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Horák P, Bulantová J, Mikeš L. Other Schistosomatoidea and Diplostomoidea. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 1454:107-155. [PMID: 39008265 DOI: 10.1007/978-3-031-60121-7_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
Trematodes of the order Diplostomida are well known as serious pathogens of man, and both farm and wild animals; members of the genus Schistosoma (Schistosomatidae) are responsible for human schistosomosis (schistosomiasis) affecting more than 200 million people in tropical and subtropical countries, and infections of mammals and birds by animal schistosomes are of great veterinary importance. The order Diplostomida is also rich in species parasitizing other major taxa of vertebrates. The "Aporocotylidae" sensu lato are pathogenic in fish, "Spirorchiidae" sensu lato in reptiles. All these flukes have two-host life cycles, with asexually reproducing larvae usually in mollusks and occasionally in annelids, and adults usually live in the blood vessels of their vertebrate hosts. Pathology is frequently associated with inflammatory reactions to eggs trapped in various tissues/organs. On the other hand, the representatives of Diplostomidae and Strigeidae have three- or four-host life cycles in which vertebrates often serve not only as definitive but also as intermediate or paratenic hosts. Pathology is usually associated with migration of metacercariae and mesocercariae within the host tissues. The impact of these trematode infections on both farm and wild animals may be significant.
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Affiliation(s)
- Petr Horák
- Department of Parasitology, Faculty of Science, Charles University, Prague, Czech Republic.
| | - Jana Bulantová
- Department of Parasitology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Libor Mikeš
- Department of Parasitology, Faculty of Science, Charles University, Prague, Czech Republic
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2
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Karami AM, Duan Y, Kania PW, Buchmann K. Responses towards eyefluke (Diplostomum pseudospathaceum) in different genetic lineages of rainbow trout. PLoS One 2022; 17:e0276895. [PMID: 36301982 PMCID: PMC9612474 DOI: 10.1371/journal.pone.0276895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 10/17/2022] [Indexed: 11/18/2022] Open
Abstract
Marker-assisted selective breeding of fish with higher levels of resistance towards specific pathogens may improve fish health, but the impact of host genotype on susceptibility to multiple pathogen infections is still poorly investigated. This study examined the resistance in rainbow trout Oncorhynchus mykiss towards infection with the eye fluke Diplostomum pseudospathaceum. We used genetically selected rainbow trout, carrying SNPs associated with resistance towards the parasitic ciliate Ichthyophthirius multifiliis, and exposed the fish to eye fluke cercariae. We showed that fish partly resistant to I. multifiliis were more susceptible to eye fluke invasion. The expression of immune relevant genes (encoding innate and adaptive factors) was also affected as these genotypes responded less strongly to a secondary fluke infection. The complexity of genome architecture in disease resistance towards multiple pathogens is discussed.
