Parasite interactions in natural populations: insights from longitudinal data

SUMMARYThe physiological and immunological state of an animal can be influenced by current infections and infection history. Consequently, both ongoing and previous infections can affect host susceptibility to another parasite, the biology of the subsequent infection (e.g. infection length) and the impact of infection on host morbidity (pathology). In natural populations, most animals will be infected by a succession of different parasites throughout the course of their lives, with probably frequent concomitant infections. The relative timing of different infections experienced by a host (i.e. the sequence of infection events), and the effects on factors such as host susceptibility and host survival, can only be derived from longitudinal data on individual hosts. Here we review some of the evidence for the impact of co-infection on host susceptibility, infection biology and pathology focusing on insights obtained from both longitudinal studies in humans and experiments that explicitly consider the sequence of infection. We then consider the challenges posed by longitudinal infection data collected from natural populations of animals. We illustrate their usefulness using our data of microparasite infections associated with field vole (Microtus agrestis) populations to examine impacts on susceptibility and infection length. Our primary aim is to describe an analytical approach that can be used on such data to identify interactions among the parasites. The preliminary analyses presented here indicate both synergistic and antagonistic interactions between microparasites within this community and emphasise that such interactions could have significant impacts on host-parasite fitness and dynamics.

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The impact of environmental change on host–parasite coevolutionary dynamics

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2010.2359 ◽

2010 ◽

Vol 278 (1716) ◽

pp. 2283-2292 ◽

Cited By ~ 48

Author(s):

Rafal Mostowy ◽

Jan Engelstädter

Keyword(s):

Environmental Change ◽

Environmental Changes ◽

Selective Pressure ◽

Time Windows ◽

Gene Interactions ◽

Genotype By Environment ◽

Host Parasite ◽

The Impact ◽

Antagonistic Interactions ◽

Gene For Gene

Environmental factors are known to affect the strength and the specificity of interactions between hosts and parasites. However, how this shapes patterns of coevolutionary dynamics is not clear. Here, we construct a simple mathematical model to study the effect of environmental change on host–parasite coevolutionary outcome when interactions are of the matching-alleles or the gene-for-gene type. Environmental changes may effectively alter the selective pressure and the level of specialism in the population. Our results suggest that environmental change altering the specificity of selection in antagonistic interactions can produce alternating time windows of cyclical allele-frequency dynamics and cessation thereof. This type of environmental impact can also explain the maintenance of polymorphism in gene-for-gene interactions without costs. Overall, our study points to the potential consequences of environmental variation in coevolution, and thus the importance of characterizing genotype-by-genotype-by-environment interactions in natural host–parasite systems, especially those that change the direction of selection acting between the two species.

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The impact of resource provisioning on the epidemiological responses of different parasites

10.1101/2021.05.22.445253 ◽

2021 ◽

Author(s):

Diana Erazo ◽

Amy B Pedersen ◽

Andy Fenton

Keyword(s):

Infectious Diseases ◽

Anthropogenic Activities ◽

Resource Provisioning ◽

Transmission Mode ◽

Host Susceptibility ◽

Host Immune System ◽

Trade Offs ◽

Duration Of Infection ◽

Host Parasite ◽

The Impact

Events such as anthropogenic activities and periodic tree masting can alter resource provisioning in the environment, directly affecting animals, and potentially impacting the spread of infectious diseases in wildlife. The effect of these supplemental resources on infectious diseases can manifest through different pathways, affecting host susceptibility, transmission and host demography. To date however, empirical research has tended to examine these different pathways in isolation, for example by quantifying the effects of provisioning on host behaviour in the wild or changes in immune responses in controlled laboratory studies. Further, while theory has investigated the interactions between these pathways, thus far this work has focussed on a narrow subset of pathogen types, typically directly-transmitted microparasites. Given the diverse ways that provisioning can affect host susceptibility, contact patterns or host demography, we may expect the epidemiological consequences of provisioning to depend on key aspects of parasite life-history, such as the duration of infection and transmission mode. We developed a suite of generic epidemiological models to compare how resource provisioning alters responses for different parasites that vary in their biology (micro- and macro-parasite), transmission mode (direct, environmental, and vector transmitted) and duration of infection (acute, latent, and chronic). Next, we parameterised these different parasite types using data from the diverse parasite community of wild wood mice as a case study. We show there are common epidemiological responses to host resource provisioning across all parasite types examined. In particular, the response to provisioning could be driven in opposite directions, depending on which host pathways (contact rate, susceptibility or host demography) are most altered by the addition of resources to the environment. Broadly, these responses were qualitatively consistent across all parasite types, emphasising the importance of identifying general trade-offs between provisioning-altered parameters. Despite the qualitative consistency in responses to provisioning across parasite types, we found notable quantitative differences between parasites, suggesting specific epidemiological outcomes could strongly depend on parasite type, infection duration and permanency of recovery, and whether the parasite is directly, environmentally, or vector transmitted. These analyses therefore highlight the importance of knowing key specific aspects of host-parasite biology, such as host contact behaviours, parasite interactions with the host immune system, and how resource availability shapes host demographics, in order to understand and predict epidemiological responses to provisioning for any specific host-parasite system.

