Ecological Parasitology Research Articles

Temporal changes in streamflow can predict parasitism levels in freshwater prawns better than host traits

Abstract Understanding how changes in the hydrological regime drive parasite loads and dynamics remains a challenging issue in ecological parasitology. Temporal changes in streamflow and rainfall are key hydrological factors that could alter interactions between the parasite and host and affect parasitism levels. However, to investigate the effect of streamflow, rainfall and its mechanisms, it is important to control host traits that can also influence parasitism levels in freshwater systems. Here, we used a cymothoid‐palaemonid prawn model to test the combined effects of streamflow and rainfall accounting for host traits to predict variations in parasite loads in stream ecosystems. We collected the palaemonid prawns monthly for 2 years and measured the variation of rainfall and streamflow (i.e. stream discharge) at the time of prawn sampling. Our best model showed that streamflow can predict parasitism levels in prawns better than host traits. We found a higher prevalence and abundance of parasites in reduced streamflow compared to increased ones. We also found higher ectoparasite loads in females rather than males and occurring in autumn and winter rather than in spring and summer. Our results also showed that ectoparasite loads also suffer an effect of host body size, sex and moult stage, but not host age. Our findings show that reduced streamflow can facilitate host finding that favours parasite transmission in dry seasons and increase parasitism levels in stream systems. Temporal variability in streamflow can have a strong influence on parasite loads and dynamics compared to host traits in stream ecosystems. Identifying how interactions between aquatic invertebrates and parasites respond to variability in the hydrological regime can help to better understand and predict disease outbreaks as habitat reduction and disturbance continue in stream ecosystems.

Comparison of qPCR and metabarcoding for environmental DNA surveillance of a freshwater parasite.

Analysis of environmental DNA (eDNA) has been successfully used across freshwater ecological parasitology to inform management of ecologically and economically important species. However, most studies have used species-specific quantitative polymerase chain reaction (qPCR) assays to detect target taxa. While generally effective, this approach limits the amount of community and management-supporting data that can be obtained from eDNA samples. If eDNA metabarcoding could be conducted with the same accuracy of a single species approach, researchers could simultaneously detect a target species while obtaining vast community data from eDNA samples. We sampled 38 freshwater sites on Fort McCoy, Wisconsin and compared qPCR to metabarcoding for eDNA detection of the ectoparasitic gill louse Salmincola edwardsii, an obligate parasite of Salvelinus fishes (chars). We found no evidence to suggest S. edwardsii occupancy or detection probabilities differed between qPCR and metabarcoding. Further, we found that the number of S. edwardsii reads from metabarcoding were negatively predictive of C T values from qPCR (C T value indicates cycle a significant amount of target eDNA is detected, with lower C Ts indicative of more DNA), demonstrating that our metabarcoding reads positively predicted qPCR DNA quantities. However, the number of reads was not predictive of overall qPCR score (number of positive qPCR replicates). In addition to S. edwardsii, metabarcoding led to the detection of a vast community of over 2600 invertebrate taxa. We underscore the necessity for conducting similar analyses across environments and target species, as the ecology of eDNA will vary on a per-study basis. Our results suggest that eDNA metabarcoding provides a highly sensitive and accurate method for detecting parasitic gill lice while also illuminating the broader biological community and co-occurrence of species in the environment.

Equal rights for parasites: Windsor 1995, revisited after ecological parasitology has come of age

Lack of data to properly model key biological characteristics like abundance or distribution, seriously hinder comprehension of biodiversity patterns and their drivers — even for historically well-studied and charismatic organisms. Knowledge shortfalls are more extreme in the case of parasites, which are mostly part of the “hidden biodiversity” and generally have a bad reputation. However, being an extremely large portion of biodiversity and a fundamental part of ecosystems, failure to consider parasites is itself an information shortfall for conservation, and can result in important consequences not only for planning strategies to conserve biological diversity, but also to understand fully the patterns and processes that shape ecosystems. Parasites exhibit a marked duality: while some species are pathogenic and do compromise their host's survival (and human interests), the majority exert apparently negligible negative effects on their hosts and could be considered non-pathogenic; indeed, parasites are beneficial as they provide important ecosystemic functions and services. Using a comprehensive dataset of fish host-helminth parasites in Mexico as a case study, we review knowledge shortfalls relating to parasites, exemplifying their impacts — both positive and negative. A holistic appreciation of parasites should consider both their (many) beneficial and (a few, proven) detrimental impacts, something which could be operationally incorporated into conservation assessments and strategies (e.g., IUCN Green and Red Lists, respectively). Outreach and education are key to modify negative perceptions towards parasites, and to induce recognition of their importance for ecosystemic function and structure.

