Host Population Structure and the Evolution of Virulence: A "Law of Diminishing Returns"

Evolution ◽  
1995 ◽  
Vol 49 (4) ◽  
pp. 743 ◽  
Author(s):  
Marc Lipsitch ◽  
Edward Allen Herre ◽  
Martin A. Nowak
Keyword(s):  
Population Structure ◽  
Host Population ◽  
Evolution Of Virulence ◽  
Diminishing Returns

scholarly journals HOST POPULATION STRUCTURE AND THE EVOLUTION OF VIRULENCE: A “LAW OF DIMINISHING RETURNS”

Evolution ◽  
1995 ◽  
Vol 49 (4) ◽  
pp. 743-748 ◽  
Author(s):  
Marc Lipsitch ◽  
Edward Allen Herre ◽  
Martin A. Nowak
Keyword(s):  
Population Structure ◽  
Host Population ◽  
Evolution Of Virulence ◽  
Diminishing Returns

EVOLUTION OF VIRULENCE IN A HETEROGENEOUS HOST POPULATION

Evolution ◽  
2000 ◽  
Vol 54 (1) ◽  
pp. 64 ◽  
Author(s):  
Roland R. Regoes ◽  
Martin A. Nowak ◽  
Sebastian Bonhoeffer
Keyword(s):  
Host Population ◽  
Evolution Of Virulence

How does a Psittacanthus robustus Mart. population structure relate to a Vochysia thyrsoidea Pohl. host population?

Flora ◽  
2010 ◽  
Vol 205 (12) ◽  
pp. 797-801 ◽  
Author(s):  
Grazielle Sales Teodoro ◽  
Eduardo van den Berg ◽  
Marcela de Castro Nunes Santos ◽  
Flávia de Freitas Coelho
Keyword(s):  
Population Structure ◽  
Host Population

scholarly journals Population structure across scales facilitates coexistence and spatial heterogeneity of antibiotic-resistant infections

2018 ◽  
Author(s):  
Madison S. Krieger ◽  
Carson E. Denison ◽  
Thayer L. Anderson ◽  
Martin A. Nowak ◽  
Alison L. Hill
Keyword(s):  
Population Structure ◽  
Evolutionary Dynamics ◽  
Resistance Management ◽  
Antibiotic Use ◽  
Antibiotic Consumption ◽  
Host Population ◽  
Antibiotic Resistant ◽  
Resistance Risk ◽  
Geographical Regions ◽  
Wide Range

ABSTRACTAntibiotic-resistant infections are a growing threat to human health, but basic features of the eco-evolutionary dynamics remain unexplained. Most prominently, there is no clear mechanism for the long-term coexistence of both drug-sensitive and resistant strains at intermediate levels, a ubiquitous pattern seen in surveillance data. Here we show that accounting for structured or spatially-heterogeneous host populations and variability in antibiotic consumption can lead to persistent coexistence over a wide range of treatment coverages, drug efficacies, costs of resistance, and mixing patterns. Moreover, this mechanism can explain other puzzling spatiotemporal features of drug-resistance epidemiology that have received less attention, such as large differences in the prevalence of resistance between geographical regions with similar antibiotic consumption or that neighbor one another. We find that the same amount of antibiotic use can lead to very different levels of resistance depending on how treatment is distributed in a transmission network. We also identify parameter regimes in which population structure alone cannot support coexistence, suggesting the need for other mechanisms to explain the epidemiology of antibiotic resistance. Our analysis identifies key features of host population structure that can be used to assess resistance risk and highlights the need to include spatial or demographic heterogeneity in models to guide resistance management.

scholarly journals Host population structure and treatment frequency maintain balancing selection on drug resistance

