scholarly journals Host age modulates within-host parasite competition

2015 ◽  
Vol 11 (5) ◽  
pp. 20150131 ◽  
Author(s):  
Rony Izhar ◽  
Jarkko Routtu ◽  
Frida Ben-Ami

In many host populations, one of the most striking differences among hosts is their age. While parasite prevalence differences in relation to host age are well known, little is known on how host age impacts ecological and evolutionary dynamics of diseases. Using two clones of the water flea Daphnia magna and two clones of its bacterial parasite Pasteuria ramosa , we examined how host age at exposure influences within-host parasite competition and virulence. We found that multiply-exposed hosts were more susceptible to infection and suffered higher mortality than singly-exposed hosts. Hosts oldest at exposure were least often infected and vice versa. Furthermore, we found that in young multiply-exposed hosts competition was weak, allowing coexistence and transmission of both parasite clones, whereas in older multiply-exposed hosts competitive exclusion was observed. Thus, age-dependent parasite exposure and host demography (age structure) could together play an important role in mediating parasite evolution. At the individual level, our results demonstrate a previously unnoticed interaction of the host's immune system with host age, suggesting that the specificity of immune function changes as hosts mature. Therefore, evolutionary models of parasite virulence might benefit from incorporating age-dependent epidemiological parameters.

2018 ◽  
Author(s):  
J. L. Hite ◽  
C. E. Cressler

AbstractParasite-mediated anorexia is a ubiquitous, but poorly understood component of host-parasite interactions. These temporary but substantial reductions in food intake (range: 4-100%) limit exposure to parasites and alter within-host physiological processes that regulate parasite development, production, and survival, such as energy allocation, immune function, host-microbiota interactions, and gastrointestinal conditions. By altering the duration, severity, and spread of infection, anorexia could substantially alter ecological, evolutionary, and epidemiological dynamics. However, these higher-order implications are typically overlooked and remain poorly understood — even though medical (e.g., non-steroidal anti-inflammatory drugs, vaccines, targeted signaling pathways, calorie restriction) and husbandry practices (e.g., antibiotic and diet use for rapid growth, nutrient supplementation) often directly or indirectly alter host appetite and nutrient intake. Here, we develop theory that helps elucidate why reduced food intake (anorexia) can enhance or diminish disease severity and illustrates that the population-level outcomes often contrast with the individual-level outcomes: treatments that increase the intake of high quality nutrients (suppressing anorexia), can drive rapid individual-level recovery, but inadvertently increase infection prevalence and select for more virulent parasites. Such a theory-guided approach offers a tool to improve targeting host nutrition to manage disease in both human and livestock populations by revealing a means to predict how nutrient-driven feedbacks will affect both the host and parasite.


Author(s):  
Jhelam N. Deshpande ◽  
Oliver Kaltz ◽  
Emanuel A. Fronhofer

AbstractWhile host-parasite interactions are ubiquitous, the large scale consequences of parasite infections are mainly driven by the spatial context. One trait of pivotal importance for the eco-evolutionary dynamics of such metapopulations is the spatial behaviour of hosts, that is, their dispersal. It is well established that dispersal is not a random process, rather dispersal is informed and may depend on internal and external factors. In host-parasite metapopulations, dispersal may be a function of a host’s infection state, but also of the local context, such as host density or parasite prevalence. Using a dynamical host-parasite metapopulation model, we explore whether host dispersal evolves to be state- and context-dependent and what shapes the evolutionarily stable dispersal reaction norms have. We show that state-dependent dispersal readily evolves in the sense that hosts disperse more when infected. This dispersal bias evolves due to kin selection which is consistent with previous studies. Most importantly, we show that prevalence-dependent dispersal evolves, especially when virulence is high and epidemiological dynamics have predictable signatures. The observed evolutionary outcome, a negatively prevalence-dependent dispersal reaction norm for susceptible hosts, seems counter-intuitive at first. However, our results can be readily explained by the emergent epidemiological dynamics, especially their spatial and temporal correlation patterns. Finally, we show that context-dependency in dispersal may rely on both, prevalence, but also host density cues. Our work provides new insights into the evolution of complex dispersal phenotypes in host-parasite metapopulations as well as on associated feedbacks between ecological dynamics and evolutionary change.


PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11555
Author(s):  
Raquel A. Rodrigues ◽  
Gabriel M.F. Felix ◽  
Mauro Pichorim ◽  
Patricia A. Moreira ◽  
Erika M. Braga

Avian haemosporidians are parasites with great capacity to spread to new environments and new hosts, being considered a good model to host-parasite interactions studies. Here, we examine avian haemosporidian parasites in a protected area covered by Restinga vegetation in northeastern Brazil, to test the hypothesis that haemosporidian prevalence is related to individual-level traits (age and breeding season), species-specific traits (diet, foraging strata, period of activity, species body weight, migratory status, and nest shape), and climate factors (temperature and rainfall). We screened DNA from 1,466 birds of 70 species captured monthly from April 2013 to March 2015. We detected an overall prevalence (Plasmodium/Haemoproteus infection) of 22% (44 host species) and parasite’s lineages were identified by mitochondrial cyt b gene. Our results showed that migration can be an important factor predicting the prevalence of Haemoproteus (Parahaemoproteus), but not Plasmodium, in hosts. Besides, the temperature, but not rainfall, seems to predict the prevalence of Plasmodium in this bird community. Neither individual-level traits analyzed nor the other species-specific traits tested were related to the probability of a bird becoming infected by haemosporidians. Our results point the importance of conducting local studies in particular environments to understand the degree of generality of factors impacting parasite prevalence in bird communities. Despite our attempts to find patterns of infection in this bird community, we should be aware that an avian haemosporidian community organization is highly complex and this complexity can be attributed to an intricate net of factors, some of which were not observed in this study and should be evaluated in future studies. We evidence the importance of looking to host-parasite relationships in a more close scale, to assure that some effects may not be obfuscated by differences in host life-history.


2020 ◽  
Vol 27 ◽  
Author(s):  
Nuria E. Campillo ◽  
Mercedes Jimenez ◽  
Matilde Canelles

: In December 2019, a novel respiratory coronavirus named SARS-CoV-2 appeared in China, causing the disease termed COVID-19 that has caused millions of infections worldwide. In this article we have analyzed existing evidence on the immune response against SARS coronaviruses in order to understand the possible outcome of a vaccine for COVID-19. From our analysis it becomes clear that there is a big difference in the immune response against SARS in children, young adults and the elderly, both at the innate and adaptive levels. Taking this information into account, we have studied the strategies that are being used for development of COVID-19 vaccines. We discuss the perspectives for obtention and worldwide distribution of reliable vaccines using this perspective. The conclusion is that different vaccines may be protective for different age segments within the population, depending on the strategy used for their design. Therefore, it will become necessary for several vaccines to reach the finish line, not only to ensure availability, but also to guarantee an adequate immune response at the individual level.


2010 ◽  
Vol 277 (1698) ◽  
pp. 3291-3297 ◽  
Author(s):  
Stuart K. J. R. Auld ◽  
Jennifer A. Scholefield ◽  
Tom J. Little

Linking measures of immune function with infection, and ultimately, host and parasite fitness is a major goal in the field of ecological immunology. In this study, we tested for the presence and timing of a cellular immune response in the crustacean Daphnia magna following exposure to its sterilizing endoparasite Pasteuria ramosa . We found that D. magna possesses two cell types circulating in the haemolymph: a spherical one, which we call a granulocyte and an irregular-shaped amoeboid cell first described by Metchnikoff over 125 years ago. Daphnia magna mounts a strong cellular response (of the amoeboid cells) just a few hours after parasite exposure. We further tested for, and found, considerable genetic variation for the magnitude of this cellular response. These data fostered a heuristic model of resistance in this naturally coevolving host–parasite interaction. Specifically, the strongest cellular responses were found in the most susceptible hosts, indicating resistance is not always borne from a response that destroys invading parasites, but rather stems from mechanisms that prevent their initial entry. Thus, D. magna may have a two-stage defence—a genetically determined barrier to parasite establishment and a cellular response once establishment has begun.


2012 ◽  
Vol 279 (1744) ◽  
pp. 4009-4014 ◽  
Author(s):  
Mike Boots ◽  
Katherine E. Roberts

Maternal effects can be adaptive and because of their intrinsic time delays may have important effects on population dynamics. In vertebrates, and increasingly invertebrates, it is well established that offspring defence is in part determined by maternal parasite exposure. It has also been suggested that there may be indirect maternal effects on immunity mediated by other components of the maternal environment, including density and resource availability. Here, we examine the effect maternal resource availability has on the immunity of offspring in an insect—virus system. We use five different maternal resource levels and examine immunity in the offspring both directly, by challenge with a virus, and by measuring a major component of the immune system, across three offspring environments. Both the direct infection assay and the measure of immunocompetence show clearly that offspring from mothers in poor environments are more resistant to parasites. This may result from life-history optimization of mothers in poor environments, or because the poor environment acts as a cue for higher disease risk in the next generation. This emphasizes the importance of maternal effects on disease resistance, mediated through indirect environmental factors that will have important implications to both the ecological and evolutionary dynamics of host–parasite interactions.


