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1.
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   

2.
Severe disease induced by porcine circovirus type 2 (PCV2) was observed in three pigs originating from a large herd affected by respiratory and digestive signs as well as wasting. Proliferative and necrotising pneumonia (PNP) was diagnosed in two animals, while severe acute interstitial pneumonia characterised by the presence of abundant hyaline membrane in the alveoli and fibrin in the bronchioles was found in one pig. In all cases, large amounts of PCV2 antigen were found in each tissue sample collected from the lungs and mediastinal lymph nodes. Neither porcine reproductive and respiratory syndrome virus (PRRSV) nor swine influenza virus (SIV) was detected, and no bacteria could be cultured in any of the cases. Vascular lesions, e.g. degeneration of endothelial cells, perivascular and intramural oedema, fibrinoid necrosis, vasculitis, perivasculitis, and vascular thrombi were observed in all cases, associated with the presence of PCV2 antigen. The viral antigen was present in the intravascular mononuclear cells, endothelial cells, myocytes and infiltrating inflammatory cells in lymph and blood vessels. In one case, obliterating thrombi in the lymph and blood vessels were directly connected to areas of tissue necrosis and were associated with abundant PCV2 antigen. The results further suggest the causative role of PCV2 infection in PNP, and the importance of the vascular system in the pathogenesis of PCV2-associated diseases of swine.  相似文献   

3.
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   

4.
From 2009 to 2015, 74 lungs from suckling (6.8%), nursing (70.3%), fattening (20.3%) pigs and pregnant sows (2.7%) with respiratory signs from pig farms in Southern Brazil were submitted to a diagnostic laboratory for necropsy and/or histologic examination and screening for respiratory agents by RT‐qPCR, immunohistochemistry (IHC), virus isolation (VI) and subtyping for influenza A virus (IAV), IHC and nested PCR for Mycoplasma hyopneumoniae (Mhyo), PCR for porcine circovirus 2 (PCV2), RT‐qPCR for porcine reproductive and respiratory syndrome virus (PRRSV) and bacterial culture. All lung samples were positive for IAV using RT‐qPCR. Seventy‐two lungs had histologic lesions associated with acute to subacute IAV infection characterized by necrotizing bronchiolitis/bronchitis or bronchointerstitial pneumonia with lymphocytic peribronchiolitis and bronchiolar/bronchial hyperplasia, respectively. Forty‐nine lungs (66.2%) were positive by IHC for IAV nucleoprotein. The H1N1/2009 was the most common subtype and the only IAV detected in 58.1% of lungs, followed by H1N2 (9.5%) and H3N2 (6.8%). Coinfection of IAV and Mhyo was seen in 23 (31%) cases. Although 14.9% of the lungs were positive for PCV2 using PCR, no suggestive lesions of PCV2 disease were observed. Porcine reproductive and respiratory syndrome virus (PRRSV) was not detected, consistent with the PRRS‐free status of Brazil. Secondary bacterial infections (8/38) were associated with suppurative bronchopneumonia and/or pleuritis. Primary IAV infection with Mhyo coinfection was the most common agents found in porcine respiratory disease complex (PRDC) in pigs in Southern Brazil.  相似文献   

5.
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   

6.
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   

7.
Three-week-old cesarean-derived colostrum-deprived (CD/CD) pigs were inoculated with porcine circovirus type 2 (PCV2, n = 19), porcine reproductive and respiratory syndrome virus (PRRSV, n = 13), concurrent PCV2 and PRRSV (PCV2/PRRSV, n = 17), or a sham inoculum (n = 12) to compare the independent and combined effects of these agents. Necropsies were performed at 7, 10, 14, 21, 35, and 49 days postinoculation (dpi) or when pigs became moribund. By 10 dpi, PCV2/PRRSV-inoculated pigs had severe dyspnea, lethargy, and occasional icterus; after 10 dpi, mortality in this group was 10/11 (91%), and all PCV2/ PRRSV-inoculated pigs were dead by 20 dpi. PCV2-inoculated pigs developed lethargy and sporadic icterus, and 8/19 (42%) developed exudative epidermitis; mortality was 5/19 (26%). PRRSV-inoculated pigs developed dyspnea and mild lethargy that resolved by 28 dpi. Microscopic lesions consistent with postweaning multisystemic wasting syndrome (PMWS) were present in both PCV2- and PCV2/PRRSV-inoculated pigs and included lymphoid depletion, necrotizing hepatitis, mild necrotizing bronchiolitis, and infiltrates of macrophages that occasionally contained basophilic intracytoplasmic inclusion bodies in lymphoid and other tissues. PCV2/ PRRSV-inoculated pigs also had severe proliferative interstitial pneumonia and more consistent hepatic lesions. The most severe lesions contained the greatest number of PCV2 antigen-containing cells. PRRSV-inoculated pigs had moderate proliferative interstitial pneumonia but did not develop bronchiolar or hepatic lesions or lymphoid depletion. All groups remained seronegative to porcine parvovirus. The results indicate that 1) PCV2 coinfection increases the severity of PRRSV-induced interstitial pneumonia in CD/CD pigs and 2) PCV2 but not PRRSV induces the lymphoid depletion, granulomatous inflammation, and necrotizing hepatitis characteristic of PMWS.  相似文献   

