scholarly journals Modeling the Effects of Resource-Driven Immune Defense on Parasite Transmission in Heterogeneous Host Populations

2019 ◽  
Vol 59 (5) ◽  
pp. 1253-1263 ◽  
Author(s):  
Richard J Hall
Keyword(s):  
Resource Allocation ◽  
Environmental Conditions ◽  
Disease Outbreaks ◽  
Population Level ◽  
Resource Scarcity ◽  
Immune Defense ◽  
Infectious Period ◽  
Resource Subsidies ◽  
Mechanistic Theory ◽  
Invasion Threshold

Abstract Individuals experience heterogeneous environmental conditions that can affect within-host processes such as immune defense against parasite infection. Variation among individuals in parasite shedding can cause some hosts to contribute disproportionately to population-level transmission, but we currently lack mechanistic theory that predicts when environmental conditions can result in large disease outbreaks through the formation of immunocompromised superspreading individuals. Here, I present a within-host model of a microparasite’s interaction with the immune system that links an individual host’s resource intake to its infectious period. For environmental scenarios driving population-level heterogeneity in resource intake (resource scarcity and resource subsidy relative to baseline availability), I generate a distribution of infectious periods and simulate epidemics on these heterogeneous populations. I find that resource scarcity can result in large epidemics through creation of superspreading individuals, while resource subsidies can reduce or prevent transmission of parasites close to their invasion threshold by homogenizing resource allocation to immune defense. Importantly, failure to account for heterogeneity in competence can result in under-prediction of outbreak size, especially when parasites are close to their invasion threshold. More generally, this framework suggests that differences in conditions experienced by individual hosts can lead to superspreading via differences in resource allocation to immune defense alone, even in the absence of other heterogeneites such as host contacts.

scholarly journals Temporal Evolution of Immunity Distributions in a Population with Waning and Boosting

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-13
Author(s):  
M. V. Barbarossa ◽  
M. Polner ◽  
G. Röst
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Temporal Evolution ◽  
Disease Outbreaks ◽  
Population Level ◽  
Coupled System ◽  
Disease Outbreak ◽  
Periodic Disease ◽  
Evolution Of Immunity

We investigate the temporal evolution of the distribution of immunities in a population, which is determined by various epidemiological, immunological, and demographical phenomena: after a disease outbreak, recovered individuals constitute a large immune population; however, their immunity is waning in the long term and they may become susceptible again. Meanwhile, their immunity can be boosted by repeated exposure to the pathogen, which is linked to the density of infected individuals present in the population. This prolongs the length of their immunity. We consider a mathematical model formulated as a coupled system of ordinary and partial differential equations that connects all these processes and systematically compare a number of boosting assumptions proposed in the literature, showing that different boosting mechanisms lead to very different stationary distributions of the immunity at the endemic steady state. In the situation of periodic disease outbreaks, the waveforms of immunity distributions are studied and visualized. Our results show that there is a possibility to infer the boosting mechanism from the population level immune dynamics.

Population Health as a Complex Adaptive System of Systems

2020 ◽  
pp. 33-44
Author(s):  
Scott E. Page ◽  
Jon Zelner
Keyword(s):  
Population Health ◽  
Systems Approach ◽  
Adaptive System ◽  
Complex Adaptive System ◽  
Disease Outbreaks ◽  
Population Level ◽  
System Of Systems ◽  
System Level ◽  
Multiple Systems ◽  
Complex Adaptive

This chapter advocates a complex adaptive system of systems approach to understanding population-level processes in population health. A complex adaptive system consists of diverse, interacting adaptive entities whose aggregated behaviors result in emergent, system-level patterns and functionalities. A complex adaptive system of systems consists of multiple, connected complex systems. The connections can be hierarchical, horizontal, or a mixture of the two. The authors provide basic definitions, describe common tools of analysis, and introduce illustrative cases. For example, increased obesity levels have no single cause, nor do they arise from a single system. Instead, they arise from the interactions of multiple systems that operate at various levels of scale. Genetics and epigenetics play roles, as do nutrition, general health, advertising, infrastructure, social norms, exercise levels, and, as recent evidence suggests, the ecology of colonies of gut bacteria. Each of these contributors can be modeled as a complex adaptive system and the whole as a system of systems. Similarly, population-level disease outbreaks can be decomposed into separate systems, each with unique dynamics.