2017 ◽  
Author(s):  
Sarah Cobey ◽  
Edward B. Baskerville ◽  
Caroline Colijn ◽  
William Hanage ◽  
Christophe Fraser ◽  
...  
Keyword(s):  
Population Structure ◽  
Balancing Selection ◽  
Antibiotic Use ◽  
Host Population ◽  
Antimicrobial Drugs ◽  
Treatment Frequency ◽  
Specific Variation ◽  
Resistant Strains ◽  
Drug Resistant Strains ◽  
The Impact

AbstractIt is a truism that antimicrobial drugs select for resistance, but explaining pathogen- and population-specific variation in patterns of resistance remains an open problem. Like other common commensals, Streptococcus pneumoniae has demonstrated persistent coexistence of drug-sensitive and drug-resistant strains. Theoretically, this outcome is unlikely. We modeled the dynamics of competing strains of S. pneumoniae to investigate the impact of transmission dynamics and treatment-induced selective pressures on the probability of stable coexistence. We find that the outcome of competition is extremely sensitive to structure in the host population, although coexistence can arise from age-assortative transmission models with age-varying rates of antibiotic use. Moreover, we find that the selective pressure from antibiotics arises not so much from the rate of antibiotic use per se but from the frequency of treatment: frequent antibiotic therapy disproportionately impacts the fitness of sensitive strains. This same phenomenon explains why serotypes with longer durations of carriage tend to be more resistant. These dynamics may apply to other potentially pathogenic, microbial commensals and highlight how population structure, which is often omitted from models, can have a large impact.

scholarly journals Identification of Hidden Population Structure in Time-Scaled Phylogenies

2020 ◽  
Vol 69 (5) ◽  
pp. 884-896 ◽  
Author(s):  
Erik M Volz ◽  
Wiuf Carsten ◽  
Yonatan H Grad ◽  
Simon D W Frost ◽  
Ann M Dennis ◽  
...  
Keyword(s):  
Population Structure ◽  
Antimicrobial Resistance ◽  
Phylogenetic Trees ◽  
Statistical Tests ◽  
Host Population ◽  
Rapid Expansion ◽  
Outbreak Detection ◽  
Hidden Population ◽  
New Methods ◽  
Fitness Advantage

Abstract Population structure influences genealogical patterns, however, data pertaining to how populations are structured are often unavailable or not directly observable. Inference of population structure is highly important in molecular epidemiology where pathogen phylogenetics is increasingly used to infer transmission patterns and detect outbreaks. Discrepancies between observed and idealized genealogies, such as those generated by the coalescent process, can be quantified, and where significant differences occur, may reveal the action of natural selection, host population structure, or other demographic and epidemiological heterogeneities. We have developed a fast non-parametric statistical test for detection of cryptic population structure in time-scaled phylogenetic trees. The test is based on contrasting estimated phylogenies with the theoretically expected phylodynamic ordering of common ancestors in two clades within a coalescent framework. These statistical tests have also motivated the development of algorithms which can be used to quickly screen a phylogenetic tree for clades which are likely to share a distinct demographic or epidemiological history. Epidemiological applications include identification of outbreaks in vulnerable host populations or rapid expansion of genotypes with a fitness advantage. To demonstrate the utility of these methods for outbreak detection, we applied the new methods to large phylogenies reconstructed from thousands of HIV-1 partial pol sequences. This revealed the presence of clades which had grown rapidly in the recent past and was significantly concentrated in young men, suggesting recent and rapid transmission in that group. Furthermore, to demonstrate the utility of these methods for the study of antimicrobial resistance, we applied the new methods to a large phylogeny reconstructed from whole genome Neisseria gonorrhoeae sequences. We find that population structure detected using these methods closely overlaps with the appearance and expansion of mutations conferring antimicrobial resistance. [Antimicrobial resistance; coalescent; HIV; population structure.]

scholarly journals A theoretical model of the evolution of virulence in sexually transmitted HIV/AIDS

