蜱传脑炎研究进展

蜱传脑炎又名森林脑炎是由蜱传脑炎病毒引起,经蜱传播的以中枢神经系统病变为主要特征的急性传染性疾病,病死率高达10%～20%,是近年来病毒学专家研究的重点和难点。本文从流行病学特点、发病机制及临床表现、转归、诊断、治疗等对蜱传脑炎进行综合性论述,为该病的预防和治疗策略的制定提供相应的理论依据。     

新疆夏尔希里自然保护区蜱传脑炎疫源地调查

目的调查新疆北部夏尔希里地区蜱传脑炎(TBE)疫源地特征,分离鉴定蜱传脑炎病毒(TBEV)。方法利用间接免疫荧光法对2011年春夏季出现的2例疑似病毒性脑炎患者及当地健康人群检测TBEV特异性IgG抗体。调查当地蜱种群特征;通过蜱研磨液接种实验小鼠与细胞分离培养TBEV;利用RT-PCR扩增检测病毒NSl基因片段,通过序列分析明确新分离毒株的系统进化特征。结果在夏尔希里自然保护区TBE疫源地采集全沟硬蜱和森林革蜱共1760只,全沟硬蜱为优势蜱种(87．5％)。2例疑似病毒性脑炎患者确诊为TBEV感染。当地健康人群中病毒IgG血清阳性率为35．4％(23／65)。BALB／c小鼠接种蜱研磨液后,发病与死亡发生率分别为72．9％(70／96)和55．7％(44／79)。从病死小鼠脑组织中扩增获得TBEV特异性条带。基于病毒NSl基因序列的系统进化分析表明,TBEV新分离株属于远东亚型,与中国东北地区分离株、俄罗斯分离株的同源性分别为99％和98％。结论首次发现新疆夏尔希里自然保护区存在TBE疫源地,病毒流行株属于远东亚型,全沟硬蜱和森林革蜱是病毒传播的重要媒介。     

俄罗斯8人死于蜱传脑炎

2007年8月9日消息:据俄罗斯媒体9日报道,最近20天中,蜱传脑炎疫情在新西伯利亚州等地已造成8人死亡,其中包括1名儿童。     

常见蜱传立克次体的研究进展

蜱携带的病原体给人类健康、家养及野生动物和畜牧业发展带来了极大的威胁。随着社会经济的发展、分子检测技术的进步,新发蜱传疾病的不断出现,使得人们对蜱传病原体及其引起的疾病更加关注。本文针对近年来较为流行的几种蜱传立克次体疾病进行了综述,以期为蜱传立克次体疾病的系统研究和综合防控提供参考。     

蜱传脑炎疑似患者中抗莱姆病螺旋体抗体的调查

作者应用间接免疫荧光抗体法，对黑龙江省林区１２０６例蜱传脑炎疑似患者分别作了抗蜱传脑炎病毒抗体和抗莱姆病螺旋体抗体检查。阳性数前者为２０１例（１６．６７％），后者为１０２例（８．４６％），两者均阳性的２８例。表明临床疑似蜱传脑炎患者中有相当数量为莱姆病，并从血清学上证实蜱传脑炎与莱姆病间存在同时或相继的双重感染。     

蜱与蜱传疾病最新研究进展

正蜱是一种吸血的节肢动物,是多种人畜共患传染病的重要传播媒介。蜱虫分类上属于动物界节肢动物门、蛛形纲、螨亚纲、寄螨目、蜱总科。全世界已经发现18个897种,而中国已发现10属,119种,100种硬、10余种软蜱[1]。近两年来,在我国山东、河南、河北、安徽等地出现一些因蜱虫叮咬而发生蜱传疾     

