猪圆环病毒病的防治

猪圆环病毒病是指一种由猪圆环病毒所引起的哺乳仔猪和育肥猪的临床或亚临床型传染病.对猪圆环病毒的临床症状、病理变化、诊断、治疗及防制措施等进行了概述.     

PCR快速检测猪圆环病毒2型的方法建立及应用

根据GenBank公布的猪圆环病毒2型保守序列设计了一对引物,建立了检测猪圆环病毒2型的PCR方法,并对其特异性、敏感性进行了研究.该PCR方法对猪圆环病毒2型扩增结果为阳性,对照毒株扩增结果均为阴性;对猪圆环病毒2型检测的灵敏性为1pg总DNA量.结果表明,该PCR方法特异性强、敏感性高、简便、快速,可用于猪圆环病毒2型的早期确诊和病毒鉴定.     

猪圆环病毒的危害与净化

猪圆环病毒是圆环病毒科圆环病毒属的DNA病毒,根据其基因型的不同可分为1型猪圆环病毒和2型猪圆环病毒。1型猪圆环病毒通常不会对猪造成任何危害,而2型猪圆环病毒则具有较大的致病性。该病毒不仅与猪细小病毒病和繁殖障碍综合症等多种疾病存在一定的相关性,同时可引发猪的肠炎以及间质性肺炎等多系统功能障碍性疾病,给生猪养殖业造成巨大的经济损失。因此,做好猪圆环病毒的净化工作具有非常重要的现实意义。     

猪圆球病毒研究进展

猪圆环病毒病是新发现的一种传染病.该病对猪的感染较高,在世界范围内广泛发生,已成为严重影响养猪业发展的传染病之一,引起世界许多国家兽医工作者的高度重视.猪圆环病毒主要侵犯机体的免疫系统,导致猪体的免疫抑制用及抵抗力下降,干扰和破坏猪对其它疫病免疫抗体的产生和维持,从而继发或并发其它疾病.本文就近几年来国内外对猪圆环病毒的研究状况进行了综述,包括猪圆环病毒的发现、研究历史,分子生物学特性,致病性,致病机理,病原的检测以及其防制及对策等方面.     

猪圆环病毒病诊断与综合防控技术

猪圆环病毒病是由猪圆环病毒2型(PCV-2)引起的,以系统功能障碍、免疫力下降为特征的一种传染病,猪是唯一的易感宿主,各年龄段的猪均可感染.我国自2001年发现该病以来,全国各地不同规模化的猪场都在发生该病,给生猪养殖行业造成了巨大的经济损失.文中从猪圆环病毒病的病原、流行特点、临床症状、诊断和防控措施进行阐述,为猪圆环病毒病的综合防治提供一定的参考依据.     

猪圆环病毒研究进展

猪圆环病毒(Porcine circovirus,PCV)是圆环病毒科圆环病毒属成员,为已知的最小动物病毒之一,分为I型(PCV-1)和II型(PCV-2)两个型.由于猪圆环病毒可以使感染猪出现免疫抑制,可以与多种病原混合感染导致多系统、多组织的损伤,造成严重的经济损失,已经成为当前世界关注的焦点.     

温度对猪圆环病毒培养滴度的影响

为了猪圆环病毒生产批次间滴度的稳定性,提高病毒产量,本实验对猪圆环病毒的培养温度参数进行了研究.结果显示,病毒培养温度36℃时,收获毒液病毒滴度明显下降,培养温度为37℃和38℃时,病毒滴度基本持平,均能稳定在较高水平.     

