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1.
Gustavo Cruz-Pacheco Lourdes Esteva Cristobal Vargas 《Bulletin of mathematical biology》2009,71(6):1378-1393
In this paper we analyze the impact of seasonal variations on the dynamics of West Nile Virus infection. We are interested
in the generation of new epidemic peaks starting from an endemic state. In many cases, the oscillations generated by seasonality
in the dynamics of the infection are too small to be observable. The interplay of this seasonality with the epidemic oscillations
can generate new outbreaks starting from the endemic state through a mechanism of parametric resonance. Using experimental
data we present specific cases where this phenomenon is numerically observed. 相似文献
2.
West Nile virus (WNV) has made considerable impact as an emerging infectious disease, spreading from coast to coast across
North America since 1999. The disease has exhibited great spatial variability in North America, making an ecosystems approach
to understanding the local human and vector ecology critical to prevention and control. This study underscores the importance
of employing both personal prevention and community participatory approaches to create messages that have been adapted to
the local ecology and are designed to reduce the risk of human infection with this mosquito-borne virus. As the virus spreads
into new areas, underlying attitudes toward mosquitoes and the local perception of environment/ecology can affect the success
of control and prevention measures. This work presents results from focus group discussions conducted in two Colorado counties
in 2003, a year of significant WNV activity in the state. Issues addressed include residents’ assessment of risk and how this
perception varied by age group and location, use or nonuse of repellents, and community attitudes toward mosquito control
in areas with different ecologies and histories of mosquito-borne disease. The need to address individual components of personal
prevention, to target prevention to specific audiences, and to disseminate prevention messages through local channels is discussed.
The authors propose including aspects of ecology and disease proximity in understanding risk perception and addressing emerging
diseases with a prominent ecological component. 相似文献
3.
In this work, we propose a spatial model to analyze the West Nile Virus propagation across the USA, from east to west. West Nile Virus is an arthropod-borne flavivirus that appeared for the first time in New York City in the summer of 1999 and then spread prolifically among birds. Mammals, such as humans and horses, do not develop sufficiently high bloodstream titers to play a significant role in the transmission, which is the reason to consider the mosquito-bird cycle. The model aims to study this propagation based on a system of partial differential reaction-diffusion equations taking the mosquito and the avian populations into account. Diffusion and advection movements are allowed for both populations, being greater in the avian than in the mosquito population. The traveling wave solutions of the model are studied to determine the speed of disease dissemination. This wave speed is obtained as a function of the model's parameters, in order to assess the control strategies. The propagation of West Nile Virus from New York City to California state is established as a consequence of the diffusion and advection movements of birds. Mosquito movements do not play an important role in the disease dissemination, while bird advection becomes an important factor for lower mosquito biting rates. 相似文献
4.
Shlomit Paz 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2015,370(1665)
West Nile virus (WNV), the most widely distributed virus of the encephalitic flaviviruses, is a vector-borne pathogen of global importance. The transmission cycle exists in rural and urban areas where the virus infects birds, humans, horses and other mammals. Multiple factors impact the transmission and distribution of WNV, related to the dynamics and interactions between pathogen, vector, vertebrate hosts and environment. Hence, among other drivers, weather conditions have direct and indirect influences on vector competence (the ability to acquire, maintain and transmit the virus), on the vector population dynamic and on the virus replication rate within the mosquito, which are mostly weather dependent. The importance of climatic factors (temperature, precipitation, relative humidity and winds) as drivers in WNV epidemiology is increasing under conditions of climate change. Indeed, recent changes in climatic conditions, particularly increased ambient temperature and fluctuations in rainfall amounts, contributed to the maintenance (endemization process) of WNV in various locations in southern Europe, western Asia, the eastern Mediterranean, the Canadian Prairies, parts of the USA and Australia. As predictions show that the current trends are expected to continue, for better preparedness, any assessment of future transmission of WNV should take into consideration the impacts of climate change. 相似文献
5.