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Affiliation(s)
- Asma M. Karami
- Laboratory of Aquatic Pathobiology, Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark
- * E-mail:
| | - Yajiao Duan
- Laboratory of Aquatic Pathobiology, Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark
| | - Per W. Kania
- Laboratory of Aquatic Pathobiology, Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark
| | - Kurt Buchmann
- Laboratory of Aquatic Pathobiology, Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark
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3
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Karvonen A, Fenton A, Sundberg L. Sequential infection can decrease virulence in a fish-bacterium-fluke interaction: Implications for aquaculture disease management. Evol Appl 2019; 12:1900-1911. [PMID: 31700534 PMCID: PMC6824072 DOI: 10.1111/eva.12850] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 07/10/2019] [Accepted: 07/12/2019] [Indexed: 12/13/2022] Open
Abstract
Hosts are typically infected with multiple strains or genotypes of one or several parasite species. These infections can take place simultaneously, but also at different times, i.e. sequentially, when one of the parasites establishes first. Sequential parasite dynamics are common in nature, but also in intensive farming units such as aquaculture. However, knowledge of effects of previous exposures on virulence of current infections in intensive farming is very limited. This is critical as consecutive epidemics and infection history of a host could underlie failures in management practices and medical intervention of diseases. Here, we explored effects of timing of multiple infections on virulence in two common aquaculture parasites, the bacterium Flavobacterium columnare and the fluke Diplostomum pseudospathaceum. We exposed fish hosts first to flukes and then to bacteria in two separate experiments, altering timing between the infections from few hours to several weeks. We found that both short-term and long-term differences in timing of the two infections resulted in significant, genotype-specific decrease in bacterial virulence. Second, we developed a mathematical model, parameterized from our experimental results, to predict the implications of sequential infections for epidemiological progression of the disease, and levels of fish population suppression, in an aquaculture setting. Predictions of the model showed that sequential exposure of hosts can decrease the population-level impact of the bacterial epidemic, primarily through the increased recovery rate of sequentially infected hosts, thereby substantially protecting the population from the detrimental impact of infection. However, these effects depended on bacterial strain-fluke genotype combinations, suggesting the genetic composition of the parasite populations can greatly influence the degree of host suppression. Overall, these results suggest that host infection history can have significant consequences for the impact of infection at host population level, potentially shaping parasite epidemiology, disease dynamics and evolution of virulence in farming environments.
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Affiliation(s)
- Anssi Karvonen
- Department of Biological and Environmental ScienceUniversity of JyvaskylaJyvaskylaFinland
| | - Andy Fenton
- Institute of Integrative BiologyUniversity of LiverpoolLiverpoolUK
| | - Lotta‐Riina Sundberg
- Department of Biological and Environmental ScienceUniversity of JyvaskylaJyvaskylaFinland
- Nanoscience CenterUniversity of JyvaskylaJyvaskylaFinland
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Horák P, Bulantová J, Mikeš L. Schistosomatoidea and Diplostomoidea. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1154:217-254. [PMID: 31297764 DOI: 10.1007/978-3-030-18616-6_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Trematodes of the order Diplostomida are well known as serious pathogens of man, and both farm and wild animals; members of the genus Schistosoma (Schistosomatidae) are responsible for human schistosomosis affecting more than 200 million people in tropical and subtropical countries, infections of mammals and birds by animal schistosomes are of great veterinary importance. The order Diplostomida is also rich in species parasitizing other major taxa of vertebrates. The Aporocotylidae are pathogenic in fish, Spirorchiidae in reptiles. All these flukes have two-host life cycles, with asexually reproducing larvae usually in molluscs and occasionally in annelids, and adults usually live in the blood vessels of their vertebrate hosts. Pathology is frequently associated with inflammatory reactions to eggs trapped in various tissues/organs. On the other hand, the representatives of Diplostomidae and Strigeidae have three- or four-host life cycles in which vertebrates often serve not only as definitive, but also as intermediate or paratenic hosts. Pathology is usually associated with migration of metacercariae and mesocercariae within the host tissues. The impact of these trematode infections on both farm and wild animals may be significant.
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Affiliation(s)
- Petr Horák
- Department of Parasitology, Faculty of Science, Charles University, Prague 2, Czechia.
| | - Jana Bulantová
- Department of Parasitology, Faculty of Science, Charles University, Prague 2, Czechia
| | - Libor Mikeš
- Department of Parasitology, Faculty of Science, Charles University, Prague 2, Czechia
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Karvonen A, Jokela J, Laine AL. Importance of Sequence and Timing in Parasite Coinfections. Trends Parasitol 2018; 35:109-118. [PMID: 30578150 DOI: 10.1016/j.pt.2018.11.007] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 11/21/2018] [Accepted: 11/25/2018] [Indexed: 12/17/2022]
Abstract
Coinfections by multiple parasites predominate in the wild. Interactions between parasites can be antagonistic, neutral, or facilitative, and they can have significant implications for epidemiology, disease dynamics, and evolution of virulence. Coinfections commonly result from sequential exposure of hosts to different parasites. We argue that the sequential nature of coinfections is important for the consequences of infection in both natural and man-made environments. Coinfections accumulate during host lifespan, determining the structure of the parasite infracommunity. Interactions within the parasite community and their joint effect on the host individual potentially shape evolution of parasite life-history traits and transmission biology. Overall, sequential coinfections have the potential to change evolutionary and epidemiological outcomes of host-parasite interactions widely across plant and animal systems.