8.
The objective of this study was to evaluate if spray dried porcine plasma (SDPP) containing porcine circovirus type 2 (PCV2) genome supplemented in feed could transmit PCV2 to pigs challenged with porcine reproductive and respiratory syndrome virus (PRRSV). Twenty-three PRRSV-free pigs, non-viraemic for PCV2, were housed in bio-safety level 3 facilities and assigned to four groups in a 2×2 factorial design consisting of PRRSV challenge and a negative control. The diet contained 0 or 8kg SDPP per 100kg of feed. PRRSV challenge groups were inoculated intranasally with 2mL of a suspension containing 10(6) TCID(50)/mL PRRSV. The SDPP used in the study contained 7.56×10(5) PCV2 genome copies per gram. Dietary treatments were fed from 4days prior to PRRSV inoculation until 28days post-inoculation (PI). All challenged pigs developed PRRSV viraemia by day 3PI and PRRSV antibodies were detected in sera by day 14PI, with no difference between diet treatments. Neither PRRSV viraemia nor seroconversion was observed in non-challenged pigs. PCV2 was not detected in the serum of any pigs throughout the experimental period. SDPP containing the PCV2 genome supplemented in feed did not result in PCV2 transmission to either healthy or PRRSV-infected pigs under these experimental conditions.  相似文献   

9.
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10.
OBJECTIVE: To identify important pathogens and characterize their serologic and pathologic effects in porcine circovirus type 2 (PCV2)-infected pigs in relation to pig age and type of swine production system. DESIGN: Cross-sectional study. ANIMALS: 583 conventionally reared pigs. PROCEDURES: 3- (n = 157), 9- (149), 16- (152), and 24-week-old (125) pigs from 41 different 1-, 2-, and 3-site production systems (5 pigs/age group/farm) were euthanized and necropsied. Pigs with and without PCV2 infection were identified (via PCR assay); infection with and serologic responses to other pathogens and pathologic changes in various tissues (including lungs) were assessed. Logistic regression models were constructed for effects overall and within each age group and type of production system. RESULTS: Compared with PCV2-negative pigs, PCV2-positive pigs were more likely to have swine influenza virus (SIV) type A and Mycoplasma hyopneumoniae infections and sample-to-positive (S:P) ratios for SIV H1N1 from 0.50 to 0.99; also, PCV2-positive pigs had higher serum anti-porcine reproductive and respiratory syndrome virus (PRRSV) antibody titers and more severe lung tissue damage. Infection with SIV (but lower SIV H1N1 S:P ratio) was more likely in 3-week-old PCV2-positive pigs and evidence of systemic disease was greater in 16-week-old PCV2-positive pigs than in their PCV2-negative counterparts. By site type, associations of coinfections and disease effects between PCV2-positive and -negative pigs were greatest in 3-site production systems. CONCLUSIONS AND CLINICAL RELEVANCE: In PCV2-positive pigs, coinfections with SIV, M. hyopneumoniae, and PRRSV are important, having the greatest effect in the early to late nursery phase and in 3-site production systems.  相似文献   

11.
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.  相似文献   

12.
A double in situ hybridization method for the simultaneous detection of porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus (PCV) genomes in the same tissue section was applied to lung tissues from 9 pigs in which PRRSV and PCV coinfection had been previously demonstrated. Paraffin-embedded tissue sections were simultaneously hybridized with a digoxigenin-labeled antisense RNA probe for PRRSV and a fluorescein-labeled antisense RNA probe for PCV, and hybridization was detected with anti-digoxigenin alkaline phosphatase/fast red and anti-fluorescein peroxidase/diaminobenzidine, respectively. PRRSV and PCV genomes were identified in the same pulmonary cell types as reported previously in all 9 pigs. In all pigs, PCV-positive cells outnumbered PRRSV-positive cells. A small proportion of alveolar macrophages contained both PRRSV and PCV genomes.  相似文献   