北亚蜱传斑点热的研究进展

北亚蜱传斑点热（North Asia Tick-Borne Spotted Fever,简称北亚热,North Asia）（ Fever）是由西伯利亚立克次体（Rickettsiasibirica）引起的一种自然疫源性疾病,人因被感染的蜱叮咬而发病。临床以虫咬溃疡（初发病灶-焦痂）、局部淋巴结肿、发热、皮疹和剧烈头痛等为主要特征。     

中国蜱传病原体分布研究概况

蜱传病原体(Tickborne agents)是指由蜱传播的某些种类的病毒、细菌和寄生虫等。我国分布的主要蜱传病毒有蜱传脑炎病毒(Tick-borne encephalitis virus,TBEV;我国称森林脑炎病毒)[1]、克里米亚-刚果出血热病毒(Crimean-Congo hemorrhagic fever viruses,CCHFV;我国称新疆出血热病毒)[1]、发热伴血小板减少综合征布尼亚病毒(Severe fever with thrombocytopenia syndrome bunyavirus,SFTSV)[2];蜱传细菌有立克次体[3-4]、伯氏疏螺旋体[5-6];蜱传寄生虫有巴贝西原虫。由于我国的疾病防控主要以行政区为单位,因此,结合行政区域图对上述蜱传病原体进行分类标注。蜱传病     

蜱叮咬致森林脑炎一例临床报告

报道一例被蜱叮咬致森林脑炎病例，从叮咬史，临床表现，实验室检查，血清抗体诊断及治疗和转归的全过程做了较为系统的报道和分析。该患属中型病例，经过４０天选择用药对症治疗症状和体征消失出院，但留有右侧肢体瘫痪，癫痫后遗症。经过一年后随防，后遗症仍未消失。     

福建省蜱类及蜱传疾病概况

蜱传疾病可能对福建某些地区的人群造成危害,当林区人群被蜱叮咬较为普遍,蜱类密度及人群被蟀叮咬频率都较高时,易引发蜱传疾病局部流行甚至暴发流行,蜱传疾病已成为一项亟须引起重视的公共卫生问题.作者根据多年课题调研资料,对福建省蟀类分布及蟀传疾病作一综述.     

Chimeric antibodies against tick-borne encephalitis virus

Two chimeric antibodies (ch) 13D6 and 10C2 against the glycoprotein E of tick-borne encephalitis virus (TBEV) were constructed by fusing variable regions of murine monoclonal antibodies (Mabs) 13D6 and 10C2 to human constant regions. Monovalent analogues of these antibodies in format of single-chain antibodies (scFv or sc) were developed, as well. The ch13D6, ch10C2, sc13D6 and sc10C2 exhibited binding characteristics similar to parental Mabs. Only the ch13D6 and sc13D6 were able to neutralize TBEV infectivity in vitro. The in vitro neutralization provided by ch13D6 suggests that this antibody can be further developed into a potent prophylaxis and therapy for tick-borne encephalitis (TBE) infection.     

Cost-effectiveness of tick-borne encephalitis vaccination in Slovenian adults

Background

Slovenia is an endemic country with a high incidence rate of tick-borne encephalitis (TBE) and low vaccination coverage. TBE causes high costs for the health care insurances as well as the society due to hospitalization and frequent long term or permanent neurological sequelae. Vaccination is effective and a safe prophylaxis against TBE.

Objective

The purpose of this study was to evaluate the incremental cost-effectiveness ratio (ICER) between vaccination and no vaccination in Slovenia. The results are shown as cost per quality-adjusted life year (QALY) gained from the view of the health care payer and the society.

Methods

Based on the natural course of the disease, the Markov model was used for comparing the economic and health outcomes of vaccinated and unvaccinated groups from 18 to 80 years of age.

Results

The incremental cost-effectiveness ratio from the current Slovenian vaccination programme for FSME-Immun^® compared to no vaccination amounts to €15,128 per QALY gained and for Encepur^® €20,099 per QALY gained from the view of the health care payer. From the view of the society vaccination is cost saving, mainly due to avoiding the high indirect costs.