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Affiliation(s)
- Anssi Karvonen
- University of Jyvaskyla, Department of Biological and Environmental Science, P.O. Box 35, FI-40014 University of Jyvaskyla, Finland.
| | - Jukka Jokela
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland; ETH Zürich, Institute of Integrative Biology (IBZ), 8092 Zürich, Switzerland
| | - Anna-Liisa Laine
- Department of Evolutionary Biology and Environmental Studies, University of Zürich, 8057 Zürich, Switzerland; Research Centre for Ecological Change, Organismal & Evolutionary Biology, P.O. Box 65 (Viikinkaari 1), FI-00014 University of Helsinki, Finland
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Blasco-Costa I, Locke SA. Life History, Systematics and Evolution of the Diplostomoidea Poirier, 1886: Progress, Promises and Challenges Emerging From Molecular Studies. ADVANCES IN PARASITOLOGY 2017; 98:167-225. [PMID: 28942769 DOI: 10.1016/bs.apar.2017.05.001] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Members of the Diplostomoidea mature in amniotes and employ vertebrates, annelids and molluscs as second intermediate hosts. Diplostomoid life cycles generally follow a three-host pattern typical of digeneans, but novelties have arisen in some species, including obligate four-host life cycles, vertical transmission, and intracellular parasitism. In this review, we summarize the basic biology of diplostomoids with reference to molecular studies, and present challenges, gaps and areas where molecular data could address long-standing questions. Our analysis of published studies revealed that most molecular surveys find more diplostomoid species than expected, but this tendency is influenced by how much effort goes into examining specimens morphologically and the number of sequenced worms. To date, molecular work has concentrated disproportionately on intraspecific or species-level diversity of larval stages in the Diplostomidae in temperate northern regions. Although the higher taxonomy of the superfamily is recognized to be in need of revision, little molecular work has been conducted at this level. Our phylogenetic analysis indicates several families and subfamilies require reconsideration, and that larval morphotypes are more reflective of evolutionary relationships than definitive hosts. The host associations of adult diplostomoids result from host-switching processes, whereas molecular surveys indicate that larval diplostomoid metacercariae have narrow ranges of second intermediate hosts, consistent with coevolution. Molecular data are often used to link diplostomoid developmental stages, and we provide data from adult Neodiplostomum and Mesoophorodiplostomum that correct earlier misidentifications of their larval stages and propose alternatives to collecting definitive hosts.
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Genotype-specific interactions between parasitic arthropods. Heredity (Edinb) 2016; 118:260-265. [PMID: 27759078 DOI: 10.1038/hdy.2016.90] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 08/22/2016] [Accepted: 08/24/2016] [Indexed: 11/08/2022] Open
Abstract
Despite the ubiquity of coinfection, we know little of the effects of intra-specific genetic variability on coinfection by distinct parasite species. Here we test the hypothesis that parasite multiplication depends on the combination of parasite genotypes that coinfect the host (that is Genotype.parasite × Genotype.parasite interaction). To that aim, we infected tomato leaves with the ecto-parasitic mites Tetranychus urticae and Tetranychus evansi. We tested all possible combinations between four T. urticae and two T. evansi populations sampled on different hosts or localities. There was no universal (that is genotype-independent) effect of coinfection on mite multiplication; in many cases the two species had no effect on each other. However, several combinations of T. evansi and T. urticae populations led to elevated T. evansi numbers. Similarly, T. urticae reproduction largely depended on the interaction between T. urticae and T. evansi populations. This evidence for genotype-by-genotype interaction between coinfecting parasites indicates that the effect of coinfection on parasite epidemiology and evolution may vary in space according to the genetic composition of local parasite populations; it further suggests the possibility of coevolution between parasites species that share the same hosts.
