猪圆环病毒2型感染的血清学分析

应用间接免疫荧光技术 ,测定了浙江省内 4 4个猪场 2 0 0 0～ 2 0 0 2年间的 2 0 39个血清样本 ,对不同地区、年龄和品种猪的血清学数据进行了系统分析。结果显示 ,浙江省 4 4个猪场均有猪圆环病毒 2型 (PCV2 )感染 ,猪场的感染率为 10 0 % ,全省猪的 PCV2感染的平均血清阳性率为 5 8.31% ,其中种猪感染的血清阳性率为 5 9.38% ,断奶后猪感染的血清阳性率为 5 6 .6 5 %。长白种猪感染的血清阳性率为 4 4 .83%、长白仔猪感染的血清阳性率为 6 4 .2 8% ,明显高于大约克和杜洛克种猪和仔猪的感染率。 PCV2感染的血清阳性率高的种猪和仔猪群 ,其 PRRSV和 Pr V的抗体阳性率低。这些结果说明 ,PCV2在猪群中的感染非常普遍 ,不同品种猪对 PCV2的易感性不同 ,PCV2的感染可降低猪群对疫苗的免疫应答     

Sow porcine circovirus type 2 (PCV2) status effect on litter mortality in postweaning multisystemic wasting syndrome (PMWS)

Previous studies have described a "litter effect" associated with mortality in postweaning multisystemic wasting syndrome (PMWS) affected farms. The main objective of this study was to evaluate litter mortality in different PMWS affected farms and to characterize it in relation to three variables of the sow: parity, porcine circovirus type 2 (PCV2) infectious status and PCV2 antibody titres. The study was performed in seven farms that experienced PMWS in nurseries and/or fattening areas. Fifteen sows from each farm were randomly selected from the same farrowing batch. Serum samples were analyzed for antibodies to PCV2 and for genomic detection of PCV2. Four piglets from each sow (60 piglets per farm) were selected and ear-tagged at birth. Out of 420 initial piglets, 104 (25%) died. Sixty three of them (60%) were necropsied, and 40 (63%) diagnosed as PMWS based on case definition criteria. Our results show that sow PCV2 viremia was significantly related to piglet mortality since more piglets per litter died from viremic than from non-viremic sows. Additionally, a significantly greater proportion of animals died from sows that had low antibody titres against PCV2 (39% vs. 18% from sows with medium to high antibody titres). The present study, of exploratory nature, confirms previous results and further characterizes the so called "litter effect" by establishing that the sow PCV2 status had a significant effect on litter mortality in PMWS affected farms.     

Post-weaning multisystemic wasting syndrome (PMWS) clinical expression under field conditions is modulated by the pig genetic background

Post-weaning multisystemic wasting syndrome (PMWS) is a worldwide distributed disease of multifactorial origin and porcine circovirus type 2 (PCV2) has been identified as its essential infectious aetiology. Pig genetic background has been pointed to influence disease expression. In the present study, three different boar lines, namely A (100% Pietrain), B (50% Large White × 50% Pietrain) and C (25% Large White × 75% Duroc), were used to inseminate sows from the same genetic line (37.5% Large White × 37.5% Duroc × 25% Landrace) located on two PMWS-affected farms (farm-1 and farm-2). The PMWS clinical expression of their offspring was studied from weaning to slaughter, evaluating three parameters: total post-weaning mortality (PWM), PWM associated to PMWS (PMWS-PWM) and body weight (BW) evolution. The effect of other variables potentially related with PMWS, including sow and piglet PCV2 exposure, sow parity, piglet gender and piglet BW at weaning, were also considered in the study design. Overall, a total of 6.5% PWM and 4.3% PMWS-PWM occurred in the monitored farms. Pigs from boar line C showed the highest PWM (16.3%) and PMWS-PWM (12.4%), and the lowest BW; pigs from boar line A showed the lowest PWM (1.8%) and the highest BW. Furthermore, PWM was also higher in piglets from farm-2 and from multiparous sows. In farm-2, PMWS-PWM was higher in piglets from multiparous sows. Finally, BW was influenced by interactions between genetics and both farm and pig age, and was lower in piglets from farm-2. This study represents a consistent observation of the genetic background effect on PMWS clinical expression under field conditions.     

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.     

