scholarly journals Coevolution of virulence and immunosuppression in multiple infections

2017 ◽  
Author(s):  
Tsukushi Kamiya ◽  
Nicole Mideo ◽  
Samuel Alizon
Keyword(s):  
Evolutionary Biology ◽  
Adaptive Dynamics ◽  
Multiple Infections ◽  
Research Attention ◽  
Background Mortality ◽  
Evolution Of Virulence ◽  
Duration Of Infection ◽  
Peer Community ◽  
The Cost ◽  
Host Parasite

AbstractThis preprint has been reviewed and recommended by Peer Community In Evolutionary Biology (http://dx.doi.org/10.24072/pci.evolbiol.100043). Many components of host-parasite interactions have been shown to affect the way virulence (i.e., parasite-induced harm to the host) evolves. However, coevolution of multiple parasite traits is often neglected. We explore how an immunosuppressive mechanism of parasites affects and coevolves with virulence through multiple infections. Applying the adaptive dynamics framework to epidemiological models with coinfection, we show that immunosuppression is a double-edged-sword for the evolution of virulence. On one hand, it amplifies the adaptive benefit of virulence by increasing the abundance of coinfections through epidemiological feedbacks. On the other hand, immunosuppression hinders host recovery, prolonging the duration of infection and elevating the cost of killing the host. The balance between the cost and benefit of immunosuppression varies across different background mortality rates of hosts. In addition, we find that immunosuppression evolution is influenced considerably by the precise trade-off shape determining the effect of immunosuppression on host recovery and susceptibility to further infection. These results demonstrate that the evolution of virulence is shaped by immunosuppression while highlighting that the evolution of immune evasion mechanisms deserves further research attention.

scholarly journals Cost of resistance: an unreasonably expensive concept

2018 ◽  
Author(s):  
Thomas Lenormand ◽  
Noémie Harmand ◽  
Romain Gallet
Keyword(s):  
Evolutionary Biology ◽  
Resistance Mutation ◽  
Evolutionary Genetics ◽  
Resistance Mutations ◽  
Fitness Effects ◽  
Current Usage ◽  
Important Addition ◽  
Cost Of Resistance ◽  
Peer Community ◽  
The Cost

AbstractThis preprint has been reviewed and recommended by Peer Community In Evolutionary Biology (https://doi.org/10.24072/pci.evolbiol.100052). The cost of resistance, or the fitness effect of resistance mutation in absence of the drug, is a very widepsread concept in evolutionary genetics and beyond. It has represented an important addition to the simplistic view that resistance mutations should solely be considered as beneficial mutations. Yet, this concept also entails a series of serious difficulties in its definition, interpretation and current usage. In many cases, it may be simpler, clearer, and more insightful to study, measure and analyze the fitness effects of mutations across environments and to better distinguish those effects from ‘pleiotropic effects’ of those mutations.

scholarly journals Immune defence, parasite evasion strategies and their relevance for ‘macroscopic phenomena’ such as virulence

2008 ◽  
Vol 364 (1513) ◽  
pp. 85-98 ◽  
Author(s):  
Paul Schmid-Hempel
Keyword(s):  
Immune Evasion ◽  
Life History Theory ◽  
Evolutionary Ecology ◽  
Parasite Clearance ◽  
Multiple Infections ◽  
Parasite Fitness ◽  
Host Parasite Interactions ◽  
Evolution Of Virulence ◽  
Host Parasite ◽  
Insight Into

The discussion of host–parasite interactions, and of parasite virulence more specifically, has so far, with a few exceptions, not focused much attention on the accumulating evidence that immune evasion by parasites is not only almost universal but also often linked to pathogenesis, i.e. the appearance of virulence. Now, the immune evasion hypothesis offers a deeper insight into the evolution of virulence than previous hypotheses. Sensitivity analysis for parasite fitness and life-history theory shows promise to generate a more general evolutionary theory of virulence by including a major element, immune evasion to prevent parasite clearance from the host. Also, the study of dose–response relationships and multiple infections should be particularly illuminating to understand the evolution of virulence. Taking into account immune evasion brings immunological processes to the core of understanding the evolution of parasite virulence and for a range of related issues such as dose, host specificity or immunopathology. The aim of this review is to highlight the mechanism underlying immune evasion and to discuss possible consequences for the evolutionary ecology analysis of host–parasite interactions.