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Klemme I, Karvonen A. Learned parasite avoidance is driven by host personality and resistance to infection in a fish-trematode interaction. Proc Biol Sci 2016; 283:20161148. [PMID: 27605504 PMCID: PMC5031654 DOI: 10.1098/rspb.2016.1148] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 08/16/2016] [Indexed: 12/22/2022] Open
Abstract
Cognitive abilities related to the assessment of risk improve survival. While earlier studies have examined the ability of animals to learn to avoid predators, learned parasite avoidance has received little interest. In a series of behavioural trials with the trematode parasite Diplostomum pseudospathaceum, we asked whether sea trout (Salmo trutta trutta) hosts show associative learning in the context of parasitism and if so, whether learning capacity is related to the likelihood of infection mediated through host personality and resistance. We show that animals are capable of learning to avoid visual cues associated with the presence of parasites. However, avoidance behaviour ceased after the likely activation of host resistance following consecutive exposures during learning, suggesting that resistance to infection outweighs avoidance. Further, we found a positive relationship between learning ability and boldness, suggesting a compensation of risky lifestyles through increased investment in cognitive abilities. By contrast, an increased risk of infection due to low resistance was not balanced by learning ability. Instead, these traits were positively related, which may be explained by inherent physiological qualities controlling both traits. Overall, the results demonstrate that parasitism, in addition to other biological interactions such as predation, is an important selective factor in the evolution of animal cognition.
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Affiliation(s)
- Ines Klemme
- Department of Biological and Environmental Science, University of Jyvaskyla, PO Box 35, 40014 University of Jyvaskyla, Finland
| | - Anssi Karvonen
- Department of Biological and Environmental Science, University of Jyvaskyla, PO Box 35, 40014 University of Jyvaskyla, Finland
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9
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Seppälä O, Jokela J. Do Coinfections Maintain Genetic Variation in Parasites? Trends Parasitol 2016; 32:930-938. [PMID: 27614425 DOI: 10.1016/j.pt.2016.08.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 07/04/2016] [Accepted: 08/16/2016] [Indexed: 11/20/2022]
Abstract
Host individuals are often infected with multiple, potentially interacting parasite species and genotypes. Such coinfections have consequences for epidemiology, disease severity, and evolution of parasite virulence. As fitness effects of coinfection can be specific to interacting parasite genotypes, coinfections may induce high fitness variation among parasite genotypes. We argue that such interactions can be an important mechanism maintaining genetic variation in parasite traits such as infectivity and virulence. We also argue that such interactions may slow coevolutionary dynamics between hosts and parasites. This is because, instead of depending only on host genotype, parasite fitness may be determined by average infection success across all coinfection scenarios.
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Affiliation(s)
- Otto Seppälä
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland; ETH Zürich, Institute of Integrative Biology (IBZ), 8092 Zürich, Switzerland.
