scholarly journals When environmentally persistent pathogens transform good habitat into ecological traps

2016 ◽  
Vol 3 (3) ◽  
pp. 160051 ◽  
Author(s):  
Clinton B. Leach ◽  
Colleen T. Webb ◽  
Paul C. Cross
Keyword(s):  
Habitat Quality ◽  
Transmission Rate ◽  
Pathogen Transmission ◽  
Ecological Trap ◽  
Patch Occupancy ◽  
Environmental Persistence ◽  
High Quality ◽  
Patch Occupancy Model ◽  
Wildlife Populations ◽  
Persistent Pathogens

Habitat quality plays an important role in the dynamics and stability of wildlife metapopulations. However, the benefits of high-quality habitat may be modulated by the presence of an environmentally persistent pathogen. In some cases, the presence of environmental pathogen reservoirs on high-quality habitat may lead to the creation of ecological traps, wherein host individuals preferentially colonize high-quality habitat, but are then exposed to increased infection risk and disease-induced mortality. We explored this possibility through the development of a stochastic patch occupancy model, where we varied the pathogen’s virulence, transmission rate and environmental persistence as well as the distribution of habitat quality in the host metapopulation. This model suggests that for pathogens with intermediate levels of spread, high-quality habitat can serve as an ecological trap, and can be detrimental to host persistence relative to low-quality habitat. This inversion of the relative roles of high- and low-quality habitat highlights the importance of considering the interaction between spatial structure and pathogen transmission when managing wildlife populations exposed to an environmentally persistent pathogen.

scholarly journals Uniform persistence and almost periodic solutions of a nonautonomous patch occupancy model

2020 ◽  
Vol 2020 (1) ◽  
Author(s):  
Hui Zhou ◽  
Jehad Alzabut ◽  
Shahram Rezapour ◽  
Mohammad Esmael Samei
Keyword(s):  
Differential Inequality ◽  
Almost Periodic Solution ◽  
Rocky Intertidal ◽  
Uniform Persistence ◽  
Almost Periodic ◽  
Patch Occupancy ◽  
Sharp Threshold ◽  
Intertidal Community ◽  
Patch Occupancy Model ◽  
Inequality Techniques

Abstract In this paper, a nonlinear nonautonomous model in a rocky intertidal community is studied. The model is composed of two species in a rocky intertidal community and describes a patch occupancy with global dispersal of propagules and occupy each other by individual organisms. Firstly, we study the uniform persistence of the model via differential inequality techniques. Furthermore, a sharp threshold of global asymptotic stability and the existence of a unique almost periodic solution are derived. To prove the main results, we construct an appropriate Lyapunov function whose conditions are easily verified. The assumptions of the model are reasonable, and the results complement previously known ones. An example with specific values of parameters is included for demonstration of theoretical outcomes.

scholarly journals A Graft-Based Chemotherapy Method for Screening Effective Molecules and Rescuing Huanglongbing-Affected Citrus Plants

2012 ◽  
Vol 102 (6) ◽  
pp. 567-574 ◽  
Author(s):  
Muqing Zhang ◽  
Charles A. Powell ◽  
Ying Guo ◽  
Melissa S. Doud ◽  
Yongping Duan
Keyword(s):  
Survival Rate ◽  
Transmission Rate ◽  
High Titer ◽  
Critical Factor ◽  
Transmission Efficiency ◽  
Pathogen Transmission ◽  
Citrus Industry ◽  
Chemical Treatments ◽  
Bacterial Titer ◽  
Transmission Studies

Huanglongbing (HLB) is the most devastating disease of citrus. The global citrus industry is in urgent need of effective chemical treatments for HLB control because of its rapid spreading worldwide. Due to the fastidious nature of the pathogens, and the poor permissibility of citrus leaf surfaces, effective screening of chemicals for the HLB control can be challenging. In this study, we developed a graft-based chemotherapy method to rapidly screen potential HLB-controlling chemical compounds. In addition, we improved transmission efficiency by using the best HLB-affected scion–rootstock combination, and demonstrated the HLB bacterial titer was the critical factor in transmission. The HLB-affected lemon scions had a high titer of HLB bacterium, survival rate (83.3%), and pathogen transmission rate (59.9%). Trifoliate, a widely used commercial rootstock, had the highest survival rate (>70.0%) compared with grapefruit (52.6%) and sour orange (50.4%). Using this method, we confirmed a mixture of penicillin and streptomycin was the most effective compounds in eliminating the HLB bacterium from the HLB-affected scions, and in successfully rescuing severely HLB-affected citrus germplasms. These findings are useful not only for chemical treatments but also for graft-based transmission studies in HLB and other Liberibacter diseases.

