Comparative serologic and virologic study of commercial swine herds with and without postweaning multisystemic wasting syndrome

A comparative serologic and virologic study was performed in pigs from 5 herds with postweaning multisystemic wasting syndrome (PMWS) and 2 herds without PMWS in Quebec. In each herd, 60 blood samples were collected at 4-wk intervals from pigs from 3 to 23 wk of age. The serum was evaluated for the presence of antibodies to porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV), as well as for the presence of nucleic acid of PCV2, PRRSV, and porcine parvovirus (PPV), by means of the polymerase chain reaction (PCR). Serologic profiles for PCV2 were very similar in 6 of the 7 herds, including the 2 without PMWS, and were characterized by a gradual decrease in antibody titres from 3 until 11 wk of age, followed by seroconversion at 15 wk, and high PCV2 antibody titres thereafter in all pigs. Only starting at 11 to 15 wk of age could PCV2 viremia be detected, except in 1 herd, in which clinical signs were observed at 6 to 7 wk of age. A PCV2 viremia could be detected within the same pigs for a minimum of 8 wk, and the virus could still be detected in 41% of the serum samples obtained at 23 wk of age. The antibody level did not appear to influence the occurrence of disease, since titres were similar in pigs in the herds with or without PMWS. Infection with PRRSV, as demonstrated by PCR and seroconversion, preceded that of PCV2 by at least 1 mo in both types of herd. Both PRRSV and PCV2 were detected in some pigs in 5 of the 7 herds, including 1 herd without PMWS. Porcine parvovirus could be detected in serum by PCR in 2 herds with PMWS after the onset of clinical signs and also in 1 herd without PMWS. Genomic analysis of PCV2 strains identified in the herds without PMWS indicated complete or very high homology (99.4% to 100%) with the PCV2 strains identified in 4 herds with PMWS. In our field study, the triggering of PMWS in the herds could not be linked to coinfection with either PRRSV or PPV or to the use of a specific immunostimulant, such as vaccines, or to particular genomic differences between the PCV2 strains identified.     

Case-control study on the association of porcine circovirus type 2 and other swine viral pathogens with postweaning multisystemic wasting syndrome.

A field-based case-control study was conducted to assess the strength of association of porcine circovirus type 2 (PCV2) and some major swine viruses with postweaning multisystemic wasting syndrome (PMWS). Cases were defined as individual pigs with a clinical history of progressive weight loss and histopathological lesions characteristic of PMWS. Controls were pigs without clinical signs and histopathological lesions typical of PMWS. A total of 31 cases and 56 controls was identified from diagnostic submissions. Serum and various tissues were collected from all animals and assayed for PCV, porcine reproductive and respiratory syndrome virus (PRRSV), porcine parvovirus, porcine enterovirus types 1-3, swine influenza virus, porcine respiratory coronavirus, transmissible gastroenteritis virus, porcine endogenous retrovirus, porcine lymphotropic herpesvirus type 1, and bovine viral diarrhea virus. The proportion of case and control pigs positive for each virus was determined and statistically compared for determining the strength of the association that each virus had with PMWS individually or in combinations. Porcine circovirus type 2 had the strongest association (OR = 9.3, P = 0.006) with PMWS among the viruses tested for. Risk for PWMS was much higher (OR = 31.2, P = 0.0009) if the animal was concurrently infected with PCV2 and PRRSV, suggesting that development of PMWS may be enhanced by cofactor(s). Because PCV2 was also found in 62.5% of the controls, PCV2 from 5 cases and 4 controls were selected and genetically compared. No significant genetic difference was observed between PCV2 from PMWS and control pigs.     

Prevalence of porcine reproductive and respiratory syndrome virus and porcine circovirus type 2 in piglets after weaning on a commercial pig farm in Japan

To investigate the transition in concentration of porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2) and antibody for these viruses in serum, serum samples were collected from 29 pigs on weaning day and at 7, 14, 21, 28, 53, 84, and 120 days after weaning. The concentration of circulated PRRSV and PCV2 in serum was measured by real-time RT-PCR and real-time PCR, respectively. The specific antibody for PRRSV and PCV2 was measured using ELISA. PRRSV was not detected on 0 days post-weaning (dpw). The specific antibody for PRRSV began to increase as the concentration of PRRSV in serum increased, and the level of PRRSV then tended to decrease. PCV2 was detected in 12 of 28 pigs on 0 dpw. The concentration of PCV2 and the specific antibody for PCV2 showed a similar tendency to those of PRRSV. The correlation analysis suggests that a decline in the daily weight gain coincided with an increase in the PRRSV concentration. Pigs with a higher antibody titer against PRRSV or PCV2 on 0 dpw showed the lower level of PRRSV or PCV2, respectively.     

