Nitric oxide in dengue and dengue haemorrhagic fever: necessity or nuisance?

Advances in free radical research show that reactive oxygen and nitrogen oxide species, for example superoxide, nitric oxide (NO) and peroxynitrite, play an important role in the pathogenesis of different viral infections, including dengue virus. The pathogenic mechanism of dengue haemorrhagic fever (DHF) is complicated and is not clearly understood. The hallmarks of the dengue disease, the antibody-dependent enhancement, the shift from T-helper type 1 (Th1) to Th2 cytokine response and the cytokine tsunami resulting in vascular leakage can now be explained much better with the knowledge gained about NO and peroxynitrite. This paper makes an effort to present a synthesis of the current opinions to explain the pathogenesis of DHF/shock syndrome with NO on centre stage.     

Influence of weather conditions on fly abundance and its implications for transmission of rabbit haemorrhagic disease virus in the North Island of New Zealand

Blowflies (Diptera: Calliphoridae) and flesh flies (Diptera: Sarcophagidae) are potential vectors of rabbit haemorrhagic disease virus (RHDV) in New Zealand. The associations between habitat and weather factors on the abundance of these flies were investigated. Between October 1999 and June 2001, flies were trapped on open pasture and in dense vegetation patches on farmland in the Himatangi area of the North Island. Five calliphorid species were trapped commonly at scrub edges and the most abundant sarcophagid, Oxysarcodexia varia Walker, was trapped mainly on open pasture. An abundance peak of O. varia was probably associated with the occurrence of a rabbit haemorrhagic disease (RHD) outbreak in the study area. Overall abundance of flies varied according to habitat and species, and species numbers differed between seasons and years. The all-day minimum temperature 3 weeks before trapping was a significant variable in all models of fly abundance, whereas average rainfall did not affect fly abundance. The all-day temperature range was significant only for O. varia. The influence of other climatic factors varied between fly species. Climate dependent variations in fly abundance may contribute to the risk of transmission of RHD, which occurred intermittently on the site during the study period.     

On the relationship between the environmental history and the epidemiological situation of Argentine hemorrhagic fever

The aim of this work was to establish the relationship between different Argentine hemorrhagic fever (AHF) epidemiological situations found at different sites and the related large-scale environmental conditions. Large-scale environmental records (vegetation index, temperature, precipitation and elevation) were obtained from a series of monthly NOAA satellite images and global databases considered suitable for modeling climatic and other environmental determinants of large-scale biogeographical regions. The temporal variation in vegetation for cycles of winter-summer showed a greater variation in the nonendemic region than in the other two regions. On the other hand, the average of the temporal variation in precipitation in cycles of spring–autumn was more different in the historic region than in the other two regions, and land surface temperatures in cycles of spring–autumn showed differences between the epidemic region and the other two regions. We found good separation among the epidemic, historic and nonendemic sites, with the greatest difference found between epidemic and nonendemic sites. The classification of sites showed a tendency for grouping according to the epidemiological situation, but there was some variation. It seems possible to establish a close relationship between the state of AHF incidence and the environmental history of sites suggesting the possibility of predicting epidemiological behavior using environmental conditions derived from satellite data.     

Epidemiology and mutational analysis of global strains of crimean-congo haemorrhagic fever virus

Crimean-Congo hemorrhagic fever (CCHF) is a severe illness with high fatality. Cases are reported in several countries in Africa, Europe, the Middle East, and Asia. Phylogenetic analyses based on the virus S (nucleocapsid), M (glycoprotein), and L (polymerase) genome segments sequences indicate distinct geographic lineages exist but their specific genetic characteristics require elucidation. In this work we collected all full length S segment sequences and generated a phylogenetic tree based on the alignment of these 62 samples. We then analyzed the alignment using entries from AAIndex, the Amino Acid Index database, to identify amino acid mutations that performed significant changes in charge, pka, hydropathy and side chain volume. Finally, we mapped these changes back to the tree and alignment to identify correlated mutations or sites that characterized a specific lineage. Based on this analysis we are able to propose a number of sites that appear to be important for virus function and which would be good candidates for experimental mutational analysis studies.     

