猪圆环病毒研究进展

自20世纪70年代Tischer等首次发现猪圆环病毒(Porcine circovirus,PCV)以来,随着对PCV的了解与研究的逐渐深入,发现由它引发的各种疾病对养猪业的影响越来越大,造成的各种损失日趋严重.     

猪圆环病毒致病机理研究进展

猪圆环病毒(PCV)是当今危害世界养猪业最严重的病毒之一,可以造成免疫抑制,引起其他相关疾病的继发和并发感染,给养猪业造成了巨大的经济损失。通过对圆环病毒的致病机理的研究进展进行总结分析,以期为猪圆环病毒病的防控提供理论依据。     

猪圆环病毒研究进展

猪圆环病毒(Porcine Circovirus,PCV)是德国学者Tischer于1974年在多株连续传代的PK-15(ATCCCCL31)细胞中发现的一种形态类似小RNA病毒的圆形小颗粒病毒和乳多泡病毒样病毒粒子,该病毒可以持续感染PK-15细胞,不会引起细胞病变(CPE).Clark报道,1991年在加拿大的猪群中存在一种被称为猪断奶多系统消耗综合征(Postweaning Multisystemic Wasting Syndrome,PMWS)的新猪病,患病猪主要表现为进行性消瘦,呼吸困难,体表淋巴结肿大,苍白和腹泻.同年,Pejsak等首先报道在苏格兰存在一种名为猪皮炎肾病综合征(Porcine dermatitis and nephropathy syndrome,PDNS)的新猪病,其特点是全身性脉管炎和肾小球肾炎.     

猪圆环病毒研究进展

猪圆环病毒与猪的多种疾病密切相关,可给养猪业带来巨大经济损失,因此了解其病原特征、基因组结构、流行病学、致病机理、诊断方法至关重要。本文针对这几方面对猪圆环病毒作了一个较为全面的概述,使人们更好了解这一病毒,从而加强对该病的防治,减轻其对养猪业造成的危害。1病原特征及基因组结构功能猪圆环病毒(PCV)为无囊膜单股环状负链DNA病毒,是迄今发现的最小动物病毒。PCV以滚环方式复制,呈20面体对称,无囊膜,直径17nm￣22nm,含有1.76kb￣2.3kb的单链环状DNA,相对分子质量58ku,沉降系数为52S。该病毒根据其抗原性及其基因组成不…     

猪圆环病毒研究进展

猪圆环病毒(Porcine circovirus，PCV)由德国学者Tischer从PK-15猪肾传代细胞系中分离获得。该病毒可长期持续感染PK-15却不表现细胞病变(CPE)。后来证实PK-15中存在的这种病毒来源于当初制备PK-15细胞的猪肾组织。该病毒基因组由一个单股圆环状的DNA链组成，是一种新发现的病毒，将其命名为圆环病毒。血清学调查发     

猪圆环病毒研究进展

猪圆环病毒(Porcine circovirus，PCV)是断奶猪多系统衰竭综合(Postweaning pigs multisystemic wasting sndrom，PMWS)的病原。随着该病的不断出现，人们越来越注意到猪圆环病毒的危害性。为了更加全面地本质地认识该病毒，本文对其流性病学、理化特性、致病机理、诊断方法及分子生物学作了较为全面的综述。     

猪圆环病毒的致病机理及其影响因素

猪圆环病毒2型(PCV2)感染可损伤猪的免疫系统,引起感染猪的胸腺萎缩、T细胞和B细胞数量减少;细胞因子的表达量改变,如IL-10的量上升,IL-8的量明显下降,IFN-γ量减少。同时,PCV2感染的靶细胞在胎儿期是心肌细胞、肝细胞和巨噬细胞,而出生后只有巨噬细胞。因而推测猪感染PCV后,机体的免疫力下降,感染猪处于亚健康状态,其它病原因子如猪繁殖与呼吸综合征病毒、细小病毒、衣原体、猪流感、肺炎支原体和胸膜肺炎放线杆菌等,或应激因素如营养元素缺乏、免疫刺激和较差的饲养管理等多种因素都可加重PCV2感染猪的病情,进而发展成临床症状和病理变化较明显的断奶后仔猪多系统综合征、猪肾病综合征等与猪圆环病毒相关痰病。     

猪Ⅱ型圆环病毒病的研究进展

圆环病毒科(Circoviridae)是国际分类委员会(ICTV)第六次学术报告新命名的一个科.本科既有植物病毒又有动物病毒,动物病毒主要有猪圆环病毒(PCV)、鸡贫血病毒(CAV)和鹦鹉喙羽病病毒(PBFDV),最近在人体内也已发现一种圆环病毒,核苷酸序列和CAV有较高的同源性,其命名为输血传播病毒(TTV).本科病毒的特性不同于迄今发现的任何病毒,因其核酸是单股负链、封闭的圆环DNA而得名.     