Porcine circovirus 2 replication in colostrum-deprived piglets following experimental infection and immune stimulation using a modified live vaccine against porcine respiratory and reproductive syndrome virus

Porcine circovirus type 2 (PCV2) infection is now recognized as the major factor in the development of post-weaning multisystemic wasting syndrome (PMWS). Although Koch's postulates have been fulfilled for PCV2 and PMWS, the severe clinical expression of the disease observed in field cases has been difficult to reproduce experimentally. Some studies have demonstrated that immune stimulation associated with the use of some commercially available swine vaccines may trigger progression of PCV2 infection to disease and lesions characteristic of PMWS. Here we describe the effects on PCV2 infection in an experimental model following the use of a commercially available modified live vaccine to porcine respiratory and reproductive syndrome virus (PRRSV). Although none of the piglets infected with PCV2 developed clinical PMWS, the severity of microscopical lesions and the PCV2 antigen load associated with these lesions were higher in the PRRSV-vaccinated piglets compared with those detected in the PCV2 only infected animals.     

豫南地区规模化猪场猪繁殖与呼吸综合征病毒和猪圆环病毒2型抗体检测与分析

为掌握豫南地区规模化猪场中猪繁殖与呼吸综合征病毒（PRRSV）和猪圆环病毒2型（PCV2）疫苗免疫场猪群抗体水平和非疫苗免疫场猪群病原感染情况,试验利用ELISA方法对该地区猪群进行了PRRSV和PCV2抗体水平检测。结果表明,在疫苗免疫猪群中,PRRSV和PCV2抗体合格率分别为68.8%和58.7%,规模越大的猪场合格率越高,200~500头母猪规模场抗体阳性率最高（分别为76.8%和77.4%）,50头母猪以下场最低（分别为48.3%和44.2%）,种猪的合格率均最高,而育肥猪群合格率均最低。在非疫苗免疫猪群中,PRRSV和PCV2抗体阳性率分别为55.6%和65.3%,PRRSV抗体阳性率最低的是100~200头母猪规模场（46.5%）,最高的是50头母猪以下规模场（68.8%）,断奶仔猪和育肥猪群抗体阳性率均在71%以上;随猪场规模越大,PCV2抗体阳性率越低,200~500头母猪规模场抗体阳性率为41.4%,50~100头规模场和50头以下场的阳性率分别为78.9%和78.6%,种公、母猪的PCV2抗体阳性率最低（分别为37.5%和40.4%）,断奶仔猪和育肥猪抗体阳性率较高（分别为82.2%和79.5%）。本研究反映了豫南地区猪繁殖与呼吸综合征（porcine reproductive and respiratory syndrome,PRRS）和猪圆环病毒病（porcine circovirus disease,PCVD）疫苗免疫猪场的疫苗免疫效果和非疫苗免疫猪场病原感染的实际情况和规律,为该地区PRRS和PCVD防制工作提供了理论依据和指导。     

Serological Investigation and Genomic Characterization of PCV2 Isolates from Different Geographic Regions of Zhejiang Province in China

Sera collected from 46 swine farms in Zhejiang province were evaluated for the presence of antibodies to PCV2 using an indirect-fluorescent antibody procedure. In addition PCV2 isolated from superficial inguinal lymph node samples collected from 40-to 90-day-old pigs with clinical signs of post-weaning multisystemic wasting syndrome (PMWS) using the PK-15 cell line were sequenced and compared. Overall seroprevalence of PCV2 antibody averaged 58.34% for all samples. Breakdown of serology by groups was as follows: 59.38% for sows, 57.41% for post-weaning piglets, 44.83% for Landrace sows and 64.28% for Landrace piglets. The seroprevalence of Landrace sows was higher than that of Yorkshire and Duroc sows, but non-significant (p > 0.05). Serological analysis also showed that seroprevalence of PCV2 antibody was a negative correlation to that of PRRSV antibody. The complete genomes of five PCV2 isolates identified in the herds with PMWS consisted of 1767nt, containing the 11 potential ORFs. Genome of the virus isolates shared 93.8% to 99.8% identity with PCV2 reference strains from GenBank, 76.6% to 77.9% identity with PCV1. Phylogenetic analysis indicated that there were two subgenotypes within PCV2: subgenotype I (1767 nt) and subgenotype II (1768 nt).     