Cytotoxic factor-autoantibodies: possible role in the pathogenesis of dengue haemorrhagic fever

During dengue virus infection a unique cytokine, cytotoxic factor (hCF), is produced that is pathogenesis-related and plays a key role in the development of dengue haemorrhagic fever (DHF). However, what regulates the adverse effects of hCF is not known. We have previously shown that anti-hCF antibodies raised in mice, neutralise the pathogenic effects of hCF. In this study we have investigated the presence and levels of hCF-autoantibodies in sera of patients with various severity of dengue illness (n=136) and normal healthy controls (n=50). The highest levels of hCF-autoantibodies (mean+/-S.D.=36+/-20 U ml(-1)) were seen in patients with mild illness, the dengue fever (DF), and 48 out of 50 (96%) of the sera were positive. On the other hand the hCF-autoantibody levels declined sharply with the development of DHF and the levels were lowest in patients with DHF grade IV (mean+/-S.D.=5+/-2 U ml(-1); P=<0.001 as compared to DF). Only one of the 13 DHF grade IV patients had an antibody level above the 'cut-off' value (mean plus 3 S.D. of the control sera). The analysis of data with respect to different days of illness further showed that the highest levels of hCF-autoantibodies were present in DF patients at >9 days of illness. Moreover, the DF patients at all time points, i.e. 1-4, 5-8 and >9 days of illness had significantly higher levels of hCF-autoantibodies (P<0.001) than patients with DHF grade I, II, III and IV. In addition DHF grade I and grade II patients had significantly more positive specimens than DHF grade III and grade IV patients at all time points. These results suggest that elevated levels of hCF-autoantibodies protect the patients against the development of severe forms of DHF and, therefore, it may be useful as a prognostic indicator.     

Impact of climate change on risk of incursion of Crimean-Congo haemorrhagic fever virus in livestock in Europe through migratory birds

Aims: To predict the risk of incursion of Crimean‐Congo haemorrhagic fever virus (CCHFV) in livestock in Europe introduced through immature Hyalomma marginatum ticks on migratory birds under current conditions and in the decade 2075–2084 under a climate‐change scenario. Methods and Results: A spatial risk map of Europe comprising 14 282 grid cells (25 × 25 km) was constructed using three data sources: (i) ranges and abundances of four species of bird which migrate from sub‐Saharan Africa to Europe each spring, namely Willow warbler (Phylloscopus trochilus), Northern wheatear (Oenanthe oenanthe), Tree pipit (Anthus trivialis) and Common quail (Coturnix coturnix); (ii) UK Met Office HadRM3 spring temperatures for prediction of moulting success of immature H. marginatum ticks and (iii) livestock densities. On average, the number of grid cells in Europe predicted to have at least one CCHFV incursion in livestock in spring was 1·04 per year for the decade 2005–2014 and 1·03 per year for the decade 2075–2084. In general with the assumed climate‐change scenario, the risk increased in northern Europe but decreased in central and southern Europe, although there is considerable local variation in the trends. Conclusions: The absolute risk of incursion of CCHFV in livestock through ticks introduced by four abundant species of migratory bird (totalling 120 million individual birds) is very low. Climate change has opposing effects, increasing the success of the moult of the nymphal ticks into adults but decreasing the projected abundance of birds by 34% in this model. Significance and Impact of the Study: For Europe, climate change is not predicted to increase the overall risk of incursion of CCHFV in livestock through infected ticks introduced by these four migratory bird species.     

Identification of potential hosts and vectors of scrub typhus and tick-borne spotted fever group rickettsiae in eastern Taiwan

Scrub typhus and tick-borne spotted fever group (SFG) rickettsioses are transmitted by chiggers (larval trombiculid mites) and hard ticks, respectively. We assessed exposure to these disease vectors by extensively sampling both chiggers and ticks and their small mammal hosts in eastern Taiwan during 2007 and 2008. The striped field mouse Apodemus agrarius Pallas (Rodentia: Muridae) was the most common of the small mammals (36.1% of 1393 captures) and presented the highest rate of infestation with both chiggers (47.8% of 110 760) and ticks (78.1% of 1431). Leptotrombidium imphalum Vercammen-Grandjean & Langston (Trombidiformes: Trombiculidae) and immature Rhipicephalus haemaphysaloides Supino (Ixodida: Ixodidae) were the most abundant chiggers (84.5%) and ticks (>99%) identified, respectively. Immunofluorescent antibody assay revealed high seropositive rates of rodents against Orientia tsutsugamushi Hyashi (Rickettsiales: Rickettsiaceae), the aetiological agent of scrub typhus (70.0% of 437 rodents), and tick-borne SFG rickettsiae (91.9% of 418 rodents). The current study represents a first step towards elucidating the potential hosts and vectors in the enzootic transmission of O. tsutsugamushi and tick-borne SFG rickettsiae in Taiwan. Further studies should focus on characterizing pathogens in L. imphalum and R. haemaphysaloides, as well as the proclivity of both vectors to humans. Uncovering the main hosts of adult ticks is also critical for the prevention of SFG rickettsial infections.     