Science school in ecological parasitology in Karelia

The ecological concept of parasitism as a general biology phenomenon underlies the understanding of the role of parasites in terrestrial and aquatic ecosystems. The review gives an account of the current positioning of parasitology in the system of biological sciences, the subject and tasks of ecological parasitology. We relate the history of the science school in parasitology at the Institute of Biology KarRC RAS, which took shape under the leadership of pupils of the founder of the Russian school in ecological parasitology, outstanding scholar from Leningrad V. A. Dogiel. Major stages and areas of research and methodological approaches to the study of parasites and host-parasite relationships are described, covering a wide range of objects: blood-sucking arthropods, parasites of fish, birds, mammals, and plants. Studies deal with the formation and dynamics of parasitic communities in natural and disturbed terrestrial and aquatic ecosystems (eutrophication, industrial pollution, alien species invasions, aquaculture). The results of these studies are of high theoretical significance and have been published in monographs and in articles in Russian and international journals. Practical recommendations are widely applied in nature management, veterinary and agricultural practices, and are annually published in the Republic of Karelia State Report on the Environment. Today, the science school in ecological parasitology in Karelia is represented by qualified specialists, who investigate a wide range of both basic and applied topics, including those of special relevance for the region.

Endoparasites of rabbits (Oryctolagus cuniculus domesticus) in Southern Ukraine

One of the main tasks of ecological parasitology at the present stage is to establish patterns of spread of invasive diseases of animals in the environment through a thorough epidemiological examination, as well as to determine the main directions and factors of spread of parasites in Ukraine. Among the many pathogens, endoparasites play a major role in a number of diseases in rabbits with increased morbidity and mortality. In the body of both wild and domestic rabbits several species of parasites that form a parasitocenosis can be localized. The latter have a pathogenic effect on organs and tissues, leading to reduced weight gain, premature slaughter and even mortality. The prevalence of endoparasitoses was studied in weaned rabbits 60 days of age, 120 days of age at fattening, 180 days of age – mating age and adults of 320 days of age to determine the extensiveness and intensity of the dominant invasion. A total of 720 head was studied, 180 animals from each age group. Three species of nematodes were recorded in the rabbits: Trichostrongylus retortaeformis (Zeder, 1800), Nematodirus leporis (Ransom, 1907) and Passalurus ambiguus (Rudolphi, 1819); the cestode Taenia pisiformis (Bloch, 1780); three species of Emeria: Eimeria stiedae (Lindermann, 1865), which parasitizes in the bile ducts of the liver and gallbladder, E. magna (Perard, 1925) and E. media (Kessel, 1929) – in the epithelial cells of the intestine. The prevalence of the infestation depends on the age of the animals. According to the data obtained, eimeriosis was one of the main parasitic diseases of the rabbits. Dominant invasions of Eimeria in the intestines of 60-day-old rabbits were found in the studied animals, their extensiveness reached 19.4%, while the spread of hepatic Eimeria was registered in 13.3% of the examined rabbits. The total infestation of weaned rabbits with helminths was 22.2%, in rabbits for fattening – 26.7%, and in rabbits of mating age and adults – 20.0% and 20.6%, respectively. Global climate change will change the distribution and dynamics of soil-borne helminthiases, but host immunity may also affect host-parasite interactions. Subsequent studies will be aimed at elucidating the effect of mono and mixed invasions on the body of rabbits. Updated data on helminthiasis will expand the screening strategy to maintain rabbit health and reduce economic losses.

