猪圆环病毒病的防控

猪圆环病毒(PCV)属于圆环病毒科圆环病毒属,为环状、单股DNA病毒,含1767-1768个核苷酸,是动物病毒中最小的一员.圆环病毒分1型和2型,其中2型(PCV2)致病性明显大于1型,临床表现的相关性疫病主要由2型引起.     

Porcine circovirus diseases

Porcine circovirus type 2 (PCV2) is a member of the family Circoviridae, a recently established virus family composed of small, non-enveloped viruses, with a circular, single-stranded DNA genome. PCV2, which is found all over the world in the domestic pig and probably the wild boar, has been recently associated with a number of disease syndromes, which have been collectively named porcine circovirus diseases (PCVD). Postweaning multisystemic wasting syndrome (PMWS), porcine dermatitis and nephropathy syndrome (PDNS) and reproductive disorders are the most relevant ones. Among them, only PMWS is considered to have a severe impact on domestic swine production. PMWS mainly affects nursery and/or fattening pigs; wasting is considered the most representative clinical sign in this disease. Diagnosis of this disease is confirmed by histopathological examination of lymphoid tissues and detection of a moderate to high amount of PCV2 in damaged tissues. Since PMWS is considered a multifactorial disease in which other factors in addition to PCV2 are needed in most cases to trigger the clinical disease, effective control measures have focused on the understanding of the co-factors involved in individual farms and the control or elimination of these triggers. PDNS, an immuno-complex disease characterized by fibrino-necrotizing glomerulonephritis and systemic necrotizing vasculitis, has been linked to PCV2, but a definitive proof of this association is still lacking. PCV2-associated reproductive disease seems to occur very sporadically under field conditions, but it has been characterized by late-term abortions and stillbirths, extensive fibrosing and/or necrotizing myocarditis in fetuses and the presence of moderate to high amounts of PCV2 in these lesions. Taking into account that scientific information on PCV2 and its associated diseases has been markedly expanded in the last 8 years, the objective of this review is to summarize the current state of knowledge of the most relevant aspects of PCV2 biology and PCVD.     

猪圆环病毒2型研究进展

猪圆环病毒2型（PCV2）已成为家猪和野猪常见的一种病毒病,由其引起的疾病称为猪圆环病毒相关疾病（PCVAD）,自猪圆环病毒相关疾病（PCVAD）暴发以来,已成为近年来阻碍养猪业发展的重要传染病。为了进一步了解该病,以便更好地预防和控制该病,本文从病原学、流行病学、致病机理、临床症状、防控措施等方面进行了综述。     

猪圆环病毒Ⅱ型感染的免疫抑制机理研究进展

猪圆环病毒感染是新发现的一种传染病。该病对猪的感染率较高,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。圆环病毒主要侵袭猪的免疫系统,干扰和破坏机体对疾病免疫抗体的产生和维持,致使抵抗力下降,从而容易继发或并发其他疾病。近年来,国内外学者对猪圆环病毒入侵免疫系统的机制做了大量研究,在病毒的复制机制、对细胞因子和淋巴细胞的影响以及与猪皮炎和肾病综合征的关系等方面均取得了一定的进展,为猪圆环病毒感染的预防和治疗奠定了基础。     

Porcine circovirus type 2 antibody detection in backyard pigs from Mexico City

PCV2 antibodies have been found in pigs from all continents. However, this finding has been mainly studied in domestic swine reared under intensive production conditions. Mexico City, with a human population over 19 million in 2005, has both urban and rural areas. The pig production in its rural area is based on small family backyard farms. Taking into account this rather unique form of rearing pigs, the objective of this study was to determine the seroprevalence in backyard pigs from the rural area of Mexico City. A total of 695 backyard pig serum samples from 108 small family farms belonging to seven municipal areas were studied by immunoperoxidase monolayer assay technique. One hundred six out of the 108 family farms (98.14%) had at least one positive serum sample. On the other hand, 136 (19.57%), 264 (37.99%) and 248 (34.82%) pigs had low, intermediate and high titres to PCV2, respectively. Only 53 samples (7.63%) were negative for PCV2 antibodies. No apparent differences in antibody titre groups were observed among backyard pigs from the different municipal areas. In conclusion, the present study, the first one performed in this kind of extensively produced pigs, indicates that PCV2 is ubiquitous in backyard pigs from Mexico City.     

Fatal bronchopneumonia in a Metastrongylus elongatus and Porcine circovirus type 2 co-infected pig

Porcine circovirus type 2 (PCV2) infection is distributed worldwide and PCV2-associated disease (PCVAD) is considered among the most economically relevant ones to the global swine industry. PCV2 is known to play a causal role in the porcine respiratory disease complex, usually in close association with a large plethora of other biologic agents. We describe herein a case of fatal parasitic bronchopneumonia by Metastrongylus elongatus in a PCV2-infected pig. Metastrongylosis may still represent a major concern for outdoor herds. Our recent experience suggests that a concurrent PCVAD condition may trigger metastrongylosis, which may subsequently result, at its turn, in severe, sometimes fatal, pulmonary disease.     