Hyalomma ticks on northward migrating birds in southern Spain: Implications for the risk of entry of Crimean‐Congo haemorrhagic fever virus to Great Britain

Crimean‐Congo haemorrhagic fever virus (CCHFV) is a zoonotic virus transmitted by Hyalomma ticks, the immature stages of which may be carried by migratory birds. In this study, a total of 12 Hyalomma ticks were recovered from five of 228 migratory birds trapped in Spring, 2012 in southern Spain along the East Atlantic flyway. All collected ticks tested negative for CCHFV. While most birds had zero Hyalomma ticks, two individuals had four and five ticks each and the statistical distribution of Hyalomma tick counts per bird is over‐dispersed compared to the Poisson distribution, demonstrating the need for intensive sampling studies to avoid underestimating the total number of ticks. Rates of tick exchange on migratory birds during their northwards migration will affect the probability that a Hyalomma tick entering Great Britain is positive for CCHFV. Drawing on published data, evidence is presented that the latitude of a European country affects the probability of entry of Hyalomma ticks on wild birds. Further data on Hyalomma infestation rates and tick exchange rates are required along the East Atlantic flyway to further our understanding of the origin of Hyalomma ticks (i.e., Africa or southern Europe) and hence the probability of entry of CCHFV into GB.     

长江上游特有种长鳍吻鮈种群数量和资源利用评估

长鳍吻鮈(Rhinogobio ventralis)为长江上游特有种, 由于过度捕捞和大坝建设, 其种群生存受到极大威胁。为了解三峡工程蓄水后、金沙江一期工程蓄水前该物种的种群动态, 作者利用2007-2009年长江上游江津和宜宾江段调查获取的体长频率数据, 评估了其生长和死亡参数、种群数量及资源利用情况。结果表明, 长江上游长鳍吻鮈渔获群体体长范围为52-250 mm, 体重范围为2.7-307.2 g, 平均体长为150.8 ± 40.7 mm, 平均体重为72.3 ± 49.7 g。江津江段长鳍吻鮈平均体长(168.6 ± 29.5 mm)显著大于宜宾江段(125.6 ± 41.2 mm)。长鳍吻鮈体长-体重关系为: W = 6.06 × 10^-6L^3.20 (R² = 0.98, P < 0.01, n = 436)。由体长频率法拟合出渐近体长(L_∞)为338 mm, 生长系数(k)为0.24/yr。由Pauly公式、Gunderson和Dygert公式、Jensen公式等3种方法估算出其平均自然死亡系数为0.43。由长度转渔获物曲线估算出江津和宜宾江段长鳍吻鮈的总死亡系数分别为2.26和2.09。江津和宜宾江段长鳍吻鮈资源开发率分别为0.81和0.79, 已超过由Beverton-Holt动态综合模型估算出的最大开发率0.57和0.62。由体长实际种群分析估算出2007、2008和2009年江津江段长鳍吻鮈种群数量分别为68,247、67,432和176,266尾, 平均为103,982尾; 宜宾江段种群数量分别为22,953尾、46,340尾和34,021尾, 平均为34,438尾, 表明江津江段种群数量高于宜宾江段。长鳍吻鮈资源已被过度开发, 建议加强种群动态监测, 延长禁渔期及开展栖息地修复等措施保护这一特有物种。     

Genetic variation in the 5' end and NS5B regions of classical swine fever virus genome among Japanese isolates.

Sixteen clinical strains of classical swine fever virus (CSFV) isolated in Japan were subjected to analyses of nucleotide sequence variations in the 5' end and NS5B regions of the genome. These isolates were divided into three genovars, CSFV-1, CSFV-2 and CSFV-3, based on palindromic nucleotide substitutions at the three variable loci in the 5' untranslated region (UTR). Phylogenetic trees constructed from nucleotide sequences in the 5'-UTR and NS5B gene indicated that the CSFV strains were divided into three clusters, I, II and III. CSFV strains included in clusters I, II and III were identical to those in the CSFV-1, CSFV-2 and CSFV-3 genovars, respectively.     