Endoparasitoses of the Eurasian collared dove (Streptopelia decaocto) on the northern Black Sea coast of Ukraine

One of the main tasks of ecological parasitology at the present stage is to determine patterns of spread of invasive diseases of poultry in the environment through a thorough epidemiological examination, as well as to determine the main directions and factors of spread of parasites in Ukraine. Some pigeon health problems can affect their populations, but parasitic infections play an important role. Our research found that 83.3% of Eurasian collared doves examined (Streptopelia decaocto) were affected by endoparasites. The commonest helminths were Raillietina spp. with the average invasion intensity of 4.9 ± 1.3 specimens/ind., Baruscapillaria spp. and Ascaridia columbae with an invasion intensity of 4.6 ± 1.5 and 3.7 ± 2.1 specimens/ind., respectively. The commonest cestodes were Raillietina spp. with the extent of invasion of 52.2% and Davainea proglottina – 6.7%. The Amoebotaenia cuneata cestodes were recorded in 3 (3.3%) doves, and Echinolepis carioca – only in 2 (2.2%) doves. Six doves (6.7%) were infected with the nematode Ascaridia columbae and 5 (5.6%) – Baruscapillaria spp. Eimerian oocysts were found in 9 (10%) collared doves, and Trichomonas gallinae was recorded in 15 (16.7%) birds. According to the results of helminthological autopsy and identification of the isolated pathogens, 8 varieties of mixinvasions were identified. In association with the Rayetins, there were the protozoa Eimeria spp. and Trichomonas gallinae and the nematode Ascaridia columbae. Two-component invasions were registered in 78.6% of doves, three-component infestations in 14.3% and four-component infestations in 7.1% of birds. Mixed infection with Raillietina spp. + Ascaridia columbae was found in the small intestine of Streptopelia decaocto, which was also pathomorphologically observed to have catarrhal-hemorrhagic enteritis, which was accompanied by the formation of a large number of spotted hemorrhages on the mucous membrane, and in the places of attachment of cestodes - necrotic-caseous areas. Temperature and other weather conditions such as humidity, precipitation, etc. of the northern Black Sea coast affect the population size of intermediate host cestodes. Continuous monitoring of invasive diseases of pigeons of different species will help to take the necessary preventive measures against endoparasitoses of birds.

Endoparasitoses of the Eurasian collared dove (Streptopelia decaocto) on the northern Black Sea coast of Ukraine

One of the main tasks of ecological parasitology at the present stage is to determine patterns of spread of invasive diseases of poultry in the environment through a thorough epidemiological examination, as well as to determine the main directions and factors of spread of parasites in Ukraine. Some pigeon health problems can affect their populations, but parasitic infections play an important role. Our research found that 83.3% of Eurasian collared doves examined (Streptopelia decaocto) were affected by endoparasites. The commonest helminths were Raillietina spp. with the average invasion intensity of 4.9 ± 1.3 specimens/ind., Baruscapillaria spp. and Ascaridia columbae with an invasion intensity of 4.6 ± 1.5 and 3.7 ± 2.1 specimens/ind., respectively. The commonest cestodes were Raillietina spp. with the extent of invasion of 52.2% and Davainea proglottina – 6.7%. The Amoebotaenia cuneata cestodes were recorded in 3 (3.3%) doves, and Echinolepis carioca – only in 2 (2.2%) doves. Six doves (6.7%) were infected with the nematode Ascaridia columbae and 5 (5.6%) – Baruscapillaria spp. Eimerian oocysts were found in 9 (10%) collared doves, and Trichomonas gallinae was recorded in 15 (16.7%) birds. According to the results of helminthological autopsy and identification of the isolated pathogens, 8 varieties of mixinvasions were identified. In association with the Rayetins, there were the protozoa Eimeria spp. and Trichomonas gallinae and the nematode Ascaridia columbae. Two-component invasions were registered in 78.6% of doves, three-component infestations in 14.3% and four-component infestations in 7.1% of birds. Mixed infection with Raillietina spp. + Ascaridia columbae was found in the small intestine of Streptopelia decaocto, which was also pathomorphologically observed to have catarrhal-hemorrhagic enteritis, which was accompanied by the formation of a large number of spotted hemorrhages on the mucous membrane, and in the places of attachment of cestodes - necrotic-caseous areas. Temperature and other weather conditions such as humidity, precipitation, etc. of the northern Black Sea coast affect the population size of intermediate host cestodes. Continuous monitoring of invasive diseases of pigeons of different species will help to take the necessary preventive measures against endoparasitoses of birds.

