猪流感的诊断及防制措施

猪流感是急性的呼吸道传染病,以发病急、传播快、发病率高、死亡率低为特征。而2009年在全球多个国家发生致人死亡的甲型H1N1流感病毒是新型变异毒株,是人类流感病毒、禽流感病毒、猪流感病毒基因片段的混合体,猪流感的基因片段只占小部分。虽然在我国猪群中尚未监测到这流感变异毒株,但是猪流感的防控工作丝毫不能懈怠。     

病毒的进化与传播

病毒没有完全的自身生命系统,必须依赖宿主的酶系统来进行病毒的自我复制、传播,以确保自身物种的繁衍。病毒的进化和传播的本质在于病毒能够在宿主体内快速增殖出数目庞大的子代病毒。通过变异,病毒能以最少的基因组合产生最大的遗传多样性,表现出对宿主环境具有惊人的适应能力。病毒基因突变（包括转换、插入、缺失、颠换、重组、重排等）、自然选择和对宿主适应性是病毒进化和传播的基础。     

H1N2亚型猪流感病毒反向遗传操作系统的建立

利用RT-PCR技术扩增猪流感病毒A/swine/Shanghai/1/07（H1N2）的8个基因片段,分别克隆至双向转录表达载体PBD上,构建出8个能在哺乳细胞中复制和表达的质粒。将8个质粒共转染293T细胞,收取转染48 h时的细胞上清并接种9～11日龄SPF鸡胚,成功拯救出有血凝活性的病毒。经序列测定,确定拯救病毒的8个基因片段均来自猪流感病毒A/swine/Shanghai/1/07（H1N2）基因组。H1N2亚型猪流感病毒反向遗传操作系统的成功建立为猪流感病毒致病机理、传播机制及病毒基因功能的研究奠定了基础;同时,为H1N2亚型猪流感新型疫苗的研制开辟了新的途径。     

猪作为禽流感病毒传播中间宿主支持禽源RNA聚合酶复制的分子机制研究

正A型流感病毒是引起人及多种动物流感的重要病原,流感病毒的跨物种传播一直是研究的热点。猪一直被认为是人、禽、猪流感的"混合器",是促进禽流感病毒(AIV)与其它物种流感病毒发生基因重排进而引起流感大流行的重要中间宿主。已知的     

牛病毒性腹泻病毒生物型转化分子机制的研究进展

从病毒基因与宿主细胞基因的重组、病毒基因的复制与重排、病毒基因的重复复制和序列插入、病毒基因的缺失和点突变几个方面阐述了牛病毒性腹泻病毒（BVDV）由非致细胞病变型（NCP）向致细胞病变型（CP）转化的分子变异机制。总结了前人对NCP型向CP型BVDV转化研究的结果，归纳了5种生物型转化形式，揭示了BVDV具有高变异性。     

新型猪流感疫苗研究进展

猪流感病毒能够跨越物种传播并广泛流行,对人畜健康与社会经济危害严重,因此防控该病毒的发生和流行意义重大。在防控方法中效果最明显,应用最广泛,研究最成熟的是用猪流感疫苗免疫。利用基因工程技术研制的猪流感疫苗能有效降低猪群中猪流感的发病率和猪作为人-禽流感储存宿主引起流感跨种传播的可能性。本文通过分析总结猪流感基因工程疫苗的种类、制作方法和免疫效果,为今后猪流感疫苗的研究提供参考。     

一株欧洲类禽H1N1猪流感病毒的分离鉴定与反向遗传系统的建立

猪流感是猪常见的呼吸道传染病,临床以高热、呼吸困难、咳嗽和衰竭、迅速康复或死亡为特征。猪流感不仅给养猪业造成巨大损失,也严重威胁着人类健康。本研究从发病猪场中分离到1株H1N1亚型猪流感病毒,序列分析结果显示,分离毒株属于欧洲类禽猪流感H1N1亚型病毒。将分离毒株分别接种到MDCK与ST细胞,观察病毒的生长特性,结果显示分离的猪流感病毒在ST细胞中复制能力较强。采用RT-PCR技术分别扩增8个基因片段,克隆到流感病毒反向遗传系统,成功拯救出猪流感病毒毒株,测序结果显示拯救的猪流感病毒与亲本毒序列一致。本研究成功分离的猪流感病毒,以及建立的反向遗传技术为研究欧洲类禽猪流感病毒跨种传播的机制以及研发新型猪流感疫苗株奠定了基础。     