13.
为掌握广西猪主要病毒性传染病流行情况,为猪传染病预防方案提供依据,本研究于2013年1月1日至2014年12月31日从广西省共收集410份样品,运用PCR及RT-PCR方法检测猪繁殖与呼吸综合征病毒(PRRSV)、猪圆环病毒2型(PCV-2)、猪瘟病毒(CSFV)、猪伪狂犬病毒(PRV)、猪流行性腹泻病毒(PEDV)、传染性胃肠炎病毒(TGEV)、轮状病毒(PORV)、猪流感病毒(SIV)的感染情况。检测结果表明,PRRSV、PCV-2、CSFV、PRV、PEDV、TGEV、 PORV和SIV的平均感染率分别为35.12%、18.54%、1.17%、0.98%、10.00%、2.44%、0和1.22%;PRRSV和PCV-2混合感染率为6.83%;PRRSV在秋、冬季节呈现高感染率为36.67%、45.31%和63.64%、48.78%,而PCV-2在春、夏、冬季节呈现高感染率为44.44%、25.00%,11.29%、19.35%和39.39%、14.63%。PRRSV和PCV-2是混合感染的主要病原,它们互相之间或是与CSFV、PEDV、PRV、SIV及副猪嗜血杆菌、链球菌等混合感染,PRRSV和PCV-2将是今后广西地区猪病防控的重点。  相似文献   

14.
为建立特异、敏感的猪流感病毒(SIV)和猪繁殖与呼吸综合征病毒(PRRSV)的双重RT-PCR检测方法,本研究根据GenBank登录的SIV M基因保守序列和PRRSV美洲型毒株的N基因保守序列,设计合成了2对特异引物,通过对扩增条件的优化,建立检测SIV和PRRSV的双重RT-PCR方法.检测结果显示:该方法可同时扩增出SIV(345 bp)和PRRSv(520 bp)的特异性片段;而猪瘟病毒、猪伪狂犬病病毒、猪细小病毒、猪圆环病毒2型及阴性鸡胚尿囊液核酸扩增结果均为阴性;对SIV和PRRSV 2种病毒混合液的最小检出量分别为102 EID50/0.1 mL和103TCID50/0.1 mL.应用双重RT-PCR和病毒分离法对12份临床疑似样品进行对比检测,结果表明:除双重RT-PCR检测到双阳性的3份混合感染病料中1份未分离到PRRSV外,其余2份均分离出病毒.证明该方法具有良好的特异性、敏感性,可以用于临床样品的早期快速检测.  相似文献   

15.
本研究通过猪圆环病毒2型(Porcine circovirus type 2,PCV2)和猪繁殖与呼吸综合征(Porcine reproductive and respiratory syndrome virus,PRRSV)强毒共感染3周龄健康仔猪来评价其致病性。试验动物随机分为3组,空白对照组(n=3头),PRRSV单独感染组(n=3头),PCV2和PRRSV共感染组(n=6头),从而比较相互之间的差异。通过临床症状、病理学变化、病原学和血清学检查,对二者混合感染仔猪的致病性进行了研究。结果表明PCV2和PRRSV共同感染能引起仔猪断奶后多系统消耗性综合征,表现为淋巴组织肿大、出血,肉芽肿性炎症,坏死性肝炎,仔猪消瘦、生长缓慢等特征性病变;混合感染能加重PRRSV对仔猪引起的间质性肺炎的严重程度。混合感染可以出现支气管肺炎和明显的肝病变,淋巴结多呈界限明显的块状出血等典型病变。  相似文献   

