Factors Influencing Microbe/Insecticide Interactions

Abstract

Hantaviruses comprise an emerging global threat for public health, affecting about 30?000 humans annually. Infection may lead to Hantavirus pulmonary syndrome (HPS) in the Americas and hemorrhagic fever with renal syndrome (HFRS) in the Europe and Asia. Humans are spillover hosts, acquiring infection primarily through the inhalation of aerosolized excreta from infected rodents and insectivores. Risk factors for infection include involvement in outdoor activities, such as rural- and forest-related activities, peridomestic rodent presence, exposure to potentially infected dust and outdoor military training; prolonged, intimate contact with infected individuals promotes transmission of Andes virus, the only Hantavirus known to be transmitted from human-to-human. The total number of Hantavirus case reports is generally on the rise, as is the number of affected countries. Knowledge of the geographical distribution, regional incidence and associated risk factors of the disease are crucial for clinicians to suspect and diagnose infected individuals early on. Climatic, ecological and environmental changes are related to fluctuations in rodent populations, and subsequently to human epidemics. Thus, prevention may be enhanced by host-reservoir control and human exposure prophylaxis interventions, which likely have led to a dramatic reduction of human cases in China over the past decades; vaccination may also play a role in the future.     

浙江省温州市啮齿动物中汉坦病毒的分子流行病学研究

目的 研究浙江省温州市啮齿动物中汉坦病毒(HV)流行情况及病毒型别,为该地区肾综合征出血热(HFRS)的预防控制提供科学依据.方法 采用间接免疫荧光法(IFA)检测鼠肺中HV抗原;用RT-PCR法扩增阳性样品中HV的部分S片段及部分M片段;构建系统发生树进行系统发生分析及分型.结果在温州市HFRS疫区共捕获啮齿动物96只,在6份鼠肺样品中检测到HV抗原,其中4只褐家鼠,1只黄胸鼠与1只黄毛鼠,病毒携带率为6.3%.用汉城病毒(SEOV)特异引物从其中5份HV抗原阳性样品中扩增出部分S片段(620～999nt)及部分M片段(2001～2301nt)并测定序列.对扩增出的部分S及M片段的核苷酸序列分析发现,5株病毒与现有的SEOV有高同源性,均为汉城型HV.但在用部分S片段及部分M片段核苷酸序列所构建的系统进化树上,5株病毒的聚集模式不同.结论温州市的褐家鼠、黄胸鼠、黄毛鼠均携带汉城型HV,并可能发生基因片段的重排.     

湖南省2005年肾综合征出血热监测研究

目的 掌握湖南省HFRS疫源地范围、类型、人群分布和流行规律以及宿主动物种类、带病毒率等情况，为防制HFRS提供科学依据。方法 按照2005年《湖南HFRS监测实施方案》，在全省系统开展HFRS的流行病学和病原学监测。采用IFA和ELISA检测健康人群隐性感染状况，采用间接免疫荧光法检查鼠肺HV—Ag，用双抗原夹心ELISA方法检测鼠血HV—Ab，并用单克隆抗体进行病毒分型，调查5个监测点媒介动物自然感染汉坦病毒情况。结果 2005年共报告病例546例，发病率0．84／10万。共捕获478只啮齿动物，总密度为3．4％，室外密度3．31％，室内密度3．59％。黑线姬鼠是野外的优势宿主（占38．29％），褐家鼠是室内的优势宿主（占46．91％），黑线姬鼠和褐家鼠占捕获总数的46．86％。抗原和抗体阳性鼠为39只，总感染率为8，16％。褐家鼠和黑线姬鼠的带毒指数分别为3，17％、2．80％。5个监测点间捕获率和带毒率差异有统计学意义。黑线姬鼠主要携带Ⅰ型HV，褐家鼠主要携带Ⅱ型HV。对17只阳性鼠肺病毒分型，Ⅰ型占41．18％，Ⅱ型占58．82％。结论 湖南省为姬鼠型和家鼠型混合型HFRS疫区，人群隐性感染较高，防制工作应以灭鼠和人群免疫相结合的综合防制措施，加强实验室诊断，提高临床诊断水平。     

Rodent host specificity of European hantaviruses: evidence of Puumala virus interspecific spillover

In order to investigate rodent host specificity of European hantaviruses, experimental infection of colonized and wild-trapped rodents was performed. In addition to the natural rodent reservoir, Clethrionomys glareolus, Puumala hantavirus (PUUV) could infect colonized Microtus agrestis and Lemmus sibiricus, but not Syrian hamsters or Balb/C mice. Neither C. glareolus, nor M. agrestis, could be readily infected by Tula hantavirus (TULV). Wild-trapped Apodemus flavicollis and A. agrarius, the natural reservoirs of Dobrava (DOBV) and Saaremaa (SAAV) hantaviruses, respectively, could both be infected by SAAV. NMRI mice could also be infected by SAAV, but with lower efficiency as compared to Apodemus mice. Balb/C and NMRI laboratory mice, but not C. glareolus, could be infected by DOBV. To our knowledge, this is the first time DOBV and SAAV have been shown to infect adult laboratory mice. Moreover, potential hantavirus spillover infections were investigated in wild-trapped rodents. In addition to the natural host C. glareolus, we also found M. arvalis and A. sylvaticus with a history of PUUV infection. We did not find any C. glareolus or A. sylvaticus infected with TULV, a hantavirus which is known to circulate in the same geographical regions of Belgium.     