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Host-pathogen coevolution increases genetic variation in susceptibility to infection

10.1101/474924 ◽

2018 ◽

Author(s):

Elizabeth ML Duxbury ◽

Jonathan P Day ◽

Davide Maria Vespasiani ◽

Yannik Thüringer ◽

Ignacio Tolosana ◽

...

Keyword(s):

Genetic Variation ◽

Genetic Variants ◽

Genetic Architecture ◽

Natural Populations ◽

Major Effect ◽

Cross Infection ◽

Host Susceptibility ◽

Susceptibility To Infection ◽

Host Parasite Interactions ◽

Host Parasite

AbstractIt is common to find considerable genetic variation in susceptibility to infection in natural populations. We have investigated whether natural selection increases this variation by testing whether host populations show more genetic variation in susceptibility to pathogens that they naturally encounter than novel pathogens. In a large cross-infection experiment involving four species of Drosophila and four host-specific viruses, we always found greater genetic variation in susceptibility to viruses that had coevolved with their host. We went on to examine the genetic architecture of resistance in one host species, finding that there are more major-effect genetic variants in coevolved host-parasite interactions. We conclude that selection by pathogens increases genetic variation in host susceptibility, and much of this effect is caused by the occurrence of major-effect resistance polymorphisms within populations.

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Characterization of vertically and cross-species transmitted viruses in the cestode parasite Schistocephalus solidus

10.1101/803247 ◽

2019 ◽

Author(s):

Megan A Hahn ◽

Karyna Rosario ◽

Pierrick Lucas ◽

Nolwenn M Dheilly

Keyword(s):

Evolutionary Dynamics ◽

Broad Distribution ◽

Parasite Fitness ◽

Virus Diversity ◽

Cestode Parasite ◽

Schistocephalus Solidus ◽

Host Parasite ◽

The Impact

AbstractParasitic flatworms (Neodermata) represent a public health and economic burden due to associated debilitating diseases and limited therapeutic treatments available. Despite their importance, there is scarce information regarding flatworm-associated microbes. We report the discovery of six RNA viruses in the cestode Schistocephalus solidus. None were closely related to classified viruses and they represent new taxa. Mining transcriptomic data revealed the broad distribution of these viruses in Alaskan and European S. solidus populations. We demonstrate through in vitro culture of S. solidus that five of these viruses are vertically transmitted. With experimental infections and field-sampling, we show that one of the viruses is transmitted to parasitized hosts. The impact of these viruses in parasite fitness and pathogenicity, and in host-parasite co-evolutionary dynamics remains to be determined. The detection of six novel viruses in this first characterization of viruses in Neodermatans likely represents a fraction of virus diversity in parasitic flatworms.

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Urbanization of fauna on the example of marsh frog (Pelophylax ridibundus)

Ecology and Noospherology ◽

10.15421/031525 ◽

2015 ◽

Vol 26 (3-4) ◽

pp. 116-123

Author(s):

A. P. Korzh ◽

T. V. Zahovalko

Keyword(s):