16.
The aim of this study was to evaluate the vasculature in porcine circovirus type 2-infected (PCV2-infected) lungs and to identify the PCV2 subtypes involved in porcine pneumonia. Pulmonary samples from 140 pigs, 2 weeks to 7 months of age, from 36 Hungarian commercial herds with clinical signs of respiratory disease were examined for the presence of respiratory pathogens, with bacterial culture, pathologic evaluation, and immunohistochemistry for PCV2, porcine reproductive respiratory syndrome virus, and swine influenza virus. PCV2 was the most commonly identified pathogen (49 cases) among the 74 of 140 cases (53%) with respiratory pathogens. PCV2 was detected immunohistochemically in the wall of 13% to 100% of pulmonary vessels (mean, 89%) in 38 of 49 cases (78%). Detection of PCV2 antigen was positively correlated with the presence of vascular lesions (P < .001, odds ratio [OR]: 159.54). Other pathogens capable of vascular injury in swine were found in 29 of 49 of the PCV2-positive cases (59%). The probability of detecting vascular lesions in PCV2-infected lung was higher than in infection with porcine reproductive respiratory syndrome virus (P < .002, OR: 14.63), Pasteurella multocida infection (P < .001, OR: 5.75), or Streptococcus spp. infection (not significant, OR: 1.45). Sequence analysis of open reading frame 2 amplicons was possible in 6 PCV2-positive cases, from which 5 cases proved to be PCV2b subtype and 1 case, PCV2a subtype. In conclusion, PCV2 antigen was commonly colocalized with pulmonary vascular lesions in pneumonia in Hungarian swine, and PCV2b was the dominant subtype.  相似文献   

17.
Thirty-three pigs affected by porcine dermatitis and nephropathy syndrome, 30 from Spain and three from the USA, were investigated in order to detect porcine circovirus (PCV) in their tissues. A standard in situ hybridisation technique using a specific DNA 317-bp probe based on a well-conserved sequence of PCV (which recognises both PCV-1 and PCV-2) was applied to formalin-fixed, paraffin-embedded tissues. Twenty-eight of the 30 Spanish pigs and all three American pigs had PCV in at least one tissue. Viral nucleic acid was detected mainly in lymphoid organs, and especially the lymph nodes. The viral genome was also found, in order of decreasing quantity, in Peyer's patches, tonsil, lung, spleen, kidney, liver, and skin. Viral nucleic acid was located mainly within the cytoplasm of monocyte/macrophage lineage cells, including follicular dendritic cells, macrophages, histiocytes and Kupffer cells. No viral nucleic acid was found in damaged glomeruli or arteriolar walls. In frozen samples available from three Spanish pigs, the virus was identified as type 2 by using the polymerase chain reaction and restriction fragment length polymorphism. Most of the pigs from which serum was available were seropositive against porcine respiratory and reproductive syndrome virus (PRRSV), and PRRSV antigen was detected in the lung of two of the Spanish pigs. These results suggested that PCV is present in tissues of almost all pigs affected by PDNS, and PCV has to be considered as a possible agent involved in the pathogenesis of the syndrome.  相似文献   

18.
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   

19.
Shi K  Li H  Guo X  Ge X  Jia H  Zheng S  Yang H 《Veterinary microbiology》2008,129(3-4):367-377
Porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2) are pathogens, which can significantly affect the swine industry worldwide. Field surveys suggest that simultaneous PRRSV and PCV2 infection is common in pigs. The objective of this study was to measure the changes in peripheral blood leukocyte subpopulations in piglets co-infected experimentally with PRRSV and PCV2, in order to analyze the synergistic influence of co-infection on the immune system. Changes in peripheral blood leukocyte subpopulations were systematically measured by flow cytometry (FCM). The levels of antibodies to PRRSV and PCV2 were detected by indirect Enzyme-Linked ImmunoSorbent Assay (ELISA) and the indirect fluorescent antibody test (IFA), respectively. Serum viral loads were measured using real-time PCR. The results showed that piglets co-infected with PRRSV and PCV2 exhibited slower generation and lower levels of antibodies to PRRSV and PCV2, and increased amounts and a prolonged presence of both PRRSV and PCV2 in serum, in comparison to the piglets infected with either virus alone. The major finding in our study was that the total and differential leukocyte counts, including white blood cells (WBCs), monocytes, granulocytes and lymphocytes (T, B and NK cells, as well as T-cell subpopulations), dramatically decreased early during co-infection with PRRSV and PCV2 for about two weeks, in contrast with animals singly infected with either PRRSV or PCV2. These results suggest that PRRSV and PCV2 co-infection results in a synergistic decrease in immune cells in the peripheral blood of piglets. These data contribute to the understanding of the immunosuppressive effects resulting from PRRSV and PCV2 co-infection in pigs.  相似文献   

20.
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   

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