. In all groups, infection was noted by representatives of the genus Myxobolus, R. campanula and Metorchis sp. with EI increasing with age. The obligate parasite of bream – C. laticeps infested fish the most in age group 3+–4+ in comparison with age groups 5+–6+ and 7+–8+. In the younger age group, the dactylogyruses were dominant parasites, in the age group 5+–6+ Gyrodactylus dominated, in the older age group – Metorchis sp.

Gastrointestinal helminth fauna and helminth communities of bleak (Alburnus alburnus, L. 1758) from lower section of Danube River

The present study presents the results from examinations of bleak’s endohelminth species and structure of helminth communities from the Bulgarian part of the Lower Danube River. In 2015 and 2016, on a seasonal manner, 91 specimens of Alburnus alburnus (Linnaeus, 1758) (bleak) were examined with standard techniques for parasites. Five species of parasites: Nicolla skrjabini (Ivanitzky, 1928), Ligula intestinalis (Linnaeus, 1758), Acanthocephalus lucii (Müller, 1776), Pomphorhynchus laevis (Müller, 1776) and Contracoecum microcephalum (Stossich, 1890), larvae were identified. The analysis of the dominant structure of the found parasite species is presented to the component and infracommunities levels. All parasite species were accidental for the parasitic communities of examined fish with the exception of P. laevis and N. skrjabini. P. laevis was a core parasite species and N. skrjabini was a component parasite species for the helminth communities of bleak. The parasite communities of A. alburnus were discussed and compared with previous research data on parasite communities of bleak from River Danube in Bulgaria. New data for helminths and helminth communities of A. alburnus from Danube River (biotope Vetren) and their seasonal occurrence are presented.

Сезонная динамика паразитофауны и структуры компонентного сообщества паразитов хариуса <i>Thymallus thymallus</i> (Linnaeus, 1758) из реки Луженьги (бассейн реки Северной Двины)

Развитие учения о паразитарных сообществах позволило оценивать нарушения структуры гидробиоценозов и популяций рыб. Сбор материала произведен с мая по сентябрь 2011 – 2013 гг. из р. Луженьга (Вологодская область). Исследовали 150 экз. хариуса по 10 выборок (61 самка, 89 самцов) по 15 экз. в каждой. Компонентное сообщество паразитов хариуса с мая по сентябрь последовательно проходит 3 стадии развития, обусловленные сменой генераций составляющих его видов. Это формирующееся сообщество в мае — начале июня, сформированное во 2-й и 3-й декадах июня, разрушающееся в июле–начале сентября и вновь формирующееся. У хариуса выявлены 16 видов паразитов. Их число колебалось от 9 в начале июня и до 13 в октябре. У рыбы на протяжении всего периода исследований присутствовали 6 видов паразитов. От мая к началу июня число особей инвадентов и их биомасса упали в 2 раза, к концу июня значения этих показателей выросли в 2,3 раза с последующим резким падением в июле числа особей в 3,7 – 3,8 раза, биомассы — в 1,8 – 2,7 раза. Далее к октябрю идёт плавный рост значений этих показателей. С мая по октябрь в сообществе паразитов лидируют автогенные виды и виды-специалисты.

Examining the role of parasites in limiting unidirectional gene flow between lake and river sticklebacks.

Parasites are important selective agents with the potential to limit gene flow between host populations by shaping local host immunocompetence. We report on a contact zone between lake and river three-spined sticklebacks (Gasterosteus aculeatus) that offers the ideal biogeographic setting to explore the role of parasite-mediated selection on reproductive isolation. A waterfall acts as a natural barrier and enforces unidirectional migration from the upstream river stickleback population to the downstream river and lake populations. We assessed population genetic structure and parasite communities over four years. In a set of controlled experimental infections, we compared parasite susceptibility of upstream and downstream fish by exposing laboratory-bred upstream river and lake fish, as well as hybrids, to two common lake parasite species: a generalist trematode parasite, Diplostomum pseudospathaceum, and a host-specific cestode, Schistocephalus solidus. We found consistent genetic differentiation between upstream and downstream populations across four sampling years, even though the downstream river consisted of ~10% first-generation migrants from the upstream population as detected by parentage analysis. Fish in the upstream population had lower genetic diversity and were strikingly devoid of macroparasites. Through experimental infections, we demonstrated that upstream fish and their hybrids had higher susceptibility to parasite infections than downstream fish. Despite this, naturally sampled upstream migrants were less infected than downstream residents. Thus, migrants coming from a parasite-free environment may enjoy an initial fitness advantage, but their descendants seem likely to suffer from higher parasite loads. Our results suggest that adaptation to distinct parasite communities can influence stickleback invasion success and may represent a barrier to gene flow, even between close and connected populations.

