scholarly journals Systematic shifts in the variation among host individuals must be considered in climate-disease theory

2021 ◽  
Author(s):  
Joseph R Mihaljevic ◽  
David J Páez
Keyword(s):  
Climate Change ◽  
Population Dynamics ◽  
Disease Ecology ◽  
Host Population ◽  
Host Susceptibility ◽  
Disease Spread ◽  
Species Variation ◽  
Trait Variation ◽  
Host Pathogen ◽  
Population Sizes

To make more informed predictions of host-pathogen interactions under climate change, studies have incorporated the thermal performance of host, vector, and pathogen traits into disease models. However, this body of work has ignored the fact that disease spread and long-term patterns of host population dynamics are largely determined by the variation in susceptibility among individuals in the host population. Furthermore, and especially for ectothermic host species, variation in susceptibility is likely to be plastic, influenced by variables such as environmental temperature. Quantifying the relationship between temperature and among-host trait variation will therefore be critical for predicting how climate change and disease will interact to influence host-pathogen population dynamics. Here, we demonstrate how short-term effects of temperature on the variation of host susceptibility drive epidemic characteristics, fluctuations in host population sizes, and probabilities of host extinction. We use this quantitative analysis as a basic framework to suggest that more research is needed in disease ecology to understand the mechanisms that shape trait variation, not just trait averages.

Climate, ticks and disease

2021 ◽  
Keyword(s):  
Climate Change ◽  
Spatial Distribution ◽  
Disease Ecology ◽  
Future Climate Change ◽  
Climate Change Scenarios ◽  
Expert Opinions ◽  
The World ◽  
Host Pathogen ◽  
The Future ◽  
Impacts Of Climate Change

Abstract This book is a collection of 77 expert opinions arranged in three sections. Section 1 on "Climate" sets the scene, including predictions of future climate change, how climate change affects ecosystems, and how to model projections of the spatial distribution of ticks and tick-borne infections under different climate change scenarios. Section 2 on "Ticks" focuses on ticks (although tick-borne pathogens creep in) and whether or not changes in climate affect the tick biosphere, from physiology to ecology. Section 3 on "Disease" focuses on the tick-host-pathogen biosphere, ranging from the triangle of tick-host-pathogen molecular interactions to disease ecology in various regions and ecosystems of the world. Each of these three sections ends with a synopsis that aims to give a brief overview of all the expert opinions within the section. The book concludes with Section 4 (Final Synopsis and Future Predictions). This synopsis attempts to summarize evidence provided by the experts of tangible impacts of climate change on ticks and tick-borne infections. In constructing their expert opinions, contributors give their views on what the future might hold. The final synopsis provides a snapshot of their expert thoughts on the future.

scholarly journals Population size impacts host–pathogen coevolution

2021 ◽  
Vol 288 (1965) ◽  
Author(s):  
Andrei Papkou ◽  
Rebecca Schalkowski ◽  
Mike-Christoph Barg ◽  
Svenja Koepper ◽  
Hinrich Schulenburg
Keyword(s):  
Population Size ◽  
Finite Population ◽  
Host Population ◽  
Major Influence ◽  
Small Populations ◽  
Selection Dynamics ◽  
Host Pathogen ◽  
Population Sizes ◽  
Size Limits ◽  
Efficiency Of Selection

Ongoing host–pathogen interactions are characterized by rapid coevolutionary changes forcing species to continuously adapt to each other. The interacting species are often defined by finite population sizes. In theory, finite population size limits genetic diversity and compromises the efficiency of selection owing to genetic drift, in turn constraining any rapid coevolutionary responses. To date, however, experimental evidence for such constraints is scarce. The aim of our study was to assess to what extent population size influences the dynamics of host–pathogen coevolution. We used Caenorhabditus elegans and its pathogen Bacillus thuringiensis as a model for experimental coevolution in small and large host populations, as well as in host populations which were periodically forced through a bottleneck. By carefully controlling host population size for 23 host generations, we found that host adaptation was constrained in small populations and to a lesser extent in the bottlenecked populations. As a result, coevolution in large and small populations gave rise to different selection dynamics and produced different patterns of host–pathogen genotype-by-genotype interactions. Our results demonstrate a major influence of host population size on the ability of the antagonists to co-adapt to each other, thereby shaping the dynamics of antagonistic coevolution.