一种猪圆环病毒Ⅱ型ELISA检测试剂盒的临床应用

本研究通过采用猪圆环病毒2-dCap-ELISA抗体检测试剂盒,对河北、山西两地共441份猪血清样品进行检测发现：河北保定地区349份血清样品中阳性样品为306份,感染率为87.68%;山西地区92份血清样品中阳性样品为77份,感染率为83.7%。与标准的间接免疫荧光检测法进行比较,发现相对于标准IFA,该ELISA检测试剂盒的诊断敏感性为95.48%(383/398),诊断特异性为93.02%(40/43),总符合率为95.24%。由此表明该试剂盒是一种简便、快速、灵敏、适于大规模临床应用的猪圆环病毒2型抗体检测试剂盒。     

国内外商品化猪圆环病毒2型疫苗分类及特点

介绍了11种商品化猪圆环病毒2型疫苗的种类、毒株组成、病毒含量及生产厂家,为了解该疫苗的商品化情况提供参考。     

猪Ⅱ型圆环病毒ORF1基因的克隆及其在大肠杆菌中的表达

根据GenBank中猪圆环病毒Ⅱ型(PCV2)0RF1基因序列,设计合成了一对引物,对PCV2广东株(GD)ORF1基因进行PCR扩增,将扩增出的ORF1基因(942 bp)克隆入pMD18-T载体,筛选获得重组质粒,命名为pMD-ORF1。将ORF1的KpnⅠ和XbaⅠ双酶切产物插入原核表达载体pBAD／gⅢC,得到重组子,命名为pBAD／gⅢ-ORF1。测序分析表明克隆的ORF1与德国分离株AF201897核苷酸序列同源性高达99.5％。与其它PCV2核苷酸序列同源性为92.1％-99.9％,推导的氨基酸序列同源性为90.2％-99.5％。同时,测序结果表明所克隆的ORF1准确插入pBAD／gⅢC的多克隆位点,未改变读码框架。用L-Arabi-nose进行诱导表达,收集茵液进行SDS-PAGE和Western blotting分析,显示PCV2 ORF1在pBAD／gⅢC中获得了高效融合表达,其表达蛋白分子量约为4.1万。     

猪捷申病毒与猪圆环病毒2型双重PCR检测方法的建立及初步应用

为建立可同时检测猪捷申病毒（PTV）与猪圆环病毒2型（PCV2）的双重PCR方法,本研究根据GenBank登录的相关病毒基因序列,选择保守区域设计引物,经过反应条件的优化,建立了可同时检测以上2种病毒的PCR诊断方法,扩增片段长度分别为187bp（PTV）、120bp（PCV2）。通过实验证明该方法具有良好的特异性和较高的敏感性,对PTV、PCV2核酸检测最低浓度分别为2．8×10^-2ng和6．6×10^-3ng。应用该方法对43份临床样品进行检测发现,PTV阳性率为23％,PCV2阳性率为38％,PTV与PCV2共感染率为16％。该方法的成功建立,为快速高效地检测以上2种病毒提供有力手段。     

Porcine circovirus type 2 (PCV2) viral components immunomodulate recall antigen responses

Porcine circovirus type 2 (PCV2) is a single-stranded circular DNA virus infecting domestic pigs worldwide. Interaction of this virus with the immune system apparently modulates the immune response of the host. In the present study, the implication of different components of PCV2 in the modulation of the immune response of the host were investigated by using PCV2 viral-like particles (VLPs) and 16 novel oligodeoxyribonucleotides containing CpG motifs (CpG-ODNs) based on the PCV2 genomic sequence. The role of these viral components was studied by evaluating the cytokine profiles (IFN-alpha, IFN-gamma, IL-10, IL-2 and IL-12) on porcine peripheral mononuclear cell (PBMC) and bone marrow-derived dendritic cell (BMDC) cultures. Also, the effect of PCV2 and its elements were examined in recall antigen (pseudorabies virus, PRV) responses. While PCV2 was a potent inducer of IL-10 by PBMCs, such effect was not observed using CpG-ODNs or VLPs. However, IFN-gamma and IL-2 production by recall antigen was repressed in presence of PCV2 and most of the studied CpG-ODNs. VLPs did not have such repressive effect. In BMDC cultures, PCV2 and most of CpG-ODNs were able to inhibit IFN-alpha secretion induced by PRV. Interestingly, CpG-ODNs with inhibitory effect were located within the PCV2 Rep gene. Additionally, PCV2 virus was a very strong IL-12 inducer in BMDC cultures. Whereas, IFN-alpha modulation on BMDC after PCV2 VLP treatment was neglectable, PCV2 VLPs were potent IL-12 inducers. Our data shows that PCV2 viral elements can distinctly regulate cytokine production depending on the cell population studied. Thus, the final immune response upon PCV2 infection seems to depend on the fine balance between the regulatory elements present in viral DNA and structural protein within the host immune system.     