上海地区出现猪繁殖与呼吸综合征和2型猪圆环病毒混合感染

上海地区6个规模化猪场断奶后仔猪出现全身消耗性综合征，剖检的18头病仔猪都表现肺脏严重病变和淋巴结肿大出血。分别设计针对猪繁殖与呼吸综合征病毒(porcine reproductive and respiratory syndrome virus，PRRSV)N蛋白和2型猪圆环病毒(porcine circovirus type2，PCV-2)部分基因的特异性PCR引物，通过RT—PCR和PCR技术从患病猪肺脏组织均扩增出PRRSV和PCV-2的特异基因片段。结合临床症状和流行病学调查，证实上海地区出现PRRSV和PCV-2的混合感染。     

Occurrence of swine salmonellosis in postweaning multisystemic wasting syndrome (PMWS) affected pigs concurrently infected with porcine reproduction and respiratory syndrome virus (PRRSV)

Fourteen diseased pigs from four farms in which there had been an outbreak of salmonellosis were investigated. Granulomatous inflammation with depletion of lymphocytes was observed in the swollen lymph nodes in these pigs. Antigens to porcine circovirus type 2 (PCV2) were immunolabeled in the lesions along with detection of viral DNA as PCV2 by polymerase chain reaction (PCR). In addition, antigens to porcine reproductive respiratory syndrome virus (PRRSV) were immunodetected in the lungs and Salmonella Choleraesuis was isolated from the affected pigs. The nine salmonellosis affected pigs, five (55.6%) with salmonellosis and PMWS concurrently infected with PRRSV were much higher than those infected with salmonellosis and PMWS (22.2%) or with salmonellosis and PPPRV (22.2%).     

河南省部分猪群主要疫病疫苗免疫抗体水平监测与效果分析

2009年1月—2011年12月,从河南省信阳和驻马店地区62个猪场共收集免疫过猪瘟病毒(CSFV)、伪狂犬病毒(PRV)、猪繁殖与呼吸综合征病毒(PRRSV)和猪圆环病毒2型(PCV2)疫苗的猪血液,利用ELISA方法对样品进行抗体水平的检测。结果显示:该地区猪场猪群的疫苗免疫合格率最高是PRV疫苗(87.06%);其次是CSFV疫苗(76.24%);PRRSV和PCV2的疫苗免疫合格率较低,分别为65.20%和50.78%。4种疫苗免疫抗体合格率在不同规模的猪场有较大的差别,规模猪场的猪群某些疫病的抗体未必比散养猪群高。种猪群的4种疫苗的免疫合格率最高,商品猪中各个生长阶段的免疫后抗体合格率比较后发现,断奶仔猪群PRRSV抗体合格率明显高于哺乳仔猪,育肥猪群合格率要比哺乳仔猪群和断奶仔猪群的抗体合格率低。     

The index herd with PMWS in Sweden: Presence of serum amyloid A,circovirus 2 viral load and antibody levels in healthy and PMWS-affected pigs

Background

Postweaning Multisystemic Wasting Syndrome (PMWS) is an emerging disease in pigs of multifactorial origin, but associated to porcine circovirus type 2 (PCV2) infection. PMWS was first diagnosed in Sweden at a progeny test station that received pigs aged five weeks from 19 different nucleus herds on the day after weaning. The objective of this study was to examine, for the first time in an index outbreak of PMWS, the relationship between PCV2 virus, antibodies to PCV2 and serum amyloid a (SAA) in sequentially collected serum samples from pigs with and without signs of PMWS.

Methods

Forty pigs of the last batch that entered the station at a mean age of 37.5 days were monitored for signs of PMWS during the first 55 days after arrival. Serum was collected on six occasions and analysed for presence of PCV2 DNA and antibodies to PCV2, as well as for levels of SAA.