Development of a deep amplicon sequencing method to determine the species composition of piroplasm haemoprotozoa

Piroplasmosis is caused by tick-borne haemoprotozoa of the genera Theileria and Babesia. These parasitic infections can seriously impact on the health of livestock and production. Piroplasms of multiple species can be present in a single host, but reliable molecular diagnostic tools are needed in order to understand the composition of these complex parasite communities. Theileria and Babesia vary in their epidemiology, drug sensitivity, pathogenicity and interaction with co-infecting species, but are similar in that infected animals become persistent carriers after recovery from primary infection, acting as reservoir hosts. Here, we describe for the first time the use of a deep amplicon sequencing platform to identify proportions of piroplasm species in co-infecting communities and develop the concept of a “haemoprotobiome”. First, four phenotypically-verified species of Theileria and Babesia were used to prepare mock DNA pools with random numbers of the parasites amplified by four different numbers of PCR cycles to assess sequence representation for each species. Second, we evaluated the detection threshold of the deep amplicon sequencing assay for each of the four species and to assess the accuracy of proportional quantification of all four species. Finally, we applied the assay to the field samples to afford insight of the species composition of piroplasm communities in small and large ruminants in the Punjab province of Pakistan. The “haemoprotobiome” concept has several potential applications in veterinary and human research, including understanding of responses to drug treatment; parasite epidemiology and ecology; species interactions during mixed infections; and parasite control strategies.

Factors linked to interannual variation in the metazoan parasite communities of black skipjack, Euthynnus lineatus (Pisces: Scombridae)

AbstractMarine parasite communities can exhibit temporal and spatial changes in response to seasonal and local variations in several biotic and abiotic environmental factors. Limited attention has been given to the influence of abiotic factors, so their effects on parasite community structure remain unclear. A total of 496 specimens of Euthynnus lineatus were collected over a 7‐year period (2012–2018) from Acapulco Bay, Mexico. Their parasite communities were analyzed to determine if they experience interannual variations due to local biotic and abiotic factors. Thirty‐three metazoan parasite species were recovered and identified: four species of Monogenea (adults); 16 of Digenea (one larvae and 15 adults); two of Acanthocephala (adults); two of Cestoda (larvae); three of Nematoda (two larvae and one adult); and six of Crustacea (three Copepoda, and three Isopoda). Species richness was greatest among the digeneans, which represented 48% of the total species recovered, followed by the crustaceans (19% of total species). Species richness at the component community level (14–24 species) was similar to reported richness in other small tuna species. The component communities and infracommunities of E. lineatus exhibited a similar pattern: high species richness and diversity, and numerical dominance by a single species, mainly by one of the didymozoids Allopseudocolocyntotrema claviforme or Pseudocolocyntotrema yaito. Parasite community structure and species composition varied among sampling years. Variations were possibly caused by a combination of abiotic and biotic factors which generated notable changes in the infection levels of several component species during the study period. These communities may therefore be unpredictable in terms of structure and species composition, as has been suggested for other communities of marine parasites.

Beta diversity of gastrointestinal helminths in two closely related South African rodents: species and site contributions.

