SEIR Model and Simulation for Vector Borne Diseases

An epidemic model is a simplified means of describing the transmission of infectious diseases through individuals. The modeling of infectious diseases is a tool which has been used to study the mechanisms by which diseases spread, to predict the future course of an outbreak and to evaluate strategies to control an epidemic. Epidemic models are of many types. Here, SEIR model is discussed. We first discuss the basics of SEIR model. Then it is applied for vector borne diseases. Steady state conditions are derived. A threshold parameter R0 is defined and is shown that the disease will spread only if its value exceeds 1. We have applied the basic model to one specific diseases-malaria and did the sensitivity analysis too using the data for India. We found sensitivity analysis very important as it told us the most sensitive parameter to be taken care of. This makes the work more of practical use. Numerical simulation is done for vector and host which shows the population dynamics in different compartments.

Evaluation of the Protection against Infectious Bursal Disease (IBD) Challenge in Progeny Born to Parents Having Received a Vaccination Program Using a Herpesvirus of Turkey-Infectious Bursal Disease (HVT-IBD) Vector Vaccine

Broiler breeder vaccination against IBD is usually based on the injection of at least one inactivated vaccine in oil adjuvant, typically included in a combined vaccine. Priming using one or several IBD vaccine (s) has been the most common way to immunize the breeders so far. In summary, protection against vvIBD challenge in chicks of one commercial genetic line vaccinated in ovo with the HVT-IBD vector vaccine was demonstrated. The parents’ IBD vaccination program, using the HVT-IBD vector vaccine alone, the HVT-IBD vector vaccine plus IBD inactivated vaccine, and inactivated IBD vaccine alone, did not impair their progeny’s in ovo HVT-IBD vector vaccine take and subsequent protection against vvIBD virus challenge. An advantage in terms of immunization of the progeny against vvIBD was shown in the chicks born to breeders vaccinated with the HVT-IBD vaccine as a primer, as compared to breeders vaccinated with the inactivated vaccine alone. High level of IBD maternally-derived antibodies transmitted to the progeny by their parents induces together with an early onset of immunity by in ovo injection of a HVT-IBD vector vaccine clinical protection, as monitored on bursas, after vvIBD virus challenge.

An Agent-Based Model for Studying the Impact of Herd Mobility on the Spread of Vector-Borne Diseases: The Case of Rift Valley Fever (Ferlo Senegal)

Vector-borne diseases are highly sensitive to environment and to environmental changes. Rift Valley Fever (RFV) is a mosquito-borne zootic virus associated with severe diseases in human beings and economic consequences to livestock sector. Animal and human movements have a fundamental impact on RVF transmission. In recent years, there has been a growing interest in the use of mathematics and agent based models to represent and analyze the dynamic of RFV transmission. However, no previous study has taken into consideration animal herds’ mobility and precipitation factors to understand the disease spread. This limitation underlines the necessity to use computational model approach based on multi-agent system in the study of vector-borne diseases transmission and diffusion. In this paper, a multi-agent system combining conceptual model expressiveness is used to study animal herds’ mobility and the precipitation parameter impact on the Rift Valley Fever outbreak in Ferlo Barkedji in Northern Senegal. Simulation scenarios with various parameters, including rain quality, hosts, vectors, camp dispersal around ponds, etc., are unrolled. The different results we have obtained show that the evolution of the number of infected hosts and infected vectors depend on the degree of animal herds’ mobility and on precipitations. Our model provides a framework that permits predicting the spread of the disease associated with the mobility of animal herds.

Asymptotic Analysis of a Stochastic Model of Mosquito-Borne Disease with the Use of Insecticides and Bet Nets

Ross’ epidemic model describing the transmission of malaria uses two classes of infection, one for humans and one for mosquitoes. This paper presents a stochastic extension of a deterministic vector-borne epidemic model based only on the class of human infectious. The consistency of the model is established by proving that the stochastic delay differential equation describing the model has a unique positive global solution. The extinction of the disease is studied through the analysis of the stability of the disease-free equilibrium state and the persistence of the model. Finally, we introduce some numerical simulations to illustrate the obtained results.