scholarly journals The roles of environmental variation and parasite survival in virulence–transmission relationships

2021 ◽  
Vol 8 (6) ◽  
pp. 210088
Author(s):  
Wendy C. Turner ◽  
Pauline L. Kamath ◽  
Henriette van Heerden ◽  
Yen-Hua Huang ◽  
Zoe R. Barandongo ◽  
...  
Keyword(s):  
Life History ◽  
Adaptive Dynamics ◽  
Life History Evolution ◽  
Infectious Agent ◽  
Environmental Context ◽  
Parasite Life Cycle ◽  
Trade Offs ◽  
Evolution Of Virulence ◽  
Parasite Survival ◽  
Host Parasite

Disease outbreaks are a consequence of interactions among the three components of a host–parasite system: the infectious agent, the host and the environment. While virulence and transmission are widely investigated, most studies of parasite life-history trade-offs are conducted with theoretical models or tractable experimental systems where transmission is standardized and the environment controlled. Yet, biotic and abiotic environmental factors can strongly affect disease dynamics, and ultimately, host–parasite coevolution. Here, we review research on how environmental context alters virulence–transmission relationships, focusing on the off-host portion of the parasite life cycle, and how variation in parasite survival affects the evolution of virulence and transmission. We review three inter-related ‘approaches’ that have dominated the study of the evolution of virulence and transmission for different host–parasite systems: (i) evolutionary trade-off theory, (ii) parasite local adaptation and (iii) parasite phylodynamics. These approaches consider the role of the environment in virulence and transmission evolution from different angles, which entail different advantages and potential biases. We suggest improvements to how to investigate virulence–transmission relationships, through conceptual and methodological developments and taking environmental context into consideration. By combining developments in life-history evolution, phylogenetics, adaptive dynamics and comparative genomics, we can improve our understanding of virulence–transmission relationships across a diversity of host–parasite systems that have eluded experimental study of parasite life history.

The effect of the acanthocephalan Pomphorhynchus laevis upon the respiration of its intermediate host, Gammarus pulex

Parasitology ◽  
1974 ◽  
Vol 68 (2) ◽  
pp. 271-284 ◽  
Author(s):  
A. E. Rumpus ◽  
C. R. Kennedy
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Uptake ◽  
Host Population ◽  
Gammarus Pulex ◽  
Multiple Infections ◽  
Pomphorhynchus Laevis ◽  
Respiration Rates ◽  
Physiological Processes ◽  
Stage Of Development ◽  
Host Parasite

The respiration rates of individual Gammarus pulex infected by larval Pomphorhynchus laevis were investigated with particular reference to the stage of development of the host and parasite and to the water temperature. At 20°C the oxygen consumption of Gammarus of all sizes was reduced by an average of 19·3 % by the presence of cystacanths of the parasite, but was unaffected by the presence of acanthellae. It is considered that the small size of this larval stage, in relation to that of its host, is responsible for the failure to detect an effect. Multiple infections did not exert any greater effect upon host respiration than single cystacanths, nor did it appear that the parasite had different effects upon hosts of different sexes. At 10°C no significant differences were observed between the respiration rates of infected and uninfected gammarids. The parasite was probably still depressing the host respiration rate at this temperature, but the oxygen uptake of G. pulex is so low that the differences between infected and uninfected individuals were too small to be detected. The parasite has a direct effect upon the physiological processes of the host, but neither the mechanism of this nor the reasons for the different effects found in different host-parasite systems are yet understood. Despite the pronounced effect of P. laevis on respiration of individual hosts, its effect upon the oxygen consumption of a natural host population is small since only a small proportion of the population carries infections and water temperatures remain below 10°C for over half the year.

scholarly journals Rapid evolution of virulence leading to host extinction under host-parasite coevolution

2015 ◽  
Vol 15 (1) ◽  
Author(s):  
Charlotte Rafaluk ◽  
Markus Gildenhard ◽  
Andreas Mitschke ◽  
Arndt Telschow ◽  
Hinrich Schulenburg ◽  
...  
Keyword(s):  
Rapid Evolution ◽  
Evolution Of Virulence ◽  
Host Parasite ◽  
Host Extinction

