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1.
The recent pandemic caused by human influenza virus A(H1N1) 2009 contains ancestral gene segments from North American and Eurasian swine lineages as well as from avian and human influenza lineages. The emergence of this A(H1N1) 2009 poses a potential global threat for human health and the fact that it can infect other species, like pigs, favours a possible encounter with other influenza viruses circulating in swine herds. In Europe, H1N1, H1N2 and H3N2 subtypes of swine influenza virus currently have a high prevalence in commercial farms. To better assess the risk posed by the A(H1N1) 2009 in the actual situation of swine farms, we sought to analyze whether a previous infection with a circulating European avian-like swine A/Swine/Spain/53207/2004 (H1N1) influenza virus (hereafter referred to as SwH1N1) generated or not cross-protective immunity against a subsequent infection with the new human pandemic A/Catalonia/63/2009 (H1N1) influenza virus (hereafter referred to as pH1N1) 21 days apart. Pigs infected only with pH1N1 had mild to moderate pathological findings, consisting on broncho-interstitial pneumonia. However, pigs inoculated with SwH1N1 virus and subsequently infected with pH1N1 had very mild lung lesions, apparently attributed to the remaining lesions caused by SwH1N1 infection. These later pigs also exhibited boosted levels of specific antibodies. Finally, animals firstly infected with SwH1N1 virus and latter infected with pH1N1 exhibited undetectable viral RNA load in nasal swabs and lungs after challenge with pH1N1, indicating a cross-protective effect between both strains.  相似文献   

2.
OBJECTIVE: To examine clinical signs, virus infection and shedding, and transmission of swine influenza virus (SIV) subtype H1N2 among seropositive pigs. ANIMALS: Eighteen 3-week-old pigs with maternal antibodies against SIV subtypes H1N1, H3N2, and H1N2. PROCEDURE: Ten pigs (principal) were inoculated intranasally with subtype H1N2 and 2 groups of contact pigs (n = 4) each were mixed with principal pigs on day 7 (group 1) or 28 (group 2). Two principal pigs each were necropsied on days 4, 14, 21, 28, and 42 days after inoculation. Four pigs in each contact group were necropsied 35 and 14 days after contact. Virus excretion was evaluated after inoculation or contact. Lung lesions and the presence of SIV in various tissues were examined. RESULTS: Mild coughing and increased rectal temperature were observed in principal pigs but not in contact pigs. Nasal virus shedding was detected in all principal pigs from day 2 for 3 to 5 days, in group 1 pigs from day 2 for 4 to 9 days after contact, and in group 2 pigs from day 4 for 2 to 6 days after contact. Trachea, lung, and lymph node specimens from infected pigs contained virus. Antibody titers against all 3 subtypes in all pigs gradually decreased. CONCLUSIONS AND CLINICAL RELEVANCE: Protection from viral infection and shedding was not observed in pigs with maternal antibodies, but clinical disease did not develop. Vaccination programs and good management practices should be considered for control of SIV subtype H1N2 infection on swine farms.  相似文献   

3.
Swine influenza viruses H1N1 and H3N2 have been reported in the swine population worldwide. From June 2008 to June 2009, we carried out serological and virological surveillance of swine influenza in the Hubei province in central China. The serological results indicated that antibodies to H1N1 swine influenza virus in the swine population were high with a 42.5% (204/480) positive rate, whereas antibodies to H3N2 swine influenza virus were low with a 7.9% (38/480) positive rate. Virological surveillance showed that only one sample from weanling pigs was positive by RT-PCR. Phylogenetic analysis of the hemagglutinin and neuraminidase genes revealed that the A/Sw/HB/S1/2009 isolate was closely related to avian-like H1N1 viruses and seemed to be derived from the European swine H1N1 viruses. In conclusion, H1N1 influenza viruses were more dominant in the pig population than H3N2 influenza viruses in central China, and infection with avian-like H1N1 viruses persistently emerged in the swine population in the area.  相似文献   