Rania Ali El Hadi Mohamed Deena M. Abdelgadir Hind M. Bashab Laila A. Al-Shuraym Fadilah Sfouq Aleanizy Fulwah Y. Alqahtani Lamya Ahmed Al-Keridis Nahla Mohamed 《Saudi Journal of Biological Sciences》2020,27(12):3359-3364
This study aimed to explore the presence of West Nile Virus (WNV) inside four species of mosquitoes: Culex univittatus (Theobald), Culex quinquefasciatus (Say) Aedes vittatus (Bigot) and Aedes vexans (Meigen). Adult wild mosquitoes were collected from different sites: Soba West, Hellat Kuku, Shambat, and Khartoum North Central Live Stock Market (KCLM). Surveys were carried out at Khartoum State during two phases: pre to the rainy season and post to the rainy season. Mosquito specimens were identified using classical keys then preserved at −80 °C freezer for two weeks till the virus examination using polymerase chain reaction (PCR) were carried out. WNV has been detected inside the three species of mosquitoes: A. vexans, C. univittatus, and C. quinquefasciatus. The species were collected from Hellat Kuku, (Shambat and Hellat Kuku), and (Shambat and KCLM) respectively. Two species of mosquitoes were positive for the virus: C. quinquefasciatus and C. univittatus. Positive results for the virus during the first phase of the study; males of C. quinquefasciatus and C. univittatus collected during the second phase of the study were also tested for the existence of the virus and they were positive. For our knowledge this study represents first record of WNV inside wild mosquitoes in Sudan. PCR technique provided reliable information because specific primer-probe sets were used for the detection of the virus. Extra studies are required to incriminate these species of mosquitoes as potential vectors of WNV. 相似文献
6.
Ravi K. Ujjinamatada Yankanagouda S. Agasimundin Peng Zhang Ramachandra S. Hosmane Roman Schuessler Peter Borowski 《Nucleosides, nucleotides & nucleic acids》2013,32(10-12):1775-1788
The attempted synthesis of a ring-expanded guanosine (1) containing the imidazo[4,5-e][1,3]diazepine ring system by condensation of 1-(2′-deoxy-β-D-erythropentofuranosyl)-4-ethoxycarbonylimidazole-5-carbaldehyde (2) with guanidine resulted in the formation of an unexpected product, 1-(2′-deoxy-β-D-erythropentofuranosyl)-5-(2,4-diamino-3,6-dihydro-1,3,5-triazin-6-yl)imidazole-4-carboxamide (7). The structure as well as the pathway of formation of 7 was corroborated by isolation of the intermediate, followed by its conversion to the product. Nucleoside 7 showed promising in vitro anti-helicase activity against the West Nile virus NTPase/ helicase with an IC 50 of 3-10 μg/mL. 相似文献
7.
Rebecca N. Adamek Roxanne V. Maniquis Sabaha Khakoo Michael D. Bridges Nicholas T. Salzameda 《Bioorganic & medicinal chemistry letters》2013,23(17):4848-4850
The West Nile Virus (WNV) has been a worldwide epidemic since the early 1990s. Currently there are no therapeutic treatments for WNV infections. One particular avenue of treatment is inhibition of the NS2B-NS3 protease, an enzyme that is crucial for WNV replication. In our effort to increase the number of NS2B-NS3 protease inhibitors, we report a novel FRET-based high throughput assay for the discovery of WNV NS2B-NS3 protease inhibitors. For this assay, a FRET-based peptide substrate was synthesized and kinetically characterized with the NS2B-NS3 protease. The new substrate exhibits a Km of 3.35 ± 0.31 μM, a kcat of 0.0717 ± 0.0016 s?1 and a kcat/Km of 21,400 ± 2000 M?1 s?1. 相似文献
8.
A reaction–diffusion model for the spatial spread of West Nile virus is developed and analysed. Infection dynamics are based on a modified version of a model for cross infection between birds and mosquitoes (Wonham et al., 2004, An epidemiological model for West-Nile virus: Invasion analysis and control application. Proc. R. Soc. Lond. B 271), and diffusion terms describe movement of birds and mosquitoes. Working with a simplified version of the model, the cooperative nature of cross-infection dynamics is utilized to prove the existence of traveling waves and to calculate the spatial spread rate of infection. Comparison theorem results are used to show that the spread rate of the simplified model may provide an upper bound for the spread rate of a more realistic and complex version of the model. 相似文献
9.
Utility of early‐season mosquito surveillance to predict West Nile virus activity in late summer was assessed in Suffolk County, NY. Dry ice‐baited CDC miniature light traps paired with gravid traps were set weekly. Maximum‐likelihood estimates of WNV positivity, minimum infection rates, and % positive pools were generally well correlated. However, positivity in gravid traps was not correlated with positivity in CDC light traps. The best early‐season predictors of WNV activity in late summer (estimated using maximum‐likelihood estimates of Culex positivity in August and September) were early date of first positive pool, low numbers of mosquitoes in July, and low numbers of mosquito species in July. These results suggest that early‐season entomological samples can be used to predict WNV activity later in the summer, when most human cases are acquired. Additional research is needed to establish which surveillance variables are most predictive and to characterize the reliability of the predictions. 相似文献
10.
