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1.
A study was carried out in 125 farrow-to-finish pig herds to assess the relationships between pathogens involved in respiratory disorders and to relate these findings to clinical signs of respiratory diseases and pneumonia and pleuritis at slaughter. Clinical examination and sampling were carried out on four different batches in each herd (pigs aged 4, 10, 16 and 22 weeks). Mycoplasma hyopneumoniae, Actinobacillus pleuropneumoniae, swine influenza viruses (SIV), porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2) were detected by serological or PCR tests. Pneumonia-like gross lesions and pleuritis were scored at the slaughterhouse. The results indicate that the percentage of pigs PCR-positive for PCV2 at 4, 10 and 16 weeks old was associated with the percentage of pigs PCR-positive for M. hyopneumoniae at these ages. On the other hand, the percentage of pigs with antibodies against PRRSV at 10, 16 and 22 weeks was positively correlated with the percentage of pigs seropositive for M. hyopneumoniae at 22 weeks, with the percentage of pigs with antibodies against SIV H1N1 and SIV H1N2 and the percentage of pigs sero-positive for A. pleuropneumoniae serotype 2. The findings also indicate that, within the five studied pathogens, M. hyopneumoniae, PRRSV and SIV H1N1 are the major pathogens involved in pneumonia-like gross lesions even though PCV2 may play a role. A. pleuropneumoniae serotype 2, in association with PRRSV, is significantly associated with extensive pleuritis. Respiratory diseases could be significantly reduced by implementing measures including appropriate management practices to control these pathogens.  相似文献   

2.
A retrospective study on pig lung tissues from 60 cases of proliferative and necrotizing pneumonia (PNP) was performed to determine the presence of porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), and porcine circovirus type 2 (PCV2) in these lesions. Cases selected included 30 cases diagnosed between 1988 and 1992 and 30 cases diagnosed between 1997 and 2001. In each group of 30 cases, 10 were from suckling piglets, whereas the other 20 were from postweaned animals representing either nursery or grower-finisher pigs. Immunohistochemistry using a monoclonal antibody to influenza virus type A was used to determine the presence of SIV, and in situ hybridization was used for the detection of PRRSV and PCV2 nucleic acids. PRRSV was detected in 55 of the 60 cases examined (92%), PCV2 in 25 cases (42%), and SIV in only 1 case (2%). In 30 cases (50%), PRRSV was the only virus detected, whereas in 25 other cases (42%), a combination of PRRSV and PCV2 could be detected in the lungs with PNP lesions. PCV2 could not be detected in the lungs of suckling pigs with PNP. All PCV2-positive cases were found in postweaned pigs and were always in combination with PRRSV. In this latter age group, PCV2 was detected in 63% of the cases (25/40). Data from our study indicate that SIV is rarely identified in PNP and that PCV2 infection is not essential for the development of PNP lesions. The results of the present study demonstrate that PRRSV is consistently and predominantly associated with PNP and should be considered the key etiologic agent for the condition.  相似文献   

3.
The role of swine torque teno sus viruses (TTSuVs) as co-factors in disease syndromes involving porcine circovirus strain 2 (PCV2) and porcine reproductive and respiratory disease syndrome virus (PRRSV) has been a debatable subject. In this study, the prevalence of TTSuVs in Iowa, the leading pork producing state in the U.S., was estimated by a duplex PCR. The PCR is capable of simultaneously detecting both teno sus viruses 1 and 2 (TTSuV1 and 2). Based on an analysis of 300 random samples representing six major geographical regions of the state, the overall prevalence rates for TTSuV1 and 2 were 47.34% and 24.67% respectively while the combined prevalence rate was 52.33%. The epidemiological association of TTSuV1 and 2 with the common etiological agents of the porcine respiratory disease complex (PRDC) namely porcine PRRSV, PCV2, Mycoplasma hyopneumoniae and swine influenza virus (SIV) was estimated in lung tissue derived from 45 pigs showing clinical signs of PRDC. Notably, 86.67% of the PRDC-suspect samples were positive for TTSuV1 in comparison to the baseline population prevalence rate of 47.34%. However, the prevalence of TTSuV2 (26.67%) was not significantly different. TTSuV1 was detected in 80.00%, 81.81%, 75.00% and 77.78% of the PRRSV, SIV, M. hyopneumoniae and PCV2 positive PRDC-suspect samples respectively. Our results indicate that TTSuV1 is strongly associated with clinical PRDC and support the hypothesis that TTSuVs might function as co-factors in PRDC. Further studies to define their possible role in the pathogenesis of swine respiratory diseases are warranted.  相似文献   

