scholarly journals Modelling interference between vectors of non-persistently transmitted plant viruses to identify effective control strategies

2021 ◽  
Vol 17 (12) ◽  
pp. e1009727
Author(s):  
Marta Zaffaroni ◽  
Loup Rimbaud ◽  
Ludovic Mailleret ◽  
Nik J. Cunniffe ◽  
Daniele Bevacqua
Keyword(s):  
Disease Transmission ◽  
Plant Disease ◽  
Control Strategies ◽  
Management Strategies ◽  
Plant Viruses ◽  
Effective Control ◽  
Agronomic Practices ◽  
Ecological Principles ◽  
Single Host ◽  
Primary Vector

Aphids are the primary vector of plant viruses. Transient aphids, which probe several plants per day, are considered to be the principal vectors of non-persistently transmitted (NPT) viruses. However, resident aphids, which can complete their life cycle on a single host and are affected by agronomic practices, can transmit NPT viruses as well. Moreover, they can interfere both directly and indirectly with transient aphids, eventually shaping plant disease dynamics. By mean of an epidemiological model, originally accounting for ecological principles and agronomic practices, we explore the consequences of fertilization and irrigation, pesticide deployment and roguing of infected plants on the spread of viral diseases in crops. Our results indicate that the spread of NPT viruses can be i) both reduced or increased by fertilization and irrigation, depending on whether the interference is direct or indirect; ii) counter-intuitively increased by pesticide application and iii) reduced by roguing infected plants. We show that a better understanding of vectors’ interactions would enhance our understanding of disease transmission, supporting the development of disease management strategies.

scholarly journals The role of interference between vectors in control of plant diseases

2021 ◽  
Author(s):  
Marta Zaffaroni ◽  
Loup Rimbaud ◽  
Ludovic Mailleret ◽  
Nik Cunniffe ◽  
Daniele Bevacqua
Keyword(s):  
Disease Transmission ◽  
Management Strategies ◽  
Viral Disease ◽  
Plant Viruses ◽  
Plant Diseases ◽  
Agronomic Practices ◽  
Ecological Principles ◽  
Single Host ◽  
Primary Vector

Aphids are the primary vector of plant viruses. Transient aphids, which probe several plants per day, are considered to be the principal vectors of non-persistently transmitted (NPT) viruses. However, resident aphids, which can complete their life cycle on a single host and are affected by agronomic practices, can transmit NPT viruses as well. Moreover, they can interfere both directly and indirectly with transient aphids, eventually shaping plant disease dynamics. By mean of an epidemiological model, originally accounting for ecological principles and agronomic practices, we explore the consequences of fertilization and irrigation, pesticide deployment and roguing of infected plants on the spread of viral disease in crops. Our results indicate that the spread of NPT viruses can be i) both reduced or increased by fertilization and irrigation, depending on whether the interference is direct or indirect; ii) counter-intuitively increased by pesticide application and iii) reduced by roguing infected plants. We show that a better understanding of vectors' interactions would enhance our understanding of disease transmission, supporting the development of disease management strategies.

scholarly journals Global Stability and Optimal Control of Dengue with Two Coexisting Virus Serotypes

MATEMATIKA ◽  
2019 ◽  
Vol 35 (4) ◽  
pp. 149-170
Author(s):  
Afeez Abidemi ◽  
Rohanin Ahmad ◽  
Nur Arina Bazilah Aziz
Keyword(s):  
Optimal Control ◽  
Global Stability ◽  
Disease Transmission ◽  
Deterministic Model ◽  
Control Strategies ◽  
Equilibrium Points ◽  
Effective Control ◽  
Asymptotically Stable ◽  
Globally Asymptotically Stable ◽  
Boundary Equilibrium