| | - Jukka Jokela
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland; ETH Zürich, Institute of Integrative Biology (IBZ), 8092 Zürich, Switzerland
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10
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Adaptive immune response in symptomatic and asymptomatic enteric protozoal infection: evidence for a determining role of parasite genetic heterogeneity in host immunity to human giardiasis. Microbes Infect 2016; 18:687-695. [PMID: 27401766 DOI: 10.1016/j.micinf.2016.06.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Revised: 06/13/2016] [Accepted: 06/29/2016] [Indexed: 11/23/2022]
Abstract
The genetic basis of the ultimate clinical outcomes of human giardiasis has been the subject of numerous investigations. We previously demonstrated roles for both host and parasite factors in determining the outcome of enteric infection in a murine model of Giardia duodenalis infection. In the current study, fecal and serum specimens from healthy controls and human subjects infected with the intestinal parasite G. duodenalis were assessed. Using a semi-nested PCR method, clinical isolates were genetically characterized based on the gdh and tpi loci, and the phylogenetic trees were constructed. Using a sandwich ELISA method, the serum levels of representative TH1 and TH2 cytokines were measured in infected human subjects and healthy controls. Here we showed that symptomatic human giardiasis was characterized by significantly elevated serum levels of the TH1 cytokine IFN-γ compared to healthy controls, whereas asymptomatic human subjects and healthy controls had comparable levels of serum IFN-γ. Further analyses showed that human subjects infected with G. duodenalis genotype AI had significantly elevated levels of serum IFN-γ and IL-10, but not IL-5, whereas human subjects infected with AII had similar levels of those cytokines compared to healthy controls. These data demonstrate roles for both host and parasite factors in the determination of the outcome of enteric infections and may further broaden our understanding of host-parasite interaction during enteric protozoal infections.
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Klemme I, Louhi KR, Karvonen A. Host infection history modifies co-infection success of multiple parasite genotypes. J Anim Ecol 2016; 85:591-7. [PMID: 26589834 DOI: 10.1111/1365-2656.12472] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 11/04/2015] [Indexed: 01/24/2023]
Abstract
Co-infections by multiple parasite genotypes are common and have important implications for host-parasite ecology and evolution through within-host interactions. Typically, these infections take place sequentially, and therefore, the outcome of co-infection may be shaped by host immune responses triggered by previous infections. For example, in vertebrates, specific immune responses play a central role in protection against disease over the course of life, but co-infection research has mostly focused on previously uninfected individuals. Here, we investigated whether sequential exposure and activation of host resistance in rainbow trout Oncorhynchus mykiss affects infection success and interactions between co-infecting parasite genotypes of the trematode eye-fluke Diplostomum pseudospathaceum. In accordance with earlier results, we show that a simultaneous attack of two parasite genotypes facilitates parasite establishment in previously uninfected hosts. However, we find for the first time that this facilitation in co-infection is lost in hosts with prior infection. We conclude that vertebrate host infection history can affect the direction of within-host-parasite interactions. Our results may have significant implications for the evolution of co-infections and parasite transmission strategies.
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Affiliation(s)
- Ines Klemme
- Department of Biological and Environmental Science, University of Jyvaskyla, PO Box 35, 40014, Jyvaskyla, Finland
| | - Katja-Riikka Louhi
- Department of Biological and Environmental Science, University of Jyvaskyla, PO Box 35, 40014, Jyvaskyla, Finland
| | - Anssi Karvonen
- Department of Biological and Environmental Science, University of Jyvaskyla, PO Box 35, 40014, Jyvaskyla, Finland
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12
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Haase D, Rieger JK, Witten A, Stoll M, Bornberg-Bauer E, Kalbe M, Reusch TBH. Immunity comes first: the effect of parasite genotypes on adaptive immunity and immunization in three-spined sticklebacks. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2016; 54:137-144. [PMID: 26400836 DOI: 10.1016/j.dci.2015.09.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 09/16/2015] [Accepted: 09/17/2015] [Indexed: 06/05/2023]
Abstract
Adaptive immunity in vertebrates can confer increased resistance against invading pathogens upon re-infection. But how specific parasite genotypes affect the temporal transition from innate to adaptive immunity under continual exposure to parasites is poorly understood. Here, we investigated the effects of homologous and heterologous exposures of genetically distinct parasite lineages of the eye fluke Diplostomum pseudospathaceum on gene expression patterns of adaptive immunity in sticklebacks (Gasterosteus aculeatus). Observable differences in gene expression were largely attributable to final exposures while there was no transcription pattern characteristic for a general response to repeated infections with D. pseudospathaceum. None of the final exposure treatments was able to erase the distinct expression patterns resulting from a heterologous pre-exposed fish. Interestingly, heterologous final exposures showed similarities between different treatment groups subjected to homologous pre-exposure. The observed pattern was supported by parasite infection rates and suggests that host immunization was optimized towards an adaptive immune response that favored effectiveness against parasite diversity over specificity.