4.
OBJECTIVE: To compare serologic testing with slaughter evaluation in assessing effects of subclinical infection on average daily weight gain (ADG) in pigs. DESIGN: Cohort study. ANIMALS: 18 cohorts (30 to 35 pigs/cohort) of pigs on/farms. PROCEDURE: Blood samples were collected, and pigs were weighed at 8, 16, and 24 weeks of age. Sera were tested for antibodies to porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), transmissible gastroenteritis virus (TGEV), pseudorabies virus, Mycoplasma hyopneumoniae, and Actinobacillus pleuropneumoniae. At slaughter, skin, nasal turbinates, lungs, and liver were examined. Associations between ADG and results of serologic testing and slaughter evaluation were examined by use of multiple linear regression. RESULTS: Pathogens that had a significant effect on any given farm during any given year and the magnitude of that effect varied. However, at 16 and 24 weeks of age, a higher antibody titer was consistently associated with a lower ADG. Mean differences in ADG between seropositive and seronegative pigs were 18 g/d (0.04 lb/d) for SIV, 40 g/d (0.09 lb/d) for PRRSV, 38 g/d (0.08 lb/d) for M hyopneumoniae, and 116 g/d (0.26 lb/d) for TGEV. Of the evaluations performed at slaughter, only detection of lung lesions was consistently associated with a decrease in ADG. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that subclinical infection with any of a variety of pathogens commonly found in swine herds was associated with a decrease in ADG. Serologic testing was more effective than slaughter evaluation in assessing the impact of subclinical infection on ADG in these pigs.  相似文献   

5.
The transmission of PRDC-pathogens (PRRSV, influenza virus A, PCV2, M. hyopneumoniae, A. pleuropneumoniae) between swine herds, which was summarized in the first part of the review, mainly occurs via pig movement. The risk of pathogen transmission by insemination with contaminated semen plays only a relevant role in the infection with PRRSV and PCV2. A risk of the aerogen transmission of pathogens between herds within a distance of 2 to 3 km is described for M. hyopneumoniae and PRRSV. Evidence for the other pathogens is not investigated. The PRDC-pathogens are frequently detected in wild boar populations. Therefore, the transmission between wild boars and domestic pigs seems possible by close contacts. PRRSV and M. hyopneumoniae can be transmitted by contaminated clothes and boots, but the use of sanitation protocols appears to limit their spread. Live vectors like rodents or birds seemed to have no special importance for the transmission of PRDC-pathogens.  相似文献   

6.
Association of porcine circovirus 2 with porcine respiratory disease complex   总被引：31，自引：0，他引：31  
A retrospective study was performed on natural cases of porcine respiratory disease complex (PRDC) to determine the association and prevalence of PRDC with porcine circovirus 2 (PCV2) and other co-existing pathogens in Korea. Histologically, alveolar septa were markedly thickened by infiltrates of mononuclear cells. Moderate to marked multifocal peribronchial and peribronchiolar fibrosis were present and often extended into the airway lamina propria. Among the 105 pigs with PRDC, 85 were positive for PCV2, 66 were positive for porcine reproductive and respiratory syndrome virus (PRRSV), 60 were positive for porcine parvovirus (PPV), and 14 were positive for swine influenza virus (SIV). There were 80 co-infections and 25 single infections. A co-infection of PCV2 with another additional bacterial pathogen is frequently diagnosed in PRDC. The combination of PCV2 and Pasteurella multocida (38 cases) was most prevalent followed by PCV2 and Mycoplasma hyopneumoniae (33 cases). The consistent presence of PCV2, but lower prevalence of other viral and bacterial pathogens in all pigs examined with PRDC, has led us to speculate that PCV2 plays an important role in PRDC.  相似文献   