scholarly journals A computationally tractable birth-death model that combines phylogenetic and epidemiological data

2020 ◽  
Author(s):  
Alexander E. Zarebski ◽  
Louis du Plessis ◽  
Kris V. Parag ◽  
Oliver G. Pybus
Keyword(s):  
Transmission Rate ◽  
Epidemiological Data ◽  
Heterogeneous Data ◽  
Pathogen Transmission ◽  
Data Sources ◽  
Primary Data ◽  
Analytic Approximation ◽  
Data Set ◽  
Combining Data ◽  
Birth Death

Inferring the dynamics of pathogen transmission during an outbreak is an important problem in both infectious disease epidemiology and phylodynamics. In mathematical epidemiology, estimates are often informed by time-series of infected cases while in phylodynamics genetic sequences sampled through time are the primary data source. Each data type provides different, and potentially complementary, insights into transmission. However inference methods are typically highly specialised and field-specific. Recent studies have recognised the benefits of combining data sources, which include improved estimates of the transmission rate and number of infected individuals. However, the methods they employ are either computationally prohibitive or require intensive simulation, limiting their real-time utility. We present a novel birth-death phylogenetic model, called TimTam which can be informed by both phylogenetic and epidemiological data. Moreover, we derive a tractable analytic approximation of the TimTam likelihood, the computational complexity of which is linear in the size of the data set. Using the TimTam we show how key parameters of transmission dynamics and the number of unreported infections can be estimated accurately using these heterogeneous data sources. The approximate likelihood facilitates inference on large data sets, an important consideration as such data become increasingly common due to improving sequencing capability.

scholarly journals Inference in road ecology research: what we know versus what we think we know

2020 ◽  
Vol 16 (7) ◽  
pp. 20200140 ◽  
Author(s):  
Fernanda Z. Teixeira ◽  
Trina Rytwinski ◽  
Lenore Fahrig
Keyword(s):  
Habitat Quality ◽  
Road Ecology ◽  
Relative Importance ◽  
Road Kill ◽  
Single Mechanism ◽  
Traffic Impacts ◽  
Wildlife Populations

Roads and traffic impacts on wildlife populations are well documented. Three major mechanisms can cause them: reduced connectivity, increased mortality and reduced habitat quality. Researchers commonly recommend mitigation based on the mechanism they deem responsible. We reviewed the 2012–2016 literature to evaluate authors' inferences, to determine whether they explicitly acknowledge all possible mechanisms that are consistent with their results. We found 327 negative responses of wildlife to roads, from 307 studies. While most (84%) of these responses were consistent with multiple mechanisms, 60% of authors invoked a single mechanism. This indicates that many authors are over-confident in their inferences, and that the literature does not allow estimation of the relative importance of the mechanisms. We found preferences in authors' discussion of mechanisms. When all three mechanisms were consistent with the response measured, authors were 2.4 and 2.9 times as likely to infer reduced habitat quality compared to reduced connectivity or increased mortality, respectively. When both reduced connectivity and increased mortality were consistent with the response measured, authors were 5.2 times as likely to infer reduced connectivity compared to increased mortality. Given these results, road ecologists and managers are likely over-recommending mitigation for improving habitat quality and connectivity, and under-recommending measures to reduce road-kill.

scholarly journals Understanding the Evolutionary Ecology of host–pathogen Interactions Provides Insights into the Outcomes of Insect Pest Biocontrol

Viruses ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 141
Author(s):  
David J. Páez ◽  
Arietta E. Fleming-Davies
Keyword(s):  
Population Dynamics ◽  
Life History ◽  
Transmission Rate ◽  
Insect Pest ◽  
Pathogen Transmission ◽  
Single Strain ◽  
Classical Biocontrol ◽  
Life History Tradeoffs ◽  
Pathogen Strains

The use of viral pathogens to control the population size of pest insects has produced both successful and unsuccessful outcomes. Here, we investigate whether those biocontrol successes and failures can be explained by key ecological and evolutionary processes between hosts and pathogens. Specifically, we examine how heterogeneity in pathogen transmission, ecological and evolutionary tradeoffs, and pathogen diversity affect insect population density and thus successful control. We first review the existing literature and then use numerical simulations of mathematical models to further explore these processes. Our results show that the control of insect densities using viruses depends strongly on the heterogeneity of virus transmission among insects. Overall, increased heterogeneity of transmission reduces the effect of viruses on insect densities and increases the long-term stability of insect populations. Lower equilibrium insect densities occur when transmission is heritable and when there is a tradeoff between mean transmission and insect fecundity compared to when the heterogeneity of transmission arises from non-genetic sources. Thus, the heterogeneity of transmission is a key parameter that regulates the long-term population dynamics of insects and their pathogens. We also show that both heterogeneity of transmission and life-history tradeoffs modulate characteristics of population dynamics such as the frequency and intensity of “boom–bust" population cycles. Furthermore, we show that because of life-history tradeoffs affecting the transmission rate, the use of multiple pathogen strains is more effective than the use of a single strain to control insect densities only when the pathogen strains differ considerably in their transmission characteristics. By quantifying the effects of ecology and evolution on population densities, we are able to offer recommendations to assess the long-term effects of classical biocontrol.

