scholarly journals The Price equation and evolutionary epidemiology

2020 ◽  
Vol 375 (1797) ◽  
pp. 20190357 ◽  
Author(s):  
Troy Day ◽  
Todd Parsons ◽  
Amaury Lambert ◽  
Sylvain Gandon
Keyword(s):  
Evolutionary Biology ◽  
Transmission Rate ◽  
Price Equation ◽  
Demographic Stochasticity ◽  
Widespread Application ◽  
Disease Evolution ◽  
Price’S Equation ◽  
Evolutionary Epidemiology ◽  
Evolutionary Consequences

The Price equation has found widespread application in many areas of evolutionary biology, including the evolutionary epidemiology of infectious diseases. In this paper, we illustrate the utility of this approach to modelling disease evolution by first deriving a version of Price’s equation that can be applied in continuous time and to populations with overlapping generations. We then show how this version of Price’s equation provides an alternative perspective on pathogen evolution by considering the epidemiological meaning of each of its terms. Finally, we extend these results to the case where population size is small and generates demographic stochasticity. We show that the particular partitioning of evolutionary change given by Price’s equation is also a natural way to partition the evolutionary consequences of demographic stochasticity, and demonstrate how such stochasticity tends to weaken selection on birth rate (e.g. the transmission rate of an infectious disease) and enhance selection on mortality rate (e.g. factors, like virulence, that cause the end of an infection). In the long term, if there is a trade-off between virulence and transmission across parasite strains, the weaker selection on transmission and stronger selection on virulence that arises from demographic stochasticity will tend to drive the evolution of lower levels of virulence. This article is part of the theme issue ‘Fifty years of the Price equation’.

scholarly journals Evolutionary epidemiology of a zoonosis

2021 ◽  
Author(s):  
Giulia I Corsi ◽  
Swapnil Tichkule ◽  
Anna Rosa Sannella ◽  
Paolo Vatta ◽  
Francesco Asnicar ◽  
...  
Keyword(s):  
Nucleotide Diversity ◽  
Virulence Genes ◽  
Population Admixture ◽  
Genome Sequences ◽  
Host Parasite Interactions ◽  
Geographic Origins ◽  
Evolutionary Epidemiology ◽  
Evolutionary Consequences ◽  
Host Parasite

Cryptosporidium parvum is a global zoonoses and a major cause of diarrhoea in humans and ruminants. The parasite's life cycle comprises an obligatory sexual phase, during which genetic exchanges can occur between previously isolated lineages. Here, we compare 32 whole genome sequences from human- and ruminant-derived parasite isolates collected across Europe, Egypt and China. We identify three strongly supported clusters that comprise a mix of isolates from different host species, geographic origins, and subtypes. We show that: (1) recombination occurs between ruminant isolates into human isolates; (2) these recombinant regions can be passed on to other human subtypes through gene flow and population admixture; (3) there have been multiple genetic exchanges, and all are likely recent; (4) putative virulence genes are significantly enriched within these genetic exchanges, and (5) this results in an increase in their nucleotide diversity. We carefully dissect the phylogenetic sequence of two genetic exchanges, illustrating the long-term evolutionary consequences of these events. Our results suggest that increased globalisation and close human-animal contacts increase the opportunity for genetic exchanges between previously isolated parasite lineages, resulting in spillover and spillback events. We discuss how this can provide a novel substrate for natural selection at genes involved in host-parasite interactions, thereby potentially altering the dynamic coevolutionary equilibrium in the Red Queens arms race.

Evolutionary epidemiology theory of vaccination

Pertussis ◽  
2018 ◽  
pp. 133-143 ◽  
Author(s):  
Sylvain Gandon
Keyword(s):  
Theoretical Framework ◽  
Host Population ◽  
Phenotypic Traits ◽  
High Coverage ◽  
Evolutionary Epidemiology ◽  
Short And Long Term ◽  
Evolutionary Consequences ◽  
Parasite Populations ◽  
Specific Parasite