北京市燕山山脉小兽种类分布及汉坦病毒感染状况调查

目的 了解北京市山区不同生境小兽种类构成及其汉坦病毒（HV）携带状况。方法 选择北京市东北部燕山山脉不同生境地区为监测点，采用夹夜法进行鼠密度测定，应用间接免疫荧光法检测捕获小兽的汉坦病毒抗原携带、抗体阳性状况。结果 北京市东北部燕山山脉共捕获社鼠、大林姬鼠、黑线姬鼠、小家鼠、棕背鼠平、褐家鼠、大仓鼠、川西长尾鼩、北小麝鼩9种；不同生境地区小兽密度为3．13％～7．33％，平均5．83％；平均带病毒率为2．83％，抗体阳性率为3．77％。在捕获的9种小兽中，社鼠、黑线姬鼠中查到汉坦病毒抗原或／和抗体，其他鼠无汉坦病毒感染。结论 北京市东北部燕山山脉小兽类中存在汉坦病毒感染。     

PCR-SSCP法分析汉坦病毒在乳鼠中的基因变异

目的：研究汉坦病毒在感染乳鼠体内有无基因变异．方法：用陈株病毒感染Ｖｅｒｏ－Ｅ６细胞并继之感染３ｄ龄乳鼠，提取病毒ＲＮＡ并反转录成ｃＤＮＡ，以ＰＣＲ分别从感染细胞和乳鼠中克隆出病毒的部分Ｇ２编码区序列，继而用非变性聚丙烯酰胺凝胶电泳对之进行单链构象多态性（ＳＳＣＰ）分析．结果：从感染细胞和乳鼠中克隆出的此位置和大小完全相同的ｃＤＮＡ片段单链电泳构像明显不同，从感染乳鼠中克隆的基因片段单链电泳速率明显快于从感染细胞中克隆的相应基因片段．结论：汉坦病毒的基因序列可因寄生宿主的不同而发生变异．     

Identification of Hantavirus serotypes by testing of post-infection sera in immunofluorescence and enzyme-linked immunosorbent assays

Serum samples were collected from 27 individuals who had been infected with a member of the genus Hantavirus in the Netherlands or Belgium during the last 15 years. These samples were tested in an immunofluorescence assay (IFA) and two enzyme-linked immunosorbent assay (ELISA) systems, using different virus strains that represented each of the four recently proposed serotypes of this genus. The serum samples from 11 individuals who had been infected through contacts with laboratory rats showed the highest reactivities with Hantaan virus (serotype I) and SR-11 (serotype II) in the IFA and ELISA systems. The samples of 16 individuals who had probably been infected through contacts with wild rodents showed the highest reactivities with H?lln?s virus (serotype III) in the IFA. All except two of these also showed the highest reactivity with H?lln?s virus in the two different ELISA systems.     

Thottapalayam virus, a prototype shrewborne hantavirus

Thottapalayam virus (TPMV) has been placed in the genus Hantavirus of the family Bunyaviridae by virtue of its morphologic features and overall genetic similarities to well-characterized rodentborne hantaviruses. This virus has been isolated from the Asian house shrew (Suncus murinus); however, whether TPMV is naturally harbored by an insectivore host or represents spillover from a rodent reservoir host is unknown. Our analysis of published and unpublished data on the experimental host range, genetics, and molecular phylogeny of TPMV supports coevolution of TPMV with its nonrodent reservoir host. Future studies on the epizootiology of TPMV and investigations of new shrewborne hantaviruses will provide additional insights into the evolutionary origin of hantaviruses in their rodent and insectivore reservoir hosts. Such investigations may also provide clues about determinants of hantavirus pathogenicity and virulence.     

Seaport as a source of hantavirus: a study on isolated isles

Since small mammals from seaports have relative higher seroprevalences of hantavirus, this seroepidemiologic study was conducted on the isles in Kinmen and Lienchiang Counties along the coast of southern mainland China to determine whether seaport may play the role as a source of hantavirus. Among six species of small mammals trapped in Kinmen County, only male Mus musculus (6.7%) and Rattus losea (5.3%) were found to be positive. In Lienchiang County, five species of small mammals were trapped and positive findings were obtained only in male R. norvegicus (9.3%), male M. musculus (7.7%), and female R. losea (1.6%). There was no significant difference in the seroprevalence between the two counties (Kinmen 3.8% vs. Lienchiang 3.9%). The positive rate in Liaolo (17.9%) of Kinmen County was significantly higher than the remaining trapping stations and those in Matsu Distillery (10.3%) and Fushing (5.8%) of Lienchiang County were significantly higher than the remaining ones. Moreover, a significant inverse correlation was found between the seropositive rate and the distance of small mammal sampling sites to the seaport (p < 0.01). These findings suggest the role of seaport as a source of hantavirus.