2,370 research outputs found
Study of Mathematical Modeling for Plant Disease Transmission: A Systematic Literature Review during 2012-2022
Many models representing disease transmission have been constructed and analyzed mathematically. However, literature studies on the mathematical models for vector-borne disease are sparse, especially on the plant disease transmission model. This study aims to obtain information about the research conducted and find room for developing the model, including mathematical analysis, intervention used, and biological factors considered. We employ a Systematic Literature Review (SLR) to explore all of the studies on plant disease transmission modeling collected from four digital databases. First, the JabRef reference manager helps conduct the inclusion and exclusion processing. Then, we obtain 60 selected articles that passed the criterion. Next, the VOSviewer application is resulting a bibliometric analysis of the database containing chosen articles. Finally, we classify the model constructed based on the system used and elaborate on the intervention used. The results show that the existing researcher clusters are not linked to each other, and the models only consider usual interventions such as roguing and insecticide spraying. Hence, there is much room to build collaboration between the researcher and develop models for plant disease transmission by considering the other various intervention and biological factors in the model to improve further
Managing Economic Risk from Invasive Species: Bug Options
Invasive insect species cause billions of dollars of direct and indirect damage to U.S. crops each year. The market for insuring insect damage is, however, far from complete. The objective of this study is to design and value insect derivatives, or "bug options," which would offer growers a market-based means for transferring risk of pest damage to speculators or others who may profit from higher insect populations. A bug option valuation model is developed and applied to Bemesia tabaci infestation in cotton. The results show that insect derivatives may become important risk management tools for a wide range of growers.Risk and Uncertainty,
A threshold policy to interrupt transmission of West Nile Virus to birds
This paper proposes a model of West Nile Virus (WNV) with a Filippov-type control strategy of culling mosquitoes implemented once the number of infected birds exceeds a threshold level. The long-term dynamical behaviour of the proposed non-smooth system is investigated. It is shown hat as the threshold value varies, model solutions ultimately approach either one of two endemic equilibria for two subsystems or a pseudo-equilibrium on the switching surface, which is a novel steady state. The results indicate that a previously chosen level of infected birds can be maintained when the threshold policy and other parameters are chosen properly. Numerical studies show that under the threshold policy, strengthening mosquito culling together with protecting bird population is beneficial to curbing the spread of WNV
Development of West Nile virus candidate vaccines in Nicotiana benthamiana
West Nile virus (WNV) is a widely disseminated flavivirus, with a geographical range that now includes Africa, America, Europe, the Middle East, West Asia and Australia. The virus is vectored by Culex mosquitoes and is maintained in a bird-mosquito transmission cycle with hundreds of bird species acting as reservoir hosts. In humans, infections can develop into febrile illness and severe meningoencephalitis and to date, there is no treatment or vaccine available. In horses, approximately 20% of infections are symptomatic, of which 90% of cases involve neurological disease, with 30-40% fatality rates. Several veterinary vaccines specific to the lineage 1 WNV strains are commercially produced in America and Europe, however, these vaccines are not easily obtainable for low and middle-income countries (LMIC) due to their high cost and that associated with importation as well as the need for annual vaccination. Due to continuous global disease outbreaks in birds, humans and horse populations with no preventative measures for humans, WNV poses a major public health threat, especially in naïve populations. The development of a vaccine that contributes to the ‘One Health' Initiative could be the answer to prevent the spread of the virus and control the disease. Current veterinary vaccines are produced in expensive cell culture systems that require sterile conditions, high-level biosafety facilities and trained personnel for their preparation. Transient plant-based expression systems have proven to be a very cost-effective means of making complex proteins. Plants can produce and modify proteins in a similar manner to mammalian cells and production does not require sterile conditions or specialised facilities. We propose that plants could be a viable means of making feasible, low-cost reagents for WNV, specifically virus-like particles (VLPs) for use as vaccines in South Africa and other LMIC. In this study, we set out to develop two particulate candidate vaccines based on a virulent South African WNV strain using Nicotiana benthamiana as the expression platform. We aimed to develop the first candidate vaccine by exploiting the virus's ability to form noninfectious VLPs by expressing only the WNV membrane (prM – precursor, M – matured) and envelope (E) proteins. Infiltration of these recombinant plasmids into plants yielded no protein expression unless co-expressed with the human chaperone protein calnexin (CNX), upon which expression of both M