Allocation of resources to sex functions in flowering plants

1991 ◽  
Vol 332 (1262) ◽  
pp. 91-102 ◽  
Keyword(s):  
Resource Allocation ◽  
Natural Selection ◽  
Population Level ◽  
Theoretical Models ◽  
Flowering Plants ◽  
Allocation Of Resources ◽  
Biological Reality ◽  
Theoretical Predictions ◽  
Allocation Patterns ◽  
Unisexual Flowers

The study of allocation of resources offers the possibility of understanding the pressures of natural selection on reproductive functions. In allocation studies, theoretical predictions are generated and the assumptions as well as the predictions can be tested in the field. Here, we review some of the theoretical models, and discuss how much biological reality can be included in them, and what factors have been left out. We also review the empirical data that have been generated as tests of this body of theory. There are many problems associated with estimating reproductive resources, and also with testing how allocation of these resources affects reproductive and other components of fitness, and we assess how important these may be in allowing empirical results to be interpreted. Finally, we discuss the relevance of resource allocation patterns to the evolution of unisexual flowers, both at the level of individual plants (monoecy, andro- and gynomonoecy) and at the population level (dioecy).

scholarly journals Environmental and social factors impacting on epidemic and endemic tuberculosis: a modelling analysis

2018 ◽  
Vol 5 (1) ◽  
pp. 170726 ◽  
Author(s):  
Chacha M. Issarow ◽  
Nicola Mulder ◽  
Robin Wood
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Social Factors ◽  
Environmental Conditions ◽  
Population Level ◽  
Transmission Probability ◽  
Infectious Dose ◽  
Air Volume ◽  
Effective Contact ◽  
Modelling Analysis ◽  
The Mean

Tuberculosis (TB) transmission results from the interaction between infective sources and susceptible individuals within enabling socio-environmental conditions. As TB is an airborne pathogen, the transmission probability is determined by the volume of air inhaled from an infected source and the concentration of Mycobacterium tuberculosis containing respirable particles (doses) per volume of air. In this study, we model the contributions of infectious dose production, prevalence of infectious cases and daily rebreathed air volume (RAV) for defining the boundary conditions necessary to sustain endemic TB transmission at the population level. Results suggest that in areas with high RAV (range 300–1000 l d −1 ), such as prisons, TB transmission is contributed by both super-spreaders (exhaling ≥10 infectious doses hr −1 ) and lower infectivity individuals (exhaling less than 10 infectious doses hr −1 ). In settings with a low quantity of RAV (less than 100 l d −1 ), TB transmission occurs only from super-spreaders. Point-source epidemics occur in low rebreathed environments when super-spreaders infect a number of susceptibles but subsequent transmission is limited by the mean infectivity of secondary cases. By contrast, endemic TB occurs in poor socio-environmental conditions where mean infectivity cases are able to maintain a sufficiently high effective contact number.

scholarly journals Dynamics of Mask Use as a Prevention Strategy against SARS-CoV-2 in Panama

2021 ◽  
Vol 18 (24) ◽  
pp. 12982
Author(s):  
Hermógenes Fernández-Marín ◽  
Gaspar Bruner-Montero ◽  
Ana Portugal-Loayza ◽  
Virginia Miranda ◽  
Alcibíades Villareal ◽  
...  
Keyword(s):  
Public Health ◽  
Low Cost ◽  
Disease Outbreaks ◽  
Population Level ◽  
Respiratory Pathogens ◽  
Behavioral Preferences ◽  
Public Areas ◽  
National Public Health ◽  
And Gender ◽  
Use Behavior