Spatial variation in diurnal surface temperatures and the distribution and abundance of an alpine grasshopper

We studied the influence of spatial differences in diurnal surface temperatures due to topography on an alpine grasshopper (Aeropedellus clavatus). Temperature measurements on east-and west-facing alpine dry meadow slopes on Niwot Ridge in Colorado demonstrated a significant difference in diurnal surface temperatures between the two slopes throughout the growing season. A. clavatus body temperature was found to be highly correlated with nearby shaded surface temperature, and individual grasshoppers enclosed on the two slopes had significantly higher relative growth rates on the warmer east slope. Temperature effects were manifest at the population level as well. A. clavatus was significantly more abundant on the east-facing than on the west-facing slope, despite similar vegetation in both areas. This study contributes to our understanding of the myriad of factors governing insect distribution and abundance by attempting to integrate the physiological and ecological, abiotic and biotic, influences on both individuals and populations.     

非洲猪瘟病毒的生物学特性与疫苗研制的难点

非洲猪瘟(African swine fever,ASF)是由非洲猪瘟病毒(African swine fever virus,ASFV)引起的一种猪烈性传染病,是全球养猪业的"头号杀手",强毒株引发的超急性和急性感染死率高达100%。2018年8月ASF首次传入我国,截止2019年6月6日,已有32个省份累计暴发137起疫情,给我国社会、经济构成巨大威胁。ASF疫苗的研制始于20世纪60年代,但均以失败而告终,其主要原因是对ASFV生物学特性缺乏深入的研究。有效控制当前ASF疫情扩散、研制安全有效的疫苗将是我国面临的巨大挑战。本文对ASFV形态与基本结构、传播途径、致病机制、基因组及编码蛋白、入侵机制、免疫逃逸等生物学特性进行了概述,并分析了当前疫苗研制面临的难点,以期为我国有效控制ASF疫情及病原研究提供参考。     

Temporal distribution and spatial pattern of abundance of the Rift Valley fever and West Nile fever vectors in Barkedji, Senegal

The temporal distribution and spatial pattern of abundance of mosquito vectors of Rift Valley fever (RVf) and West Nile fever (WNf) were studied during the 2005 and 2006 rainy seasons at Barkedji, Senegal. Mosquitoes were collected every two weeks with CDC light traps with dry ice at 79 sites including temporary ponds, barren, shrubby savannah, wooded savannah, steppes, and villages at different distances (between 0 and 600 m) from the nearest pond. The temporal distributions of these vectors varied between 2005 and 2006 and were positively correlated with rainfall for Aedes (Aedimorphus) vexans Patton, with rainfall after a lag time of one month for Culex (Culex) poicilipes (Theobald) and Culex (Culex) neavei Theobald. All the vectors had their highest abundances and parity rates between September and November. The highest vector abundances were observed in the barren and temporary ponds. The distance of trap location to the nearest ponds was negatively correlated to the abundance of the vectors. Taking into account the linear regression equations, it was predicted that mosquitoes would not disperse and be collected by the light trap, up to 1,500 m to the nearest ponds. The implications of these findings in the epidemiology and control of RVF and WNF at Barkedji are discussed.     

A comparison of the susceptibility of Culicoides imicola and C. bolitinos to oral infection with eight serotypes of epizootic haemorrhagic disease virus

Abstract. The mechanisms involved in introduction, maintenance and perpetuation of epizootic haemorrhagic disease virus (EHDV) in South Africa are not fully understood. This paper reports on the susceptibility of South African livestock associated Culicoides (Diptera: Ceratopogonidae) species to oral infection with eight EHDV serotypes. Virus was recovered from eight of 17 field-collected Culicoides species 10 days after oral feeding on blood/virus mixtures. Six EHDV serotypes were recovered from C. (Avaritia) imicola Kieffer, and seven serotypes were recovered from C. (A.) bolitinos Meiswinkel. Virus recovery rates in C. imicola ranged from 0.4% for EHDV 2 to 14.4% for EHDV 7, and in C. bolitinos from 0.6% for EHDV 6 to 12.3% for EHDV 2. There was a significant difference in virus recovery rates between serotypes in both species. Other Culicoides species that yielded EHDV after 10 days extrinsic incubation included C. (Meijerehelea) leucostictus Kieffer, C. (Culicoides) magnus Colaço, C. (Beltranmyia) nivosus de Meillon, C. (A.) gulbenkiani Caeiro, C. (Hoffmania) zuluensis de Meillon and C. onderstepoortensis Fiedler. Culicoides midges shown in this study to be susceptible to oral infection with EHDV are widely distributed in South Africa but differ considerably in their abundance, host preference and breeding sites.     