West Nile virus (WNV) infection can be fatal to many bird species, including numerous raptors, though population- and ecosystem-level
impacts following introduction of the virus to North America have been difficult to document. Raptors occupy a diverse array
of habitats worldwide and are important to ecosystems for their role as opportunistic predators. We documented initial (primary)
WNV infection and then regularly measured WNV-specific neutralizing antibody titers in 16 resident raptors of seven species,
plus one turkey vulture. Most individuals were initially infected and seroconverted between July and September of 2003, though
three birds remained seronegative until summer 2006. Many of these birds became clinically ill upon primary infection, with
clinical signs ranging from loss of appetite to moderate neurological disease. Naturally induced WNV neutralizing antibody
titers remained essentially unchanged in some birds, while eight individuals experienced secondary rises in titer presumably
due to additional exposures at 1, 2, or 3 years following primary infection. No birds experienced clinical signs surrounding
or following the time of secondary exposure, and therefore antibodies were considered protective. Results of this study have
implications for transmission dynamics of WNV and health of raptor populations, as well as the interpretation of serologic
data from free-ranging and captive birds. Antibodies in raptors surviving WNV may persist for multiple years and protect against
potential adverse effects of subsequent exposures. 相似文献
11.
CHRISTOPHER J. KATZ SCOTT C. ANDERSON ROBERT W. HOWE ANDREW R. HINICKLE NICOLE T. WALISZEWSKI STACY A. NYE AARON M. WUNDERLIN 《The Journal of wildlife management》2007,71(2):634-636
ABSTRACT Knowledge of the distribution and pathology of West Nile virus (WNV) in black bears is a necessary tool that allows wildlife managers to implement a management plan, set harvest quotas, and relocate nuisance bears. We studied the presence and significance of WNV titers in free-roaming black bears (Ursus americanus) in northeastern Wisconsin between February 2003 and March 2005. Serum neutralizing antibodies to WNV, with confirmation by plaque-reduction neutralization test to both WNV and Saint Louis encephalitis, identified exposure in 13 of 74 (17.6%) bears. This compares with a 6% infection rate in black bears in Virginia and 22% in European brown bears (Ursus arctos). Pathologic effects from exposure to WNV were not seen in any of the black bears studied. 相似文献
12.
Threshold Conditions for West Nile Virus Outbreaks 总被引:1,自引:0,他引:1
Jifa Jiang Zhipeng Qiu Jianhong Wu Huaiping Zhu 《Bulletin of mathematical biology》2009,71(3):627-647
In this paper, we study the stability and saddle-node bifurcation of a model for the West Nile virus transmission dynamics.
The existence and classification of the equilibria are presented. By the theory of K-competitive dynamical systems and index
theory of dynamical systems on a surface, sufficient and necessary conditions for local stability of equilibria are obtained.
We also study the saddle-node bifurcation of the system. Explicit subthreshold conditions in terms of parameters are obtained
beyond the basic reproduction number which provides further guidelines for accessing control of the spread of the West Nile
virus. Our results suggest that the basic reproductive number itself is not enough to describe whether West Nile virus will
prevail or not and suggest that we should pay more attention to the initial state of West Nile virus. The results also partially
explained the mechanism of the recurrence of the small scale endemic of the virus in North America.
Supported by the Chinese NSF grants 10531030 and 10671143.
Supported by the Chinese NSF grants 10801074.
Supported by Canada Research Chairs Program, Mathematics for Information Technology and Complex Systems (MITACS), National
Microbiology Laboratory, Natural Sciences and Engineering Research Council (NSERC), Canadian Foundation of Innovation (CFI)
and Ontario Innovation Trust (OIT), Ontario Ministry of Health and Long-term Care, Peel, Toronto, Chat-Kent Health Units,
and Public Health Agency of Canada (PHAC).
Supported by NSERC, MITACS, CFI/OIT a new opportunity fund, Early Research Award of Ministry of Research and Innovation (ERA)
of Ontario, Infectious Diseases Branch of Ministry of Health and Long Term Care (MOH) of Ontario and PHAC. 相似文献
13.
西尼罗病毒研究进展 总被引:1,自引:0,他引:1
西尼罗病毒(West Nile virus,WNV)属黄病毒科,为正单链RNA病毒。它在人类中的感染导致以发热为主要症状的传染性疾病,主要由蚊虫叮咬传播。自20世纪50年代首例报告西尼罗病毒自然感染所致脑炎后的几十年内,西尼罗病毒脑炎在欧洲及中亚地区散在、小规模流行。西尼罗病毒脑炎于1999年在美国的爆发及随后几年在北美的流行引起了极大的关注。这次爆发流行中新出现的种种迹象,如其中间宿主——野生鸟类的大量死亡,人类感染者中中枢神经系统受损比例的增高等,提示近期的遗传变异已使西尼罗病毒感染的病理学与流行病学发生了较显著的变化。另外,随着感染的流行,蚊虫叮咬以外的传播途径,如输血、器官移植、母婴传播等日益受到人们重视。同时,人们对阻止疫情所急需的疫苗的研制也在进行之中。本文就近几年来对西尼罗病毒的感染、免疫与流行病学方面的研究进展进行了综述。 相似文献
14.