The aim of vaccination is to prevent or limit the risk of pathogen infections for individual hosts but large vaccination coverage often has dramatic epidemiological consequences at the scale of the whole host population. This massive perturbation of the ecology and transmission of the pathogen can also have important evolutionary effects. In particular, vaccine-driven evolution may lead to the spread of new pathogen variants that may erode the benefits of vaccination. This chapter presents a theoretical framework for modelling the short- and long-term epidemiological and evolutionary consequences of vaccination. This framework can be used to make quantitative predictions about the speed of such evolutionary processes. This work helps identify the relevant phenotypic traits that need to be measured in specific parasite populations in order to evaluate the potential evolutionary consequences of vaccination. In particular, this may help in the debate regarding the involvement of evolution in the re-emergence of pertussis in spite of the high coverage of vaccination.

scholarly journals The evolutionary epidemiology of vaccination

2007 ◽  
Vol 4 (16) ◽  
pp. 803-817 ◽  
Author(s):  
Sylvain Gandon ◽  
Troy Day
Keyword(s):  
Fitness Costs ◽  
Parasite Fitness ◽  
Different Types ◽  
Evolutionary Epidemiology ◽  
Short And Long Term ◽  
Parasite Evolution ◽  
Evolutionary Consequences ◽  
Parasite Populations ◽  
Specific Parasite

Vaccination leads to dramatic perturbations of the environment of parasite populations and this can have both demographic and evolutionary consequences. We present a theoretical framework for modelling the short- and long-term epidemiological and evolutionary consequences of vaccination. This framework integrates previous theoretical studies of vaccine-induced parasite evolution, and it allows one to make some useful qualitative predictions regarding the outcome of the competition between different types of vaccine-favoured variants. It can also be used to make quantitative predictions about the speed of such evolutionary processes. This work may help define the relevant parameters that need to be measured in specific parasite populations in order to evaluate the potential evolutionary consequences of vaccination. In particular, we argue that more work should be done evaluating the nature and magnitude of parasite fitness costs associated with adaptation to vaccinated hosts.

scholarly journals Spatial evolutionary epidemiology of spreading epidemics

2016 ◽  
Vol 283 (1841) ◽  
pp. 20161170 ◽  
Author(s):  
S. Lion ◽  
S. Gandon
Keyword(s):  
Evolutionary Dynamics ◽  
Spatial Models ◽  
Spatial Differentiation ◽  
Spatial Moment ◽  
Novel Approach ◽  
Evolutionary Epidemiology ◽  
Pathogen Populations ◽  
Evolutionary Consequences ◽  
Host Parasite

Most spatial models of host–parasite interactions either neglect the possibility of pathogen evolution or consider that this process is slow enough for epidemiological dynamics to reach an equilibrium on a fast timescale. Here, we propose a novel approach to jointly model the epidemiological and evolutionary dynamics of spatially structured host and pathogen populations. Starting from a multi-strain epidemiological model, we use a combination of spatial moment equations and quantitative genetics to analyse the dynamics of mean transmission and virulence in the population. A key insight of our approach is that, even in the absence of long-term evolutionary consequences, spatial structure can affect the short-term evolution of pathogens because of the build-up of spatial differentiation in mean virulence. We show that spatial differentiation is driven by a balance between epidemiological and genetic effects, and this quantity is related to the effect of kin competition discussed in previous studies of parasite evolution in spatially structured host populations. Our analysis can be used to understand and predict the transient evolutionary dynamics of pathogens and the emergence of spatial patterns of phenotypic variation.

scholarly journals Price's equation made clear

2020 ◽  
Vol 375 (1797) ◽  
pp. 20190361 ◽  
Author(s):  
Andy Gardner
Keyword(s):  
General Theory ◽  
Evolutionary Biology ◽  
Social Evolution ◽  
Evolutionary Change ◽  
Price Equation ◽  
Theme Issue ◽  
Price’S Equation ◽  
Scientific Disciplines ◽  
Wide Range ◽  
Mathematical Foundations

Price's equation provides a very simple—and very general—encapsulation of evolutionary change. It forms the mathematical foundations of several topics in evolutionary biology, and has also been applied outwith evolutionary biology to a wide range of other scientific disciplines. However, the equation's combination of simplicity and generality has led to a number of misapprehensions as to what it is saying and how it is supposed to be used. Here, I give a simple account of what Price's equation is, how it is derived, what it is saying and why this is useful. In particular, I suggest that Price's equation is useful not primarily as a predictor of evolutionary change but because it provides a general theory of selection. As an illustration, I discuss some of the insights Price's equation has brought to the study of social evolution. This article is part of the theme issue ‘Fifty years of the Price equation’.