猪圆环病毒研究进展

猪圆环病毒(Porcine circovirus,PCV)是迄今发现的最小的动物病毒之一.PCV具有PCV1和PCV2两种基因型.PCV1无致病性.PCV2有致病性,它不仅是断奶猪多系统衰竭综合症(Post -weaning multisystemic wasting syndrome,PMWS)的主要病原(Bolin等,2001;McNeilly等,2001),而且是其他诸多传染病的病原之一.世界各国的兽医与养猪业者认为它是继猪繁殖与呼吸道综合征之后新发的重要的猪传染病,引起了国内外学者的广泛关注.     

新型猪圆环病毒疫苗的研究进展

从20世纪90年代开始流行到现在,全球范围内暴发的猪圆环病毒相关疾病(PCVAD)给世界各国的养猪业造成了巨大的经济损失。我国是世界的养猪大国和猪肉制品消费大国,PCVAD对我国的养猪业的发展产生了很大的影响。疫苗是预防PCVAD最直接有效的方法,文中对近年来国内外猪圆环病毒疫苗的研究进展进行综述。     

Effect of porcine circovirus type 2 (PCV2) vaccination on porcine reproductive and respiratory syndrome virus (PRRSV) and PCV2 coinfection

The objectives were to determine if PCV2 vaccination is effective in reducing disease and lesions associated with PRRSV and PCV2 coinfection and if there is a difference between intradermal (ID) and intramuscular (IM) route of PCV2 vaccination. Seventy-four, 21-day-old pigs were randomly allocated into one of six groups. On day 0, pigs were vaccinated with 2ml Suvaxyn((R)) PCV2 One Dose (Fort Dodge Animal Health, Inc.) by intramuscular (VAC-M-COINF) or intradermal (VAC-D-COINF) routes. On day 28, pigs were either singularly (PRRSV-only, PCV2-only) or coinfected (COINF) with PRRSV and PCV2. All pigs in all groups were necropsied on day 42. All vaccinated pigs seroconverted (IgM, IgG, and neutralizing antibodies) to PCV2 between 14 and 28 days post-vaccination. After challenge, all groups inoculated with PRRSV had reduced average daily gain compared to CONTROLS and PCV2-only (P<0.001). COINF pigs had significantly (P<0.05) reduced anti-PCV2-IgG antibody levels and neutralizing antibody levels compared to both vaccinated groups. COINF pigs had more severe lung lesions compared to VAC-M-COINF (P<0.05). COINF pigs had higher amounts of PCV2 DNA in serum samples and feces (P<0.05) and increased amounts of PCV2 in lymphoid tissues (P<0.05) compared to both vaccinated groups. In summary, PCV2 vaccination was effective at inducing a neutralizing antibody response and significantly reducing PCV2-associated lesions and PCV2 viremia in pigs coinfected with PCV2 and PRRSV. Differences between intradermal and intramuscular routes of vaccine administration were not observed.     

Epidemiology and horizontal transmission of porcine circovirus type 2 (PCV2)

Porcine circovirus type 2 (PCV2) is a small, non-enveloped, circular, single-stranded DNA virus of economic importance in the swine industry worldwide. Based on the sequence analyses of PCV2 strains, isolates can be divided into five subtypes (PCV2a-e). PCV2 is an ubiquitous virus based on serological and viremia data from countries worldwide. In addition, PCV2 DNA was discovered in archived samples prior to the first recognition of clinical disease. Recently, a worldwide shift in PCV2 subtype from PCV2a to PCV2b occurred. PCV2 DNA can be detected in fecal, nasal, oral and tonsillar swabs as well as in urine and feces from both naturally and experimentally infected pigs. PCV2 DNA can be detected early in the infectious process and persists for extended periods of time. The effectiveness of disinfectants for reducing PCV2 in vitro is variable and PCV2 is very stable in the pig environment. Limited data exist on the horizontal transmission of PCV2. Direct transmission of PCV2 between experimentally or naturally infected animals and na?ve animals has been documented and the incorporation of clinical or subclinically infected animals into a population represents a risk to the herd. Indirect transmission through the oral, aerosol or vaccine routes is likely a lesser risk for the transmission of PCV2 in most swine populations but may be worth evaluating in high heath herds. The objective of this review was to discuss data on the epidemiology and horizontal transmission of PCV2.     