西尼罗病毒(West Nile virus, WNV)非结构蛋白NS5是病毒基因组复制的关键蛋白.以病毒全长cDNA克隆为模板,PCR扩增获得NS5的RNA依赖的RNA聚合酶(RdRp)活性区(NS5pol)及该蛋白完整的编码序列(NS5F),分别克隆于原核表达载体pET-28a 并转化至大肠杆菌E.coliBL21(DE3)中诱导表达.表达的可溶性重组蛋白经Ni柱亲和层析纯化后进行SDS-PAGE和Western印迹鉴定.结果显示,二者均为病毒特异蛋白,且纯度均在90%以上.进一步的体外RdRp分析及EMSA的结果表明,NS5pol和NSF5均有较高的RdRp活性,且该活性具有RNA模板序列和二级结构的特异性.获得的具有RdRp活性的NS5pol和NS5F为西尼罗病毒基因组复制相关元件的研究奠定了基础. 相似文献
15.
西尼罗病毒的RT-PCR检测与鉴定 总被引:4,自引:0,他引:4
建立西尼罗病毒敏感、特异、快速的RT-PCR检测方法用于实验室诊断和流行病学监测。采用一步RT-PCR和套式PCR法对西尼罗病毒感染的乳鼠脑和细胞培养上清进行扩增,并对扩增产物进行序列测定。两种方法均可分别从两种组织中扩增出与预期大小相一致的片段,套式PCR法比一步RT-PCR法更为敏感,该扩增片段与西尼罗病毒埃及Eg101株相应序列的同源性为99%。 相似文献
16.
Lewis MA Rencławowicz J van den Driessche P Wonham M 《Bulletin of mathematical biology》2006,68(3):491-509
The first recorded North American epidemic of West Nile virus was detected in New York state in 1999, and since then the virus has spread and become established in much of North America. Mathematical models for this vector-transmitted disease with cross-infection between mosquitoes and birds have recently been formulated with the aim of predicting disease dynamics and evaluating possible control methods. We consider discrete and continuous time versions of the West Nile virus models proposed by Wonham et al. [Proc. R. Soc. Lond. B 271:501–507, 2004] and by Thomas and Urena [Math. Comput. Modell. 34:771–781, 2001], and evaluate the basic reproduction number as the spectral radius of the next-generation matrix in each case. The assumptions on mosquito-feeding efficiency are crucial for the basic reproduction number calculation. Differing assumptions lead to the conclusion from one model [Wonham, M.J. et al., [Proc. R. Soc. Lond. B] 271:501–507, 2004] that a reduction in bird density would exacerbate the epidemic, while the other model [Thomas, D.M., Urena, B., Math. Comput. Modell. 34:771–781, 2001] predicts the opposite: a reduction in bird density would help control the epidemic. 相似文献
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19.
Since it was first detected in 1999, West Nile virus (WNV) quickly spread, becoming the dominant vector-borne disease in North
America. Sometimes fatal to humans, WNV is even more widespread among birds, with hundreds of species known to be susceptible
to WNV infection in North America alone. However, despite considerable mortality and local declines observed in American crows
(Corvus brachyrhynchos), there has been little evidence of a large regional association between WNV susceptibility and population declines of any
species. Here we demonstrate a correlation between susceptibility to WNV measured by large-scale testing of dead birds and
two indices of overall population change among bird species following the spread of WNV throughout California. This result
was due primarily to declines in four species of Corvidae, including all species in this family except common ravens (Corvus corax). Our results support the hypothesis that susceptibility to WNV may have negative population consequences to most corvids on
regional levels. They also provide confirmation that dead animal surveillance programs can provide important data indicating
populations most likely to suffer detrimental impacts due to WNV. 相似文献
20.
We assessed the changes in abundance of American crows in the northeastern U.S. following the arrival of West Nile virus (WNV), with two aims. First, we determined the impact and spatial extent of the initial epizootic that began in New York City. Second, we examined whether two existing surveillance programs monitoring for WNV (data from 2000 New York State dead bird testing, and 2000 mosquito testing) accurately predicted the observed impact of the disease on crow populations as measured using data from the North American Christmas Bird Count. The rationale for this second aim was that the two WNV surveys were new and with unknown biases and sensitivity, while the Christmas Bird Count has existed for decades, providing monitoring before the arrival of WNV in North America and a long time series of data useful in gauging sensitivity. As a result, the Christmas Bird Count represents a good benchmark against which to compare the two new surveillance programs. Consistency among these three sources of information was low, suggesting that while dead bird and mosquito surveys can currently indicate the later stages of severe outbreaks, the ability to consistently detect early stages of outbreaks is questionable. 相似文献