Results

Four of the pigs (10%) were concluded to have developed PMWS, with necropsy confirmation in three of them. These pigs displayed low levels of maternal antibodies to PCV2, more than 10⁷ PCV2 viral DNA copies per ml serum and failed to mount a serological response to the virus. Starting between day 23 and 34 after arrival, an increase in PCV2 viral load was seen in all pigs, but PCV2 did not induce any SAA-response. Pigs that remained healthy seroconverted to PCV2 as the viral load was increased, regardless of initially having low or high levels of PCV2-antibodies.

Conclusion

In this index case of PMWS in Sweden, pigs affected by PMWS were not able to mount a relevant serum antibody response which contributed to the disease progression. The maximal PCV2 virus load was significantly higher and was also detected at an earlier stage in PMWS-affected pigs than in healthy pigs. However, a viral load above 10⁷ PCV2 DNA copies per ml serum was also recorded in 18 out of 34 pigs without any clinical signs of PMWS, suggesting that these pigs were able to initiate a protective immune response to PCV2.     

猪圆环病毒2型感染对猪繁殖与呼吸综合征灭活疫苗体液免疫的影响

本试验采用ELISA方法对单独接种猪繁殖与呼吸综合征病毒(PRRSV)变异株灭活苗组(HP组,n=3)和PCV2感染且出现病毒血症后接种PRRSV变异株灭活苗组(PCV2/HP组,n=3)不同时相血清中的PRRSV抗体进行检测;并对HP和PCV2/HP组血清中PCV2特异的抗体和核酸分别进行ELISA和荧光定量PCR检测。结果表明,在首免后70 d HP组血清平均抗体效价极显著高于PCV2/HP组(P<0.01);首免后56、63和77 d HP组平均抗体效价明显高于PCV2/HP组。其中在首免后56和63 d HP组抗体阳性率均达67%(2/3),PCV2/HP组在相应时相抗体阳性率为0;在首免后70和77 d HP组抗体阳性率均达100%(3/3),PCV2/HP组在相应时相抗体阳性率仅为0和33%(1/3)。结果提示PCV2感染可在一定程度上抑制PRRSV变异株(JXA1)特异性的抗体反应。     

Profiles of seroconversion to porcine circovirus type 2 in herds affected and not affected by postweaning multisystemic wasting syndrome

The aim of the present study was to explore the usefulness of serological methods in the diagnosis of postweaning multisystemic wasting syndrome (PMWS). The study was carried out in 4 PMWS-affected and 6 control farms. Based on the serological profiles, infection with porcine circovirus type 2 (PCV2) was determined to take place at 3-7 weeks of age in the PMWS-affected and at 3-11 weeks of age in the control farms. To compare the dynamics of seroconversion to PCV2 among farms, cross-sectional serological profiles were normalised in relation to the inferred age of infection. The results indicated that the proportion of seropositive pigs increased significantly slower in the affected herds. The most pronounced difference was observed about 4 weeks after infection, when the proportion of seropositive pigs ranged from 0 to 53.3% and from 70 to 100% in PMWS-affected and control herds, respectively. Mean antibody titres at that age were also significantly lower in the affected farms. These observations suggest a delay in the production of PCV2-specific antibodies and indicate that serological methods may be helpful in identifying herds with a high risk of PMWS.     

猪圆环病毒2型免疫过氧化物酶单层细胞试验抗体检测试剂盒的研制及应用

本研究建立了一种免疫过氧化物酶单层细胞试验（Immunoperoxidase monolayer assay,IPMA）,用于猪圆环病毒2型血清抗体检测,通过对IPMA反应条件的优化,组装了诊断试剂盒。研究结果表明,用IPMA检测猪圆环病毒2型人工感染猪血清,于感染后3周抗体阳转,第3周～10周抗体阳性检出率为92.8%（52/56）,对照组猪血清抗体检测均为阴性（33/33）。试剂盒在-20℃稳定保存18个月与其他几种猪病毒参考血清无交叉反应,与用重组蛋白抗原建立的rcELISA符合率为89.2%。对来自黑龙江、吉林、河北、上海、内蒙古、云南、江西等地猪场健康成年猪血清480份和发病猪血清424份进行了检测,抗体检出率分别为91.7%和79.2%,表明我国猪群中猪圆环病毒2型污染相当严重。该试剂盒的研制为我国PCV2流行病学调查和疫苗免疫效果的评价提供了技术手段。     

Dynamics of serum antibodies to and load of porcine circovirus type 2 (PCV2) in pigs in three finishing herds,affected or not by postweaning multisystemic wasting syndrome

Background

Despite that PMWS commonly affects pigs aged eight to sixteen weeks; most studies of PMWS have been conducted during the period before transfer to finishing herds. This study focused on PCV2 load and antibody dynamics in finishing herds with different PMWS status.