Index to Titles and Authors/Editors of Books Reviewed Volume 92 (2017)

Index to Titles and Authors/Editors of Books Reviewed Volume 92 (2017)

Parasites as drivers of key processes in aquatic ecosystems: Facts and future directions

Despite the advances in our understanding of the ecological importance of parasites that we have made in recent years, we are still far away from having a complete picture of the ecological implications connected to parasitism. In the present paper we highlight key issues that illustrate (1) important contributions of parasites to biodiversity, (2) their integral role in ecosystems, (3) as well as their ecological effects as keystone species (4) and in biological invasion processes. By using selected examples from aquatic ecosystems we want to provide an insight and generate interest into the topic, and want to show directions for future research in the field of ecological parasitology. This may help to convince more parasitologists and ecologists contributing and advancing our understanding of the complex and fascinating interplay of parasites, hosts and ecosystems.

Особливості морфометричної будови імаго Oesophagostomum venulosum (Rudolphi, 1809)

The study of biodiversity, morphological and biological peculiarities of pathogens of invasive animal diseases in natural and anthropogenically transformed ecosystems is an important task of modern population and applied ecological parasitology. The dominant position among helminthiasis of the digestive organs in ruminants occupy strongylatoses of the gastrointestinal tract. One of the components of the strongylates fauna, which parasitizes on sheep, is Oesophagostomum venulosum Rudolphi, 1809.In order to study the morphological features of the structure of imaginal forms of nematodes of the species Oe. venulosum and determination of their differential metric characteristics, the study of sexually mature oesophagostomes isolated from the intestines of sheep was conducted. Collection of helminths was carried out by the method of complete helminthology of the thick intestine of animals. The congenital morphological features of oesophagostomes are the presence of a clearly separated main vesicle, well-developed major papillae, the outer and inner radial corona around the mouth. Species Oe. venulosum in females is characterized by peculiarities in the structure of the caudal end, vulva, oviduct, vagina. It was found that the length of the body and main vesicle in females was 27.73 and 9.3% higher than that of males and averaged 18.75 ± 0.58 mm and 0.43 ± 0.01 mm, respectively. Indices of body width and major vesicles of mature males and females ranged 0,30–0,64 mm, 0,34–0,43 mm and did not differ significantly. New data on morphological and metric parameters of females Oe. venulosum, which increase the effectiveness of differentiation of helminths to the species. The parameters of the esophagus width in different sites, the width of the body in the vulva and the anus, the width and length of the spherical protrusion in the vulva area are determined. It was found that the length of the eggs in the femoral cavity and in the secretion it secretes significantly changes, the eggs are thickened, decreasing by 13.97%. The length and width of the eggs allocated by the female Oe. venulosum, on average, is 82.51 ± 2.37 and 53.51 ± 1.17 μm, respectively, and have a structure characteristic of the strongylidsc type eggs.

Does moving up a food chain increase aggregation in parasites?

General laws in ecological parasitology are scarce. Here, we evaluate data on numbers of fish parasites published by over 200 authors to determine whether acquiring parasites via prey is associated with an increase in parasite aggregation. Parasite species were grouped taxonomically to produce 20 or more data points per group as far as possible. Most parasites that remained at one trophic level were less aggregated than those that had passed up a food chain. We use a stochastic model to show that high parasite aggregation in predators can be solely the result of the accumulation of parasites in their prey. The model is further developed to show that a change in the predators feeding behaviour with age may further increase parasite aggregation.

Mammalian gastrointestinal parasites in rainforest remnants of Anamalai Hills, Western Ghats, India.