scholarly journals High-efficiency CO2 separation using hybrid LDH-polymer membranes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xiaozhi Xu ◽  
Jiajie Wang ◽  
Awu Zhou ◽  
Siyuan Dong ◽  
Kaiqiang Shi ◽  
...  
Keyword(s):  
Self Assembly ◽  
High Efficiency ◽  
Transmission Rate ◽  
Spray Coating ◽  
Separation Performance ◽  
Pdms Layer ◽  
Operational Testing ◽  
Enhanced Solubility ◽  
Double Hydroxide

AbstractMembrane-based gas separation exhibits many advantages over other conventional techniques; however, the construction of membranes with simultaneous high selectivity and permeability remains a major challenge. Herein, (LDH/FAS)n-PDMS hybrid membranes, containing two-dimensional sub-nanometre channels were fabricated via self-assembly of unilamellar layered double hydroxide (LDH) nanosheets and formamidine sulfinic acid (FAS), followed by spray-coating with a poly(dimethylsiloxane) (PDMS) layer. A CO2 transmission rate for (LDH/FAS)25-PDMS of 7748 GPU together with CO2 selectivity factors (SF) for SF(CO2/H2), SF(CO2/N2) and SF(CO2/CH4) mixtures as high as 43, 86 and 62 respectively are observed. The CO2 permselectivity outperforms most reported systems and is higher than the Robeson or Freeman upper bound limits. These (LDH/FAS)n-PDMS membranes are both thermally and mechanically robust maintaining their highly selective CO2 separation performance during long-term operational testing. We believe this highly-efficient CO2 separation performance is based on the synergy of enhanced solubility, diffusivity and chemical affinity for CO2 in the sub-nanometre channels.

scholarly journals Long-term remission of acromegaly after somatostatin analogues withdrawal: a single-centre experience

2021 ◽  
Author(s):  
E. Sala ◽  
G. Carosi ◽  
G. Del Sindaco ◽  
R. Mungari ◽  
A. Cremaschi ◽  
...  
Keyword(s):  
Median Time ◽  
Pituitary Surgery ◽  
Somatostatin Analogues ◽  
Exclusion Criterion ◽  
Single Centre ◽  
Disease Evolution ◽  
Single Centre Experience ◽  
Pituitary Irradiation

Abstract Purpose A long-lasting remission of acromegaly after somatostatin analogues (SAs) withdrawal has been described in some series. Our aim was to update the disease evolution after SAs withdrawal in a cohort of acromegalic patients. Methods We retrospectively evaluated 21 acromegalic patients previously included in a multicentre study (Ronchi et al. 2008), updating data at the last follow-up. We added further 8 patients selected for SAs withdrawal between 2008–2018. Pituitary irradiation represented an exclusion criterion. The withdrawal was suggested after at least 9 months of clinical and hormonal disease control. Clinical and biochemical data prior and after SAs withdrawal were analysed. Results In the whole cohort (29 patients) mean age was 50 ± 14.9 years and 72.4% were females. In 69% pituitary surgery was previously performed. Overall, the median time of treatment before SAs withdrawal was 53 months (IQR = 24–84). At the last follow up in 2019, 23/29 patients (79.3%) had a disease relapse after a median time of 6 months (interquartile range or IQR = 3–12) from the drug suspension, while 6/29 (20.7%) were still on remission after 120 months (IQR = 66–150). IGF-1 levels were significantly lower before withdrawal in patients with persistent remission compared to relapsing ones (IGF-1 SDS: -1.5 ± 0.6 vs -0.11 ± 1, p = 0.01). We did not observe any other difference between patients with and without relapse, including SAs formulation, dosage and treatment duration. Conclusion A successful withdrawal of SAs is possible in a subset of well-controlled acromegalic patients and it challenges the concept that medical therapy is a lifelong requirement.