A meta-analysis on experimental infections with porcine circovirus type 2 (PCV2)

A meta-analysis was performed with the aim to identify factors with a relevant influence on the expression of clinical postweaning multisystemic wasting syndrome (PMWS) under experimental conditions. Data from 44 studies were included in the analysis. Several variables were studied: number of pigs in the experiment, intake of colostrum, serological status against porcine circovirus type 2 (PCV2), strain of PCV2 used for inoculation, the route and dose of inoculation, and use of potential triggering factors (such as co-infections, vaccinations, or immunomodulator products). Multiple correspondence analysis and log-linear regression methods were used to establish the relationships between the studied variables and the number of PCV2 infected pigs that developed PMWS. Based on the results of the meta-analysis, the most successful animal experiment aimed to develop PMWS should include: (1) colostrum-deprived pigs, (2) age of inoculation below 3 weeks, (3) high doses of PCV2 inoculum, (4) PCV2 strain from genotype 1, and (5) co-infection with another swine pathogen as a triggering factor.     

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.     

猪圆环病毒3型感染的流行情况与检测方法研究进展

猪圆环病毒3型(porcine circovirus 3,PCV3)是猪群中流行的一种新型猪圆环病毒。2016—2017年,世界范围陆续报道在猪群中发现PCV3,包括美国、中国、美国、韩国、巴西、波兰和意大利等。PCV3感染多见于具有皮炎肾病综合征(PDNS)和繁殖障碍症状的猪群,目前病毒尚未分离成功。本文综述了已报道的PCV3在世界范围内的流行情况,介绍了当前研究的PCV3分子和血清学诊断方法。     

猪圆环病毒2型细胞培养适应毒株的培育和鉴定

从临床表现为仔猪断奶后多系统衰竭综合征（PMWS）淋巴组织病料，经聚合酶链式反应（PCR）证实为猪圆环病毒2型（PCV2）感染，采用无污染的猪肾细胞系（PK15）分离培养，并连续传代培育成一株细胞培养适应毒，命名为PCV2／LG株。分离毒株经细胞培养，于第25代后毒价显著升高，于第35代毒价可达10^5.6TCID 50/mL。采用免疫过氧化物酶单层细胞染色法（IPMA）、免疫电镜技术、分子克隆及核酸序列分析等鉴定表明，分离株感染细胞后病毒抗原主要分布在细胞核及细胞质中；病毒感染的阳性细胞呈散在分布，阳性细胞数可达50％以上；免疫电镜观察到与PCV2特异抗体结合形成的病毒免疫复合物呈实心小颗粒样粒子团，病毒粒子直径约为17nm；病毒抗原基因组由1768个核苷酸组成，与GenBank登录的8个PCV2基因组序列同源性达96．2％以上。用2mL的病毒细胞培养物（10^5.6TCID 50/mL）接种30日龄PCV2抗体阴性仔猪3头，可引起典型PMWS临床症状。本研究为进一步开展该病毒的致病性、疫苗免疫、诊断及分子生物学等研究奠定了基础。     

Reproduction in porcine circovirus type 2 (PCV2) seropositive gilts inseminated with PCV2b spiked semen

Background

Since 1999, field evidence of transplacental infection by porcine circovirus type 2 (PCV2) and reproductive failure has been reported in pigs. The objective of this study was to evaluate the clinical and pathological consequences of PCV2 infection in conventional PCV2-seropositive gilts by insemination with PCV2b-spiked semen.

Results

Six PCV2 seropositive gilts were inseminated with PCV2b-supplemented semen (infected) and three animals with semen and cell culture medium (controls). Only three out of the six infected animals were pregnant by ultrasonography on day 29 after insemination, while two out of the three controls were pregnant. One control gilt aborted on day 23 after insemination but not due to PVC2. Viraemia was demonstrated in four out of six infected and in one control gilt that became infected with PCV2a. Anti-PCV2 antibody titres showed dynamic variations in the infected group throughout the study. Among infected gilts, the animal with the lowest anti-PCV2 titre (1/100) at the beginning of the experiment and another that reached a similar low value during the experiment showed evident seroconversion over time and had also PCV2 positive foetuses. One placenta displayed mild focal necrosis of the chorionic epithelium positively stained by immunohistochemistry for PCV2 antigen.

Conclusions

PCV2-seropositive gilts can be infected with PCV2 after intrauterine exposure and low maternal antibody titre may increase the probability of a foetal infection.     

Shedding and infection dynamics of porcine circovirus type 2 (PCV2) after natural exposure

The objective of this study was to determine the amount of porcine circovirus type 2 (PCV2) shed in nasal, oral and fecal secretions over time following natural PCV2 infection. Fecal, oral and nasal swabs and blood were collected at regular intervals starting at 28 days post-farrowing (DPF) until 209 DPF from four pigs naturally infected with PCV2. PCV2 DNA was detected in all sample types. There were no differences in the amount of PCV2 DNA present in different sample types over time. PCV2 DNA was detectable in sera and secretions in pigs through 209 DPF. Natural exposure to PCV2 results in a long term infection and PCV2 is shed in similar amounts by nasal, oral and fecal routes.