scholarly journals Disease and climate effects on individuals jointly drive post-reintroduction population dynamics of an endangered amphibian

2018 ◽  
Author(s):  
Maxwell B. Joseph ◽  
Roland A. Knapp
Keyword(s):  
Population Dynamics ◽  
Disease Ecology ◽  
Batrachochytrium Dendrobatidis ◽  
Species Conservation ◽  
Infection Intensity ◽  
Host Population ◽  
Negative Effects ◽  
Conservation Actions ◽  
In The Wild ◽  
Amphibian Chytrid Fungus

AbstractThe emergence of novel pathogens often has dramatic negative effects on previously unexposed host populations. Subsequent disease can drive populations and even species to extinction. After establishment in populations, pathogens can continue to affect host dynamics, influencing the success or failure of species recovery efforts. However, quantifying the effect of pathogens on host populations in the wild is challenging because individual hosts and their pathogens are difficult to observe. Here we use long-term mark-recapture data to describe the dynamics of reintroduced populations of an endangered amphibian (Rana sierrae) and evaluate the success of these recovery efforts in the presence of a recently-emerged pathogen, the amphibian chytrid fungus Batrachochytrium dendrobatidis. We find that high B. dendrobatidis infection intensities are associated with increases in detectability, reductions in survival, and more infected adults. We also find evidence for intensity-dependent survival, with heavily infected individuals suffering higher mortality. These results highlight the need in disease ecology for probabilistic approaches that account for uncertainty in infection intensity using imperfect observational data. Such approaches can advance the understanding of disease impacts on host population dynamics, and in the current study will improve the effectiveness of species conservation actions.

Wild Bird Populations in the Face of Disease

2021 ◽  
pp. 121-144
Author(s):  
Kathryn P. Huyvaert
Keyword(s):  
Population Dynamics ◽  
Disease Ecology ◽  
Population Level ◽  
Host Population ◽  
Infection Prevalence ◽  
Imperfect Detection ◽  
Statistical Parameters ◽  
Bird Populations ◽  
The Face

Parasites and pathogens typically have detectable negative fitness impacts on individual avian hosts, but the role of parasites in driving population dynamics is less straightforward. Questions about whether and under what conditions parasites influence host population dynamics have been long-standing in infectious disease ecology for many years. Understanding the role of parasites in host population dynamics requires estimating statistical parameters such as infection prevalence and host abundance at population scales. Mathematical approaches such as process-based models are also often used to simulate population-level dynamics of host and parasite interactions over time. This chapter first describes tools commonly used in disease ecology to estimate these key parameters, with a focus on accounting for imperfect detection of individual animals or their disease or infection status and mark-recapture approaches. Some of the mathematical approaches, including SIR models, network approaches, and agent-based models, that are commonly used to simulate and predict the population dynamics of host–parasite interactions are presented. Through a series of case studies, the chapter finishes by considering whether and under what conditions parasites affect the overall growth of populations, whether parasites have a tendency to cause cycles or to regulate populations of wild birds, and some examples of parasite-induced local extinctions.

Theoretical and empirical studies of metapopulations: population and genetic dynamics of the Silene–Ustilago system

1995 ◽  
Vol 73 (S1) ◽  
pp. 1249-1258 ◽  
Author(s):  
Peter H. Thrall ◽  
Janis Antonovics
Keyword(s):  
Population Dynamics ◽  
Empirical Studies ◽  
Previous History ◽  
High Rate ◽  
Disease Spread ◽  
Plant Host ◽  
Theoretical Approaches ◽  
Population Turnover ◽  
Host Pathogen ◽  
Anther Smut

Host–pathogen population dynamics may often only be understood by a multifaceted approach designed to understand processes at a regional as well as local scale. We have investigated the regional population dynamics of the anther-smut Ustilago violacea, a pollinator-transmitted fungal disease, and its plant host Silene alba, using descriptive, experimental, and theoretical approaches. A 7-year survey of multiple natural populations revealed persistence of host and pathogen despite a high rate of population turnover. In an experimental metapopulation, disease spread was greater and more rapid in populations that were relatively isolated or had a previous history of disease occurrence. A computer simulation showed that spatial substructuring can drastically alter expectations based on analytical results from single population models of host–pathogen systems. Moreover, the simulation reproduced many of the patterns detected in the long-term survey and predicted that healthy populations should be more resistant than diseased ones, as found experimentally. Key words: metapopulations, host–pathogen dynamics, spatial models, anther-smut diseases.