Serological investigation of vector-borne disease in dogs from rural areas of China

Objective:To evaluate the Anaplasma phagocytophilum(A.phagocytophilum),Ehrlichia canis(E.canis,Dirofilaria immitis(D.immitis)(canine heartworm),Borrelia burgdorferi(B.burgdorferi)infections in countryside dogs from Yunnan,Hainan and Anhui provinces.Methods:Serum samples were collected from 26 dogs in Yunnan.Hainan and Anhui provinces.The samples were tested using a commercial ELISA rapid diagnostic assay kit(SNAP^(?)4Dx^(?);IDEXX Laboratories,Inc.U.S.A.).Meaiiwliile,indirect immunofluorescence assay(IFA)recommended by WHO was conducted to delect IgG to A.phagocytophilum.Two methods were analyzed and compared.Results:The number of serologically positive dogs for IgG to A.phagocytophilum was only 2which was from Hainan province and none of the 26 dogs responded positive for E.canu.D.immitis(canine heartworm,and B.burgdorferi by ELISA rapid diagnostic method.The number of serologically positive dogs for IgG to A.phagocytophilum was 13(50%)by IFA method.Data of the two methods were analyzed by statistical software and the difference was statistically significant(P=0.002).Conclusions:It can be concluded that IFA method was more sensitive than ELISA rapid diagnostic method.However,we need conduct further and intensive epidemiology survey on tick-born diseases pathogens including.4.phagocytophilum,E.canis,D.immitis(canine heartworm),and B.burgdorferi which have public health significance.

Global Dynamic Analysis of a Vector-Borne Plant Disease Model with Discontinuous Treatment

This paper proposes a vector-borne plant disease model with discontinuous treatment strategies. Constructing Lyapunov function and applying non-smooth theory to analyze discontinuous differential equations, the basic reproductive number R0 is proved, which determines whether the plant disease will be extinct or not. If R0 R0 > 1 , there exists a unique endemic equilibrium which is globally stable. The numerical simulations are provided to verify our theoretical results, which indicate that after infective individuals reach some level, strengthening treatment measures is proved to be beneficial in controlling disease transmission.

Dynamic of Non-Autonomous Vector Infectious Disease Model with Cross Infection

In the article, we established a non-autonomous vector infectious disease model, studied the long-term dynamic behavior of the system, and obtained sufficient conditions for the extinction and persistence of infectious diseases by constructing integral functions.

Effective Control Strategies on the Transmission Dynamics of a Vector-Borne Disease

In this paper, we have rigorously analyzed a model to find the effective control strategies on the transmission dynamics of a vector-borne disease. It is proved that the global dynamics of the disease are completely determined by the basic reproduction number. The numerical simulations (using MatLab and Maple) of the model reveal that the precautionary measures at the aquatic and adult stage decrease the number of new cases of dengue virus. Numerical simulation indicates that if we take the precautionary measures seriously then it would be more effective than even giving the treatment to the infected individuals.

Vector-borne disease and climate change adaptation in African dryland socialecological systems