A fundamental aim of parasite ecology is to understand the mechanisms behind spatial variation in diversity and structure of parasite assemblages. To understand the contribution of individual parasite species and their assemblages to spatial variation in parasite communities, we examined species contributions to beta diversity (SCBD) and local contributions to beta diversity (LCBD) of parasitic gastrointestinal helminths (nematodes and cestodes) in two closely related rodents, Rhabdomys dilectus and Rhabdomys pumilio, from 20 localities across South Africa. Although the two Rhabdomys spp. are morphologically similar, they differ substantially in body size, habitat preference, and sociality. We asked whether the variation in life history traits and infection parameters are associated with SCBD of helminths and whether variation in environmental factors, host population density, and species richness of host communities are associated with LCBD of component assemblages of helminths. We also considered spatial factors to test whether LCBD of helminth assemblages demonstrate geographic structure. We found that the contribution of helminth species parasitic in both hosts to beta diversity significantly increased with characteristic prevalence of these species, whereas mean abundance, type of life cycle, and location in the host's gut had no effect on SCBD. The LCBD of helminth assemblages showed a significant positive correlation with environmental factors in both host species. Our results suggest that predictors of variation in SCBD and LCBD may substantially differ between parasites with different infection parameters and/or parasite communities at different hierarchical scales.

Species composition and structure of parasites component communities of tugun <i>Coregonus tugun</i> (Pallas, 1814) from the Khatanga and Yenisei Rivers

Tugun Coregonus tugun (Pallas, 1814) is an endemic of Siberia. Information about the species composition and structure of tugun parasite community on the stage of spawning migration is described in this paper. We carried out ichtioparasitologic studies in the Yenisey and the Khatanga Rivers in 20112014. Tugun parasite complex from the Khatanga River remains statistically identical in species composition, number of individuals and biomass and differs from those of the Yeniseis tugun over the entire study period. Apparently two different stocks of tugun were investigated in the Yenisei River. One of them lives in the Yeniseis streambed, the other one lives in the Podkamennaya Tunguska River. The composition of the parasitic fauna of tugun from two rivers is formed by generalist species. Tugun parasites component communities from all material collection stations have high values of the Shannon index and two dominant species (by numbers of parasites and by biomass). We found out that the species biomasses differ significantly on the graphic community structure. The description of tugun parasite communities corresponds to characteristic of a climax community on the stage of destruction except the graphic structure. In the analyzed parasitic communities the processes of egg laying and larval appearance, the death of parasites of previous year generation and infection with this year parasites occur simultaneously. The stages of formation and destruction of the community overlap. The described state of tugun parasites communities has an adaptive value. The load on the host body is reduced which ensures the long-term existence of parasites.

Variation in Local and Systemic Pro-Inflammatory Immune Markers of Wild Wood Mice after Anthelmintic Treatment.

The immune system represents a host’s main defense against infection to parasites and pathogens. In the wild, a host’s response to immune challenges can vary due to physiological condition, demography (age, sex), and coinfection by other parasites or pathogens. These sources of variation, which are intrinsic to natural populations, can significantly impact the strength and type of immune responses elicited after parasite exposure and infection. Importantly, but often neglected, a host’s immune response can also vary within the individual, across tissues and between local and systemic scales. Consequently, how a host responds at each scale may impact its susceptibility to concurrent and subsequent infections. Here we analyzed how characteristics of hosts and their parasite infections drive variation in the pro-inflammatory immune response in wild wood mice (Apodemus sylvaticus) at both the local and systemic scale by experimentally manipulating within-host parasite communities through anthelmintic drug treatment. We measured concentrations of the pro-inflammatory cytokine tumor necrosis factor alpha (TNF-α) produced in vitro in response to a panel of toll-like receptor agonists at the local (mesenteric lymph nodes [MLNs]) and systemic (spleen) scales of individuals naturally infected with two gastrointestinal parasites, the nematode Heligmosomoides polygyrus and the protozoan Eimeria hungaryensis. Anthelmintic-treated mice had a 20-fold lower worm burden compared to control mice, as well as a four-fold higher intensity of the non-drug targeted parasite E. hungaryensis. Anthelmintic treatment differentially impacted levels of TNF-α expression in males and females at the systemic and local scales, with treated males producing higher, and treated females lower, levels of TNF-α, compared to control mice. Also, TNF-α was affected by host age, at the local scale, with MLN cells of young, treated mice producing higher levels of TNF-α than those of old, treated mice. Using complementary, but distinct, measures of inflammation measured across within-host scales allowed us to better assess the wood mouse immune response to changes in parasite infection dynamics after anthelmintic treatment. This same approach could be used to understand helminth infections and responses to parasite control measures in other systems in order to gain a broader view of how variation impacts the immune response.