scholarly journals Parasitism of Aedes albopictus by Ascogregarina taiwanensis lowers its competitive ability against Aedes triseriatus

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Emma Stump ◽  
Lauren M. Childs ◽  
Melody Walker
Keyword(s):  
Population Dynamics ◽  
Competitive Advantage ◽  
Aedes Albopictus ◽  
Abiotic Factors ◽  
Mosquito Species ◽  
Disease Spread ◽  
Aedes Triseriatus ◽  
La Crosse Virus ◽  
The Impact ◽  
Ascogregarina Taiwanensis

Abstract Background Mosquitoes are vectors for diseases such as dengue, malaria and La Crosse virus that significantly impact the human population. When multiple mosquito species are present, the competition between species may alter population dynamics as well as disease spread. Two mosquito species, Aedes albopictus and Aedes triseriatus, both inhabit areas where La Crosse virus is found. Infection of Aedes albopictus by the parasite Ascogregarina taiwanensis and Aedes triseriatus by the parasite Ascogregarina barretti can decrease a mosquito’s fitness, respectively. In particular, the decrease in fitness of Aedes albopictus occurs through the impact of Ascogregarina taiwanensis on female fecundity, larval development rate, and larval mortality and may impact its initial competitive advantage over Aedes triseriatus during invasion. Methods We examine the effects of parasitism of gregarine parasites on Aedes albopictus and triseriatus population dynamics and competition with a focus on when Aedes albopictus is new to an area. We build a compartmental model including competition between Aedes albopictus and triseriatus while under parasitism of the gregarine parasites. Using parameters based on the literature, we simulate the dynamics and analyze the equilibrium population proportion of the two species. We consider the presence of both parasites and potential dilution effects. Results We show that increased levels of parasitism in Aedes albopictus will decrease the initial competitive advantage of the species over Aedes triseriatus and increase the survivorship of Aedes triseriatus. We find Aedes albopictus is better able to invade when there is more extreme parasitism of Aedes triseriatus. Furthermore, although the transient dynamics differ, dilution of the parasite density through uptake by both species does not alter the equilibrium population sizes of either species. Conclusions Mosquito population dynamics are affected by many factors, such as abiotic factors (e.g. temperature and humidity) and competition between mosquito species. This is especially true when multiple mosquito species are vying to live in the same area. Knowledge of how population dynamics are affected by gregarine parasites among competing species can inform future mosquito control efforts and help prevent the spread of vector-borne disease.

scholarly journals Effects of Infectious Diseases on Population Dynamics of Marine Organisms in Chesapeake Bay

2021 ◽  
Author(s):  
Jerelle A. Jesse ◽  
M. Victoria Agnew ◽  
Kohma Arai ◽  
C. Taylor Armstrong ◽  
Shannon M. Hood ◽  
...  
Keyword(s):  
Climate Change ◽  
Population Dynamics ◽  
Infectious Diseases ◽  
Chesapeake Bay ◽  
Eastern Oyster ◽  
Marine Organisms ◽  
Ecosystem Dynamics ◽  
Climate Change Effects ◽  
Pathogen Dynamics ◽  
Growth And Reproduction

AbstractDiseases are important drivers of population and ecosystem dynamics. This review synthesizes the effects of infectious diseases on the population dynamics of nine species of marine organisms in the Chesapeake Bay. Diseases generally caused increases in mortality and decreases in growth and reproduction. Effects of diseases on eastern oyster (Crassostrea virginica) appear to be low in the 2000s compared to effects in the 1980s–1990s. However, the effects of disease were not well monitored for most of the diseases in marine organisms of the Chesapeake Bay, and few studies considered effects on growth and reproduction. Climate change and other anthropogenic effects are expected to alter host-pathogen dynamics, with diseases of some species expected to worsen under predicted future conditions (e.g., increased temperature). Additional study of disease prevalence, drivers of disease, and effects on population dynamics could improve fisheries management and forecasting of climate change effects on marine organisms in the Chesapeake Bay.