4.
This paper reports on a serological and virological survey for swine influenza virus (SIV) in densely populated pig areas in Spain. The survey was undertaken to examine whether the H1N2 SIV subtype circulates in pigs in these areas, as in other European regions. Six hundred sow sera from 100 unvaccinated breeding herds across Northern and Eastern Spain were examined using haemagglutination inhibition (HI) tests against H1N1, H3N2 and H1N2 SIV subtypes. Additionally, 225 lung samples from pigs with respiratory problems were examined for the presence of SIV by virus isolation in embryonated chicken eggs and by a commercial membrane immunoassay. The virus isolates were further identified by HI and RT-PCR followed by partial cDNA sequencing. The HI test on sera revealed the presence of antibodies against at least one of the SIV subtypes in 83% of the herds and in 76.3% of the animals studied. Of the 600 sow sera tested, 109 (18.2%), 60 (10%) and 41 (6.8%) had SIV antibodies to subtype H1N2 alone, H3N2 alone and H1N1 alone, respectively. Twelve H3N2 viruses, 9 H1N1 viruses and 1 H1N2 virus were isolated from the lungs of pigs with respiratory problems. The analysis of a 436 nucleotide sequence of the neuraminidase gene from the H1N2 strain isolated further confirmed its identity. Demonstrably, swine influenza is still endemic in the studied swine population and a new subtype, the H1N2, may be becoming established and involved in clinical outbreaks of the disease in Spain.  相似文献   

5.
本研究2012年底从辽宁省某屠宰场猪鼻咽拭子样品中分离到1株流感病毒,经HA—HI试验和RT—PCR鉴定为H1N1亚型猪流感病毒株,命名为A／swine/Liaoning／01／2012（H1N1）,通过对病毒的8个基因片段克隆并测序,并利用分子生物学软件进行遗传演化分析。结果表明,分离株HA基因裂解位点附近的氨基酸序列为IPSIQSRjG,符合低致病力流感病毒的分子特征。全基因组进化树结果表明,分离株的8个基因片段与A／swine／Jiangsu／40／2011（H1N1）株核苷酸同源性最高,分离株处在类禽型H1N1亚型遗传进化分支上;由于类禽型H1N1猪流感病毒具有潜在感染人的潜力,在国外和国内均有感染人的报道,因此,辽宁省首次分离到该型猪流感病毒对全省养猪业和公共卫生安全具有重要意义,值得深入研究。  相似文献   

6.
Swine influenza virus (SIV) of H1N1 and H3N2 subtypes are dominated in European pigs population. "Classical swine" H1N1 subtype was replaced by "avian-like" H1N1 subtype. It co-circulates with H3N2 reassortant possessing "avian" genes. In the present study, 41 SIV strains isolated from pigs with pneumonia, raised in 20 Polish farms, were identified and characterised. Since it was evidenced that isolates from the same geographic district and the same year of isolation are in 100% similar, 15 strains representing different district and different year of isolation were chosen to construct phylogenetic trees. Two genes, conservative matrix 1 (M1) and the most variable, haemagglutynin (HA), were sequenced and subjected into phylogenetic analysis. The results of the analysis confirmed that "avian-like" swine H1N1 strains evolved faster than classical SIV strains. HA gene of these isolates have been derived from contemporary strains of "avian-like" SIV. In contrast, the M1 gene segment may have originated from avian influenza viruses. H3N2 strain is located in swine cluster, in the main prevalent European group of H3N2 isolates called A/Port Chalmers/1/73-like Eurasian swine H3N2 lineage, which has evolved separately from the human H3N2 virus lineage around 1973.  相似文献   

7.
猪流感是猪常见的呼吸道传染病,临床以高热、呼吸困难、咳嗽和衰竭、迅速康复或死亡为特征。猪流感不仅给养猪业造成巨大损失,也严重威胁着人类健康。本研究从发病猪场中分离到1株H1N1亚型猪流感病毒,序列分析结果显示,分离毒株属于欧洲类禽猪流感H1N1亚型病毒。将分离毒株分别接种到MDCK与ST细胞,观察病毒的生长特性,结果显示分离的猪流感病毒在ST细胞中复制能力较强。采用RT-PCR技术分别扩增8个基因片段,克隆到流感病毒反向遗传系统,成功拯救出猪流感病毒毒株,测序结果显示拯救的猪流感病毒与亲本毒序列一致。本研究成功分离的猪流感病毒,以及建立的反向遗传技术为研究欧洲类禽猪流感病毒跨种传播的机制以及研发新型猪流感疫苗株奠定了基础。  相似文献   