猪圆环病毒病

猪圆环病毒病（PCVD）是指一种由圆环病毒科、圆环病毒属的猪圆环病毒（Porcinecircovirus，PCV）所引起的哺乳仔猪和育肥猪的临床或亚临床型传染病。猪圆环病毒是一种高度异质的单股环状DNA病毒，具有严格的种属和组织特异性，主要感染猪的皮肤和粘膜组织，引起相应部位上皮组织的增生性病变，猪圆环病毒还能加重猪呼吸和繁殖障碍综合征病毒（PRRS），猪细小病毒（PPV）等感染。现已确认猪圆环病毒病（PCVD）发生于全世界，对养猪业带来了严重的经济损失。从而本文对猪圆环病毒的病原学、流行病学、临床症状、病理变化、诊断、治疗及防制措施等作一简要概述。     

猪圆环病毒的复制

猪圆环病毒是环状的单链DNA病毒,可以感染家猪和野猪。猪圆环病毒有两种型。猪圆环病毒2型可以引起断奶后多系统衰竭综合征,与此相反,猪圆环病毒1型没有致病性。猪圆环病毒DNA通过滚环复制机制进行复制。另有研究显示,质粒和单链病毒有类似的滚环复制机制,如双生病毒。滚环复制中重要的3种元件:①编码启动蛋白的基因;②双链起始位点;③单链起始位点。但是病毒与质粒之间以及不同的病毒之间存在着不同。猪圆环病毒的复制是采用融合型滚环复制机制,而不是交叉型滚环复制机制。作者对当前有关以猪圆环病毒复制作为圆环病毒属模型的研究进展进行了总结。通过多方面的研究,确定了影响复制的因素,并对复制不同时期的机制进行了描述或提出了假设。     

关注猪圆环病毒

近年来,尽管国内外学者在猪圆环病毒的研究方面取得了不小成就,但到目前为止,仍还没有找到有效的方法和措施来控制猪圆环病毒对养猪业的危害,尤其在我国养猪业是一个亟待解决的问题。本期关注郑四清在《关注猪圆环病毒》一文中详细介绍了猪圆环病毒的来由、危害、以及发生严重危害的原因、病毒的诊断、控制等几方面的内容,希望能为广大养殖户在猪圆环病毒防治上有所启示。     

ORF1 but not ORF2 dependent differences are important for in vitro replication of PCV2 in porcine alveolar macrophages singularly or coinfected with PRRSV

The objective of this study was to investigate cytokine expression and in vitro replication of porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV) in pulmonary alveolar macrophages (PAMs) emphasizing PCV2 open-reading frame (ORF) origin (PCV2a or PCV2b) and PRRSV strain. Chimeric PCV2 viruses composed of different combinations of ORF1 and ORF2 of PCV2a or PCV2b (chimera PCV2a-2b and chimera PCV2b-2a) were constructed and five different PRRSV isolates were utilized: Type 1 (SD 01-08) or type 2 (NC16845b, VR-2332, MN-184, JA-142). PAMs were infected singularly or with combinations of PCV2b, PCV2a, chimera PCV2a-2b, and chimera PCV2b-2a, and one of the five PRRSV isolates. Real-time PCR was used to test PAMs (PCV2 mRNA) and supernatants (PRRSV RNA, PCV2 DNA, PCV2 mRNA) harvested at 24, 48, 72 and 96h post inoculation (hpi). Levels of IFN-γ, TNF-α and IL-10 were determined by quantitative ELISAs. PCV2 replication in PAMs was limited to groups inoculated with PCV2 strains containing ORF1 of PCV2a (PCV2a, chimera PCV2a-2b). Furthermore, in supernatants, PCV2 mRNA was only detected in groups coinfected with PRRSV regardless of strain at 48hpi supporting an enhancing effect of PRRSV on PCV2 infection. Changes in cytokine levels were minimal and associated with PRRSV strain for TNF-α. In summary, in vitro differences in PCV2 replication in PAMs inoculated with different PCV2-PRRSV combinations were independent of PCV2 ORF2 origin with minimal effects of concurrent PRRSV infection perhaps indicating that PCV2-specific changes in ORF1 may be more important than those in ORF2.     