Spatial and temporal patterns of brown rat (Rattus norvegicus) abundance variation in poultry farms

The temporal and spatial patterns of rat abundance variations were studied, and which factors might affect these patterns in poultry farms. Forty-eight poultry farms were sampled from spring 1999 to winter 2001 in Buenos Aires, Argentina. Environmental variables of farms, meteorological variables and distances among farms were registered to evaluate a possible association with rat abundance estimated by trap success. Rattus norvegicus was the dominant rat species in the study area. Rat abundance did not vary temporally and there was reproduction at all times. Trap success was more similar among neighboured farms than among farms further apart. Contrary to the abundance of other small rodents, rat abundance was not significantly related to farm characteristics. The lack of coincidence between rats and other small rodents suggests the existence of a differential response of rats to environmental factors of the poultry farms.     

Spatial and temporal variation of abundance,biomass and diversity within marine reserves in the Philippines

Aim The objective of this study was to investigate the influence of protection duration (years of fishing closure) and location (distance from shore) on reef fish diversity. Location Danajon Double Barrier Reef, Bohol, Philippines. Methods Reef fish abundance and size structure, by species, were obtained monthly using replicated underwater visual belt transects (n = 8; 70 × 5‐m belt transects) over 3 years (2002–2005) at eight sites that included six marine reserves and two unprotected reef areas. We analysed species accumulation curves, diversity indices and abundance–biomass comparison (ABC) curves within and across the study sites to assess the influence of protection duration and location. Results Analyses showed that longer protection duration impacted reef fish diversity at both inshore and offshore sites by shifting ABC curves from higher abundance than biomass curves at fished sites to higher biomass than abundance curves at most of the protected sites. Protection duration did not significantly influence either the rate of species accumulation within sites or the 12 diversity indices measured across the study sites. The offshore sites consistently showed higher rates of species accumulation and diversity indices values than inshore sites with similar protection duration. One protected offshore young marine reserve site that has been assessed as the least well‐managed showed patterns more consistent with the fished sites. Main conclusions Analyses showed that protection duration mainly impacted diversity by increasing the dominance of large‐bodied species and enhancing total biomass. Besides protection duration, reserve location influenced species accumulation curves and diversity indices.     

表达兔出血症病毒VP60蛋白的重组兔粘液瘤病毒的构建与初步评价

兔出血症病毒(Rabbit hemorrhagic disease virus,RHDV)及兔粘液瘤病毒(Myxoma virus,MYXV)分别引起兔出血症(兔瘟)和兔粘液瘤病,是两种严重危害家兔养殖业以及导致原产地欧洲野兔-穴兔(Oryctolagus cuniculus)种群近濒危的重要病原。VP60为构成RHDV衣壳的主要抗原蛋白。为研制能同时免疫预防该两种疫病的重组二联疫苗,本研究分别以MYXV和其复制非必需基因——胸腺激酶(Thymidine kinase,TK)基因为重组载体和同源重组靶基因,构建穿梭载体p7.5-VP60-GFP。将p7.5-VP60-GFP载体转染被MYXV感染的兔肾细胞株RK13,经同源重组后,在荧光显微镜下筛选出表达GFP的重组病毒,并将其命名为rMV-VP60-GFP。通过PCR和Western blotting进行重组病毒vp60基因特异性插入和表达验证结果显示,vp60和gfp基因成功插入MYXV基因组中并且可成功表达,表明成功构建了表达RHDV衣壳蛋白基因vp60的重组MYXV。动物攻毒保护试验表明,制备的重组病毒能保护家兔抵抗MYXV的致死性攻击,这为后续疫苗的研发奠定了基础。     

猪瘟病毒Core蛋白核仁定位序列鉴定

黄病毒科病毒核衣壳蛋白的核仁定位在病毒颗粒包装与病毒复制中发挥重要作用。为鉴定黄病毒科的猪瘟病毒Core蛋白核仁定位序列,本研究构建了将Core蛋白、截短突变体和氨基酸位点突变体分别与增强型绿色荧光蛋白(enhanced green fluorescent protein, EGFP )融合的真核表达质粒,转染至PK15细胞后进行表达和定位分析,结果显示 Core蛋白核仁定位序列为PESRKKL,其关键氨基酸为R76K77,对理解猪瘟病毒Core蛋白结构与功能和为后续研究Core蛋白在病毒复制及颗粒包装中的作用有重要意义。     

Development of multiple elisas for the detection of antibodies against classical swine fever virus in pig sera

The major immunogenic proteins (Ems,E2 and NS3) of classical swine fever virus (CSFV) (Shimen strain) were expressed in E.coli and purified by affinity chromatography.The recombinant antigens were appl...