Urban Areas ◽

Cognitive Modeling ◽

Negative Impact ◽

Natural Populations ◽

Cellular Level ◽

Anthropogenic Factors ◽

Migration Routes ◽

Corrective Effect ◽

The Impact ◽

The City

Recently, the number of published works devoted to the processes of synanthropization of fauna, is growing like an avalanche, which indicates the extreme urgency of this theme. In our view, the process of forming devices to coexist with human and the results of his life reflects the general tandency of the modern nature evolution. Urbanization is characteristic for such a specific group of animals like amphibians, the evidence of which are numerous literature data. Many researchers use this group to assess the bioindicative quality of the environment. For this aim a variety of indicators are used: from the cellular level of life of organization up to the species composition of the group in different territories. At the same time, the interpretation of the results is not always comparable for different areas and often have significantly different interpretations by experts. Urban environment, primarily due to the contamination is extremely aggressive to amphibians. As a consequence, the urban populations of amphibians may be a change in the demographic structure, affecting the reproductive ability of the population, the disappearance of the most sensitive species or individuals, resizing animals, the appearance of abnormalities in the development, etc. At the same time play an important amphibians in the ecosystems of cities, and some species in these conditions even feel relatively comfortable. Therefore, it is interesting to understand the mechanisms of self-sustaining populations of amphibians in urban environments. To assess the impact of natural and anthropogenic factors on the development of amphibian populations were used cognitive modeling using the program Vensim PLE. Cognitive map of the model for urban and suburban habitat conditions were the same. The differences concerned the strength of connections between individual factors (migration, fertility, pollution) and their orientation. In general, factors like pollution, parasites, predators had negative impact on the population, reducing its number. The birth rate, food and migration contributed to raising number of individuals. Some of the factors affected on the strength to of each other as well: the majority of the factors affected the structure of the population, had an influence on the fertility. Thanks to it the model reflects the additive effect of complex of factors on the subsequent status of the population. Proposed and analyzed four scenarios differing strength and duration of exposure. In the first scenario, a one-time contamination occurs and not subsequently repeated. The second and third scenario assumes half board contamination, 1 year (2 scenario) and two years (scenario 3). In the fourth scenario, the pollution affected the population of amphibians constantly. In accordance with the results of simulation, much weaker than the natural populations respond to pollution - have them as an intensive population growth and its disappearance at constant pollution is slow. Changes to other parameters of the model showed that this pollution is the decisive factor -only the constant action leads to a lethal outcome for the populations. All other components of the model have a corrective effect on the population dynamics, without changing its underlying trand. In urban areas due to the heavy impact of pollution maintaining the population is only possible thanks to the migration process – the constant replenishment of diminishing micropopulations of natural reserves. This confirms the assumption that the form of existence metapopulations lake frog in the city. In order to maintain the number of amphibians in urban areas at a high level it is necessary to maintain existing migration routes and the creation of new ones. Insular nature of the placement of suitable habitats in urban areas causes the metapopulation structure of the types of urbanists. Therefore, the process of urbanization is much easier for those species whicht are capable of migration in conditions of city. In the initial stages of settling the city micropopulationis formed by selective mortality of the most susceptible individuals to adverse effects. In future, maintaining the categories of individuals is provided mainly due to migration processes metapopulisation form of the species of existence is supported). It should be noted that the changes in the previous levels are always saved in future. In the case of reorganizations of individuals we of morphology can assume the existence of extremely adverse environmental conditions that threaten the extinction of the micropopulations.

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Does parental permissiveness toward cigarette smoking and alcohol use influence illicit drug use among adolescents? A longitudinal study in seven European countries

Social Psychiatry and Psychiatric Epidemiology ◽

10.1007/s00127-021-02118-5 ◽

2021 ◽

Author(s):

Emina Mehanović ◽

Federica Vigna-Taglianti ◽

Fabrizio Faggiano ◽

Maria Rosaria Galanti ◽

Barbara Zunino ◽

...

Keyword(s):

Alcohol Use ◽

Drug Use ◽

Cigarette Smoking ◽

Longitudinal Data ◽

Illicit Drug ◽

Large Population ◽

Illicit Drug Use ◽

European Countries ◽

The Impact

Abstract Purpose Adolescents’ perceptions of parental norms may influence their substance use. The relationship between parental norms toward cigarette and alcohol use, and the use of illicit substances among their adolescent children is not sufficiently investigated. The purpose of this study was to analyze this relationship, including gender differences, using longitudinal data from a large population-based study. Methods The present study analyzed longitudinal data from 3171 12- to 14-year-old students in 7 European countries allocated to the control arm of the European Drug Addiction Prevention trial. The impact of parental permissiveness toward cigarettes and alcohol use reported by the students at baseline on illicit drug use at 6-month follow-up was analyzed through multilevel logistic regression models, stratified by gender. Whether adolescents’ own use of cigarette and alcohol mediated the association between parental norms and illicit drug use was tested through mediation models. Results Parental permissive norms toward cigarette smoking and alcohol use at baseline predicted adolescents’ illicit drug use at follow-up. The association was stronger among boys than among girls and was mediated by adolescents’ own cigarette and alcohol use. Conclusion Perceived parental permissiveness toward the use of legal drugs predicted adolescents’ use of illicit drugs, especially among boys. Parents should be made aware of the importance of norm setting, and supported in conveying clear messages of disapproval of all substances.