7.
Two common viral pathogens of swine, namely, porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV), were investigated in regard to their effects on monolayer cultures of swine alveolar macrophages (AMs). The purpose was to identify selected cellular changes and responses potentially associated with the clinical reactions of pigs infected with either or both of these viruses. Measurements included the (1) absolute and relative numbers of infected, viable, and apoptotic cells; (2) distribution of viral antigens; (3) levels of interferon-alpha (IFN-alpha) and tumor necrosis factor-alpha (TNF-alpha) produced and their association with the extent of virus-induced cytopathology. Four groups of AMs were studied, including mock-infected, PCV2 alone-infected (PCV2-A), PRRSV alone-infected (PRRSV-A), and PCV2 and PRRSV dually infected (PCV2/PRRSV) groups. The AMs of PCV2-A group had high antigen-containing rate without cell death. There was a marked increase in cell death and apoptosis in PRRSV-A group. However, a lower PRRSV-induced infectious rate, cell death, and apoptosis were seen in PCV2/PRRSV group. High levels of IFN-alpha production were detected in PCV2-infected groups, but not in mock-infected and PRRSV-A groups. The PRRSV-induced cytopathic effect (CPE) on MARC-145 cells or swine AMs was markedly reduced by pre-incubation of the cells with UV-treated or non-UV-treated supernatants of PCV2-infected AMs. In addition, the reduction in CPE was abolished when the supernatants of PCV2-infected AMs were pre-treated with a mouse anti-recombinant porcine IFN-alpha antibody. The results suggest that swine AMs were an important reservoir of PCV2; PCV2 infection reduced PRRSV infection and PRRSV-associated CPE in PCV2/PRRSV AMs; the reduction of PRRSV infection in AMs was mediated by IFN-alpha generated by PCV2 infection. The reduced PRRSV-associated CPE in AMs and increased pro-inflammatory cytokine production may lead to a more severe pneumonic lesion in those dually infected pigs.  相似文献   

8.
Proliferative and necrotizing pneumonia (PNP) is a severe form of interstitial pneumonia characterised by hypertrophy and proliferation of pneumocytes type 2 and presence of necrotic cells within alveoli lumen. Many viral agents have been linked to PNP aetiology, with especial emphasis on porcine reproductive and respiratory syndrome virus (PRRSV). To gain knowledge on PNP causality, a retrospective study on 74 PNP cases from postweaning pigs from Spain was carried out. Coupled with histopathological examinations, the presence of porcine circovirus type 2 (PCV2) by in situ hybridization (ISH), and PRRSV, swine influenza virus (SIV) and Aujeszky's disease virus (ADV) by immunohistochemical (IHC) methods, were investigated. PCV2 was the most prevalent viral agent in PNP cases (85.1%) followed by PRRSV (44.6%); 39.1% of PNP cases showed PCV2 as the solely detected agent, while only 4.1% had PRRSV as the unique pathogen. SIV and ADV were very sporadically detected in PNP cases, and always in co-infection with PCV2. Therefore, present data indicate that PCV2 is the most important aetiological agent in PNP cases from Spain and that PRRSV is not essential for the development of PNP. Taking into account the presented results and available literature, we suggest that PCV2 is possibly the main contributor to PNP cases in Europe while PRRSV could play a similar role in North America.  相似文献   

9.
Lymphocyte subsets isolated from germ-free piglets experimentally infected with swine influenza virus (SIV), porcine reproductive and respiratory syndrome virus (PRRSV) or porcine circovirus type 2 (PCV2) were studied and the profile of these subsets among these three infections was monitored. Germ-free piglets were used since their response could be directly correlated to the viral infection. Because SIV infections are resolved even by colostrum-deprived neonates whereas PRRSV and PCV2 infections are not, SIV was used as a benchmark for an effectively resolved viral infection. PRRSV caused a large increase in the proportion of lymphocytes at the site of infection and rapid differentiation of B cells leading to a high level of Ig-producing cells but a severe reduction in CD2—CD21+ primed B cells. Unlike SIV and PCV2, PRRSV also caused an increase in terminally differentiated subset of CD2+CD8α+ γδ cells and polyclonal expansion of major Vβ families suggesting that non-specific helper T cells drive swift B cell activation. Distinct from infections with SIV and PRRSV, PCV2 infection led to the: (a) prevalence of MHC-II+ T cytotoxic cells, (b) restriction of the T helper compartment in the respiratory tract, (c) generation of a high proportion of FoxP3+ T cells in the blood and (d) selective expansion of IgA and IgE suggesting this virus elicits a mucosal immune response. Our findings suggest that PRRSV and PCV2 may negatively modulate the host immune system by different mechanisms which may explain their persistence.