1株禽源猪流感H6N6病毒的反向遗传系统的建立

为建立禽源猪流感病毒A/swine/Guangdong/K6/2010(H6N6)的反向遗传系统,本试验构建了包含有GDK6毒株基因组的8个重组质粒,转染293T细胞后成功拯救出病毒r GDK6。救获病毒与亲本病毒拥有相同基因序列,其抗原性、经HI试验、TCID50试验和小鼠攻毒试验表明,救获病毒的生物学特性与对小鼠的致病性与亲本病毒一致。禽源猪流感H6N6病毒的反向遗传系统的成功建立为进一步研究H6亚型流感病毒的分子致病机理与病毒基因功能及新型疫苗创制提供了技术平台。     

猪流感的综合防治

猪流感是甲型流感病毒引起的猪或人的一种急性、人畜共患呼吸道传染性疾病,通过污染的空气飞沫或与感染猪流感病毒的病畜或人接触而传播。病猪以发热、呼吸道炎症及肌肉关节痛为特征,人感染猪流感后的临床早期症状与普通流感类似,出现发烧、咳嗽、疲劳、食欲不振等症状,还可出现腹泻或呕吐。近年来,全球各地陆续发生人感染猪流感病例,造成巨大的公共安全威胁。2009年3月墨西哥和美国等地先后发生人感染H1N1亚型猪流感,该病毒具有猪流感、禽流感和人流感三种流感病毒的基因片断,是一种新型猪流感病毒,可人群间传播,随着病情的发展,出现高热、肺炎等症状,重者可出现呼吸衰竭、多器官损伤,导致死亡。     

猪流行性感冒

猪流行性感冒(Swineinfluenza,SI)简称猪流感,是由A型猪流感病毒引起的一种急性、热性、高度接触性的呼吸道传染病。其特征为,发病急骤,传播快,咳嗽,呼吸困难。发病率高,病死率低。本病的病程、病性及严重程度随病毒毒株、猪的年龄、免疫状态、环境因素以及并发和继发感染的不同而异。本病自1918年在美国首次报道,1931年Shope首次分离到猪流感病毒以来,在世界分布范围有了很大扩展。现世界上许多国家都先后发现猪流感病毒和与之相应的抗体。病原猪流感病毒(Swineinfluenzavirus,SIV)属于正黏病毒科流感病毒属。根据病毒粒子蛋白的抗原性…     

Genetic diversity of H9N2 influenza viruses from pigs in China: a potential threat to human health?

Pandemic strains of influenza A virus might arise by genetic reassortment between viruses from different hosts. Pigs are susceptible to both human and avian influenza viruses and have been proposed to be intermediate hosts or mixing vessels, for the generation of pandemic influenza viruses through reassortment or adaptation to the mammalian host. In this study, we summarize and report for the first time the coexistence of 10 (A-J) genotypes in pigs in China by analyzing the eight genes of 28 swine H9N2 viruses isolated in China from 1998 to 2007. Swine H9N2 viruses in genotype A and B were completely derived from Y280-like and Shanghai/F/98-like viruses, respectively, which indicated avian-to-pig interspecies transmission of H9N2 viruses did exist in China. The other eight genotype (C-J) viruses might be double-reassortant viruses, in which six genotype (E-J) viruses possessed 1-4 H5-like gene segments indicating they were reassortants of H9 and H5 viruses. In conclusion, genetic diversity of H9N2 influenza viruses from pigs in China provides further evidence that avian to pig interspecies transmission of H9N2 viruses did occur and might result in the generation of new reassortant viruses by genetic reassortment with swine H1N1, H1N2 and H3N2 influenza viruses, therefore, these swine H9N2 influenza viruses might be a potential threat to human health and continuing to carry out swine influenza virus surveillance in China is of great significance.     