1999 ◽  
Vol 33 (4) ◽  
pp. 329-333 ◽  
Author(s):  
FAB Coutinho ◽  
E Massad ◽  
RX Menezes ◽  
MN Burattini
Keyword(s):  
Sexual Activity ◽  
Virulent Strain ◽  
Host Population ◽  
Sexual Partners ◽  
High Rate ◽  
Potential Influence ◽  
Sexually Transmitted ◽  
Evolution Of Virulence ◽  
The Subject ◽  
Host Parasite

INTRODUCTION: The evolution of virulence in host-parasite relationships has been the subject of several publications. In the case of HIV virulence, some authors suggest that the evolution of HIV virulence correlates with the rate of acquisition of new sexual partners. In contrast some other authors argue that the level of HIV virulence is independent of the sexual activity of the host population. METHODS: Provide a mathematical model for the study of the potential influence of human sexual behaviour on the evolution of virulence of HIV is provided. RESULTS: The results indicated that, when the probability of acquisition of infection is a function both of the sexual activity and of the virulence level of HIV strains, the evolution of HIV virulence correlates positively with the rate of acquisition of new sexual partners. CONCLUSION: It is concluded that in the case of a host population with a low (high) rate of exchange of sexual partners the evolution of HIV virulence is such that the less (more) virulent strain prevails.

Factors affecting the evolution of virulence: nematode parasites of fig wasps as a case study

Parasitology ◽  
1995 ◽  
Vol 111 (S1) ◽  
pp. S179-S191 ◽  
Author(s):  
E. A. Herre
Keyword(s):  
Horizontal Transmission ◽  
Host Population ◽  
Lifetime Reproductive Success ◽  
Evolutionary Relationships ◽  
Parameter Estimates ◽  
Fig Wasps ◽  
Evolution Of Virulence ◽  
Wide Range ◽  
The Individual ◽  
Host Parasite

SUMMARYThe natural history of fig-pollinating wasps and their associated species-specific nematodes allows the measurement of many parameters which are relevant to testing hypotheses concerning host-parasite ecology and evolution. Within fig wasps species, it is possible to estimate lifetime reproductive success of foundress wasps as a function of presence or absence of nematode parasitism (virulence). Across species, there is a wide range of host population structures which, in turn, results in a range of opportunities for either horizontal or vertical nematode transmission. Therefore, estimates of virulence can be related to opportunities for transmission across a group of closely related hosts and their parasites. Further, the dynamics of the nematode infections over ecological and short-term evolutionary timescales can be monitored, giving added insight into the interpretation of the virulence estimates. Moreover, several scales of longer term evolutionary relationships are either known directly from fossil evidence or can be inferred from molecular data, providing deeper temporal context for the observed patterns. This combination of attributes permits detailed testing of hypotheses concerning the factors that potentially influence the evolution of virulence in host-parasite systems, and further, population and simulation models of the system that incorporate the parameter estimates can clarify the interpretation of how those factors act. There is little evidence suggesting that intermediate and long-term evolutionary relationships explain current levels of virulence. That is, it appears that virulence can change rapidly relative to speciation events, and that the nematodes do not tend to become ‘benign over time’. Instead, it appears that host population structure can influence the evolution of parasite virulence by affecting the relative opportunities for horizontal to vertical transmission, which, in turn, influences the relative costs and benefits of virulence to the nematodes. At one level, increased opportunities for horizontal transmission decouple the reproductive interests of the individual nematodes from those of the individual hosts that they are directly parasitizing, thereby reducing the cost of virulence to individual nematodes. At another level, increased opportunities of horizontal transmission also increases the relative frequency of hosts infected by multiple strains of nematodes. This promotes the evolution of more virulent forms by increasing the relative importance of within-host competition among nematode strains, thereby favouring strains that ‘eat more host sooner’. An interesting property of the fig-nematode systems is that the proportion of infected hosts does not change dramatically through time. This finding implies that there can be considerable negative effects on survival of infected hosts in addition to the previously documented reductions in fecundity of infected foundresses, because the latter are insufficient to account for the observed stability of wasp infection rates.

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