Habitat fragmentation is postulated to be a major factor influencing infectious disease dynamics in wildlife populations and may also be responsible, at least in part, for the recent spurt in the emergence, or re-emergence, of infectious diseases in humans. The mechanism behind these relationships are poorly understood due to the lack of insights into the interacting local factors and insufficient baseline data in ecological parasitology of wildlife. Here, we studied the gastrointestinal parasites of nonhuman mammalian hosts living in 10 rainforest patches of the Anamalai Tiger Reserve, India. We examined 349 faecal samples of 17 mammalian species and successfully identified 24 gastrointestinal parasite taxa including 1 protozoan, 2 trematode, 3 cestode and 18 nematode taxa. Twenty of these parasites are known parasites of humans. We also found that as much as 73% of all infected samples were infected by multiple parasites. In addition, the smallest and most fragmented forest patches recorded the highest parasite richness; the pattern across fragments, however, seemed to be less straightforward, suggesting potential interplay of local factors.

Parasite epidemiology in a changing world: can molecular phylogeography help us tell the wood from the trees?

SUMMARY Molecular phylogeography has revolutionised our ability to infer past biogeographic events from cross-sectional data on current parasite populations. In ecological parasitology, this approach has been used to address fundamental questions concerning host-parasite co-evolution and geographic patterns of spread, and has raised many technical issues and problems of interpretation. For applied parasitologists, the added complexity inherent in adding population genetic structure to perceived parasite distributions can sometimes seem to cloud rather than clarify approaches to control. In this paper, we use case studies firstly to illustrate the potential extent of cryptic diversity in parasite and parasitoid populations, secondly to consider how anthropogenic influences including movement of domestic animals affect the geographic distribution and host associations of parasite genotypes, and thirdly to explore the applied relevance of these processes to parasites of socio-economic importance. The contribution of phylogeographic approaches to deeper understanding of parasite biology in these cases is assessed. Thus, molecular data on the emerging parasites Angiostrongylus vasorum in dogs and wild canids, and the myiasis-causing flies Lucilia spp. in sheep and Cochliomyia hominovorax in humans, lead to clear implications for control efforts to limit global spread. Broader applications of molecular phylogeography to understanding parasite distributions in an era of rapid global change are also discussed.

Parasitism and ecological parasitology

Parasitism as one of the life modes is a general biological phenomenon and is a characteristic of all viruses, many taxa of bacteria, fungi, protists, metaphytes, and metazoans. Zooparasitology is focused on studies of parasitic animals, particularly, on their taxonomy, anatomy, life cycles, host-parasite relations, biocoenotic connections, and evolution. Ecological parasitology is a component of ecology, as the scientific study of the relation of living organisms with each other and their surroundings. In the present paper, critical analysis of the problems, main postulates, and terminology of the modern ecological parasitology is given.

Significance of ixodid tick (Parasitiformes, Ixodidae) population structure for maintenance of natural foci of infection

Basic postulates of the theory of natural focality of infections are considered in terms of modern ecological parasitology using the example of Ixodes ricinus and I. persulcatus ticks, the main vectors of tickborne encephalitis and borrelioses in Eurasia. Consideration is given to data on the population structure of ticks, their distribution in ecosystems, abundance, mortality at different stages of the life cycle, seasonal dynamics of activity, occurrence on different vertebrate species, relationships with potential hosts, and connections agents of infections. Due to long individual life span and development of one generation over 3–6 years, tick vector provide not only for transmission of pathogens, but also for their long-term storage and amplification. Several alternative routes of tick infection of ticks provide for pathogen exchange between individuals at different phases of development within one generation and between feeding ticks of different generations.