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Reproduction in Trypanosomatids: Past and Present

Biology ◽

10.3390/biology10060471 ◽

2021 ◽

Vol 10 (6) ◽

pp. 471

Author(s):

Camino Gutiérrez-Corbo ◽

Bárbara Domínguez-Asenjo ◽

María Martínez-Valladares ◽

Yolanda Pérez-Pertejo ◽

Carlos García-Estrada ◽

...

Keyword(s):

Low Income ◽

Phenotypic Diversity ◽

Natural Populations ◽

Genetic Exchange ◽

Health Concern ◽

Current Debate ◽

Naturally Occurring ◽

Experimental Works ◽

Genomic Recombination ◽

The Impact

Diseases caused by trypanosomatids (Sleeping sickness, Chagas disease, and leishmaniasis) are a serious public health concern in low-income endemic countries. These diseases are produced by single-celled parasites with a diploid genome (although aneuploidy is frequent) organized in pairs of non-condensable chromosomes. To explain the way they reproduce through the analysis of natural populations, the theory of strict clonal propagation of these microorganisms was taken as a rule at the beginning of the studies, since it partially justified their genomic stability. However, numerous experimental works provide evidence of sexual reproduction, thus explaining certain naturally occurring events that link the number of meiosis per mitosis and the frequency of mating. Recent techniques have demonstrated genetic exchange between individuals of the same species under laboratory conditions, as well as the expression of meiosis specific genes. The current debate focuses on the frequency of genomic recombination events and its impact on the natural parasite population structure. This paper reviews the results and techniques used to demonstrate the existence of sex in trypanosomatids, the inheritance of kinetoplast DNA (maxi- and minicircles), the impact of genetic exchange in these parasites, and how it can contribute to the phenotypic diversity of natural populations.

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Sex Chromosome Meiotic Drive in Stalk-Eyed Flies

Genetics ◽

10.1093/genetics/147.3.1169 ◽

1997 ◽

Vol 147 (3) ◽

pp. 1169-1180 ◽

Cited By ~ 6

Author(s):

Daven C Presgraves ◽

Emily Severance ◽

Gerald S Willrinson

Keyword(s):

Sex Ratio ◽

Sex Chromosome ◽

Sex Ratios ◽

Natural Populations ◽

Meiotic Drive ◽

Operational Sex Ratio ◽

Genetic Modifiers ◽

Ratio Distortion ◽

The Impact ◽

Sex Ratio Distortion

Meiotically driven sex chromosomes can quickly spread to fixation and cause population extinction unless balanced by selection or suppressed by genetic modifiers. We report results of genetic analyses that demonstrate that extreme female-biased sex ratios in two sister species of stalk-eyed flies, Cyrtodiopsis dalmanni and C. whitei, are due to a meiotic drive element on the X chromosome (Xd). Relatively high frequencies of Xd in C. dalmanni and C. whitei (13–17% and 29%, respectively) cause female-biased sex ratios in natural populations of both species. Sex ratio distortion is associated with spermatid degeneration in male carriers of Xd. Variation in sex ratios is caused by Y-linked and autosomal factors that decrease the intensity of meiotic drive. Y-linked polymorphism for resistance to drive exists in C. dalmanni in which a resistant Y chromosome reduces the intensity and reverses the direction of meiotic drive. When paired with Xd, modifying Y chromosomes (Ym) cause the transmission of predominantly Y-bearing sperm, and on average, production of 63% male progeny. The absence of sex ratio distortion in closely related monomorphic outgroup species suggests that this meiotic drive system may predate the origin of C. whitei and C. dalmanni. We discuss factors likely to be involved in the persistence of these sex-linked polymorphisms and consider the impact of Xd on the operational sex ratio and the intensity of sexual selection in these extremely sexually dimorphic flies.

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