Evolution: Medicine’s most basic science

2020 ◽  
pp. 39-42
Author(s):  
Randolph M. Nesse ◽  
Richard Dawkins
Keyword(s):  
Population Genetics ◽  
Natural Selection ◽  
Basic Science ◽  
Evolutionary Biology ◽  
Phylogenetic Trees ◽  
The Body ◽  
Clinical Implications ◽  
Trade Offs ◽  
The Cost

The role of evolutionary biology as a basic science for medicine is expanding rapidly. Some evolutionary methods are already widely applied in medicine, such as population genetics and methods for analysing phylogenetic trees. Newer applications come from seeking evolutionary as well as proximate explanations for disease. Traditional medical research is restricted to proximate studies of the body’s mechanism, but separate evolutionary explanations are needed for why natural selection has left many aspects of the body vulnerable to disease. There are six main possibilities: mismatch, infection, constraints, trade-offs, reproduction at the cost of health, and adaptive defences. Like other basic sciences, evolutionary biology has limited direct clinical implications, but it provides essential research methods, encourages asking new questions that foster a deeper understanding of disease, and provides a framework that organizes the facts of medicine.

Heterogeneity in helminth infections: factors influencing aggregation in a simple host–parasite system

Parasitology ◽  
2019 ◽  
Vol 147 (1) ◽  
pp. 65-77 ◽  
Author(s):  
Richard C. Tinsley ◽  
Hanna Rose Vineer ◽  
Rebecca Grainger-Wood ◽  
Eric R. Morgan
Keyword(s):  
Post Infection ◽  
Evolutionary Biology ◽  
Negative Binomial ◽  
Parasite Population ◽  
Trout Population ◽  
Helminth Infections ◽  
Transmission Period ◽  
Binomial Parameter ◽  
Host Parasite ◽  
Direct Life Cycle

AbstractThe almost universally-occurring aggregated distributions of helminth burdens in host populations have major significance for parasite population ecology and evolutionary biology, but the mechanisms generating heterogeneity remain poorly understood. For the direct life cycle monogenean Discocotyle sagittata infecting rainbow trout, Oncorhynchus mykiss, variables potentially influencing aggregation can be analysed individually. This study was based at a fish farm where every host individual becomes infected by D. sagittata during each annual transmission period. Worm burdens were examined in one trout population maintained in isolation for 9 years, exposed to self-contained transmission. After this year-on-year recruitment, prevalence was 100% with intensities 10–2628, mean 576, worms per host. Parasite distribution, amongst hosts with the same age and environmental experience, was highly aggregated with variance to mean ratio 834 and negative binomial parameter, k, 0.64. The most heavily infected 20% of fish carried around 80% of the total adult parasite population. Aggregation develops within the first weeks post-infection; hosts typically carried intensities of successive age-specific cohorts that were consistent for that individual, such that heavily-infected individuals carried high numbers of all parasite age classes. Results suggest that host factors alone, operating post-infection, are sufficient to generate strongly overdispersed parasite distributions, rather than heterogeneity in exposure and initial invasion.

Estimating Activity Costs: How the Provision of Accurate Historical Activity Data from a Biased Cost System Can Improve Individuals' Cost Estimation Accuracy

2007 ◽  
Vol 19 (1) ◽  
pp. 133-159 ◽  
Author(s):  
Dan L. Heitger
Keyword(s):  
Cost Estimation ◽  
Estimation Accuracy ◽  
Activity Data ◽  
Research Attention ◽  
Cost System ◽  
Initial Cost ◽  
Activity Cost ◽  
Historical Activity ◽  
The Cost ◽  
Activity Costs