Scarcity of parasite assemblages in the Adriatic-reared European sea bass ( Dicentrarchus labrax) and sea bream ( Sparus aurata)

The shaping forces of parasite community structure still is the main subject in the ecological parasitology whilst community predictability and repeatability showed that hardly a generally applicable role is ever going to be assessed. Defining and describing parasite communities can be very useful from the epizootiological point, in order to help in the assessment of the medical and economical impact of certain parasitosis, moreover when hosts are economically valuable species. Since parasite assemblages in reared European sea bass ( Dicentrarchus labrax) and sea bream ( Sparus aurata) in Adriatic cage systems can play an important role in the economic feasibility of the rearing process, we evaluated their character through assessing diversity indices, nestedness of parasite communities and their differences in respect to season and composition, as well as fish growth. We observed colonization of a new monogenean species ( Furnestinia echeneis) and general impoverishment of parasites populations over time in the Adriatic-reared fish parasite assemblages. Parasite assemblages differed significantly between seasons for both fish species, while species richness, evenness, diversity indices and nestedness of parasitic communities in the sea bream showed to be significantly higher compared to those in the sea bass. Such characteristics define parasite communities of both Adriatic-reared fish as species poor although structured and ordered assemblages.

Cost of co-infection controlled by infectious dose combinations and food availability

To what extent the combined effect of several parasite species co-infecting the same host (i.e. polyparasitism) affects the host's fitness is a crucial question of ecological parasitology. We investigated whether the ecological setting can influence the co-infection's outcome with the mosquito Aedes aegypti and two parasites: the microsporidium Vavraia culicis and the gregarine Ascogregarina culicis. The cost of being infected by the two parasites depended on the interaction between the two infectious doses and host food availability. The age at pupation of the mosquito was delayed most when the doses of the two parasites were highest and little food was available. As infectious dose increases with the parasites' prevalence and intensity of transmission, the cost of being co-infected depends on the epidemiological status of the two parasite species.

Functional and Evolutionary Ecology of Fleas, a Model for Ecological Parasitology

Functional and Evolutionary Ecology of Fleas, a Model for Ecological Parasitology

Functional and evolutionary ecology of fleas: a model for ecological parasitology

Fleas are one of the most interesting and fascinating taxa of ectoparasites. All species in this relatively small order are obligatory haematophagous (blood-feeding) parasites of higher vertebrates. This book examines how functional, ecological and evolutionary patterns and processes of host-parasite relationships are realized in this particular system. As such it provides an in-depth case study of a host-parasite system, demonstrating how fleas can be used as a model taxon for testing ecological and evolutionary hypotheses. The book moves from basic descriptive aspects, to functional issues and finally to evolutionary explanations. It extracts several general principles that apply equally well to other host-parasite systems, so it appeals not only to flea biologists but also to 'mainstream' parasitologists and ecologists.

Parasitological analyses of the male chimpanzees (Pan troglodytes schweinfurthii) at Ngogo, Kibale National Park, Uganda

Numerous intestinal parasites identified in populations of wild nonhuman primates can be pathogenic to humans. Furthermore, nonhuman primates are susceptible to a variety of human pathogens. Because of increasing human encroachment into previously nonimpacted forests, and the potential for disease transmission between human and nonhuman primate populations, further detailed investigations of primate ecological parasitology are warranted. For meaningful comparisons to be made, it is important for methods to be standardized across study sites. One aspect of methodological standardization is providing reliable estimates of parasite prevalence and knowing how many samples are needed to adequately estimate an individual's parasite prevalence. In this study the parasitic fauna of 37 adult, adolescent, and juvenile male chimpanzees from the Ngogo group, Kibale National Park, Uganda, were assessed from 121 fecal samples collected over a 3-month period. Twelve taxa of intestinal species (five helminth and seven protozoan) were recovered from the samples. The four most prevalent species were Troglodytella abrassarti (97.3%), Oesophagostomum sp. (81.1%), Strongyloides sp. (83.8%), and Entamoeba chattoni (70.3%). No one species was found in all samples from any one animal, and Troglodytella abrassarti, the most common intestinal organism, was found in all of the serial samples of only 69.4% of the chimpanzees. The cumulative species richness for individuals significantly increased for every sequential sample (up to three to four samples) taken per animal during this study. The results indicate that to accurately diagnose total intestinal infection and evaluate group prevalence, three to four sequential samples from each individual must be collected on nonconsecutive days. This conclusion applies only to short study periods in which possible seasonal effects are not taken into consideration. Validation of these results at different study sites in different regions with different climatic patterns is needed.