This study presents a two-strain deterministic model which incorporates Dengvaxia vaccine and insecticide (adulticide) control strategies to forecast the dynamics of transmission and control of dengue in Madeira Island if there is a new outbreak with a different virus serotypes after the first outbreak in 2012. We construct suitable Lyapunov functions to investigate the global stability of the disease-free and boundary equilibrium points. Qualitative analysis of the model which incorporates time-varying controls with the specific goal of minimizing dengue disease transmission and the costs related to the control implementation by employing the optimal control theory is carried out. Three strategies, namely the use of Dengvaxia vaccine only, application of adulticide only, and the combination of Dengvaxia vaccine and adulticide are considered for the controls implementation. The necessary conditions are derived for the optimal control of dengue. We examine the impacts of the control strategies on the dynamics of infected humans and mosquito population by simulating the optimality system. The disease-freeequilibrium is found to be globally asymptotically stable whenever the basic reproduction numbers associated with virus serotypes 1 and j (j 2 {2, 3, 4}), respectively, satisfy R01,R0j 1, and the boundary equilibrium is globally asymptotically stable when the related R0i (i = 1, j) is above one. It is shown that the strategy based on the combination of Dengvaxia vaccine and adulticide helps in an effective control of dengue spread in the Island.

Targeting Vulnerable Life-Stages of Sericea Lespedeza (Lespedeza cuneata) with Prescribed Burns

2012 ◽  
Vol 5 (4) ◽  
pp. 487-493 ◽  
Author(s):  
Bryant M. Wong ◽  
Gregory R. Houseman ◽  
Sarah E. Hinman ◽  
Bryan L. Foster
Keyword(s):  
Invasive Species ◽  
Seedling Survival ◽  
Control Strategies ◽  
Abiotic Factors ◽  
Management Strategies ◽  
Effective Control ◽  
Life Stages ◽  
Lespedeza Cuneata ◽  
Sericea Lespedeza ◽  
Invasive Species Control

AbstractThere is growing interest in whether invasive species may be controlled by utilizing management strategies that target vulnerable life stages. We manipulated the timing of fire and measured its effects on sericea lespedeza germination and seedling survival. Although fire strongly decreased germination in the laboratory, fire increased germination under field conditions. Additionally, fire caused small decreases in seedling survival in the field. Therefore, controlled burns are likely to encourage spread of sericea lespedeza and are unlikely to effectively control this invasive species. Although targeting vulnerable life stages is a promising strategy for invasive species control, our results illustrate that system-specific studies may be needed to unravel potentially complex interactions between biotic and abiotic factors before effective control strategies can be devised.

Dilution effect and identity effect by wildlife in the persistence and recurrence of bovine tuberculosis

Parasitology ◽  
2014 ◽  
Vol 141 (7) ◽  
pp. 981-987 ◽  
Author(s):  
Z. Y. X. HUANG ◽  
C. XU ◽  
F. VAN LANGEVELDE ◽  
H. H. T. PRINS ◽  
K. BEN JEBARA ◽  
...  
Keyword(s):  
Risk Factors ◽  
Disease Transmission ◽  
Bovine Tuberculosis ◽  
Disease Risk ◽  
Control Strategies ◽  
Dilution Effect ◽  
Effective Control ◽  
African Buffalo ◽  
Mammal Species ◽  
Positive Interaction

SUMMARYCurrent theories on disease-diversity relationships predict a strong influence of host richness on disease transmission. In addition, identity effect, caused by the occurrence of particular species, can also modify disease risk. We tested the richness effect and the identity effects of mammal species on bovine tuberculosis (bTB), based on the regional bTB outbreak data in cattle from 2005–2010 in Africa. Besides, we also tested which other factors were associated with the regional bTB persistence and recurrence in cattle. Our results suggested a dilution effect, where higher mammal species richness (MSR) was associated with reduced probabilities of bTB persistence and recurrence in interaction with cattle density. African buffalo had a positive effect on bTB recurrence and a positive interaction effect with cattle density on bTB persistence, indicating an additive positive identity effect of buffalo. The presence of greater kudu had no effect on bTB recurrence or bTB persistence. Climatic variables only act as risk factors for bTB persistence. In summary, our study identified both a dilution effect and identity effect of wildlife and showed that bTB persistence and recurrence were correlated with different sets of risk factors. These results are relevant for more effective control strategies and better targeted surveillance measures in bTB.