Risk for interspecies transmission of zoonotic pathogens during poultry processing and pork production in Peru: A qualitative study

Interspecies transmission of pathogens is an unfrequent but naturally occurring event and human activities may favour opportunities not previously reported. Reassortment of zoonotic pathogens like influenza A virus can result from these activities. Recently, swine and birds have played a central role as “mixing vessels” for epidemic and pandemic events related to strains like H1N1 and H5N1. Unsafe practices in poultry markets and swine farms can lead to interspecies transmission, favouring the emergence of novel strains. Thus, understanding practices that lead to interspecies interactions is crucial. This qualitative study aimed to evaluate poultry processing practices in formal and informal markets and the use of leftovers by swine farmers in three Peruvian cities: Lima (capital), Tumbes (coastal) and Tarapoto (jungle). We conducted 80 direct observations at formal and informal markets and interviewed 15 swine farmers. Processors slaughter and pluck chickens and vendors and/or processors eviscerate chickens. Food safety and hygiene practices were suboptimal or absent, although some heterogeneity was observed between cities and chicken vendors versus processors. Both vendors (76%) and processors (100%) sold the chicken viscera leftovers to swine farmers, representing the main source of chicken viscera for swine farms (53%). Swine farmers fed the chicken viscera to their swine. Chicken viscera cooking times varied widely and were insufficient in some cases. Non‐abattoired poultry leads to the sale of poultry leftovers to small‐scale swine farms, resulting in indirect but frequent interspecies contacts that can lead to interspecies transmission of bacterial pathogens or the reassortment of influenza A viruses. These interactions are exacerbated by suboptimal safety and hygiene conditions. People involved in these activities constitute an at‐risk population who could play a central role in preventing the transmission of pathogens between species. Educational interventions on hygiene and food safety practices will be important for reducing the risk of interspecies influenza transmission.     

Serological and virological surveillance of swine H1N1 and H3N2 influenza virus infection in two farms located in Hubei province, central China

Swine influenza viruses H1N1 and H3N2 have been reported in the swine population worldwide. From June 2008 to June 2009, we carried out serological and virological surveillance of swine influenza in the Hubei province in central China. The serological results indicated that antibodies to H1N1 swine influenza virus in the swine population were high with a 42.5% (204/480) positive rate, whereas antibodies to H3N2 swine influenza virus were low with a 7.9% (38/480) positive rate. Virological surveillance showed that only one sample from weanling pigs was positive by RT-PCR. Phylogenetic analysis of the hemagglutinin and neuraminidase genes revealed that the A/Sw/HB/S1/2009 isolate was closely related to avian-like H1N1 viruses and seemed to be derived from the European swine H1N1 viruses. In conclusion, H1N1 influenza viruses were more dominant in the pig population than H3N2 influenza viruses in central China, and infection with avian-like H1N1 viruses persistently emerged in the swine population in the area.     

Swine influenza viruses isolated in 1983, 2002 and 2009 in Sweden exemplify different lineages

Swine influenza virus isolates originating from outbreaks in Sweden from 1983, 2002 and 2009 were subjected to nucleotide sequencing and phylogenetic analysis. The aim of the studies was to obtain an overview on their potential relatedness as well as to provide data for broader scale studies on swine influenza epidemiology. Nonetheless, analyzing archive isolates is justified by the efforts directed to the comprehension of the appearance of pandemic H1N1 influenza virus. Interestingly, this study illustrates the evolution of swine influenza viruses in Europe, because the earliest isolate belonged to ''classical'' swine H1N1, the subsequent ones to Eurasian ''avian-like'' swine H1N1 and reassortant ''avian-like'' swine H1N2 lineages, respectively. The latter two showed close genetic relatedness regarding their PB2, HA, NP, and NS genes, suggesting common ancestry. The study substantiates the importance of molecular surveillance for swine influenza viruses.     

Serologic surveillance of swine H1 and H3 and avian H5 and H9 influenza A virus infections in swine population in Korea

Influenza A is a respiratory disease common in the swine industry. Three subtypes, H1N1, H1N2 and H3N2 influenza A viruses, are currently co-circulating in swine populations in Korea. An outbreak of the highly pathogenic avian influenza H5N1 virus occurred in domestic bird farms in Korea during the winter season of 2003. Pigs can serve as hosts for avian influenza viruses, enabling passage of the virus to other mammals and recombination of mammalian and avian influenza viruses, which are more readily transmissible to humans. This study reports the current seroprevalence of swine H1 and H3 influenza in swine populations in Korea by hemagglutination inhibition (HI) assay. We also investigated whether avian H5 and H9 influenza transmission occurred in pigs from Korea using both the HI and neutralization (NT) tests. 51.2% (380/742) of serum samples tested were positive against the swine H1 virus and 43.7% (324/742) were positive against the swine H3 virus by HI assay. The incidence of seropositivity against both the swine H1 virus and the swine H3 virus was 25.3% (188/742). On the other hand, none of the samples tested showed seropositivity against either the avian H5 virus or the avian H9 virus by the HI and NT tests. Therefore, we report the high current seroprevalence and co-infectivity of swine H1 and H3 influenza viruses in swine populations and the lack of seroepidemiological evidence of avian H5 and H9 influenza transmission to Korean pigs.     