Background:Drylands,which are among the biosphere's most naturally limiting and environmentally variable ecosystems,constitute three-quarters of the African continent.As a result,environmental sustainability and human development along with vector-borne disease(VBD)control historically have been especially challenging in Africa,particularly in the sub-Saharan and Sahelian drylands.Here,the VBD burden,food insecurity,environmental degradation,and social vulnerability are particularly severe.Changing climate can exacerbate the legion of environmental health threats in Africa,the social dimensions of which are now part of the international development agenda.Accordingly,the need to better understand the dynamics and complex coupling of populations and environments as exemplified by drylands is increasingly recognized as critical to the design of more sustainable interventions.Main body:This scoping review examines the challenge of vector-borne disease control in drylands with a focus on Africa,and the dramatic,ongoing environmental and social changes taking place.Dryland societies persisted and even flourished in the past despite changing climates,extreme and unpredictable weather,and marginal conditions for agriculture.Yet intrusive forces largely out of the control of traditional dryland societies,along with the negative impacts of globalization,have contributed to the erosion of dryland's cultural and natural resources.This has led to the loss of resilience underlying the adaptive capacity formerly widely exhibited among dryland societies.A growing body of evidence from studies of environmental and natural resource management demonstrates how,in light of dryland system's inherent complexity,these factors and top-down interventions can impede sustainable development and vector-borne disease control.Strengthening adaptive capacity through community-based,participatory methods that build on local knowledge and are tailored to local ecological conditions,hold the best promise of reversing current trends.Conclusions:A significant opportunity exists to simultaneously address the increasing threat of vector-borne diseases and climate change through methods aimed at strengthening adaptive capacity.The integrative framework and methods based on social-ecological systems and resilience theory offers a novel set of tools that allow multiple threats and sources of vulnerability to be addressed in combination.Integration of recent advances in vector borne disease ecology and wider deployment of these tools could help reverse the negative social and environmental trends currently seen in African drylands.

Investigation of Spatial Risk Factors for RVF Disease Occurrence Using Remote Sensing &GIS—A Case Study: Sinnar State, Sudan

Rift Valley Fever (RVF) is an emerging, mosquito-borne disease with serious economical and negative implications on human and animal health. This study was conducted to verify the factors which influenced the spatial pattern of Rift Valley Fever occurrence and identified the high risk areas for the occurrence of the disease at Sinner State, Sudan. The normalized difference vegetation index (NDVI) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite and rainfall data in addition to the point data of RVF clinical cases in humans were used in this study. In order to identify the RVF high risk areas, remote sensing data and rainfall data were integrated in a GIS with other information including, soil type, water body, DEM (Digital Elevation Model), and animal routes and analyzed using Spatial Analysis tools. The information on clinical cases was used for verification. The Normalized Difference Vegetation Index (NDVI) was used to describe vegetation patterns of the study area by calculating the mean NDVI. The results of the study showed that, RVF risk increased with the increase in vegetation cover (high NDVI values), and increase in rainfall, which both provided suitable conditions for disease vectors breeding and a good indicator for RVF epizootics. The study concluded that, identification of high risk area for RVF disease improved the understanding of the spatial distribution of the disease and helped in locating the areas where disease was likely to be endemic and therefore preparedness measures should be taken. The identification represents the first step of prospective predictions of RVF outbreaks and provides a baseline for improved early warning, control, response planning, and mitigation. Further detailed studies are recommended in this domain.

Laboratory Diagnosis of Dengue Infection: Current Techniques and Future Strategies

Dengue is an increasingly significant vector-borne infectious disease, with over 50 million cases reported in more than half the world’s recognised independent states. Dengue fever, dengue haemorrhagic fever and dengue shock syndrome are distinct clinical forms of an infection that is caused by Dengue Virus, a member of the Flaviviridae family. All four well characterized serotypes of the virus can cause the full spectrum of disease from asymptomatic infection to life-threatening symptoms. For effective prevention and/or treatment of disease symptoms, early and rapid detection of virus in specimens collected from clinically suspected persons is a requirement that remains challenging. A positive laboratory diagnosis is essential to confirm dengue virus infection and hence to inform patient therapy. Here, we consider the pros and cons of currently available methods for identification, ranging from conventional to sophisticated tests. Reports indicate the use of a variety of diagnostic methods of varying sensitivity, highlighting the necessity for standardisation and quality control. Several novel approaches are in development and demand further evaluation.