Electronic supplementary material

The online version of this article (doi:10.1186/s13567-014-0091-x) contains supplementary material, which is available to authorized users.  相似文献   

10.
Dual infection of pigs with swine influenza virus (SIV) and Mycoplasma hyopneumoniae was carried out to compare the clinical and pathological effects of dual infection in caesarian derived and colostrums deprived (CDCD) pigs, with that of a single infection with M. hyopneumoniae. In Experiment 1, 40-day-old CDCD pigs were inoculated only with SIV (A/Sw/Hok/2/81, H1N1). The virus was isolated from nasal swabs for 5-6 days. None of these pigs showed clinical signs of infection throughout the experimental period. These results suggested that this strain can infect pigs but is only slightly pathogenic when it is inoculated singly to a CDCD pig. In Experiment 2, 60-day-old CDCD pigs were inoculated with M. hyopneumoniae and then were inoculated with SIV (A/Sw/Hok/2/81) at 1 week (MHYO-7d-SIV-7d group) or 3 weeks (MHYO-21d-SIV-7d group) after M. hyopneumoniae inoculation. Macroscopically, dark red-to-purple lung lesions were observed in all of pigs at 14 or 28 days post-inoculation. Percentages of dark red-to-purple lung lesions in dual infection groups (MHYO-7d-SIV-7d group: 18.7 +/- 4.2%, MHYO-21d-SIV-7d group: 23.0 +/- 8.0%) were significantly (P < 0.05) increased compared to those of each control group in which pigs were inoculated only with M. hyopneumoniae (MHYO-14d group: 4.7 +/- 2.9%, MHYO-28 group: 3.3 +/- 2.4%). Microscopically, bronchial epithelial lesions (epithelial disruption, degeneration, hyperplasia and formation of microabscess) were frequently observed in dark red-to-purple lung lesions of only the dual infection groups. These results demonstrate that the lung lesion of pigs inoculated with M. hyopneumoniae and SIV is more severe than that of pigs inoculated only with M. hyopneumoniae.  相似文献   

11.
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.  相似文献   

12.
Polymicrobial respiratory disease in pigs   总被引：2，自引：0，他引：2  
Respiratory disease in pigs is common in modern pork production worldwide and is often referred to as porcine respiratory disease complex (PRDC). PRDC is polymicrobial in nature, and results from infection with various combinations of primary and secondary respiratory pathogens. As a true multifactorial disease, environmental conditions, population size, management strategies and pig-specific factors such as age and genetics also play critical roles in the outcome of PRDC. While non-infectious factors are important in the initiation and outcome of cases of PRDC, the focus of this review is on infectious factors only. There are a variety of viral and bacterial pathogens commonly associated with PRDC including porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), porcine circovirus type 2 (PCV2), Mycoplasma hyopneumoniae (MHYO) and Pasteurella multocida (PMULT). The pathogenesis of viral respiratory disease is typically associated with destruction of the mucocilliary apparatus and with interference and decrease of the function of pulmonary alveolar and intravascular macrophages. Bacterial pathogens often contribute to PRDC by activation of inflammation via enhanced cytokine responses. With recent advancements in pathogen detection methods, the importance of polymicrobial disease has become more evident, and identification of interactions of pathogens and their mechanisms of disease potentiation has become a topic of great interest. For example, combined infection of pigs with typically low pathogenic organisms like PCV2 and MHYO results in severe respiratory disease. Although the body of knowledge has advanced substantially in the last 15 years, much more needs to be learned about the pathogenesis and best practices for control of swine respiratory disease outbreaks caused by concurrent infection of two or more pathogens. This review discusses the latest findings on polymicrobial respiratory disease in pigs.  相似文献   