猪流感病毒蛋白研究进展

猪流感（swine influenza,SI）是由猪流感病毒（swine influenza virus,SIV）引起的猪的一种传染病,其在世界各地的广泛存在和流行,给养猪业带来了巨大的经济损失。猪流感病毒属于正黏病毒科A型流感病毒属,作者就猪流感病毒蛋白,包括血凝素（HA）、神经氨酸酶（NA）、核蛋白（NP）、基质蛋白（M）、聚合酶蛋白（PA、PB1和PB2）和非结构蛋白（NS）进行简要概述,以期为猪流感病毒的致病机制、诊断、分子流行病学等方面的研究提供参考。     

H3N2亚型猪流感病毒HA基因序列测定及抗原性分析

采用RT-PCR技术对4株H3N2亚型猪流感病毒的HA基因进行了扩增,将获得的PCR产物分别与pMD18-T克隆载体连接,进行序列测定。测序结果显示,4个毒株均含有完整的开放阅读框,并且均未发现核苷酸插入或缺失现象;分离毒株间核苷酸同源性为99.4%~99.7%,氨基酸同源性为98.2%~99.3%。同源性分析表明,4个毒株与2003年的猪流感病毒广东分离株有很高同源性(均在99%以上),说明近段时间我国H3N2亚型的猪流感病毒变异不大,重组的频率不是很高,同时又与人流感病毒香港分离株有较高的同源性(均为99.4%)。交叉血凝抑制试验显示,S3株与其他3毒株抗原性差异明显。鉴于猪在流感病毒传播与复制间的特殊地位,应密切监测猪流感。     

Identification and characterization of H2N3 avian influenza virus from backyard poultry and comparison with novel H2N3 swine influenza virus

In early 2007, H2N3 influenza virus was isolated from a duck and a chicken in two separate poultry flocks in Ohio. Since the same subtype influenza virus with hemagglutinin (H) and neuraminidase (N) genes of avian lineage was also identified in a swine herd in Missouri in 2006, the objective of this study was to characterize and compare the genetic, antigenic, and biologic properties of the avian and swine isolates. Avian isolates were low pathogenic by in vivo chicken pathogenicity testing. Sequencing and phylogenetic analyses revealed that all genes of the avian isolates were comprised of avian lineages, whereas the swine isolates contained contemporary swine internal gene segments, demonstrating that the avian H2N3 viruses were not directly derived from the swine virus. Sequence comparisons for the H and N genes demonstrated that the avian isolates were similar but not identical to the swine isolates. Accordingly, the avian and swine isolates were also antigenically related as determined by hemagglutination-inhibition (HI) and virus neutralization assays, suggesting that both avian and swine isolates originated from the same group of H2N3 avian influenza viruses. Although serological surveys using the HI assay on poultry flocks and swine herds in Ohio did not reveal further spread of H2 virus from the index flocks, surveillance is important to ensure the virus is not reintroduced to domestic swine or poultry. Contemporary H2N3 avian influenza viruses appear to be easily adaptable to unnatural hosts such as poultry and swine, raising concern regarding the potential for interspecies transmission of avian viruses to humans.     

猪流感病毒研究进展

猪流感是由猪流感病毒引起的一种呼吸道传染病。目前 ,此病在世界各地都有发生 ,危害严重 ,经济损失巨大 ,并对人类的健康构成威胁。猪流感病毒属于正黏病毒科 A型流感病毒属 ,病毒粒子多形态。该病毒对热、消毒剂敏感 ,而对干燥和低温的抵抗力强大。其分子特性为多节段的 RNA病毒 ,由 8个片段组成 ,分别编码 1 0种蛋白质。猪流感病毒能够在多种动物的细胞上增殖 ,但病毒分离和疫苗生产时 ,经常采用鸡胚接种。病毒具有血凝活性 ,但不同毒株的抗原性无明显的区分。由于病毒受到抗体的压力很大 ,因此病毒的变异频繁 ,其机理涉及分子水平的抗原漂移和抗原转变。文章对病毒的理化、生物学特性、分子特性、病毒的蛋白和基因变异等方面的研究情况进行了综述