临床输血科经血传播相关病原体分子生物学检测规范管理中国专家共识

为了减少医疗机构院内交叉感染,降低医护人员的职业暴露风险,提高经血传播性疾病溯源性,确保临床输血安全,规避医患纠纷,中国输血协会临床输血管理学专业委员会结合国内外临床研究成果和相关规范指南,召集了临床输血、感染病学等领域的专家共同制定了此专家共识。以期能够规范临床输血科开展经血传播相关病原体分子生物学检测相关规则,降低经血传染性疾病发生率。

病毒载体疫苗研究进展

近十年来,中东呼吸综合征、埃博拉出血热、寨卡病毒感染、新型冠状病毒肺炎等重大传染性疾病疫情相继出现,对疫苗的快速研发提出重大挑战。其中病毒载体疫苗是新型疫苗研发的重要形式,它可以通过雾化吸入或口服等方式进行无创免疫,在没有佐剂的情况下发挥免疫作用,同时诱导体液、细胞和黏膜免疫反应,具有良好的免疫原性和安全性。随着对病毒基因组和结构蛋白等元件认识的不断深入,利用合成生物学研究思路系统设计、改造病毒载体,从而赋予重组病毒载体疫苗高滴度生产、高安全性和高免疫原性等生物学特征,对疫苗研发具有重要指导意义。本文综述了复制型、非复制型等病毒载体疫苗研发策略,以及具有临床应用价值的疫苗病毒载体,如腺病毒载体、痘病毒载体、水疱性口炎病毒载体等,希望对利用合成生物学进行新型病毒载体疫苗的研发提供一定的参考。未来,病毒载体疫苗必将向着更高的安全性、更强的保护性、更好的依从性、更低的生产成本等方向迭代发展。

外泌体在蚊媒黄病毒感染中的调控作用研究

外泌体是一种广泛存在于人体体液中的由真核细胞分泌的一种细胞外囊泡,直径30~100nm。根据其生物发生和结构的特性,外泌体可以携带宿主细胞中的生物信息物质至其他细胞,在细胞间通信、生理病理反应中起着重要作用。受全球气候环境影响,蚊媒传染病逐渐对人类健康造成威胁,其中一种重要的病原体为黄病毒科病毒,包括登革病毒、寨卡病毒和流行性乙型脑炎病毒等。外泌体在黄病毒感染的过程中起着至关重要的作用,可促进病毒传播或激活宿主的免疫反应对抗病毒。本文主要总结了外泌体在蚊媒黄病毒科病毒感染中发挥调控作用的研究进展,以便更深入地了解病毒与宿主细胞的相互作用,从而开发出可作为防治蚊媒传染病的候选细胞靶点。

具有环境传播和复发的年龄结构传染病模型研究

基于潜伏者、恢复者和环境中病原体的舱室年龄(即类年龄结构),提出了一类具有环境传播和复发的多组类年龄结构媒介传染病模型,给出了基本再生数R_(0)的准确表达式,并通过构造Lyapunov函数研究模型的全局动力学.结果表明:当R_(0)<1时,无病平衡点是全局渐近稳定的;当R_(0)>1时,地方病平衡点是全局渐近稳定的.

具有媒体报道和个人防护意识的多时滞媒介传染病模型Hopf分支分析

考虑到媒体报道、个人防护意识和时滞效应对媒介传染病传播与防控的影响,建立一类具有媒体报道延迟和潜伏期时滞影响的媒介传染病模型.首先,给出基本再生数的精确表达式,并用其刻画平衡态的存在性与稳定性,以及Hopf分支的存在性.即,当基本再生数小于1时,媒体报道延迟和病原体在媒介体内的潜伏期时滞不会影响模型无病平衡点的稳定性,而当基本再生数大于1时,媒体报道的延迟会影响地方病平衡点的稳定性,模型会产生Hopf分支.进一步,通过使用分支定理讨论Hopf分支的方向并得到周期解稳定性的充分条件.最后,通过一些数值算例解释主要的理论结果.

