scholarly journals Controlling the Spatial Spread of a Xylella Epidemic

2021 ◽  
Vol 83 (4) ◽  
Author(s):  
Sebastian Aniţa ◽  
Vincenzo Capasso ◽  
Simone Scacchi
Keyword(s):  
Spatial Structure ◽  
Numerical Simulations ◽  
Control Strategies ◽  
Xylella Fastidiosa ◽  
Cost Effective ◽  
Olive Tree ◽  
Control Measures ◽  
Weed Biomass ◽  
Spatial Spread ◽  
Olive Trees

AbstractIn a recent paper by one of the authors and collaborators, motivated by the Olive Quick Decline Syndrome (OQDS) outbreak, which has been ongoing in Southern Italy since 2013, a simple epidemiological model describing this epidemic was presented. Beside the bacterium Xylella fastidiosa, the main players considered in the model are its insect vectors, Philaenus spumarius, and the host plants (olive trees and weeds) of the insects and of the bacterium. The model was based on a system of ordinary differential equations, the analysis of which provided interesting results about possible equilibria of the epidemic system and guidelines for its numerical simulations. Although the model presented there was mathematically rather simplified, its analysis has highlighted threshold parameters that could be the target of control strategies within an integrated pest management framework, not requiring the removal of the productive resource represented by the olive trees. Indeed, numerical simulations support the outcomes of the mathematical analysis, according to which the removal of a suitable amount of weed biomass (reservoir of Xylella fastidiosa) from olive orchards and surrounding areas resulted in the most efficient strategy to control the spread of the OQDS. In addition, as expected, the adoption of more resistant olive tree cultivars has been shown to be a good strategy, though less cost-effective, in controlling the pathogen. In this paper for a more realistic description and a clearer interpretation of the proposed control measures, a spatial structure of the epidemic system has been included, but, in order to keep mathematical technicalities to a minimum, only two players have been described in a dynamical way, trees and insects, while the weed biomass is taken to be a given quantity. The control measures have been introduced only on a subregion of the whole habitat, in order to contain costs of intervention. We show that such a practice can lead to the eradication of an epidemic outbreak. Numerical simulations confirm both the results of the previous paper and the theoretical results of the model with a spatial structure, though subject to regional control only.

scholarly journals Detection of Bactrocera oleae (Diptera: Tephritidae) DNA in the gut of the soil species Pseudoophonus rufipes (Coleoptera: Carabidae)

2018 ◽  
Vol 16 (3) ◽  
pp. e1007
Author(s):  
Alice Albertini ◽  
Sónia A. P. Santos ◽  
Fátima Martins ◽  
José A. Pereira ◽  
Teresa Lino-Neto ◽  
...  
Keyword(s):  
Control Strategies ◽  
Cost Effective ◽  
Olive Tree ◽  
Carabid Beetles ◽  
Bactrocera Oleae ◽  
Negative Effects ◽  
Cytochrome Oxidase Subunit ◽  
Mtdna Sequences ◽  
Olive Orchard ◽  
Control Service

Pest control service provided by natural enemies of Bactrocera oleae, the key pest of the olive tree, is nowadays recognized as fundamental. B. oleae has developed resistance to common insecticides, and negative effects both on consumers’ health and non-target species are the major drawbacks of conventional control strategies. Carabid beetles are potential B. oleae pupae predators, but their predation on field still need to be assessed. We tested adult Pseudoophonus rufipes, a species known to be active in olive orchard when pest pupae are abundant in the soil, in order to detect B. oleae pupae consumption at different post feeding times for both male and female carabids. An already existing protocol was used for detecting B. oleae mtDNA sequences of the cytochrome oxidase subunit I gene in carabids’ gut, and its versatility improved. B. oleae mtDNA was detected up to 20 h after pupa ingestion with a high percentage of success, without significant differences between sexes and pair primers used. Prey DNA extraction was tested from both dissected and non-dissected carabids, obtaining comparable results. The trapping system used to collect carabids for molecular assays and the new elements introduced in the protocol represent cost-effective solutions that may be beneficial for future laboratory trials and, mostly, for the analysis of field-collected predators. Fostering the investigation of soil predators in olive orchard may increase the design of conservation control strategies against B. oleae.

scholarly journals Modelling, Simulations and Analysis of the First and Second COVID-19 Epidemics in Beijing

2021 ◽  
Author(s):  
Lequan Min
Keyword(s):  
Numerical Simulations ◽  
Prevention And Control ◽  
Control Strategies ◽  
Equation Model ◽  
Control Measures ◽  
Disease Spreading ◽  
Prevention And Control Measures ◽  
Asymptomatic Individuals ◽  
Reported Data ◽  
And Control