2021 ◽  
Author(s):  
Kingsley Badu ◽  
Amma Aboagyewa Larbi ◽  
Kwadwo Boampong

As countries move from intense malaria transmission to low transmission there will be a demand for more sensitive tools and approaches in tracking malaria transmission dynamics. Surveillance tools that are sensitive in tracking real time infectious bites as well as infectious reservoir will be preferred to counting number of cases in the hospital or parasite prevalence. The acquisition and maintenance of anti-malarial antibodies is a direct function of parasite exposure, seroprevalence rates has been used as an efficient tool in assessing malaria endemicity and confirming malaria elimination. Plasmodium antibodies are explicit biomarkers that can be utilised to track parasite exposure over more extensive time spans than microscopy, rapid diagnostic testing or molecular testing and the conventional entomological inoculation rate. Seroprevalence studies can therefore help monitor the impact of malaria control interventions, especially when the parasite occurrence is low. As a result, antibody responses to Anopheles salivary proteins or Plasmodium species may potentially offer reliable information of recent or past exposure; recognise short-term or gradual changes in exposure to Plasmodium infection or to estimate individual-level exposure to infection. This book chapter will present about four studies we have conducted across eastern and western Africa on the efficiency of salivary gland proteins and antimalarial antibodies in tracking malaria transmission intensity. We hope that these could be used as surveillance tools in malaria elimination efforts.


2019 ◽  
Vol 59 (5) ◽  
pp. 1243-1252 ◽  
Author(s):  
Matthew Malishev ◽  
David J Civitello

Abstract The consequences of parasite infection for individual hosts depend on key features of host–parasite ecology underpinning parasite growth and immune defense, such as age, sex, resource supply, and environmental stressors. Scaling these features and their underlying mechanisms from the individual host is challenging but necessary, as they shape parasite transmission at the population level. Translating individual-level mechanisms across scales could inherently improve the way we think about feedbacks among parasitism, the mechanisms driving transmission, and the consequences of human impact and disease control efforts. Here, we use individual-based models (IBMs) based on general metabolic theory, Dynamic Energy Budget (DEB) theory, to scale explicit life-history features of individual hosts, such as growth, reproduction, parasite production, and death, to parasite transmission at the population level over a range of resource supplies focusing on the major human parasite, Schistosoma mansoni, and its intermediate host snail, Biomphalaria glabrata. At the individual level, infected hosts produce fewer parasites at lower resources as competition increases. At the population level, our DEB–IBM predicts brief, but intense parasite peaks early during the host growth season when resources are abundant and infected hosts are few. The timing of these peaks challenges the status quo that high densities of infected hosts produce the highest parasite densities. As expected, high resource supply boosts parasite output, but parasite output also peaks at modest to high host background mortality rates, which parallels overcompensation in stage-structured models. Our combined results reveal the crucial role of individual-level physiology in identifying how environmental conditions, time of the year, and key feedbacks within host–parasite ecology interact to define periods of elevated risk. The testable forecasts from this physiologically-explicit epidemiological model can inform disease management to reduce human risk of schistosome infection.


2018 ◽  
Author(s):  
Anaïs Portet ◽  
Eve Toulza ◽  
Ana Lokmer ◽  
Camille Huot ◽  
David Duval ◽  
...  

SummaryHost-associated microbiota cari affect the fitness of its host i η a number of ways, including the modification of host-parasite interactions and thus the outcome of disease.Biomphalaria glabratais the vector snail of the trematodeSchistosoma mansoni,the agent of human schistosomiasis, causing hundreds of thousands of deaths every year. Here, we present the first study of the snail bacterial microbiota in response toSchistosomainfection. To examine the interplay betweenB. glabrata, S. mansoniand snail microbiota, snails were infected and the microbiota composition was analysed by massive 16S rDNA amplicon sequencing approach. We characterized theBiomphalariabacterial microbiota at the individual level in both naive and infected snails. Sympatric and allopatric strains of parasites were used for infections and re­infections to analyse the modification or dysbiosis of snail microbiota in different host-parasite co-evolutionary contexts. Concomitantly, using RNAseq data, we investigated the link between bacterial microbiota dysbiosis and snail anti-microbial peptide immune response. This work paves the way for a better understanding of snail/schistosome interaction, and would have critical consequences in terms of snail control strategies for fighting schistosomiasis disease in the field.


2020 ◽  
Vol 51 (3) ◽  
pp. 183-198
Author(s):  
Wiktor Soral ◽  
Mirosław Kofta

Abstract. The importance of various trait dimensions explaining positive global self-esteem has been the subject of numerous studies. While some have provided support for the importance of agency, others have highlighted the importance of communion. This discrepancy can be explained, if one takes into account that people define and value their self both in individual and in collective terms. Two studies ( N = 367 and N = 263) examined the extent to which competence (an aspect of agency), morality, and sociability (the aspects of communion) promote high self-esteem at the individual and the collective level. In both studies, competence was the strongest predictor of self-esteem at the individual level, whereas morality was the strongest predictor of self-esteem at the collective level.


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