县级医院护理人员血源性传染病职业暴露现状调查

目的 了解涡阳县县级公立医院护理人员发生血源性传染病职业暴露的现状及其影响因素,为制定该人群的干预措施提供依据。方法 对涡阳县县级公立医院的在职护理人员开展职业暴露问卷调查。结果 共调查655名在职护理人员。从执业开始至今发生过职业暴露的为20.61%,近1年发生过职业暴露的为6.11%。多因素logistic回归分析显示,本科及以上文化程度、工龄越长、最近1年发生过割伤、黏膜暴露的护理人员更容易发生血源性传染病职业暴露;手术室、传染科以及大内科的护理人员相比其他科室更容易发生血源性传染病职业暴露。结论 涡阳县县级公立医院护理人员发生血源性传染病职业暴露的风险较高。医院应继续完善院感防控工作,加强护理操作流程的标准化建设,规范开展护理工作,进一步降低护理人员血源性传染病的职业暴露风险。

On the Range of Action of Adult Culex pipiens s.l.

Mosquitoes are an interesting topic due to their medical importance, as they play an active role in the transmission of many pathogens and parasites, acting as vectors for various pathologies that are deadly to humans, such as dengue, yellow fever, chikungunya, West Nile virus, encephalitis and malaria, among many others that are less common. In terms of morbidity and mortality caused by vector-borne diseases, mosquitoes are the most dangerous animals for humanity and, although they also play a role in the ecosystem as a food source for other organisms, their importance for public health cannot be overlooked. As highly efficient vectors, they put more than three billion people at risk, mainly in tropical and subtropical regions as well as in Europe, since heat waves and flooding are becoming more frequent and severe, and summers are getting longer and warmer, accelerating mosquito development, biting rates, and the incubation of the pathogens within their bodies. Female mosquitoes bite to acquire proteins for the development of their ovaries and eggs and, in the process, acquire pathogens and/or parasites from one vertebrate host and transmit them to another, usually after a short period of replication. Three of their four life stages are lived in still freshwater, so it is crucial to understand their range of action when they reach adulthood and leave the water, in order to plan and implement local prevention measures. A set of georeferenced abundance data collected in mainland Portugal over seven years was linked to cartographed water bodies in a geographic information system to estimate the distances at which Culex pipiens s.l. had a significant presence, with criteria based on the size of the catches. The result allows for an estimate of the fly range of those mosquitoes, which can be used to focus countermeasures.

济源市2019年至2022年蚊虫监测结果及蚊媒传染病流行病学分析

目的探讨济源市2019年至2022年蚊虫监测结果及蚊媒传染病流行病学特征。方法2019年至2022年采用诱蚊灯在成蚊活动高峰期捕获成蚊,选择5个监测点,比较不同种类、不同生境蚊虫特点,分析蚊媒传染病流行病特征。结果2019年至2022年济源市共捕获成蚊151只,其中中华按蚊108只,占捕获总数71.52%,为优势蚊种。2019年至2022年济源市居民区、医院、公园、农户、牲畜棚均以中华按蚊为主,构成比分别为62.50%、66.67%、68.18%、72.00%、75.71%,不同生境蚊种构成比差异有统计学意义(χ^(2)=355.999,P<0.05)。2019年至2022年捕获成蚊平均密度3.15,其中2022年成蚊密度水平最低,为0.71只/(灯·h),2020年成蚊密度水平最高,为2.57只/(灯·h)。结论济源市优势蚊种为中华按蚊,牲畜棚是蚊虫侵害高发场所,济源市输入性蚊媒传染病主要病种为疟疾。

国境口岸输入性虫媒传染病及媒介生物风险分析和风险管理系统研究：风险分析

为在口岸传染病防控方面探索新的思路和方法，建立科学的风险评估机制，采用澳大利亚和新西兰联合开发的风险管理标准，对境外的虫媒传染病及其媒介生物传人我国口岸的风险建立评估方法和体系。结果显示，通过对国际国内传染病疫情进行有效评估，分析传染病传播模式和趋势，确定输入输出风险等级和主要防控环节，及时发出预警信息，然后有针对性地在重点地区口岸和重点环节采取措施，能够有效控制媒介生物以及携带病原体的传播。引入风险分析理论，建立风险评估机制，对有效减少传染病疫情所带来的危害，保障我国口岸公共卫生安全十分必要。