and E proteins were observed. We investigated the assembly of prM and E into VLPs by transmission electron microscopy (TEM), however, purification of these particles proved difficult with poor reproducibility and VLP yield. This led to the development of an alternative candidate vaccine making use of the antigendisplay technology based on the SpyTag (ST) and SpyCatcher (SC) peptides. The immunodominant epitope of the WNV E protein, domain III (EdIII), was selected for antigen display. Two constructs of the EdIII gene were generated, one with the SC peptide on the 5'- (SC-EdIII) and the other on the 3' end (EdIII-SC). Both SC-EdIII and EdIII-SC proteins were successfully expressed in the presence of the human chaperone protein calreticulin, and purified with yields of 9 mg/kg and 69 mg/kg fresh leaf weight (FLW), respectively. The VLP core selected for the display of the SC-linked EdIII proteins comprised the coat protein of the bacteriophage AP205 with the ST peptide linked to its N-terminus (ST-AP205). Spytagged-VLPs were purified by density gradient ultracentrifugation at a yield of approximately 50 mg/kg FLW. The purified SC-linked EdIII proteins and ST-AP205 VLPs were coupled in vitro, but successful complex formation of AP205:EdIII was only observed between ST-AP205 and EdIII-SC and not when the SC peptide was located on the N-terminus of EdIII. We further demonstrated the successful complex formation of AP205:EdIII in vivo by coinfiltration of the EdIII-SC and ST-AP205 constructs, as well as by extracting leaves of plants infiltrated individually with either of the constructs. Due to the ease of purification and the high yields of AP205:EdIII achieved, the co-extraction process was optimised to obtain the best coupling yield possible by evaluating different FLW extraction ratios and the formation of VLPs was confirmed by TEM. The optimal co-extraction process was established at a FLW ratio of 1:2 ST-AP205 to EdIII-SC yielding approximately 23 mg/kg AP205:EdIII/FLW processed. In this study, we describe the successful production of two particulate candidate vaccines. The first is based on the expression of the WNV prM and E genes in the presence of human CNX and the second is based on the ST/SC antigen-display technology. These outcomes exhibit the potential plants have of being used as biofactories for making significant pharmaceutical products for the ‘One Health' Initiative and could be used to address the need for their local production in LMIC
A baseline appraisal of water-dependant ecosystem services, the roles they play within desakota livelihood systems and their potential sensitivity to climate change
This report forms part of a larger research programme on 'Reinterpreting the Urban-Rural Continuum', which conceptualises and investigates current knowledge and research gaps concerning 'the role that ecosystems services play in the livelihoods of the poor in regions undergoing rapid change'. The report aims to conduct a baseline appraisal of water-dependant ecosystem services, the roles they play within desakota livelihood systems and their potential sensitivity to climate change. The appraisal is conducted at three spatial scales: global, regional (four consortia areas), and meso scale (case studies within the four regions). At all three scales of analysis water resources form the interweaving theme because water provides a vital provisioning service for people, supports all other ecosystem processes and because water resources are forecast to be severely affected under climate change scenarios. This report, combined with an Endnote library of over 1100 scientific papers, provides an annotated bibliography of water-dependant ecosystem services, the roles they play within desakota livelihood systems and their potential sensitivity to climate change.
After an introductory, section, Section 2 of the report defines water-related ecosystem services and how these are affected by human activities. Current knowledge and research gaps are then explored in relation to global scale climate and related hydrological changes (e.g. floods, droughts, flow regimes) (section 3). The report then discusses the impacts of climate changes on the ESPA regions, emphasising potential responses of biomes to the combined effects of climate change and human activities (particularly land use and management), and how these effects coupled with water store and flow regime manipulation by humans may affect the functioning of catchments and their ecosystem services (section 4). Finally, at the meso-scale, case studies are presented from within the ESPA regions to illustrate the close coupling of human activities and catchment performance in the context of environmental change (section 5). At the end of each section, research needs are identified and justified. These research needs are then amalgamated in section 6
Topographic effects on dispersal patterns of Phytophthora cinnamomi at a stand scale in a Spanish heathland