Early in the SARS-CoV-2 pandemic, many national public health authorities implemented non-pharmaceutical interventions to mitigate disease outbreaks. Panamá established mandatory mask use two months after its first documented case. Initial compliance was high, but diverse masks were used in public areas. We studied behavioral dynamics of mask use through the first two COVID-19 waves in Panama, to improve the implementation of effective, low-cost public health containment measures when populations are exposed to novel air-borne pathogens. Mask use behavior was recorded from pedestrians in four Panamanian populations (August to December 2020). We recorded facial coverings and if used, the type of mask, and gender and estimated age of the wearer. Our results showed that people were highly compliant (>95%) with mask mandates and demonstrated important population-level behaviors: (1) decreasing use of cloth masks over time, and increasing use of surgical masks; (2) mask use was 3-fold lower in suburban neighborhoods than other public areas and (3) young people were least likely to wear masks. Results help focus on highly effective, low-cost, public health interventions for managing and controlling a pandemic. Considerations of behavioral preferences for different masks, relative to pricing and availability, are essential for optimizing public health policies. Policies to increase the availability of effective masks, and behavioral nudges to increase acceptance, and to facilitate mask usage, during the ongoing SARS-CoV-2 pandemic, and for future pandemics of respiratory pathogens, are key tools, especially for nations lagging in access to expensive vaccines and pharmacological approaches.

scholarly journals Food for contagion: synthesis and future directions for studying host–parasite responses to resource shifts in anthropogenic environments

2018 ◽  
Vol 373 (1745) ◽  
pp. 20170102 ◽  
Author(s):  
Sonia Altizer ◽  
Daniel J. Becker ◽  
Jonathan H. Epstein ◽  
Kristian M. Forbes ◽  
Thomas R. Gillespie ◽  
...  
Keyword(s):  
Regional Scale ◽  
Population Level ◽  
Food Resources ◽  
Resource Subsidies ◽  
Conservation Implications ◽  
Contact Rates ◽  
Animal Aggregation ◽  
Infection Processes ◽  
Host Parasite ◽  
Future Work

Human-provided resource subsidies for wildlife are diverse, common and have profound consequences for wildlife–pathogen interactions, as demonstrated by papers in this themed issue spanning empirical, theoretical and management perspectives from a range of study systems. Contributions cut across scales of organization, from the within-host dynamics of immune function, to population-level impacts on parasite transmission, to landscape- and regional-scale patterns of infection. In this concluding paper, we identify common threads and key findings from author contributions, including the consequences of resource subsidies for (i) host immunity; (ii) animal aggregation and contact rates; (iii) host movement and landscape-level infection patterns; and (iv) interspecific contacts and cross-species transmission. Exciting avenues for future work include studies that integrate mechanistic modelling and empirical approaches to better explore cross-scale processes, and experimental manipulations of food resources to quantify host and pathogen responses. Work is also needed to examine evolutionary responses to provisioning, and ask how diet-altered changes to the host microbiome influence infection processes. Given the massive public health and conservation implications of anthropogenic resource shifts, we end by underscoring the need for practical recommendations to manage supplemental feeding practices, limit human–wildlife conflicts over shared food resources and reduce cross-species transmission risks, including to humans. This article is part of the theme issue ‘Anthropogenic resource subsidies and host–parasite dynamics in wildlife’.

scholarly journals Inter- and intraspecific phenotypic plasticity of three phytoplankton species in response to ocean acidification

2017 ◽  
Vol 13 (2) ◽  
pp. 20160774 ◽  
Author(s):  
Giannina S. I. Hattich ◽  
Luisa Listmann ◽  
Julia Raab ◽  
Dorthe Ozod-Seradj ◽  
Thorsten B. H. Reusch ◽  
...  
Keyword(s):  
Phenotypic Plasticity ◽  
Ocean Acidification ◽  
Growth Rates ◽  
Environmental Conditions ◽  
Population Level ◽  
Reaction Norms ◽  
Short Time Scale ◽  
Sampling Effort ◽  
Phytoplankton Species ◽  
Species Response