PCV2感染对仔猪NO-NOS系统的动态影响

将19头PCV2和PRRSV血清抗体阴性的普通断奶仔猪分为对照组(4头)和攻毒组(15头),攻毒组每头仔猪滴鼻接种PCV2病毒悬液4mL(5×105 TCID50/mL)并用KLH刺激,分别在攻毒后14、21、35d各扑杀5头仔猪采集血清和脾脏、淋巴结、胸腺(对照组4头在攻毒当天扑杀)。检测各种组织中NO、TNOS和iNOS的含量。结果显示,攻毒猪各组织中NO含量均在攻毒后14d显著升高(P<0.05),然后缓慢下降;血清和3种免疫器官中NOS(包括TNOS和iNOS)活性的变化趋势比较一致,均表现出先升高然后再逐渐降低的特点。此外,iNOS活性变化与其相应的组织中NO含量呈显著正相关(P<0.01)。结果表明,PCV2在感染早期(1～14d)可激活仔猪多种组织中NO-NOS系统,中后期逐渐恢复,这种变化与PCV2所致的组织损伤密切相关,因此,NO-NOS系统可能是PCV2相关疾病发生发展的重要信号。     

Isolation and characterization of porcine circovirus type-2 from sera of stillborn fetuses

In order to examine an association between porcine circovirus type-2 (PCV2) infection and reproductive failure in pigs, sera (n = 171) from stillborn fetuses were collected from 3 different farms with prolonged histories of reproductive problems. These sera were tested for the presence of antibodies to PCV2 using an immunoperoxidase monolayer assay. Of the 171 sera tested, 28 had PCV2 antibody titers of ≥ 1:16. When these 28 samples were tested by a polymerase chain reaction assay, 13 were found to contain PCV2 viral DNA. Of these 13 samples containing both PCV2 antibodies and viral DNA, 9 yielded PCV2 on virus isolation. Amino acid sequences comprising open reading frame 2 of PCV2 from 2 of these isolates were compared to PCV2 isolates from cases of post-weaning multi-systemic wasting syndrome (PMWS). The amino acid sequences of the 2 isolates from stillborn pigs were shown to be nearly identical to each other, as well as to other PCV2 isolates associated with reproductive failure. When compared with PMWS isolates, the isolates from the stillborn fetuses showed differences of at least 2 amino acids. These results confirm previous findings that transplacental infection of PCV2 occurs in the field and that stillbirths in pigs may be associated with PCV2 infections. At present, the significance of minor differences in amino acid sequences is not known.     

Multiply-primed rolling-circle amplification (MPRCA) of PCV2 genomes: Applications on detection, sequencing and virus isolation

Multiply-primed rolling-circle amplification (MPRCA) was used to amplify porcine circovirus type 2 (PCV2) genomes isolated from tissues of pigs with signs of post-weaning multisystemic wasting syndrome (PMWS). Two of the amplified PCV2 genomes were cloned in prokaryotic plasmids and sequenced. Both were nearly identical (1767 nt) except for one silent substitution in the region coding for the capsid protein (ORF2). In addition, they showed high nucleotide sequence similarity with PCV2 isolates from others countries (93–99%). To investigate whether the MPRCA amplified PCV2 genomes could be used to produce infectious virus, the cloned genomes were isolated from the plasmids, recircularized and used for transfection in PK-15 cells. This procedure led to the production of infectious virus to titres up to 10^5.55 TCID₅₀/mL. It was concluded that MPRCA is a useful tool to amplify PCV2 genomes aiming at sequencing and virus isolation strategies, where particularly useful is the fact that it allows straightforward construction of PCV2 infectious clones from amplified genomes. However, it was less sensitive than PCR for diagnostic purposes.     

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.     

Fetal infections and antibody profiles in pigs naturally infected with porcine circovirus type 2 (PCV2)