AbstractTo date, over 130 million people on infected with COVID-19. It causes more 2.8 millions deaths. This paper introduces a symptomatic-asymptomatic-recoverer-dead differential equation model (SARDDE). It gives the conditions of the asymptotical stability on the disease-free equilibrium of SARDDE. It proposes the necessary conditions of disease spreading for the SARDDE. Based on the reported data of the first and the second COVID-19 epidemics in Beijing and simulations, it determines the parameters of SARDDE, respectively. Numerical simulations of SARDDE describe well the outcomes of current symptomatic and asymptomatic individuals, recovered symptomatic and asymptomatic individuals, and died individuals, respectively. The numerical simulations suggest that both symptomatic and asymptomatic individuals cause lesser asymptomatic spread than symptomatic spread; blocking rate of about 90% cannot prevent the spread of the COVID19 epidemic in Beijing; the strict prevention and control strategies implemented by Beijing government is not only very effective but also completely necessary. The numerical simulations suggest also that using the data from the beginning to the day after about two weeks at the turning point can estimate well or approximately the following outcomes of the two COVID-19 academics, respectively. It is expected that the research can provide better understanding, explaining, and dominating for epidemic spreads, prevention and control measures.

scholarly journals Modelling, Simulations and Analysis of the First COVID-19 Epidemic in Shanghai

2021 ◽  
Author(s):  
Lequan Min
Keyword(s):  
Numerical Simulations ◽  
Prevention And Control ◽  
Control Strategies ◽  
Equation Model ◽  
Control Measures ◽  
Differential Equation Model ◽  
Blocking Rate ◽  
Prevention And Control Measures ◽  
Asymptomatic Individuals ◽  
And Control

To date, over 178 million people on infected with COVID-19. It causes more 3.8 millions deaths. Based on a previous symptomatic-asymptomatic-recoverer-dead differential equation model (SARDDE) and the clinic data of the first COVID-19 epidemic in Shanghai, this paper determines the parameters of SARDDE. Numerical simulations of SARDDE describe well the outcomes of current symptomatic individuals, recovered symptomatic individuals, and died individuals, respectively. The numerical simulations suggest that both symptomatic and asymptomatic individuals cause lesser asymptomatic spread than symptomatic spread; blocking rate of about 95.5\% cannot prevent the spread of the COVID19 epidemic in Shanghai. The strict prevention and control strategies implemented by Shanghai government is not only very effective but also completely necessary. The numerical simulations suggest also that using the data from the beginning to the day after about 19 days at the turning point can estimate well the following outcomes of the COVID-19 academic. It is expected that the research can provide better understanding, explaining, and dominating for epidemic spreads, prevention and control measures.

scholarly journals A non-targeted metabolomics study on Xylella fastidiosa infected olive plants grown under controlled conditions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Asmae Jlilat ◽  
Rosa Ragone ◽  
Stefania Gualano ◽  
Franco Santoro ◽  
Vito Gallo ◽  
...  
Keyword(s):  
Xylella Fastidiosa ◽  
Bacterial Pathogen ◽  
Olive Tree ◽  
Susceptible Variety ◽  
Leaf Extracts ◽  
Metabolomics Study ◽  
Olive Quick Decline Syndrome ◽  
Olive Trees ◽  
Test Plants ◽  
Targeted Approach

AbstractIn the last decade, the bacterial pathogen Xylella fastidiosa has devastated olive trees throughout Apulia region (Southern Italy) in the form of the disease called “Olive Quick Decline Syndrome” (OQDS). This study describes changes in the metabolic profile due to the infection by X. fastidiosa subsp. pauca ST53 in artificially inoculated young olive plants of the susceptible variety Cellina di Nardò. The test plants, grown in a thermo-conditioned greenhouse, were also co-inoculated with some xylem-inhabiting fungi known to largely occur in OQDS-affected trees, in order to partially reproduce field conditions in terms of biotic stress. The investigations were performed by combining NMR spectroscopy and MS spectrometry with a non-targeted approach for the analysis of leaf extracts. Statistical analysis revealed that Xylella-infected plants were characterized by higher amounts of malic acid, formic acid, mannitol, and sucrose than in Xylella-non-infected ones, whereas it revealed slightly lower amounts of oleuropein. Attention was paid to mannitol which may play a central role in sustaining the survival of the olive tree against bacterial infection. This study contributes to describe a set of metabolites playing a possible role as markers in the infections by X. fastidiosa in olive.

scholarly journals Lessons from One Fastidious Bacterium to Another: What Can We Learn about Liberibacter Species from Xylella fastidiosa

Insects ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 300 ◽  
Author(s):  
Angela Kruse ◽  
Laura A. Fleites ◽  
Michelle Heck
Keyword(s):  
Control Strategies ◽  
Xylella Fastidiosa ◽  
Historical Context ◽  
Control Plant ◽  
Bacterial Pathogen ◽  
Pathogen Transmission ◽  
Control Measures ◽  
Insect Vector ◽  
Potential Applicability ◽  
Candidatus Liberibacter