Rich Sliding Motion and Dynamics in a Filippov Plant-Disease System

2018 ◽  
Vol 28 (01) ◽  
pp. 1850012 ◽  
Author(s):  
Can Chen ◽  
Xi Chen
Keyword(s):  
Disease Transmission ◽  
Plant Disease ◽  
Sliding Mode ◽  
Control Strategies ◽  
Disease Model ◽  
Threshold Value ◽  
Plant Diseases ◽  
Positive Equilibrium ◽  
Threshold Values ◽  
Periodic Trajectories

In order to reduce the spread of plant diseases and maintain the number of infected trees below an economic threshold, we choose the number of infected trees and the number of susceptible plants as the control indexes on whether to implement control strategies. Then a Filippov plant-disease model incorporating cutting off infected branches and replanting susceptible trees is proposed. Based on the theory of Filippov system, the sliding mode dynamics and conditions for the existence of all the possible equilibria and Lotka–Volterra cycles are presented. We find that model solutions ultimately approach the positive equilibrium that lies in the region above the infected threshold value [Formula: see text], or the periodic trajectories that lie in the region below [Formula: see text], or the pseudo-attractor [Formula: see text], as we vary the susceptible and infected threshold values. It indicates that the plant-disease transmission is tolerable if the trajectories approach [Formula: see text] or the periodic trajectories lie in the region below [Formula: see text]. Hence an acceptable level of the number of infected trees can be achieved when the susceptible and infected threshold values are chosen appropriately.

scholarly journals Methods to infer transmission risk factors in complex outbreak data

2011 ◽  
Vol 9 (68) ◽  
pp. 456-469 ◽  
Author(s):  
Simon Cauchemez ◽  
Neil M. Ferguson
Keyword(s):  
Risk Factors ◽  
Missing Data ◽  
Disease Transmission ◽  
Control Strategies ◽  
Model Fitting ◽  
Structured Populations ◽  
Transmission Risk ◽  
Effective Control ◽  
Reconstruction Methods ◽  
History Of

Data collected during outbreaks are essential to better understand infectious disease transmission and design effective control strategies. But analysis of such data is challenging owing to the dependency between observations that is typically observed in an outbreak and to missing data. In this paper, we discuss strategies to tackle some of the ongoing challenges in the analysis of outbreak data. We present a relatively generic statistical model for the estimation of transmission risk factors, and discuss algorithms to estimate its parameters for different levels of missing data. We look at the problem of computational times for relatively large datasets and show how they can be reduced by appropriate use of discretization, sufficient statistics and some simple assumptions on the natural history of the disease. We also discuss approaches to integrate parametric model fitting and tree reconstruction methods in coherent statistical analyses. The methods are tested on both real and simulated datasets of large outbreaks in structured populations.

scholarly journals Effect of high and low risk susceptibles in the transmission dynamics of COVID-19 and control strategies

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0257354
Author(s):  
Adnan Khan ◽  
Mohsin Ali ◽  
Wizda Iqbal ◽  
Mudassar Imran
Keyword(s):  
Disease Transmission ◽  
Deterministic Model ◽  
Control Strategies ◽  
Relative Proportion ◽  
Risk Groups ◽  
Low Risk ◽  
Effective Control ◽  
Population Groups ◽  
Severity Of The Disease ◽  
Image Position

In this study, we formulate and analyze a deterministic model for the transmission of COVID-19 and evaluate control strategies for the epidemic. It has been well documented that the severity of the disease and disease related mortality is strongly correlated with age and the presence of co-morbidities. We incorporate this in our model by considering two susceptible classes, a high risk, and a low risk group. Disease transmission within each group is modelled by an extension of the SEIR model, considering additional compartments for quarantined and treated population groups first and vaccinated and treated population groups next. Cross Infection across the high and low risk groups is also incorporated in the model. We calculate the basic reproduction number R0 and show that for R0<1 the disease dies out, and for R0>1 the disease is endemic. We note that varying the relative proportion of high and low risk susceptibles has a strong effect on the disease burden and mortality. We devise optimal medication and vaccination strategies for effective control of the disease. Our analysis shows that vaccinating and medicating both groups is needed for effective disease control and the controls are not very sensitive to the proportion of the high and low risk populations.

scholarly journals A Mathematical Model For Lassa Fever Transmission Dynamics With Impacts of Control Measures: Analysis And Simulation

2021 ◽  
Vol 2 (2) ◽  
pp. 19-28
Author(s):  
Oke Isaiah Idisi ◽  
Tunde Tajudeen Yusuf
Keyword(s):  
Disease Transmission ◽  
Control Strategies ◽  
Disease Outbreaks ◽  
Lassa Fever ◽  
Control Measures ◽  
Transmission Dynamics ◽  
Effective Control ◽  
Lassa Virus ◽  
Long Run ◽  
Globally Stable