The aim of this study was to describe early infections with porcine circovirus type 2 (PCV2) in naturally infected piglets and the piglets' serologic profiles. A total of 20 sows (15 PCV2-vaccinated and 5 unvaccinated) and 100 newborn piglets were studied. Colostrum and serum of the sows and serum of the presuckling piglets were obtained on the day of parturition. Milk samples were collected on day 20 postpartum. Blood samples were taken and the piglets weighed on days 1, 20, 42, 63, and 84 postpartum. Colostrum and milk were evaluated for infectious PCV2 and for PCV2 total antibody (TA), neutralizing antibody (NA), and IgA. Serum samples were evaluated for PCV2 TA, NA, IgA, IgM, and DNA. The sows had high levels of TA and NA in serum and colostrum; however, 11 and 5, respectively, of the 20 colostrum and milk samples contained infectious PCV2. In the serum, PCV2 DNA and IgM were detected in 17 and 5, respectively, of the 20 sows. Nine piglets were born with PCV2 antibodies, which indicates in utero transmission of PCV2 after the period of immunocompetence (> 70 d of gestation). On day 1 postpartum, PCV2 DNA was detected in 29 of the 100 serum samples from the piglets. There was no difference between the weights of viremic and nonviremic piglets throughout the study. In conclusion, even on farms with sows that have high PCV2 antibody titers, vertical transmission of PCV2 may occur, resulting in piglet infection.     

Distribution of antibodies against porcine circovirus type-2 (PCV2) in single site and multi-site farrow-to-finish farms in Brazil

A comparative serologic study was performed in seven single site (SS) farrow-to-finish farms and four multi-site (MS) farrow-to-finish farms, with or without post-weaning multisystemic wasting syndrome (PMWS). In each farm, 30 blood samples were collected for each category of the production cycle: sows, farrowing crate, nursery, grower pigs, and finishing pigs. Sera were evaluated for the presence of antibodies to porcine circovirus type-2 (PCV2) via immunoperoxidase monolayer assay. Serologic profiles for PCV2 were different between SS and MS farms. Seroconversion following the decline in maternal antibodies occurred at a later stage on SS farms (grower pigs) than MS farms (nursery pigs). MS farms tended to have lower antibody titers than SS farms in the categories of sow, piglet, and nursery, while higher antibody titers were found in grower pigs. Characterization of serologic profiles for different farms may provide important information for the adoption of vaccination programs.     

Distribution of antibodies against porcine circovirus type-2 (PCV2) in single site and multi-site farrow-to-finish farms in Brazil

A comparative serologic study was performed in seven single site (SS) farrow-to-finish farms and four multi-site (MS) farrow-to-finish farms, with or without post-weaning multisystemic wasting syndrome (PMWS). In each farm, 30 blood samples were collected for each category of the production cycle: sows, farrowing crate, nursery, grower pigs, and finishing pigs. Sera were evaluated for the presence of antibodies to porcine circovirus type-2 (PCV2) via immunoperoxidase monolayer assay. Serologic profiles for PCV2 were different between SS and MS farms. Seroconversion following the decline in maternal antibodies occurred at a later stage on SS farms (grower pigs) than MS farms (nursery pigs). MS farms tended to have lower antibody titers than SS farms in the categories of sow, piglet, and nursery, while higher antibody titers were found in grower pigs. Characterization of serologic profiles for different farms may provide important information for the adoption of vaccination programs.     

Experimental reproduction of postweaning multisystemic wasting syndrome in cesarean-derived, colostrum-deprived piglets inoculated with porcine circovirus type 2 (PCV2): investigation of quantitative PCV2 distribution and antibody responses.

Sixteen cesarean-derived, colostrum-deprived piglets were inoculated intranasally with porcine circovirus type 2 (PCV2), originally isolated from a pig affected with postweaning multisystemic wasting syndrome (PMWS). At 1 day postinoculation (PI), 3 of the 5 piglets in the uninoculated control group were moved to the room of inoculated piglets for contact exposure. Porcine circovirus type 2 was detected by polymerase chain reaction (PCR) in swabs from inoculated piglets from 1 day PI and from contact piglets from 2 days after cohabitation. Porcine circovirus type 2 was also detected in all serum samples but not in control piglets 7 days PI. Until the end of study, PCV2 was detected in swabs and serum samples by PCR but not in the control piglets. One inoculated piglet died suddenly without clinical signs 19 days PI. Beginning at 14 days PI, 5 piglets, including 1 contact piglet, had clinical signs of depression, anorexia, and icterus, and 1 inoculated piglet died 21 days PI. Most of the piglets exhibiting the above clinical signs became moribund and were necropsied 21 and 28 days PI. In the piglets that showed clinical signs, gross lesions, including icterus of liver and hemorrhage in stomach, and typical histopathological lesions of PMWS, such as lymphoid depletion and basophilic intracytoplasmic inclusion bodies in lymph nodes and other tissues, were observed. Porcine circovirus type 2 was detected by PCR in all tissue samples except in those of the control piglets. Porcine circovirus type 2 was recovered from several tissue samples of the piglets necropsied until 35 days PI. In particular, PCV2 was recovered in high titer from most of the tissue samples of the piglets exhibiting clinical signs. Serum antibody against PCV2 was mostly detected in inoculated piglets and in contact piglets 14 and 21 days PI by an indirect fluorescence antibody test but was not detected in the piglets exhibiting clinical signs until 28 days PI. These results indicate that PCV2 was able to induce clinical PMWS in the absence of other swine pathogens and that there were significant differences in both the quantitative PCV2 distribution in tissues and the antibody response between the piglets that were infected and developed PMWS and those that were infected but remained healthy.     