scholarly journals Health quality and reduction of pathogenic transmission in tomato seeds using plant extracts

2019 ◽  
Vol 13 ((04) 2019) ◽  
pp. 635-641
Author(s):  
Mônica Shirley Brasil dos Santos e Silva ◽  
Antônia Alice Costa Rodrigues ◽  
Erlen Keila Candido e Silva ◽  
Anna Christina Sanazário de Oliveira ◽  
Leonardo de Jesus Machado Gois de Oliveira ◽  
...  
Keyword(s):  
Plant Extracts ◽  
Plant Pathogens ◽  
Transmission Rate ◽  
Pathogen Transmission ◽  
Tomato Seed ◽  
Tomato Seeds ◽  
Seed Analysis ◽  
Seed Health ◽  
Health Quality ◽  
Health Test

The objective of the present study was to assess the seed health quality, quantification of seed-seedling pathogen transmission and the effect of plant extracts in reducing plant pathogens in the seeds of the tomato varieties San Marzano and Ipa 6. For the seed health, the samples were disinfested, plated and assessed after seven days, according to the Brazilian Seed Analysis Rule. For the transmission rate, 12 trays were prepared with 100 seeds each and assessed at 7, 14 and 21 d.a.s. (days after seeding) using 100 seedlings. The plant (main root, stalk and leaves) tissues were plated in PDA culture medium and assessed after seven days of incubation. Aqueous extracts were prepared from cinnamon, basil, neem and eucalyptus with 0.5% concentration and the seeds were immersed in each solution for 10 minutes. Then, they plated and assessed after seven days. The health test showed that biggest incidences of Aspergillus fumigatus (26 %) and Aspergillus flavus (26 %) were occurred in the seeds of the varieties Ipa 6 and San Marzano, respectively. The fungi A. flavus, A. fumigatus, A. niger, R. stolonifer and Curvularia sp. were detected in quantification of transmission in the seeds of the two tomato varieties. The treatment with basil extract resulted in the least fungus incidence in the transmission quantification of ‘San Marzano’ tomato seeds, while on Ipa 6 seeds the eucalyptus treatment performed better. The interference of treatments was not observed in tomato seed germination. However, there was decrease in incident of pathogens in seeds treated with the plant extracts and different effects was observed based on type and species of the pathogen.

scholarly journals Network-based vaccination improves prospects for disease control in wild chimpanzees

2014 ◽  
Vol 11 (97) ◽  
pp. 20140349 ◽  
Author(s):  
Julie Rushmore ◽  
Damien Caillaud ◽  
Richard J. Hall ◽  
Rebecca M. Stumpf ◽  
Lauren Ancel Meyers ◽  
...  
Keyword(s):  
Large Scale ◽  
Vaccination Strategy ◽  
Pathogen Transmission ◽  
Wild Chimpanzee ◽  
Contact Rates ◽  
Individual Traits ◽  
Pathogen Control ◽  
Wildlife Populations ◽  
And Control ◽  
Biological Differences

Many endangered wildlife populations are vulnerable to infectious diseases for which vaccines exist; yet, pragmatic considerations often preclude large-scale vaccination efforts. These barriers could be reduced by focusing on individuals with the highest contact rates. However, the question then becomes whether targeted vaccination is sufficient to prevent large outbreaks. To evaluate the efficacy of targeted wildlife vaccinations, we simulate pathogen transmission and control on monthly association networks informed by behavioural data from a wild chimpanzee community (Kanyawara N = 37, Kibale National Park, Uganda). Despite considerable variation across monthly networks, our simulations indicate that targeting the most connected individuals can prevent large outbreaks with up to 35% fewer vaccines than random vaccination. Transmission heterogeneities might be attributed to biological differences among individuals (e.g. sex, age, dominance and family size). Thus, we also evaluate the effectiveness of a trait-based vaccination strategy, as trait data are often easier to collect than interaction data. Our simulations indicate that a trait-based strategy can prevent large outbreaks with up to 18% fewer vaccines than random vaccination, demonstrating that individual traits can serve as effective estimates of connectivity. Overall, these results suggest that fine-scale behavioural data can help optimize pathogen control efforts for endangered wildlife.

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