Antigenic subtyping and epitopes' competition analysis of porcine circovirus type 2 using monoclonal antibodies

Porcine circovirus type 2 (PCV2) strains have been classified into two major genotypes (PCV2a and PCV2b) and 8 genetic clusters: PCV2b-1A to PCV2b-1C and PCV2a-2A to PCV2a-2E. To date, no studies have been performed to antigenically subtype PCV2 strains enclosing eight PCV2 clusters. The present study aimed to antigenically subtype PCV2 and perform epitopes' competition analysis using monoclonal antibodies (mAbs). Fourteen PCV2 strains representative for eight clusters were tested with 20 mAbs (fifteen of them were generated against PCV2a strain Stoon-1010 and 5 of them against PCV2b strain 1147) in immunoperoxidase monolayer assays. Four mAbs reacted to all 14 PCV2 strains and one mAb reacted with all strains except for a PCV2a-2C strain. One mAb reacted with all PCV2a strains, except for a PCV2a-2C strain and one mAb reacted with all PCV2b strains, except for a PCV2b-1C strain. Nine mAbs reacted with the strains of PCV2b-1A/1B, PCV2a-2A and PCV2a-2E. Three mAbs only reacted with the strains of PCV2a-2A and PCV2a-2E. One mAb reacted specifically with the strains of PCV2b-1A/1B. This suggests that discrete antigenic differences exist between different PCV2 genetic clusters and that these clusters can be discriminated by the use of a panel of universal and cluster-specific mAbs. Six mAbs were selected for cross-competition analysis by a competitive ELISA using PCV2 strain Stoon-1010. Six overlapping epitopes were identified on the PCV2 capsid protein. The universal mAbs recognized larger epitopes than the cluster-specific mAbs. These findings are helpful in the development of diagnostic tests and new generation vaccines against PCV2.     

猪圆环病毒2型分子流行病学及疫苗研究进展

猪圆环病毒2型(PCV2)在世界范围内广泛分布,主要以PCV2a和PCV2b两种基因型为主,PCV2b亚型为当前流行基因型。现有商品化疫苗主要针对PCV2a型病毒,也可对PCV2b型病毒产生部分交叉保护,但不能显著控制PCV2b型病毒在猪群中的传播。除此之外,由于已有的商品化疫苗以传统疫苗为主,存在种毒增殖难、疫苗生产周期长等缺点。因此,研发PCV2b新型疫苗可能成为未来PCV2疫苗研制的主要方向。对PCV2的分子流行病学及疫苗研究现状进行了综述,以期为PCV2疫苗的研究提供参考。     

Retrospective serological survey of antibodies to porcine circovirus type 1 and type 2.

A retrospective serological survey was performed to determine the presence of antibodies to porcine circovirus type 1 (PCV1) and porcine circovirus type 2 (PCV2) in serum samples collected from sows at slaughterhouses in Canada in 1985, 1989, and 1997. Each serum sample was tested by indirect immunofluorescence on PCV-free PK15 cells, on PCV1-infected PK15 cells and on PCV2-infected PK15 cells. For the 3 years studied, sera positive to PCV1 and PCV2 were identified and the number of sera positive for PCV2 was greater than the number of sera positive for PCV1. The results indicated 1) that PCV2 appears to be the main PCV type circulating in the Canadian pig population, 2) that PCV2 had been circulating in the Canadian pig population at least 10 years before the postweaning multisystemic wasting syndrome (PMWS) was reported, and 3) that serological evaluation using PCV1 underestimates the seroprevalence of PCV2.     

Effect of porcine circovirus type 2 (PCV2) vaccination on PCV2-viremic piglets after experimental PCV2 challenge