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.     

High prevalence of porcine circovirus viremia in newborn piglets in five clinically normal swine breeding herds in North America

Porcine circovirus type 2 (PCV2) can be vertically transmitted resulting in fetal infection with or without clinical signs and lesions. The primary objective of this study was to assess the prevalence of intrauterine PCV2 infection in clinically normal newborn piglets in conventional pork production facilities. Five commercial breeding herds located in the U.S. and Mexico were included in the study. A total of 125 sows and 3-5 neonatal piglets per sow were arbitrarily selected. Blood and colostrum samples were collected from sows. Blood was collected from piglets prior to suckling. All samples were analyzed for the presence of anti-PCV2 IgG antibodies and presence and amount of PCV2 DNA. In addition, PCV2 DNA positive samples were further subtyped into PCV2a and PCV2b. All (125/125) sow colostrum samples and 96.8% (121/125) of the sow serum samples and 21.4% (107/499) of the piglet pre-suckle serum samples were positive for anti-PCV2 IgG antibody. The overall PCV2 DNA prevalence was 47.2% (59/125) in sow serum, 40.8% (51/125) in sow colostrum, and 39.9% (199/499) in pre-suckle piglet serum. In the PCV2 DNA positive samples, PCV2b was detected at a higher frequency (69.5% for sow serum, 84.3% for sow colostrum, and 74.4% for piglet serum) compared to PCV2a (18.6% for sow serum, 9.8% for sow colostrum, and 15.6% for piglet serum). Concurrent PCV2a and PCV2b infection was detected in 11.9% of the sow serum, in 5.9% of the colostrum samples, and in 10.0% of the piglet serum samples. In conclusion, an unexpectedly high prevalence of PCV2 viremia was detected in healthy sows (serum and colostrum) and their pre-suckle piglets in the five breeding herds investigated and PCV2b was more prevalent than PCV2a. This information adds to the knowledge of PCV2 infection in breeding herds.     

Reproduction of postweaning multisystemic wasting syndrome in pigs by prenatal porcine circovirus 2 infection and postnatal porcine parvovirus infection or immunostimulation

Postweaning multisystemic wasting syndrome (PMWS) was reproduced in prenatally porcine circovirus 2 (PCV2)-infected pigs by either postnatal infection with porcine parvovirus (PPV) or by immunostimulation. Twenty-four randomly selected piglets from 3 sows, which had been experimentally infected during gestation with PCV2, were randomly divided into 3 groups; group 1 (prenatal PCV2 infection, with postnatal PPV infection), group 2 (prenatal PCV2 infection, with postnatal keyhole limpet hemocyanin, emulsified in incomplete Freund's adjuvant [KLH/ICFA] injection), and group 3 (prenatal PCV2 infection only). Twenty-four randomly selected piglets from 3 uninfected sows were randomly divided into 3 groups; group 4 (no prenatal infection, with postnatal PCV2 and PPV infection), group 5 (no prenatal infection, with postnatal PCV2 infection), and group 6 (negative control pigs). Body weight in negative control pigs (group 6) was increased significantly compared with pigs in groups 1, 2, and 4 at 49, 52, 56, 59, and 63 days of age. The granulomatous inflammatory reaction and lymphoid depletion that are typical lesions in pigs with PMWS were observed in the lymph node of piglets in groups 1, 2, and 4 at 63 days of age. Pigs in group 3 had significantly fewer PCV2-positive cells than those from groups 1, 2, 4, or 5. When the prenatally PCV2-infected pigs were infected with PPV or injected with immunostimulant in the postnatal period, they developed PMWS. Thus, factors that potentiate the progression of prenatal PCV2 infection to PMWS are postnatal infection with PPV or immune stimulation.     

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.     