Conclusions

According to the cost-effectiveness threshold as proposed by the Slovenian Health Council, the current Slovenian vaccination programme against TBE is cost-effective from the health care payer's perspective and also economical from the society's perspective.     

Predicting tick-borne encephalitis using Google Trends

Data generated through public Internet searching offers a promising alternative source of information for monitoring and forecasting of infectious disease. Here future cases of tick-borne encephalitis (TBE) were predicted using traditional weekly case reports, both with and without Google Trends data (GTD). Data on the weekly number of acute, confirmed TBE cases in Germany were obtained from the Robert Koch Institute. Data relating to the volume of Internet searching on TBE was downloaded from the Google Trends website. Data were split into training and validation parts. A SARIMA (0,1,1) (1,1,1) [52] model was used to describe the weekly TBE case number time series. Google Trends Data was used as an external regressor in a second, as optimal identified SARIMA (4,1,1) (1,1,1) [52] model. Predictions for the number of future cases were made with both models and compared with the validation dataset. GTD showed a significant correlation with reported weekly case numbers of TBE (p < 0.0001). A comparison of forecasted values with reported ones resulted in an RMSE (residual mean squared error) of 0.71 for the model without Google search values, and an RMSE of 0.70 for the Google Trends values enhanced model. However, difference between predictive performances was not significant (Diebold Mariano test, p-value = 0.14).     

Recombinant chimeric Japanese encephalitis virus/tick-borne encephalitis virus is attenuated and protective in mice

Tick-borne encephalitis virus (TBEV) represents one of the most dangerous human pathogens circulating in Europe and East Asia. No effective treatment for TBEV infection currently exists, and vaccination is the primary preventive measure. Although several inactivated vaccines have been licensed, the development of novel vaccines against TBEV remains a high priority in disease-endemic countries. In the present study, a live chimeric recombinant TBEV (ChinTBEV) was created by substituting the major structural genes of TBEV for the corresponding regions of Japanese encephalitis virus (JEV) live vaccine strain SA14-14-2. The resulting chimera had a small-plaque phenotype, replicated efficiently in both mammalian and mosquito cells. The preliminary data from in vitro passaging indicated the potential for stability of ChinTBEV. ChinTBEV also exhibited significantly attenuated neuroinvasiveness in mice upon either intraperitoneal or subcutaneous inoculation in comparison with its parental TBEV. Importantly, a single immunisation with ChinTBEV elicited TBEV-specific IgG and neutralising antibody responses in a dose-dependent manner, providing significant protection against lethal TBEV challenge in mice. Taken together, the results of this proof-of-concept study indicate that ChinTBEV can be further developed as a potential vaccine candidate against TBEV infection. Moreover, the construction of this type of flavivirus chimera using a JEV vaccine strain as the genetic backbone represents a universal vaccine approach.     

Smell impairment after tick-borne encephalitis vaccination: Case report

We present a case of hyposmia following administration of a tick-borne encephalitis (TBE) vaccine. The olfactory impairment did not recover during 1-year follow up. In the literature, there is no report of smell deterioration after vaccination against TBE. Physicians should be aware of this rare neurological complication.     

Vaccines against tick-borne encephalitis: WHO position paper--recommendations

This article presents the WHO recommendations on the use of vaccines against tick-borne encephalitis excerpted from the recently published Vaccines against tick-borne encephalitis: WHO position paper. This is the first WHO position paper on the use of tick-borne encephalitis. It was published in the Weekly Epidemiological Record in June 2011. In this paper, footnotes provide a limited number of core references including references to grading tables that assess the quality of scientific evidence for a few key conclusions; a more comprehensive list of references is offered in the Background document on vaccines and vaccination against tick-borne encephalitis available at http://www.who.int/immunization/sage/6_TBE_backgr_18_Mar_net_apr_2011.pdf.In accordance with its mandate to provide guidance to Member States on health policy matters, WHO issues a series of regularly updated position papers on vaccines and combinations of vaccines against diseases that have an international public health impact. These papers are concerned primarily with the use of vaccines in large-scale immunization programmes; they summarize essential background information on diseases and vaccines, and conclude with WHO's current position on the use of vaccines in the global context. This paper reflects the recommendations of WHO's Strategic Advisory Group of Experts (SAGE) on immunization. These recommendations were discussed by SAGE at its April 2011 meeting. Evidence presented at the meeting can be accessed at http://www.who.int/immunization/sage/previous/en/index.html.     