Huanglongbing is causing economic devastation to the citrus industry in Florida, and threatens the industry everywhere the bacterial pathogens in the Candidatus Liberibacter genus and their insect vectors are found. Bacteria in the genus cannot be cultured and no durable strategy is available for growers to control plant infection or pathogen transmission. However, scientists and grape growers were once in a comparable situation after the emergence of Pierce’s disease, which is caused by Xylella fastidiosa and spread by its hemipteran insect vector. Proactive quarantine and vector control measures coupled with interdisciplinary data-driven science established control of this devastating disease and pushed the frontiers of knowledge in the plant pathology and vector biology fields. Our review highlights the successful strategies used to understand and control X. fastidiosa and their potential applicability to the liberibacters associated with citrus greening, with a focus on the interactions between bacterial pathogen and insect vector. By placing the study of Candidatus Liberibacter spp. within the current and historical context of another fastidious emergent plant pathogen, future basic and applied research to develop control strategies can be prioritized.

scholarly journals Epidemiology of Ectoparasites (Ticks, Lice, and Mites) in the Livestock of Pakistan: A Review

2021 ◽  
Vol 8 ◽  
Author(s):  
Ali Muhammad ◽  
Rida Bashir ◽  
Majid Mahmood ◽  
Muhammad Sohail Afzal ◽  
Sami Simsek ◽  
...  
Keyword(s):  
Control Strategies ◽  
Cost Effective ◽  
Well Being ◽  
Climatic Conditions ◽  
Control Measures ◽  
Veterinary Services ◽  
Future Studies ◽  
Factors Associated ◽  
And Control ◽  
Ectoparasite Infestation

Ectoparasites, including lice, ticks, and mites, inhabit the host skin and depend on their host for sustenance, maturation, and multiplication. Among these, ticks are more prevalent in various regions of Pakistan because of favorable climatic conditions, lack of awareness of livestock keepers' regarding ectoparasite infestation rate, insufficient veterinary services, and inadequate control measures. Ectoparasitic infestation is a primary threat to cost-effective livestock production by damaging skin and transmitting multiple diseases between animals. This review aimed to determine the infestation rates of various ectoparasites in cattle, buffaloes, sheep, goats, camels, equids and to ascertain the prevalence and epidemiology of ectoparasites in different regions of Pakistan. This review could be useful in devising prevention and control strategies and identifying the risk factors associated with ectoparasites to enhance animal productivity. It provides directions for veterinary schools, researchers, and organizations aiming to collaborate with neighboring countries to eradicate these parasites. Future studies could support working veterinarians and administrators and contribute to human well-being.

scholarly journals Modelling, Simulations and Analysis of the First and Second COVID-19 Epidemics in Beijing

2021 ◽  
Author(s):  
Lequan Min
Keyword(s):  
Numerical Simulations ◽  
Prevention And Control ◽  
Control Strategies ◽  
Equation Model ◽  
Control Measures ◽  
Virtual Simulations ◽  
Prevention And Control Measures ◽  
Asymptomatic Individuals ◽  
Reported Data ◽  
And Control

To date, over 182 million people on infected with COVID-19. It causes more 3.9 millions deaths. This paper introduces a symptomatic-asymptomatic-recoverer-dead differential equation model (SARDDE). It gives the conditions of the asymptotical stability on the disease-free equilibrium of SARDDE. It proposes the necessary conditions of disease spreading for the SARDDE. Based on the reported data of the first and the second COVID-19 epidemics in Beijing and simulations, it determines the parameters of SARDDE, respectively. Numerical simulations of SARDDE describe well the outcomes of current symptomatic and asymptomatic individuals, recovered symptomatic and asymptomatic individuals, and died individuals, respectively. The numerical simulations suggest that both symptomatic and asymptomatic individuals cause lesser asymptomatic spread than symptomatic spread; the blocking rates of about 80% and 97.5% to the symptomatic individuals cannot prevent the spread of the first and second COVID19 epidemics in Beijing, respectively. Virtual simulations suggest that the strict prevention and control strategies implemented by Beijing government are not only very effective but also completely necessary. The numerical simulations suggest also that using the data from the beginning to the day after about 14 -- 17 days at the turning point can estimate well the following outcomes of the two COVID-19 academics, respectively. It is expected that the research can provide better understanding, explaining, and dominating for epidemic spreads, prevention and control measures.