Methods

Sequentially collected blood samples from 40 pigs in each of two Swedish (A and B) and one Norwegian (C) finishing herds were analysed for serum PCV2-load and -antibodies and saliva cortisol. The two Swedish herds differed in PMWS status, despite receiving animals from the same sow pool (multi-site production). However, the PMWS-deemed herd (A) had previously also received pigs from the spot market. ResultsThe initial serum PCV2 load was similar in the two Swedish herds. In herd A, it peaked after two weeks in the finishing herd and a high number of the pigs had serum PCV2 levels above 10⁷ per ml. The antibody titres increased continually with exception for the pigs that developed PMWS, that had initially low and then declining antibody levels. Pigs in the healthy herd B also expressed high titres of antibodies to PCV2 on arrival but remained at that level throughout the study whereas the viral load steadily decreased. No PCV2 antibodies and only low amounts of PCV2 DNA were detected in serum collected during the first five weeks in the PMWS-free herd C. Thereafter a peak in serum PCV2 load accompanied by an antibody response was recorded. PCV2 from the two Swedish herds grouped into genotype PCV2b whereas the Norwegian isolate grouped into PCV2a. Cortisol levels were lower in herd C than in herds A and B.

Conclusions

The most obvious difference between the Swedish finishing herds and the Norwegian herd was the time of infection with PCV2 in relation to the time of allocation, as well as the genotype of PCV2. Clinical PMWS was preceded by low levels of serum antibodies and a high load of PCV2 but did not develop in all such animals. It is notable that herd A became affected by PMWS after errors in management routine, emphasising the importance of proper hygiene and general disease-preventing measures.     

The involvement of Fas/FasL interaction in porcine circovirus type 2 and porcine reproductive and respiratory syndrome virus co-inoculation-associated lymphocyte apoptosis in vitro

Lymphoid depletion of various lymphoid organs is one of the major lesions in pigs suffering from postweaning multisystemic wasting syndrome (PMWS). The co-existence of porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV) in PMWS-affected pigs along with the more severe and wider range of lymphocyte depletion of lymphoid organs in PCV2 and PRRSV dually-inoculated pigs imply that PCV2 and PRRSV may interact in the pathogenesis of PMWS. The mechanism for the development of lymphoid depletion in PMWS-affected pigs remains controversial. The objective of the present study was to evaluate and compare the effects of inoculation of both viruses, singularly or in combination, on swine splenic macrophages (SMs) and co-cultured splenic (SLs) and peripheral blood (PBLs) lymphocytes in vitro. A significant reduction in the survival rate and increase in the apoptotic rate of the co-cultured SLs and PBLs and concurrent increase in the expression levels of Fas ligand (FasL) in SMs and Fas in co-cultured SLs and PBLs were demonstrated in PRRSV alone- and PCV2 and PRRSV dually-inoculated groups with the latter more prominent. The increased FasL was proven capable of inducing Fas/FasL-mediated apoptosis in co-cultured FasL-sensitive Jurkat T cells. The de novo expression and production of FasL in PCV2 and PRRSV dually-inoculated SMs and concurrently increased surface expression of Fas in co-cultured lymphocytes may contribute, at least partially, to lymphoid depletion in PMWS-affected pigs with PCV2 and PRRSV dual infection.     