The objective of this study was to evaluate the effect of porcine circovirus type 2 (PCV2) vaccines on PCV2-viremic and -seropositive piglets born from naturally PCV2-infected sows against postnatal PCV2 challenge. The experimental design was aimed at mimicking commercial swine rearing conditions to evaluate the response of the PCV2 vaccine on PCV2-viremic and -seropositive piglets after experimental PCV2 challenge. PCV2a (or 2b)-viremic piglets received a PCV2 vaccine at 21 days of age followed by a PCV2b (or 2a) challenge at 49 days of age (28 days post vaccination). The PCV2 vaccines elicited a high level of humoral (as measured by immunoperoxidase monolayer assay and neutralizing antibody titers) and cellular (as measured by the frequency of PCV2-specific interferon-γ-secreting cells) immune response in the PCV2-viremic piglets after vaccination even in the presence of maternally derived antibodies (MDA). The initial infection of PCV2 in the pigs was not affected by PCV2 vaccination, however the challenging PCV2 was reduced by PCV2 vaccination on PCV2-viremic pigs. The results from this study demonstrate that the PCV2 vaccine used in this study is effective at reducing PCV2 viremia and lymphoid PCV2 DNA, even for PCV2-viremic pigs with passively acquired MDA at the time of vaccination.     

Establishment and Rudimentary Application of the nano-dPCR for Detection of PCV2 and PCV3

This study was aimed to establish a duplex nanoparticle-assisted PCR (nano-dPCR) method for the simultaneous detection of porcine circovirus type 2 (PCV2) and PCV3, and to apply this method in the detection of PCV2 and PCV3. Primers specific to PCV2 and PCV3 were designed by reference to the respective gene sequences in GenBank. The reaction conditions of nano-dPCR were also optimized. An evaluation of the specificity and sensitivity of the established nano-dPCR protocol proved the method to be both specific and sensitive, with the lower detection limit for the amount of nucleic acid in PCV2 and PCV3 to be 93.2 and 91.6 copies/μL, respectively. This sensitivity was 100 times higher than that of conventional PCR. The method was applied to inspect 265 clinical samples sent for testing, and the results showed that PCV2 and PCV3 infection in pig was rather common, with 16.6% positive for PCV3, 14.7% positive for PCV2, and 6.8% for mixed infection. The detection results on clinical samples supported the newly established nano-dPCR method as a rapid and sensitive differential diagnosis for the early infection of PCV2 and PCV3.     

PCV2和PCV3双重纳米PCR方法的建立及初步应用

本研究旨在建立一种同时检测猪圆环病毒2型（PCV2）和猪圆环病毒3型（PCV3）的双重纳米PCR（nano-dPCR）方法,同时应用该方法对PCV2和PCV3进行检测。参考GenBank中登录的PCV2和PCV3型基因序列分别设计特异性引物,对nano-dPCR的反应条件进行优化;同时考察所建立的nano-dPCR检测方法的特异性和敏感性。结果显示,所建方法的特异性和敏感性良好,对PCV2和PCV3两种病毒的最低核酸检测量分别为93.2和91.6拷贝/μL,其敏感性比普通PCR高100倍。应用该方法对送检的265份临床样本进行检测,结果显示,PCV2和PCV3在猪群中存在普遍感染,PCV3和PCV2的阳性率分别为16.6%和14.7%,混合感染阳性率为6.8%。临床样品的检测结果表明,本试验建立的nano-dPCR方法为PCV2和PCV3早期感染进行快速、敏感鉴别诊断提供了新方法。     

Porcine reproductive and respiratory syndrome virus (PRRSV) influences infection dynamics of porcine circovirus type 2 (PCV2) subtypes PCV2a and PCV2b by prolonging PCV2 viremia and shedding