STRUCTURED INFLUENZA MODEL FOR META-POPULATION

2009 ◽  
Vol 02 (04) ◽  
pp. 525-541 ◽  
Author(s):  
MARIJA ŽIVKOVIĆ GOJOVIĆ ◽  
DONG LIANG ◽  
JIANHONG WU
Keyword(s):  
Control Strategies ◽  
Influenza Pandemic ◽  
Influenza Infection ◽  
Control Measures ◽  
Disease Spread ◽  
Behavior Changes ◽  
Spatial Spread ◽  
Structured Population ◽  
Age Structured ◽  
The Impact

We present a mathematical model parameterized to simulate the 1918 pandemic and modified to account for today's achievements in medical care and technology. Our goal is to use the model with carefully selected parameters to analyze and simulate different scenarios in a changing environment including behavior changes and reduction of mobility as the disease progresses. The model is structured by the disease age, representing the time elapsed since the exposure to influenza infection, and most of the parameters used in this study are thus disease-age dependent. We also consider the case where an influenza pandemic affects two distinct regions, connected only through controlled mobility. We evaluate the influence of different control measures on temporal patterns of disease dynamics and consider the impact of the movement of disease age structured population on spatial spread. A special example is examined that considers different scenarios of disease spread between Canada and USA when different border control strategies are implemented.

scholarly journals The Multi-Millennial Olive Agroecosystem of Salento (Apulia, Italy) Threatened by Xylella Fastidiosa Subsp. Pauca: A Working Possibility of Restoration

2020 ◽  
Vol 12 (17) ◽  
pp. 6700
Author(s):  
Marco Scortichini
Keyword(s):  
Cell Concentration ◽  
Control Strategies ◽  
Xylella Fastidiosa ◽  
First Record ◽  
Interdisciplinary Studies ◽  
Insect Vector ◽  
Infected Area ◽  
Olive Groves ◽  
Olive Trees ◽  
Spray Treatment

In Salento, the olive agro-ecosystem has lasted more than 4000 years, and represents an invaluable local heritage for landscape, trade, and social traditions. The quarantine bacterium Xylella fastidiosa subsp. pauca was introduced in the area from abroad and has been widely threatening olive groves in the area. The successful eradication of quarantine phytopathogens requires a prompt identification of the causative agent at the new site, a restricted infected area, a highly effective local organization for crop uprooting and biological features of the micro-organism that would guarantee its complete elimination. However, at the time of the first record, these criteria were not met. Interdisciplinary studies showed that a zinc-copper-citric acid biocomplex allowed a consistent reduction of field symptoms and pathogen cell concentration within infected olive trees. In this perspective article, it is briefly described the implementation of control strategies in some olive farms of Salento. The protocol includes spray treatment with the biocomplex during spring and summer, regular pruning of the trees and mowing of soil between February and April to reduce the juvenile of the insect vector(s). Thus far, more than 500 ha have begun to follow this eco-friendly strategy within the “infected” and “containment” areas of Salento.

scholarly journals Cost effective reproduction number based strategies for reducing deaths from COVID-19

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Christopher Thron ◽  
Vianney Mbazumutima ◽  
Luis V. Tamayo ◽  
Léonard Todjihounde
Keyword(s):  
High Risk ◽  
Reproduction Number ◽  
Control Strategies ◽  
Cost Model ◽  
Cost Effective ◽  
Control Measures ◽  
Effective Control ◽  
Target Value ◽  
Heuristic Strategies ◽  
Implementation Costs

AbstractIn epidemiology, the effective reproduction number $R_{e}$ R e is used to characterize the growth rate of an epidemic outbreak. If $R_{e} >1$ R e > 1 , the epidemic worsens, and if $R_{e}< 1$ R e < 1 , then it subsides and eventually dies out. In this paper, we investigate properties of $R_{e}$ R e for a modified SEIR model of COVID-19 in the city of Houston, TX USA, in which the population is divided into low-risk and high-risk subpopulations. The response of $R_{e}$ R e to two types of control measures (testing and distancing) applied to the two different subpopulations is characterized. A nonlinear cost model is used for control measures, to include the effects of diminishing returns. Lowest-cost control combinations for reducing instantaneous $R_{e}$ R e to a given value are computed. We propose three types of heuristic strategies for mitigating COVID-19 that are targeted at reducing $R_{e}$ R e , and we exhibit the tradeoffs between strategy implementation costs and number of deaths. We also consider two variants of each type of strategy: basic strategies, which consider only the effects of controls on $R_{e}$ R e , without regard to subpopulation; and high-risk prioritizing strategies, which maximize control of the high-risk subpopulation. Results showed that of the three heuristic strategy types, the most cost-effective involved setting a target value for $R_{e}$ R e and applying sufficient controls to attain that target value. This heuristic led to strategies that begin with strict distancing of the entire population, later followed by increased testing. Strategies that maximize control on high-risk individuals were less cost-effective than basic strategies that emphasize reduction of the rate of spreading of the disease. The model shows that delaying the start of control measures past a certain point greatly worsens strategy outcomes. We conclude that the effective reproduction can be a valuable real-time indicator in determining cost-effective control strategies.

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