Phytophthora cinnamomi es uno de los patógenos de plantas más importantes del mundo, causando la putrefacción de las raíces en más de mil especies de plantas. Este estudio de observación se llevó a cabo en un brezal infectado con P. cinnamomi de Erica umbellata utilizado como pasto para cabras. Los patrones y formas de los focos de la enfermedad y su distribución se describieron en un contexto espacial y temporal mediante un registro de fotografías aéreas. Se seleccionó un conjunto de rasgos topográficos sobre la base de una hipótesis de dinámica de la enfermedad y se analizaron sus efectos en los patrones espaciales de la enfermedad observados. Las infecciones incipientes situadas en terreno llano se expandieron como patrones de frente circular compacto con una baja tasa de crecimiento. En las laderas, los parches de la enfermedad se desarrollaron más rápidamente en la pendiente, formando formas parabólicas. La dirección del eje de las parábolas estaba altamente correlacionada con el aspecto del terreno, mientras que la amplitud parabólica se asociaba con la curvatura y la pendiente del terreno. Con el paso de los años aparecieron nuevos focos secundarios que produjeron un aumento acelerado de la superficie afectada. Estos nuevos focos se observaron en sitios donde la densidad de la enfermedad era mayor o cerca de sitios más frecuentemente visitados por animales como el establo o el cultivo de forraje. Por el contrario, un menor número de focos de enfermedad se producen en zonas que los animales son reacios a visitar, por ejemplo, donde tienen un corto alcance de visión. Nuestros resultados sugieren que 1) el crecimiento de los focos existentes de P. cinnamomi se controla mediante una combinación de contacto de raíz a raíz y flujos de agua, 2) el aumento del área enferma surge principalmente de la multiplicación de parches, 3) la formación de nuevos focos está mediada por el transporte a larga distancia debido al movimiento de animales y humanos a lo largo de ciertas rutas preferenciales, y 4) los rasgos de geomorfología y topografía están asociados con la epidemiología de este patógeno transmitido por el suelo.Phytophthora cinnamomi is one of the most important plant pathogens in the world, causing root rot in more than a thousand plant species. This observational study was carried out on a P. cinnamomi infected heathland of Erica umbellata used as goat pasture. The patterns and shapes of disease foci and their distribution were described in a spatial and temporal context using an aerial photograph record. A set of topographic traits was selected on the basis of a disease dynamic hypothesis and their effects on observed spatial disease patterns were analyzed. Incipient infections situated in flat terrain expanded as compact circular front patterns with a low growth rate. On slopes, disease patches developed more rapidly down slope, forming parabolic shapes. The axis direction of the parabolas was highly correlated with terrain aspect, while the parabolic amplitude was associated with land curvature and slope. New secondary foci appeared over the years producing an accelerated increase of the affected surface. These new foci were observed in sites where disease density was higher or near sites more frequently visited by animals such as the stable or the forage crop. In contrast, a smaller number of disease foci occur in areas which animals are reluctant to visit, such as where they have a short range of vision. Our results suggest that 1) the growth of existing P. cinnamomi foci is controlled by a combination of root-to-root contact and wáter flows, 2) the increase in the diseased area arises mainly from the multiplication of patches, 3) the formation of new foci is mediated by long-distance transport due to the movement of animals and humans along certain preferential pathways, and 4) geomorphology and topography traits are associated with the epidemiology of this soil-borne pathogen.• Gobierno de Extremadura. Ayuda
• Ministerio de Economía y Competitividad. Proyecto FIS2016-76359-P, para Enrique Alfonso Abad JarillopeerReviewe
Linkages Between Extreme Precipitation, Water Quality, and Gastrointestinal Illness.
Background: The frequency, intensity, and duration of extreme weather events are expected to increase based on current climate model projections. Such changes, particularly those associated with extreme precipitation, will likely threaten water quality and exacerbate global health disparities. Vulnerable subpopulations include children, the elderly, and the poor.
Objectives: This dissertation evaluates the association between extreme precipitation and hospital admissions among: 1) a population in Chennai, India during 2004-2007, 2) the elderly in the Great Lakes Region in relation to beach closures during 2000-2006, and 3) the elderly in 132 U.S. cities during 1992-2006.
Methods: Daily hospital admissions were merged with daily meteorological data. Hospital admissions were examined for seasonal trends. Poisson regression and case-crossover models were fit to evaluate the association between extreme precipitation and daily hospital admissions. Season and age were explored as potential effect modifiers.
Results: In India, extreme precipitation (greater than or equal to the 90th percentile) was positively associated with hospital admissions related to gastrointestinal illness (GI). The cumulative risk, estimated over a 15-day lag period, was 1.61 (95% confidence interval (CI): 1.29, 2.00) and was elevated among the young 2.65 (95% CI: 1.21, 5.80) and the old 1.68 (95% CI: 1.01, 2.80). Risk varied across seasons, peaking during pre-monsoon 1.58 (95% CI: 1.24, 1.90). In the Great Lakes Region, beaches were closed 10% of summer days. Precipitation above the 90th percentile at lag 1 significantly predicted (p <0.05) beach closures in 8 of the 12 cities. No consistent associations between beach closures and hospital admissions were seen when pooled across the 12 cities, 0.98 (95% CI: 0.94, 1.01). In 132 U.S. cities, nearly 1 million GI-related hospital admissions occurred. Overall, no positive associations between extreme precipitation and GI-related hospital admissions were observed. The overall national pooled estimate for risk of GI-related hospital admission at lag 15 was 1.01 (95% CI: 1.00, 1.02).