Phenotypic plasticity describes the phenotypic adjustment of the same genotype to different environmental conditions and is best described by a reaction norm. We focus on the effect of ocean acidification on inter- and intraspecific reaction norms of three globally important phytoplankton species ( Emiliania huxleyi, Gephyrocapsa oceanica and Chaetoceros affinis ). Despite significant differences in growth rates between the species, they all showed a high potential for phenotypic buffering (similar growth rates between ambient and high CO 2 conditions). Only three coccolithophore genotypes showed a reduced growth in high CO 2 . Diverging responses to high CO 2 of single coccolithophore genotypes compared with the respective mean species responses, however, raise the question of whether an extrapolation to the population level is possible from single-genotype experiments. We therefore compared the mean response of all tested genotypes with a total species response comprising the same genotypes, which was not significantly different in the coccolithophores. Assessing species reaction norms to different environmental conditions on short time scale in a genotype-mix could thus reduce sampling effort while increasing predictive power.

scholarly journals Pathogenicity effector candidates and accessory genome revealed by pan-genomic analysis of Parastagonospora nodorum

2021 ◽  
Author(s):  
Darcy A. B. Jones ◽  
Kasia Rybak ◽  
Stefania Bertazzoni ◽  
Kar-Chun Tan ◽  
Huyen T. T. Phan ◽  
...  
Keyword(s):  
Local Population ◽  
Disease Outbreaks ◽  
Genomic Analysis ◽  
Population Level ◽  
Orthologous Gene ◽  
Fungal Species ◽  
Pan Genome ◽  
Crop Disease ◽  
Regional Population ◽  
Parastagonospora Nodorum

AbstractThe wheat pathogen Parastagonospora nodorum has emerged as a model necrotrophic fungal species with growing genomic resources. Recent population-level pan-genome studies were leveraged to provide novel insights into pathogen evolution and effector-like gene contents relevant to local crop disease outbreaks. In this study, we examined 156 isolates representing a regional population from the Western Australian (WA) wheat-belt region, and 17 internationally sourced isolates. We observed a highly diverse local population, within which were numerous small and highly similar clusters of isolates from hotter and drier regions. Pan-genome assembly and orthologous gene datasets resulted in 3579 predicted effector candidates, 2291 of which exhibited presence-absence variation (PAV) across the population, and 1362 were specific to WA isolates. There was an abundance of mutations (including repeat-induced point mutation (RIP)), distributed in ‘hot-spots’ within the pan-genomic landscape that were rich in effector candidates. Three characterised effector loci (ToxA, Tox1 and Tox3) were located within sub- telomeric regions of lower diversity, but were nestled within larger high-diversity regions. RIP was widespread across the genome, but non-synonymous RIP-like mutations were strongly selected against. These improved bioinformatic resources for P. nodorum, represent progressive advancements in fungal pan-genomics, with a view towards supporting region- specific surveillance of host-pathogen interactions.

scholarly journals Testing, tracing and isolation in compartmental models

2021 ◽  
Vol 17 (3) ◽  
pp. e1008633
Author(s):  
Simone Sturniolo ◽  
William Waites ◽  
Tim Colbourn ◽  
David Manheim ◽  
Jasmina Panovska-Griffiths
Keyword(s):  
Computational Cost ◽  
Disease Outbreaks ◽  
Population Level ◽  
Compartmental Models ◽  
Contact Tracing ◽  
Adaptive Planning ◽  
Agent Based ◽  
Individual Level ◽  
Individual Based Models ◽  
The Individual

Existing compartmental mathematical modelling methods for epidemics, such as SEIR models, cannot accurately represent effects of contact tracing. This makes them inappropriate for evaluating testing and contact tracing strategies to contain an outbreak. An alternative used in practice is the application of agent- or individual-based models (ABM). However ABMs are complex, less well-understood and much more computationally expensive. This paper presents a new method for accurately including the effects of Testing, contact-Tracing and Isolation (TTI) strategies in standard compartmental models. We derive our method using a careful probabilistic argument to show how contact tracing at the individual level is reflected in aggregate on the population level. We show that the resultant SEIR-TTI model accurately approximates the behaviour of a mechanistic agent-based model at far less computational cost. The computational efficiency is such that it can be easily and cheaply used for exploratory modelling to quantify the required levels of testing and tracing, alone and with other interventions, to assist adaptive planning for managing disease outbreaks.

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