2010年国内部分省份猪场常见病毒性疾病的病原学调查

随着规模化养猪业的发展,传染性疾病越来越多,混合感染或多重感染十分普遍,给疾病的诊断和预防带来很大困难。本文将我们实验室2010年分别采自福建、广西、河南、上海、内蒙、浙江、江苏和山西等地发病猪场的185份病料,通过RT-PCR和PCR方法对其进行猪繁殖与呼吸综合征病毒（Porcine reproductive and respiratory syndrome virus,PRRSV）、猪繁殖障碍的猪瘟病毒（Classical swine fever virus,CSFV）、猪圆环病毒2（Porcine circovirus type 2,PCV2）、猪细小病毒（Porcine parvovirus,PPV）、猪伪狂犬病毒（Pseudorabies virus,PRV）、细环病毒2（Torque teno virus 2,TTV2）等病毒检测。结果表明在所检的病料中PRRSV、PCV2和TTV2的阳性率比较高,分别为49.2%、62.2%和95.1%。有些地方TTV2的阳性率高达100%;同时,还存在很普遍的PRRSV与PCV2、PRRSV与TTV2、PCV2与TTV2等混合感染,混合感染率分别为27.6%、45.4%、58.4%;以及PRRSV、PCV2与TTV2的三重感染率为24.9%。同时对部分PRRSV阳性病料的PRRSV GP5和nsp2基因分别进行测序,分析测序结果表明病料中的PRRSV的GP5和nsp2序列与PRRSV HuN4株的相应序列的亲缘关系分别在98.2%和96.2%以上,且在nsp2区域都存在30个不连续氨基酸的缺失,说明现在临床中所流行的PRRSV可能仍是与高致病性PRRSV基因型相似的病毒。通过本文可以及时了解当前养猪场的病毒性疾病的流行情况,为猪场病毒性疾病的防控提供依据。     

一例猪圆环病毒2型和大肠杆菌、溶血葡萄球菌混合感染的诊断

山东德州某猪场发生猪高热、呼吸系统疾病甚至死亡的疫情。采集病料提取病变组织总DNA或RNA进行猪繁殖与呼吸综合征病毒、猪圆环病毒2型、猪细小病毒、猪伪狂犬病病毒、猪瘟病毒的PCR或RT-PCR检测。PCR扩增出353 bp的猪圆环病毒2型特异性条带。同时进行细菌分离培养、生化鉴定等试验,诊断为猪圆环病毒2型和大肠杆菌、溶血葡萄球菌混合感染。     

An ORF2 protein-based ELISA for porcine circovirus type 2 antibodies in post-weaning multisystemic wasting syndrome

Porcine circovirus type 2 (PCV2) plays a crucial role in the pathogenesis of post-weaning multisystemic wasting syndrome (PMWS) in swine. As PCV2 displays significant homology with PCV1 (a non-pathogenic virus) at the nucleotide and amino-acid level, a discriminative antigen is needed for specific serological diagnosis. The ORF2-encoded capsid protein from PCV2 was used to develop an indirect enzyme-linked immunosorbent assay (ELISA). GST-fused capsid protein from PCV2 and GST alone (both expressed in recombinant baculovirus-infected cells) were used as antigens for serodiagnosis. The specificity of the ELISA for detection of PCV2 antibodies was demonstrated in sera from pigs experimentally infected with PCV1, PCV2 and other swine viruses. The semi-quantitative nature of the test was evaluated versus an immunoperoxidase monolayer assay (IPMA). The ELISA was performed on 322 sera from pigs in eight Brittany herds and compared with IPMA. The sensitivity (98.2%) and specificity (94.5%) of this test were considered suitable for individual serological detection. High PCV2 seroprevalence was found in sows and pigs at the end of the growth phase (18-19 weeks) in all eight herds. The seroprevalence in piglets (11-17 weeks) was statistically correlated with clinical symptoms of PMWS (93% in affected versus 54%, in non-affected farms). A cohort study performed in PMWS-free farms showed that 57% of piglets exhibited active seroconversion after 13 weeks, indicating that PCV2 infection occurred earlier in PMWS-affected piglets.     

Reproduction of postweaning multisystemic wasting syndrome in pigs experimentally inoculated with a Swedish porcine circovirus 2 isolate.

In recent years, porcine circovirus type 2 (PCV2)-associated postweaning multisystemic wasting syndrome (PMWS) has been reported worldwide. However, to date, PMWS has not been reported in Sweden despite the demonstration of serum antibodies to a PCV2-like virus in Swedish pigs. This communication reports the experimental reproduction of clinical PMWS after inoculation of colostrum-deprived (CD) pigs, derived from a Northern Ireland herd, with an isolate of PCV2 virus recovered from a clinically normal Swedish pig that was necropsied in 1993. The clinical disease and histological lesions observed in CD pigs inoculated with this virus were indistinguishable from those observed in previous studies on CD pigs inoculated with a PCV2 virus isolate recovered from pigs with PMWS. These results highlight the disease potential of PCV2 isolated from regions apparently free of PMWS and suggest that the status of the host and its environment is an important factor in the development of clinical PMWS.