Conclusions: This work highlights the potential impacts of climate change on waterborne disease in the U.S. and India. The threat of more extreme weather events necessitates further study of how climate and weather are associated with hospital admissions and overall health.Ph.D.Environmental Health SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91518/1/kfbush_1.pd
2013 Conference Abstracts: Annual Undergraduate Research Conference at the Interface of Biology and Mathematics
URC Schedule and Abstract Book for the Fifth Annual Undergraduate Research Conference at the Interface of Biology and Mathematics
Date: November 16-17, 2013Plenary Speaker: Mariel Vazquez, Associate Professor of Mathematics at San Francisco State UniversityFeatured Speaker: Andrew Liebhold, Research Entomologist for the USDA Forest Servic
Transcriptional cellular responses in midgut tissue of Aedes aegypti larvae following intoxication with Cry11Aa toxin from Bacillus thuringiensis.
BackgroundAlthough much is known about the mechanism of action of Bacillus thuringiensis Cry toxins, the target tissue cellular responses to toxin activity is less understood. Previous transcriptomic studies indicated that significant changes in gene expression occurred during intoxication. However, most of these studies were done in organisms without a sequenced and annotated reference genome. A reference genome and transcriptome is available for the mosquito Aedes aegypti, and its importance as a disease vector has positioned its biological control as a primary health concern. Through RNA sequencing we sought to determine the transcriptional changes observed during intoxication by Cry11Aa in A. aegypti and to analyze possible defense and recovery mechanisms engaged after toxin ingestion.ResultsIn this work the changes in the transcriptome of 4(th) instar A. aegypti larvae exposed to Cry11Aa toxin for 0, 3, 6, 9, and 12 h were analyzed. A total of 1060 differentially expressed genes after toxin ingestion were identified with two bioconductoR packages: DESeq2 and EdgeR. The most important transcriptional changes were observed after 9 or 12 h of toxin exposure. GO enrichment analysis of molecular function and biological process were performed as well as Interpro protein functional domains and pBLAST analyses. Up regulated processes include vesicular trafficking, small GTPase signaling, MAPK pathways, and lipid metabolism. In contrast, down regulated functions are related to transmembrane transport, detoxification mechanisms, cell proliferation and metabolism enzymes. Validation with RT-qPCR showed large agreement with Cry11Aa intoxication since these changes were not observed with untreated larvae or larvae treated with non-toxic Cry11Aa mutants, indicating that a fully functional pore forming Cry toxin is required for the observed transcriptional responses.ConclusionsThis study presents the first transcriptome of Cry intoxication response in a fully sequenced insect, and reveals possible conserved cellular processes that enable larvae to contend with Cry intoxication in the disease vector A. aegypti. We found some similarities of the mosquito responses to Cry11Aa toxin with previously observed responses to other Cry toxins in different insect orders and in nematodes suggesting a conserved response to pore forming toxins. Surprisingly some of these responses also correlate with transcriptional changes observed in Bti-resistant and Cry11Aa-resistant mosquito larvae
Data mining techniques on satellite images for discovery of risk areas
The high rates of cholera epidemic mortality in less developed countries is a challenge for health fa- cilities to which it is necessary to equip itself with the epidemiological surveillance. To strengthen the capacity of epidemiological surveillance, this paper focuses on remote sensing satellite data processing using data mining methods to discover risk areas of the epidemic disease by connecting the environ- ment, climate and health. These satellite data are combined with field data collected during the same set of periods in order to explain and deduct the causes of the epidemic evolution from one period to another in relation to the environment. The existing technical (algorithms) for processing satellite im- ages are mature and efficient, so the challenge today is to provide the most suitable means allowing the best interpretation of obtained results. For that, we focus on supervised classification algorithm to process a set of satellite images from the same area but on different periods. A novel research method- ology (describing pre-treatment, data mining, and post-treatment) is proposed to ensure suitable means for transforming data, generating information and extracting knowledge. This methodology consists of six phases: (1.A) Acquisition of information from the field about epidemic, (1.B) Satellite data acquisition, (2) Selection and transformation of data (Data derived from images), (3) Remote sensing measurements, (4) Discretization of data, (5) Data treatment, and (6) Interpretation of results. The main contributions of the paper are: to establish the nature of links between the environment and the epidemic, and to highlight those risky environments when the public awareness of the problem and the prevention policies are absolutely necessary for mitigation of the propagation and emergence of the epidemic. This will allow national governments, local authorities and the public health officials to effective management according to risk areas. The case study concerns the knowledge discovery in databases related to risk areas of the cholera epidemic in Mopti region, Mali (West Africa). The results generate from data mining association rules indicate that the level of the Niger River in the wintering periods and some societal factors have an impact on the variation of cholera epidemic rate in Mopti town. More the river level is high, at 66% the rate of contamination is high
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