Mass extinctions alter extinction and origination dynamics with respect to body size

2021 ◽  
Vol 288 (1960) ◽  
Author(s):  
Pedro M. Monarrez ◽  
Noel A. Heim ◽  
Jonathan L. Payne
Keyword(s):  
Body Size ◽  
Mass Extinction ◽  
Evolutionary Biology ◽  
Marine Animal ◽  
Mass Extinctions ◽  
Extinction Selectivity ◽  
Extinction Events ◽  
Mass Extinction Events ◽  
Marine Biosphere

Whether mass extinctions and their associated recoveries represent an intensification of background extinction and origination dynamics versus a separate macroevolutionary regime remains a central debate in evolutionary biology. The previous focus has been on extinction, but origination dynamics may be equally or more important for long-term evolutionary outcomes. The evolution of animal body size is an ideal process to test for differences in macroevolutionary regimes, as body size is easily determined, comparable across distantly related taxa and scales with organismal traits. Here, we test for shifts in selectivity between background intervals and the ‘Big Five’ mass extinction events using capture–mark–recapture models. Our body-size data cover 10 203 fossil marine animal genera spanning 10 Linnaean classes with occurrences ranging from Early Ordovician to Late Pleistocene (485–1 Ma). Most classes exhibit differences in both origination and extinction selectivity between background intervals and mass extinctions, with the direction of selectivity varying among classes and overall exhibiting stronger selectivity during origination after mass extinction than extinction during the mass extinction. Thus, not only do mass extinction events shift the marine biosphere into a new macroevolutionary regime, the dynamics of recovery from mass extinction also appear to play an underappreciated role in shaping the biosphere in their aftermath.

Clustering-based Energy Efficient Multipath Adaptive Routing Protocols for Underwater Wireless Sensor Networks

2020 ◽  
Vol 6 (2) ◽  
pp. EC-54-EC-62
Author(s):  
Edy Victor Haryanto ◽  
Keyword(s):  
Routing Protocol ◽  
Routing Protocols ◽  
Energy Efficient ◽  
Transmission Rate ◽  
Adaptive Routing ◽  
Maximum Energy ◽  
Wireless Sensor ◽  
Energy Usage ◽  
Underwater Wireless Sensor Networks

In an underwater wireless sensor network (UWSN), research challenges occur in the availability of new connectivity protocols, sensors, and utilization of energy. One of the issues is to enhance the lifespan of the network without increasing the supply, cost, and level of resources. This paper proposes a conceptual routing protocol for UWSN, known as Energy-Efficient Multipath Adaptive Routing (E2MAR) protocols, which is primarily intended for long-term control with greater energy efficiency and transmission rate. Key development conditions were set by the E2MR and forward nodes are chosen based on the performance index. Different tests are carried out by evaluating E2MR in terms of the number of live nodes, end-to-end latency, packet delivery rate, and maximum energy usage efficiently compared to some other Routing protocols. The lifespan of the network has also been greatly enhanced.

scholarly journals Disentangling niche theory and beta diversity change

2021 ◽  
Author(s):  
William Godsoe ◽  
Peter J Bellingham ◽  
Elena Moltchanova
Keyword(s):  
Beta Diversity ◽  
Price Equation ◽  
Short Term ◽  
Before And After ◽  
Environmental Requirements ◽  
Habitat Specialists ◽  
Montane Tropical Forest ◽  
Ecological Drift ◽  
Over Time

Beta diversity describes the differences in species composition among communities. Changes in beta diversity over time are thought to be due to selection based on species' niche characteristics. For example, theory predicts that selection that favours habitat specialists will increase beta diversity. In practice, ecologists struggle to predict how beta diversity changes. To remedy this problem, we propose a novel solution that formally measures selection's effects on beta diversity. Using the Price equation, we show how change in beta diversity over time can be partitioned into fundamental mechanisms including selection among species, variable selection among communities, drift, and immigration. A key finding of our approach is that a species' short-term impact on beta diversity cannot be predicted using information on its long-term environmental requirements (i.e. its niche). We illustrate how our approach can be used to partition causes of diversity change in a montane tropical forest before and after an intense hurricane. Previous work in this system highlighted the resistance of habitat specialists and the recruitment of light-demanding species but was unable to quantify the importance of these effects on beta diversity. Using our approach, we show that changes in beta diversity were consistent with ecological drift. We use these results to highlight the opportunities presented by a synthesis of beta diversity and formal models of selection.

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