An integral component of effective cost control and performance evaluation is the ability to accurately estimate relationships between activities and overhead costs (i.e., activity costs). Individuals using a single cost pool system often have to rely on memory of historical activity data when estimating activity costs. If individuals' recall of data is representative of the historical data, then reliance on memory should not be detrimental to cost estimation accuracy. However, individuals often possess incorrect initial beliefs about activity costs. These incorrect beliefs are expected to serve as an anchor from which individuals make insufficient adjustments when estimating activity costs based on memory of historical activity data. Multiple cost pool systems frequently provide biased standard rates; however, such systems also provide accurate historical activity data when individuals estimate costs. I extend prior accounting research by experimentally examining whether a multiple cost pool system's provision of accurate historical activity data improves activity cost estimation for individuals with incorrect cost beliefs even when the cost system also provides biased standard rates. The main contribution of the study is its finding that the multiple cost pool system's provision of historical activity data improves individuals' adjustments from their incorrect initial cost beliefs when estimating activity costs, thereby increasing their estimation accuracy. The results suggest that this improved adjustment from incorrect initial cost beliefs occurs because the provision of historical activity data improves individuals' recognition of how wrong their initial cost beliefs were in reality. This result is achieved even though the cost system provides biased standard rates. The ability of flawed cost systems to improve individuals' activity cost estimation in other such ways has received little research attention and is important because of its potential for improving managerial decision making.

scholarly journals Bacteriophage Migration via Nematode Vectors: Host-Parasite-Consumer Interactions in Laboratory Microcosms

2006 ◽  
Vol 72 (3) ◽  
pp. 1974-1979 ◽  
Author(s):  
John J. Dennehy ◽  
Nicholas A. Friedenberg ◽  
Yul W. Yang ◽  
Paul E. Turner
Keyword(s):  
Experimental Studies ◽  
Virus Transmission ◽  
Growth Dynamics ◽  
Model System ◽  
Pathogen Transmission ◽  
Trophic Levels ◽  
Future Research ◽  
Evolution Of Virulence ◽  
Consumer Interactions ◽  
Host Parasite

ABSTRACT Pathogens vectored by nematodes pose serious agricultural, economic, and health threats; however, little is known of the ecological and evolutionary aspects of pathogen transmission by nematodes. Here we describe a novel model system with two trophic levels, bacteriophages and nematodes, each of which competes for bacteria. We demonstrate for the first time that nematodes are capable of transmitting phages between spatially distinct patches of bacteria. This model system has considerable advantages, including the ease of maintenance and manipulation at the laboratory bench, the ability to observe many generations in short periods, and the capacity to freeze evolved strains for later comparison to their ancestors. More generally, experimental studies of complex multispecies interactions, host-pathogen coevolution, disease dynamics, and the evolution of virulence may benefit from this model system because current models (e.g., chickens, mosquitoes, and malaria parasites) are costly to maintain, are difficult to manipulate, and require considerable space. Our initial explorations centered on independently assessing the impacts of nematode, bacterium, and phage population densities on virus migration between host patches. Our results indicated that virus transmission increases with worm density and host bacterial abundance; however, transmission decreases with initial phage abundance, perhaps because viruses eliminate available hosts before migration can occur. We discuss the microbial growth dynamics that underlie these results, suggest mechanistic explanations for nematode transmission of phages, and propose intriguing possibilities for future research.

Diagnosing genetically diverse avian malarial infections using mixed-sequence analysis and TA-cloning

Parasitology ◽  
2005 ◽  
Vol 131 (1) ◽  
pp. 15-23 ◽  
Author(s):  
J. PÉREZ-TRIS ◽  
S. BENSCH
Keyword(s):  
Dna Sequences ◽  
Accurate Method ◽  
The Other ◽  
Multiple Infections ◽  
Template Switching ◽  
Mixed Infections ◽  
Nucleotide Substitutions ◽  
Single Nucleotide ◽  
In The Wild ◽  
Host Parasite

Birds harbouring several malarial parasites are common in the wild, and resolving such multiple infections is important for our understanding of host–parasite relationships. We propose a simple and reasonably accurate method for detecting and resolving multiple infections, based on the analysis of parasite cytochrome b DNA sequences: genetically mixed infections are first identified by double nucleotide peaks on sequence electropherograms, and later retrieved by TA-cloning. We applied this method to wild birds, and to experimentally created mixes with varying proportion of two parasites (Plasmodium spp. and Haemoproteus spp.). In general, the method was very efficient in detecting and resolving multiple infections, but some problems were encountered. Several multiple infections were erroneously scored as simple, either because one of the parasite lineages was a better target for the primers used, or because it was much more abundant in the mix. On the other hand, single nucleotide substitutions and template switching during PCR produced artificial sequences in some clones. We discuss the utility of the method, and propose a framework for its use when screening for genetically diverse avian malarial parasites.

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