Vaccine failures after active immunisation against tick-borne encephalitis

Tick-borne encephalitis (TBE) is a major disease of the central nervous system in Europe and is endemic in Sweden with about 200 notified cases annually. The far most effective protective measure against TBE is active immunisation. The vaccines available today induce a high degree of protection in field studies. However, vaccine failures have occasionally been reported and may be overlooked due to different, and sometimes confusing, antibody kinetics in vaccinees with TBEV infection. In this study, 27 patients with clinical and serological evidences of TBE despite adequate immunisation are presented. Vaccination failure is characterized by a slow, and initially non-detectable, development of the specific TBEV-IgM response, seen together with a rapid rise of IgG and neutralising antibodies in serum. The majority (70%) of the patients were more than 50 years of age, which may implicate a need for a modified immunisation strategy in the elderly.     

Characteristics of antibody responses in tick-borne encephalitis vaccination breakthroughs

Tick-borne encephalitis (TBE) virus is an important human pathogenic flavivirus that is endemic in Europe and Asia. The disease can be effectively prevented by inactivated vaccines and vaccination breakthroughs (VBTs) are rare. We investigated the characteristics of antibody responses in such VBTs in comparison to those in unvaccinated TBE patients. In contrast to the unvaccinated controls, most of the VBTs displayed a delayed IgM antibody response and had high avidity and strongly neutralizing antibodies already in the first sample taken upon hospitalization. The antibody profile of these patients therefore had the characteristics of an anamnestic immune response. In the VBTs analyzed, immunological priming and memory were apparently not sufficient or fast enough to prevent the disease.     

Dermacentor reticulatus is a vector of tick-borne encephalitis virus

Tick-borne encephalitis virus (TBEV; family Flaviviridae) is the most medically important tick-borne virus in Europe and Asia. Ixodes ricinus and I. persulcatus ticks are considered to be the main vector ticks of TBEV in nature due to their specific ecological associations with the vertebrate hosts. Nevertheless, recent TBEV prevalence studies in ticks suggest that Dermacentor reticulatus ticks might play a relevant role in the maintenance of TBEV in nature. The goal of this study was to evaluate the vector competency of D. reticulatus for TBEV through experimental tick infections and comparative in vivo transmission studies involving D. reticulatus and I. ricinus ticks.We observed that after a transcoxal micro-capillary inoculation, adult female D. reticulatus ticks efficiently replicated TBEV during the observed period of 21 days. The mean virus load reached up to 2.5 × 10⁵ gene copies and 6.4 × 10⁴ plaque forming units per tick. The infected D. reticulatus ticks were able to transmit the virus to mice. The course of infection in mice was comparable to the infection after a tick bite by I. ricinus while the virus spread and clearance was slightly faster. Moreover, D. reticulatus ticks were capable of tick-to-tick non-viraemic transmission of TBEV to the Haemaphysalis inermis nymphs during co-feeding on the same animal. The co-feeding transmission efficiency was overall slightly lower (up to 54 %) in comparison with I. ricinus (up to 94 %) and peaked 1 day later, at day 3.In conclusion, our study demonstrated that D. reticulatus is a biologically effective vector of TBEV. In line with the recent reports of its high TBEV prevalence in nature, our data indicate that in some endemic foci, D. reticulatus might be an underrecognized TBEV vector which contributes to the expansion of the TBEV endemic areas.