13.
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.  相似文献   

14.
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.  相似文献   

15.
A cross-sectional serological study was conducted in Bhutan between October 2011 and February 2012 to determine the prevalence of antibodies to classical swine fever virus (CSFV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV2), swine influenza virus (SIV) subtype H1N1 and Aujeszky's disease virus (ADV). Furthermore, risk factors for the seropositive status were investigated.  相似文献   

16.
根据GenBank登录的猪伪狂犬病毒（PRV）、猪圆环病毒2型（PCV2）和猪繁殖与呼吸综合征病毒（PRRSV）的参考基因序列,设计3对引物分别用于扩增PCV2的ORF2基因、PRV的gE基因、PRRSV的N基因的目的片段,通过优化反应中各个影响因素,建立了PRV、PCV2、PRRSV的多重PCR（mPCR）检测方法。敏感性和特异性的结果表明,该方法对这3种病毒的最低核酸检出量分别为32.5（PRV）、25.2（PCV2）、35.9pg（PRRSV）。该方法对猪流感病毒（SIV）、猪圆环病毒1型（PCV1）、大肠杆菌、猪瘟病毒（CSFV）、猪流行性腹泻病毒（TGE）等病毒的检测结果均为阴性。200份临床样品的多重PCR结果表明,PCV2感染率为80%（160/200）,PRV感染率为21%（42/200）,PRRSV的感染率为78%（156/200）。200份临床样品主要为PCV2和PRRSV混合感染,阳性率达56.0%（112/200）。该方法的建立对这3种病毒病的早期快速检测和指导临床实践具有十分重要的意义。  相似文献   

17.
5种猪病多重PCR检测方法的建立   总被引：1，自引：0，他引：1  
To establish a method for simultaneous detection of classical swine fever virus (CSFV), porcine reproductive and respiratory syndrome virus (PRRSV), pseudorabies virus (PRV), porcine circovirus type 2 (PCV2) and porcine parvovirus (PPV), a multiplex PCR was developed with a set of specific primers designed based on the conserved sequences of CSFV, PRRSV, PRV, PCV2 and PPV. Under the optimized conditions of multiplex PCR,five special fragments of 167 (CSFV),433 (PRRSV),305 (PRV), 559 (PCV2) and 882 bp (PPV) were amplified with a detection limit of 220, 1.6, 72, 400 and 370 pg, respectively. But the multiplex PCR amplification results of swine influenza virus （SIV）, Japanese encephalitis virus （JEV）, Streptococcus suis （SS） and porcine epidemic diarrhea virus （PEDV） were negative．The results showed that the multiplex PCR method was capable of CSFV, PRV, PRRSV, PCV2, PPV infection of single or mixed clinical samples for rapid diagnosis.  相似文献   

18.
为确诊广东省阳江市某规模化猪场（存栏800头母猪）保育猪发病死亡的原因,本试验对从该发病猪场采集的3份肺脏、肝脏、脾脏临床样品进行细菌学检测及药敏试验,采用PCR/RT-PCR检测临床样品中猪伪狂犬病病毒（PRV）、猪瘟病毒（CSFV）、猪繁殖与呼吸综合征病毒（PRRSV）、猪圆环病毒2型（PCV2）、猪圆环病毒3型（PCV3）和猪肺炎支原体等病原。对特异性扩增的3株PRRSV的ORF5基因产物进行序列测定,与VR2332、HuN4、JXA1、CH-1a等代表毒株进行核苷酸序列同源性分析,并构建系统进化树。结果表明,试验分离鉴定出1株副猪嗜血杆菌（Hps）,对7种临床常用药如阿莫西林、头孢拉定等均有较强的敏感性。同源性比对结果表明,3株PRRSV （LJW1、LJW2和LJW3）ORF5基因核苷酸同源性为99.3%~99.8%,与欧洲型代表毒株Lelystad核苷酸同源性为64.0%~64.2%,与HP-PRRSV毒株JXA1、HuN4、CH-1a和TJ核苷酸同源性较高,分别为99.2%~99.5%、99.0%~99.3%、94.5%~94.9%和98.8%~99.2%;与中国河南和广西分离的HP-PRRSV毒株HeNzm1-16和GXLZ05-2015核苷酸同源性较高,分别为99.3%~99.7%和99.2%~99.7%,与美洲型经典疫苗株MLV、美洲型标准株NC、美洲型经典株VR2332核苷酸同源性较低,分别为88.5%~88.8%、85.2%~85.5%和82.3%~82.6%。PRRSV ORF5基因系统进化树分析表明,3株PRRSV均属于美洲型毒株,与国内HP-PRRSV代表毒株JXA1、HuN4和TJ等处于同一分支,亲缘关系较近。本研究揭示了该场保育猪发病病原,并从分子水平上明确了分离的3株PRRSV与不同代表毒株的亲缘关系,为弱毒疫苗的合理选择使用和综合防控PRRSV提供了参考依据。  相似文献   