猪圆环病毒病

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。尽管最近全世界许多实验室对此病进行的研究使我们获得了大量的有关知识,但我们对其病程的了解仍有重要缺陷,因而仍然无法对其进行有效防制。     

猪细小病毒、伪狂犬病病毒和猪圆环病毒2型多重PCR检测方法的建立及应用

根据猪细小病毒(PPV)、伪狂犬病病毒(PRV)和猪圆环病毒2型(PCV-2)的基因序列,分别选取各自的保守区段设计引物,通过反应条件的优化,建立了检测PPV、PRV和PCV-2的多重PCR方法.用建立的方法对采自陕西省部分猪场的286份病料及血样进行检测,从对临床健康猪全血样品中PPV、PRV和PCV-2的检测结果看...     

Porcine circovirus type 2 detection in in vitro produced porcine blastocysts after virus sperm exposure

This study was aimed at assessing the capability of semen experimentally infected with porcine circovirus type 2 (PCV2) to produce porcine blastocysts PCR positive for PCV2. Embryos were obtained from in vitro maturation (IVM) and in vitro fertilization (IVF) of porcine oocytes or by parthenogenesis. Sperm suspension was exposed to PCV2b and utilized for IVF. PCV2 spiked semen did not reveal any reduction in sperm viability or motility but its ability to produce infected blastocysts was irrelevant as only one out of 15 blastocysts obtained by IVF were PCV2b; however two blastocysts were PCV2a positive. Furthermore, the presence of PCV2 was demonstrated also in embryos obtained by parthenogenesis (one out of 17 was PCV2b and one PCV2a positive). Even if PCV2 firmly attaches to the surface of spermatozoa, experimentally spiked sperm were not effective in infecting oocytes during IVF and in producing PCR positive embryos. The infected blastocysts we obtained derived most probably from infected oocytes recovered at the abattoir.     

Pathological findings associated with naturally acquired porcine circovirus type 2 associated disease

Porcine circovirus type 2 (PCV2) is a novel virus of the Circoviridae family which is considered the cause of postweaning multisystemic wasting syndrome (PMWS). PCV2 has also been associated to a number of pathological conditions of pigs, including porcine dermatitis and nephropathy syndrome, reproductive failure, porcine respiratory disease complex, proliferative and necrotising pneumonia and congenital tremor type AII. Pathological studies have been used to describe and characterise PMWS and these emerging conditions associated with PCV2. The objective of this review is to concentrate on the gross, microscopic and ultrastructural pathology associated with natural cases of PCV2 associated disease, along with some speculations on the pathogenesis of naturally occurring PMWS.     

猪圆环病毒2型广西流行株序列比较分析

参考GenBank发表的猪圆环病毒2型(Porcine circovirus type 2,PCV-2)全基因组序列,设计引物,通过反向PCR技术,从广西部分市区疑似"高热病"病猪的组织中,扩增9株PCV-2流行株的全基因,并进行了序列测定分析.结果表明,9个PCV-2分离株基因组全长为1 767 bp或1 768 bp.同源性比较发现,9个分离株之间的核苷酸同源性为94.6%～99.9%,与GenBank上已发表的国外分离株比较,同源性为94.4%～100%;9个分离株ORF2之间的核苷酸及其所推导的氨基酸序列同源性分别为93.7%～99.4%和93.6%～99.1%;系统发育树显示,其中7个分离株与法国株、新西兰株关系较近,与美国株和加拿大株关系较远;另外2个分离株与澳大利亚株、美国株亲缘关系较近.     

Detection of Porcine circovirus type 2 viremia and seroconversion in naturally infected pigs in a farrow-to-finish barn

Porcine serum was assayed by 2 polymerase chain reaction (PCR) protocols (nested PCR [nPCR] and non-nested PCR) and a competitive enzyme-linked immunosorbent assay to determine when Porcine circovirus type 2 (PCV2) viremia and a rise in the serum level of PCV2-specific antibody occurred in pigs raised in a large Canadian farrow-to-finish barn. Eight serial blood samples were collected from each of 40 pigs from 5 to 156 (+/- 1.5) d of age; 6 pigs were removed from the study for various reasons at various times. Viremia was not detected in the samples collected before 72 d of age but was detected in those collected on or after 72 d: of 33 pigs, 7 (21%) had only 1 serum sample positive for PCV2 DNA by nPCR after day 72; 11 (33%) were intermittently positive by nPCR, non-nested PCR, or both between 72 and 156 d; and the remaining 15 (45%) were repeatedly positive (in 2 to 4 samples). The level of serum antibody against PCV2 declined after weaning and increased between 72 and 107 d of age, only after PCV2 was detected in serum. Our results show that PCV2 viremia persists in the presence of elevated levels of PCV2-specific antibody.