Lassa Fever, caused by Lassa virus, is a vector-host transmitted infectious disease whose prevalence has been on the upsurge over the past few decades. Thus, considering the grave implications of the continuous spread of the disease, an epidemic model was developed to describe the disease transmission dynamics with impacts of proposed control measures. This is to help inform effective control strategies that would successfully curtail and contain the disease in its endemic areas. The model is qualitatively analyzed in order to contextualize the long run behavior of the model while the model associated basic reproduction number $(\mathcal{R}_0)$ is derived. The model analysis reveals that the disease-free equilibrium is locally and globally stable whenever $ \mathcal{R}_0 < 1 $ and the disease prevalence would be high as long as $ \mathcal{R}_0 > 1 $. Finally, the model is numerically solved and simulated for different scenarios of the disease outbreaks while the findings from simulations are discussed.

Analysis of Different Management Strategies for Annual Ryegrass (Lolium rigidum) Based on a Population Dynamic Model

2018 ◽  
Vol 28 (12) ◽  
pp. 1830041 ◽  
Author(s):  
María Belén D’Amico ◽  
Guillermo L. Calandrini ◽  
José L. González-Andujar ◽  
Guillermo R. Chantre
Keyword(s):  
Weed Management ◽  
Control Strategies ◽  
Management Strategies ◽  
Planning Horizon ◽  
Threshold Level ◽  
Effective Control ◽  
Lolium Rigidum ◽  
Weed Species ◽  
Population Dynamic Model ◽  
Seed Bank Dynamics

Weed species present high competitive capacity, rapid adaptability and herbicide resistance, hindering their effective control across worldwide cropping regions. Since field-conducted experiments are very time-consuming and usually expensive, mathematical population-based models are valuable tools to test and develop long-term weed management programs. Within this context, the objective of this paper is to formalize analytically the possible seed bank dynamics of the Lolium rigidum, subjected to different control strategies. The first focus is on studying in detail the effects of integrating constant actions, promoting more environmentally and economically sustainable scenarios. From the same perspective, an alternative to applying time-variant programs is introduced. The proposed control guarantees that the weed population is sufficiently small or, alternatively, is kept below a given economic threshold level in a ten-year planning horizon. Furthermore, an optimization criterion is adopted for distributing necessary efficiency into diverse integrated options. Numerical simulations are included to illustrate the analytical findings.

scholarly journals Inter-provincial disparity of COVID-19 transmission and control in Nepal

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Buddhi Pantha ◽  
Subas Acharya ◽  
Hem Raj Joshi ◽  
Naveen K. Vaidya
Keyword(s):  
Growth Rate ◽  
Disease Transmission ◽  
Reproduction Number ◽  
Control Strategies ◽  
National Level ◽  
Effective Control ◽  
Data Set ◽  
Control Policies ◽  
Local Spread ◽  
And Control

AbstractDespite the global efforts to mitigate the ongoing COVID-19 pandemic, the disease transmission and the effective controls still remain uncertain as the outcome of the epidemic varies from place to place. In this regard, the province-wise data from Nepal provides a unique opportunity to study the effective control strategies. This is because (a) some provinces of Nepal share an open-border with India, resulting in a significantly high inflow of COVID-19 cases from India; (b) despite the inflow of a considerable number of cases, the local spread was quite controlled until mid-June of 2020, presumably due to control policies implemented; and (c) the relaxation of policies caused a rapid surge of the COVID-19 cases, providing a multi-phasic trend of disease dynamics. In this study, we used this unique data set to explore the inter-provincial disparities of the important indicators, such as epidemic trend, epidemic growth rate, and reproduction numbers. Furthermore, we extended our analysis to identify prevention and control policies that are effective in altering these indicators. Our analysis identified a noticeable inter-province variation in the epidemic trend (3 per day to 104 per day linear increase during third surge period), the median daily growth rate (1 to 4% per day exponential growth), the basic reproduction number (0.71 to 1.21), and the effective reproduction number (maximum values ranging from 1.20 to 2.86). Importantly, results from our modeling show that the type and number of control strategies that are effective in altering the indicators vary among provinces, underscoring the need for province-focused strategies along with the national-level strategy in order to ensure the control of a local spread.

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