规模化猪场猪圆环病毒2型的血清流行病学调查

为了解规模化猪场猪圆环病毒2型(PCV2)血清学流行情况,采用ELISA进行PCV2抗体检测。结果表明,运城地区规模化猪场广泛存在PCV2感染,未免疫接种猪圆环病毒疫苗的外观健康猪血清样品中PCV2抗体平均阳性率为49.66%,其中种猪感染率达67%,哺乳仔猪感染率4.55%,保育猪感染率43%,育肥猪感染率64.71%;外观健康猪群检测结果提示,随着年龄的增长PCV2感染有升高趋势。为了进一步研究猪圆环病毒感染各症候群在规模化场发病特点及流行规律,采集临床疑似断奶仔猪多系统衰竭综合征(PMWS)、仔猪先天性震颤(Congenital tremors,CT)、猪肾炎皮炎综合征(PDNS)、猪的繁殖障碍(Reproductive failure)、PCV2相关性肺炎等症状猪血清400份进行PCV2抗体检测。检测结果显示,疑似PMWS症状PCV2抗体阳性率最高,达86.25%,然后依次是疑似PCV2相关性肺炎阳性率56.25%,疑似PDNS阳性率46.25%,疑似繁殖障碍阳性率26.25%,最低的是疑似CT阳性率11.25%。研究结果表明,运城地区规模化猪场PCV2感染以PMWS和PCV2相关性肺炎为主,其次是PDNS和繁殖障碍,仔猪先天性震颤感染率最低。     

A review of porcine circovirus 2-associated syndromes and diseases

Clinical expression of porcine circovirus 2 (PCV2) infection in swine may result in several distinct syndromes and diseases including post-weaning multisystemic wasting syndrome (PMWS), porcine dermatitis and nephropathy syndrome (PDNS), reproductive failure, porcine respiratory disease complex, granulomatous enteritis, necrotizing lymphadenitis, and possibly exudative epidermitis. Association of PCV2 with congenital tremor in piglets is still controversial. The extent of the involvement of PCV2 in swine disease other than PMWS is currently poorly understood. This review concentrates on PCV-2-associated syndromes and diseases other than PMWS.     

The presence of co-infections in pigs with clinical signs of PMWS in The Netherlands: a case-control study

In this study, 60 pigs with clinical signs of post-weaning multisystemic wasting syndrome (PMWS) from 20 different pig herds and 180 control pigs (without clinical signs of PMWS) were examined to get more insights into the frequencies of porcine circovirus 2 infections and the presence of co-infections in pigs with and without clinical signs of PMWS in the Netherlands. Porcine circovirus type 2 was detected in 100% of the pigs with clinical signs of PMWS by virus isolation and/or PCR and in 50% of the pigs from PMWS-free herds. There was an association between the levels of infectious PCV2 and/or PCV2 DNA load and the severity of clinical signs as described for PMWS. A high variation in PCV2 antibody titres was found in the clinically affected pigs, and 27% of these pigs did not mount PCV2 antibody titres higher than 1:200. A concurrent infection of PCV2 and porcine reproductive and respiratory syndrome virus (PRRSV) was found in at least 83% of the pigs with clinical signs of PMWS and in 35% of the pigs from PMWS-free herds. Co-infections of European- and American-type PRRSV were detected only in PMWS herds and in one control herd with a history of PMWS clinical signs.     

PCR detection of porcine circovirus type 2 (PCV2) DNA in blood, tonsillar and faecal swabs from experimentally infected pigs

PCV2 infection is now recognized as the major factor in the development of post-weaning multisystemic wasting syndrome (PMWS). In this study we evaluated the use of PCR to detect the presence of PCV2 DNA in blood, faecal and tonsillar swabs collected from 12 pigs experimentally infected with PCV2 and sampled at selected time points post-infection. The PCR results were evaluated together with the presence of PMWS typical histopathological lesions and the presence of PCV2 antigen. PCV2 DNA was present in the blood of all 12 infected pigs at the end of the experiment and faecal and tonsillar swabs of 11 of the 12 pigs. The rate of PCR-positive serum and plasma samples was significantly higher in four pigs that showed virological and pathological evidence of PMWS, than in infected pigs without evidence of disease. In conclusion this study confirms that PCR cannot substitute for the traditional methods used for diagnosis of PMWS, however, PCR amplification of PCV2 DNA from serum or plasma could be a useful tool to support an early diagnosis of PMWS in live animals.