scholarly journals Lessons learned from comparing spatially explicit models and the Partners in Flight approach to estimate population sizes of boreal birds in Alberta, Canada

The Condor ◽  
2020 ◽  
Vol 122 (2) ◽  
Author(s):  
Péter Sólymos ◽  
Judith D Toms ◽  
Steven M Matsuoka ◽  
Steven G Cumming ◽  
Nicole K S Barker ◽  
...  
Keyword(s):  
North America ◽  
Time Of Day ◽  
Lessons Learned ◽  
Population Estimates ◽  
Spatially Explicit ◽  
Species Variation ◽  
Detection Distance ◽  
Spatially Explicit Models ◽  
Population Sizes ◽  
Partners In Flight

Abstract Estimating the population abundance of landbirds is a challenging task complicated by the amount, type, and quality of available data. Avian conservationists have relied on population estimates from Partners in Flight (PIF), which primarily uses roadside data from the North American Breeding Bird Survey (BBS). However, the BBS was not designed to estimate population sizes. Therefore, we set out to compare the PIF approach with spatially explicit models incorporating roadside and off-road point-count surveys. We calculated population estimates for 81 landbird species in Bird Conservation Region 6 in Alberta, Canada, using land cover and climate as predictors. We also developed a framework to evaluate how the differences between the detection distance, time-of-day, roadside count, and habitat representation adjustments explain discrepancies between the 2 estimators. We showed that the key assumptions of the PIF population estimator were commonly violated in this region, and that the 2 approaches provided different population estimates for most species. The average differences between estimators were explained by differences in the detection-distance and time-of-day components, but these adjustments left much unexplained variation among species. Differences in the roadside count and habitat representation components explained most of the among-species variation. The variation caused by these factors was large enough to change the population ranking of the species. The roadside count bias needs serious attention when roadside surveys are used to extrapolate over off-road areas. Habitat representation bias is likely prevalent in regions sparsely and non-representatively sampled by roadside surveys, such as the boreal region of North America, and thus population estimates for these regions need to be treated with caution for certain species. Additional sampling and integrated modeling of available data sources can contribute towards more accurate population estimates for conservation in remote areas of North America.

scholarly journals Rapid evolution of decreased host susceptibility drives a stable relationship between ultrasmall parasite TM7x and its bacterial host

2018 ◽  
Vol 115 (48) ◽  
pp. 12277-12282 ◽  
Author(s):  
Batbileg Bor ◽  
Jeffrey S. McLean ◽  
Kevin R. Foster ◽  
Lujia Cen ◽  
Thao T. To ◽  
...  
Keyword(s):  
Host Cell ◽  
Rapid Evolution ◽  
Host Population ◽  
Host Cells ◽  
Host Susceptibility ◽  
Bacterial Host ◽  
Narrow Host Range ◽  
Stable Relationship ◽  
Candidate Phyla Radiation

Around one-quarter of bacterial diversity comprises a single radiation with reduced genomes, known collectively as the Candidate Phyla Radiation. Recently, we coisolated TM7x, an ultrasmall strain of the Candidate Phyla Radiation phylum Saccharibacteria, with its bacterial host Actinomyces odontolyticus strain XH001 from human oral cavity and stably maintained as a coculture. Our current work demonstrates that within the coculture, TM7x cells establish a long-term parasitic association with host cells by infecting only a subset of the population, which stay viable yet exhibit severely inhibited cell division. In contrast, exposure of a naïve A. odontolyticus isolate, XH001n, to TM7x cells leads to high numbers of TM7x cells binding to each host cell, massive host cell death, and a host population crash. However, further passaging reveals that XH001n becomes less susceptible to TM7x over time and enters a long-term stable relationship similar to that of XH001. We show that this reduced susceptibility is driven by rapid host evolution that, in contrast to many forms of phage resistance, offers only partial protection. The result is a stalemate where infected hosts cannot shed their parasites; nevertheless, parasite load is sufficiently low that the host population persists. Finally, we show that TM7x can infect and form stable long-term relationships with other species in a single clade of Actinomyces, displaying a narrow host range. This system serves as a model to understand how parasitic bacteria with reduced genomes such as those of the Candidate Phyla Radiation have persisted with their hosts and ultimately expanded in their diversity.

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