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Affiliation(s)
- David Haase
- Evolutionary Ecology of Marine Fishes, GEOMAR Helmholtz-Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany.
| | - Jennifer K Rieger
- Evolutionary Ecology of Marine Fishes, GEOMAR Helmholtz-Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
| | - Anika Witten
- Institute of Human Genetics, Genetic Epidemiology, University of Münster, Albert-Schweitzer-Campus 1, 48149 Münster, Germany
| | - Monika Stoll
- Institute of Human Genetics, Genetic Epidemiology, University of Münster, Albert-Schweitzer-Campus 1, 48149 Münster, Germany
| | - Erich Bornberg-Bauer
- Institute for Evolution and Biodiversity, University of Münster, Huefferstr. 1, 48149 Münster, Germany
| | - Martin Kalbe
- Max-Planck Institute for Evolutionary Biology, August-Thienemann-Str. 2, 24306 Plön, Germany
| | - Thorsten B H Reusch
- Evolutionary Ecology of Marine Fishes, GEOMAR Helmholtz-Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
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Relative reproductive success of co-infecting parasite genotypes under intensified within-host competition. INFECTION GENETICS AND EVOLUTION 2015; 36:450-455. [PMID: 26296607 DOI: 10.1016/j.meegid.2015.08.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 08/06/2015] [Accepted: 08/12/2015] [Indexed: 12/24/2022]
Abstract
In nature, host individuals are commonly simultaneously infected with more than one genotype of the same parasite species. These co-infecting parasites often interact, which can affect their fitness and shape host-parasite ecology and evolution. Many of such interactions take place through competition for limited host resources. Therefore, variation in ecological factors modifying the host resource level could be important in determining the intensity of competition and the outcome of co-infections. We tested this hypothesis by measuring the relative reproductive success of co-infecting genotypes of the trematode parasite Diplostomum pseudospathaceum in its snail host Lymnaea stagnalis while experimentally manipulating snail resource level using contrasting feeding treatments (ad libitum food supply, no food). We found that food deprivation constrained the overall parasite within-host reproduction as the release of parasite transmission stages (cercariae) was reduced. This indicates intensified competition among the parasite genotypes. The genotypic composition of the released cercariae, however, was not affected by the feeding treatments. This suggests that in this system, the relative reproductive success of co-infecting parasite genotypes, which is an important component determining their fitness, is robust to variation in ecological factors modifying the strength of resource competition.
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14
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Bashey F. Within-host competitive interactions as a mechanism for the maintenance of parasite diversity. Philos Trans R Soc Lond B Biol Sci 2015; 370:20140301. [PMID: 26150667 PMCID: PMC4528499 DOI: 10.1098/rstb.2014.0301] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/14/2015] [Indexed: 12/11/2022] Open
Abstract
Variation among parasite strains can affect the progression of disease or the effectiveness of treatment. What maintains parasite diversity? Here I argue that competition among parasites within the host is a major cause of variation among parasites. The competitive environment within the host can vary depending on the parasite genotypes present. For example, parasite strategies that target specific competitors, such as bacteriocins, are dependent on the presence and susceptibility of those competitors for success. Accordingly, which parasite traits are favoured by within-host selection can vary from host to host. Given the fluctuating fitness landscape across hosts, genotype by genotype (G×G) interactions among parasites should be prevalent. Moreover, selection should vary in a frequency-dependent manner, as attacking genotypes select for resistance and genotypes producing public goods select for cheaters. I review competitive coexistence theory with regard to parasites and highlight a few key examples where within-host competition promotes diversity. Finally, I discuss how within-host competition affects host health and our ability to successfully treat infectious diseases.
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Affiliation(s)
- Farrah Bashey
- Department of Biology, Indiana University, 1001 East Third Street, Bloomington, IN 47405, USA
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