The objective of this study was to determine the effect of porcine reproductive and respiratory syndrome virus (PRRSV) infection on porcine circovirus type 2 (PCV2) subtypes a (PCV2a) or b (PCV2b) viremia and shedding characteristics in oral, nasal and fecal samples in experimentally infected pigs. Twenty-three, 2- to 6-week-old pigs were randomly divided into five groups: negative control (n=3), PCV2a-I (n=5), PCV2a-PRRSV-CoI (n=5), PCV2b-I (n=5), and PCV2b-PRRSV-CoI (n=5). Blood, oral, nasal and fecal swabs were collected in regular intervals from day post inoculation (dpi) 0 until dpi 70 and tested by quantitative real-time PCR for the presence and amount of PCV2 DNA and by ELISA for the presence of PCV2-specific antibodies. The results indicate that there were significantly (P<0.05) higher loads of PCV2a and PCV2b DNA in serum, oral swabs, nasal swabs and fecal swabs and a higher prevalence of detectable PCV2 antigen in tissues of pigs concurrently infected with PCV2 and PRRSV compared to pigs singularly infected with PCV2 further confirming that PRRSV enhances replication of PCV2. Moreover, PRRSV infection significantly prolonged the presence of PCV2 DNA in serum and increased the amount of PCV2 DNA in oral and nasal secretions and fecal excretions in the later stages of infection between dpi 28 and 70. Shedding patterns were similar between groups infected with PCV2a and PCV2b, indicating that there was no subtype-specific interaction with the PRRSV isolate used in this study. The results from this study highlight the interaction between PRRSV and PCV2 and the importance of controlling PRRSV infection in order to reduce PCV2 virus loads in pig populations.     

The detection of porcine circovirus in the Australian pig herd

OBJECTIVE: To determine if porcine circovirus (PCV) type 1 (PCV1) or type 2 (PCV2) is present in the Australian pig herd, to conduct preliminary genetic characterisation of any viruses detected, and to determine if there is any obvious virological reason why post-weaning multisystemic wasting disease (PMWS), associated with PCV infection in other countries, has not been detected in Australia. DESIGN: Serum samples were collected from 14 randomly selected pig farms in Western Australia and used for detection of PCV antibody. Additional samples from one farm were obtained at 2-week intervals from pigs between 2 and 12 weeks of age to detect any age-associated variations in prevalence of infection. Veterinary practitioners from four Australian states submitted tissues of dead or unthrifty weaned pigs, and these were examined for evidence of PCV1 and PCV2 infection. PROCEDURE: Sera were tested for antibody to PCV using an indirect immunofluorescence assay (IFA). Tissues were tested for PCV1 and PCV2 genomic material using a multiplex PCR. RESULTS: PCV antibody was detected in approximately 30% of Western Australian pigs tested. PCV1 DNA was detected in tissue samples from Western Australia, South Australia and New South Wales and PCV2 DNA was detected in tissue samples from Western Australia, New South Wales and Queensland. Sequence analysis of the PCR products indicated the PCV1 and PCV2 present in Australia were very similar to strains in other countries where PMWS is endemic. CONCLUSION: Both PCV1 and PCV2 are present in Australia and the viruses present appear similar to those in countries with PMWS. The absence of PCV2-associated PMWS in Australia may be due to absence of essential secondary factors required for PCV2 to produce PMWS.     

Effect of porcine circovirus type 2 (PCV2) infection on reproduction: disease, vertical transmission, diagnostics and vaccination

Porcine circovirus type 2 (PCV2) causes great economic losses in growing pigs and there are several reviews on disease manifestations and lesions associated with PCV2 in growing pigs. Reproductive failure in breeding herds, predominately associated with increased numbers of mummies and non-viable piglets at parturition, is one of the disease manifestations of PCV2 infection. Boars shed low amounts of infectious PCV2 in semen for extended time periods, and vertical transmission of PCV2 to fetuses during PCV2 viremia of the dam has been experimentally confirmed. However, intrauterine-infected piglets often are clinically normal. Nevertheless, pigs infected with PCV2 by the intrauterine route can be born viremic, possibly contributing to horizontal spread of PCV2 within the breeding herd and into the nursery. Shedding of PCV2 in semen and prevalence of intrauterine-infected piglets can both be greatly reduced by PCV2 vaccination well ahead of expected PCV2 exposure. This review is a discussion on current knowledge on the effects of PCV2 infection in the dam and in in utero fetuses, including clinical signs, lesions, diagnosis and prevention through vaccination. Infection of boars with PCV2, the potential for PCV2 transmission via semen and prevention of PCV2 shedding are also discussed.