19.
To determine differences in infection kinetics of two temporally and genetically different type 2 porcine reproductive and respiratory syndrome virus (PRRSV) isolates in vivo with and without concurrent porcine circovirus (PCV) type 2a or 2b infection, 62 pigs were randomly assigned to one of seven groups: negative controls (n=8); pigs coinfected with a 1992 PRRSV strain (VR-2385) and PCV2a (CoI-92-2a; n=9), pigs coinfected with VR-2385 and PCV2b (CoI-92-2b; n=9), pigs coinfected with a 2006 PRRSV strain (NC16845b) and PCV2a (CoI-06-2a; n=9), pigs coinfected with NC16845b and PCV2b (CoI-06-2b; n=9), pigs infected with VR-2385 (n=9), and pigs infected with NC16845b (n=9). Blood samples were collected before inoculation and at day post-inoculation (dpi) 3, 6, 9 and 12 and tested for the presence of PRRSV antibody and RNA, PCV2 antibody and DNA, complete blood counts, and interferon gamma (IFN-γ) levels. Regardless of concurrent PCV2 infection, VR-2385 initially replicated at higher levels and reached peak replication levels at dpi 6. Pigs infected with VR-2385 had significantly higher amounts of viral RNA in serum on both dpi 3 and dpi 6, compared to pigs infected with NC16845b. The peak of NC16845b virus replication occurred between dpi 9 and dpi 12 and was associated with a delayed anti-PRRSV antibody response in these pigs. PCV2 coinfection resulted in significantly more severe macroscopic and microscopic lung lesions and a stronger anti-PRRSV IgG response compared to pigs infected with PRRSV alone. This work further emphasizes in vivo replication differences among PRRSV strains and the importance of coinfecting pathogens.  相似文献   

20.
The objective of this study was to determine whether vaccination with bacterins commonly used in the USA, when administered at a time typical of US protocol, enhances porcine circovirus type 2 (PCV2) replication and the incidence and severity of clinical signs and lesions characteristic of postweaning multisystemic wasting syndrome (PMWS) in conventional pigs. Sixty-one pigs free of PCV2 were randomly assigned to four groups. Groups 1 (n = 15) and 2 (n = 15) pigs served as sham-inoculated negative controls. Groups 3 (n = 14) and 4 (n = 17) pigs were inoculated intralymphoid with PCV2 field isolate ISU-40895. Pigs in groups 2 and 4 were vaccinated with Actinobacillus pleuropneumoniae (APP) and Mycoplasma hyopneumoniae (M. hyopneumoniae) bacterins 21 days before and again 1 day before inoculation with PCV2. Mild transient respiratory disease and diarrhea were observed from 13 to 34 days postinoculation (DPI) in pigs in groups 3 and 4. Half the pigs from each group were necropsied at 22 and 34 DPI, respectively. Moderately enlarged, tan-colored lymph nodes were observed in the majority of pigs in groups 3 and 4. There was a significantly (P < 0.05) longer length of viremia (2.14 +/- 0.26 versus 4.44 +/- 0.23 weeks), a higher copy number of the PCV2 genome in serum, a wider range of tissue distribution of PCV2 antigen, and an increased severity of lymphoid depletion in pigs vaccinated with commercial APP and M. hyopneumoniae vaccines and inoculated with PCV2 compared with PCV2-inoculated unvaccinated pigs. Swine producers and veterinarians may need to consider changes in vaccination protocols in herds with recurrent PCV2-associated PMWS.  相似文献   

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