8.
Quail has been proposed to be an intermediate host of influenza A viruses. However, information on the susceptibility and pathogenicity of pandemic H1N1 2009 (pH1N1) and swine influenza viruses in quails is limited. In this study, the pathogenicity, virus shedding, and transmission characteristics of pH1N1, swine H1N1 (swH1N1), and avian H3N2 (dkH3N2) influenza viruses in quails was examined. Three groups of 15 quails were inoculated with each virus and evaluated for clinical signs, virus shedding and transmission, pathological changes, and serological responses. None of the 75 inoculated (n = 45), contact exposed (n = 15), or negative control (n = 15) quails developed any clinical signs. In contrast to the low virus shedding titers observed from the swH1N1-inoculated quails, birds inoculated with dkH3N2 and pH1N1 shed relatively high titers of virus predominantly from the respiratory tract until 5 and 7 DPI, respectively, that were rarely transmitted to the contact quails. Gross and histopathological lesions were observed in the respiratory and intestinal tracts of quail inoculated with either pH1N1 or dkH3N2, indicating that these viruses were more pathogenic than swH1N1. Sero-conversions were detected 7 DPI in two out of five pH1N1-inoculated quails, three out of five quails inoculated with swH1N1, and four out of five swH1N1-infected contact birds. Taken together, this study demonstrated that quails were more susceptible to infection with pH1N1 and dkH3N2 than swH1N1.  相似文献   

9.
We compared the efficacy of 3 commercial vaccines against swine influenza A virus (SIV) and an experimental homologous vaccine in young pigs that were subsequently challenged with a variant H3N2 SIV, A/Swine/Colorado/00294/2004, selected from a repository of serologically and genetically characterized H3N2 SIV isolates obtained from recent cases of swine respiratory disease. The experimental vaccine was prepared from the challenge virus. Four groups of 8 pigs each were vaccinated intramuscularly at both 4 and 6 wk of age with commercial or homologous vaccine. Two weeks after the 2nd vaccination, those 32 pigs and 8 nonvaccinated pigs were inoculated with the challenge virus by the deep intranasal route. Another 4 pigs served as nonvaccinated, nonchallenged controls. The serum antibody responses differed markedly between groups. After the 1st vaccination, the recipients of the homologous vaccine had hemagglutination inhibition (HI) titers of 1:640 to 1:2560 against the challenge (homologous) virus. In contrast, even after 2nd vaccination, the commercial-vaccine recipients had low titers or no detectable antibody against the challenge (heterologous) virus. After the 2nd vaccination, all the groups had high titers of antibody to the reference H3N2 virus A/Swine/Texas/4199-2/98. Vaccination reduced clinical signs and lung lesion scores; however, virus was isolated 1 to 5 d after challenge from the nasal swabs of most of the pigs vaccinated with a commercial product but from none of the pigs vaccinated with the experimental product. The efficacy of the commercial vaccines may need to be improved to provide sufficient protection against emerging H3N2 variants.  相似文献   

10.
猪流感病毒H1、H3、N1、N2亚型分型 RT-PCR方法的建立   总被引：1，自引：0，他引：1  
根据GenBank中H1N1和H3N2亚型猪流感病毒(SIV)血凝素(hemagglutinin,HA)、神经氨酸酶(neuraminidase,NA)和M基因保守序列,分别设计合成了5对特异性引物,利用RT-PCR技术对SIV的型和亚型进行鉴定。结果表明,该方法的型RT-PCR可以检测出104 EID50病毒量所提取的RNA;H1、H3、N1和N2的亚型RT-PCR均可以检测出104 EID50病毒量所提取的RNA。除每对特异性引物所对应的亚型外,对其他亚型及猪繁殖与呼吸综合征病毒(PRRSV)和猪瘟病毒(CSFV)的检测均为阴性,应用该方法对临床样品进行检测,其结果与病毒分离结果符合率为100%。结果表明,该方法特异性好、敏感性高,有望成为SIV的一种特异、敏感、快速的分型检测方法,为猪流感分子流行病学的调查奠定了良好的基础。  相似文献   

11.
The efficacy of a commercial swine influenza vaccine based on A/New Jersey/8/76 (H1N1) and A/Port Chalmers/1/73 (H3N2) strains was tested against challenge with an H1N2 swine influenza virus. Influenza virus-seronegative pigs were vaccinated twice with the vaccine when they were four and eight weeks old, or with the same vaccine supplemented with an H1N2 component. Control pigs were left unvaccinated. Three weeks after the second vaccination, all the pigs were challenged intratracheally with the swine influenza strain Sw/Gent/7625/99 (H1N2). The commercial vaccine induced cross-reactive antibodies to H1N2, as detected by the virus neutralisation (VN) assay, but VN antibody titres were 18 times lower than in the pigs vaccinated with the H1N2-supplemented vaccine. The challenge produced severe respiratory signs in nine of 10 unvaccinated control pigs, which developed high H1N2 virus titres in the lungs 24 and 72 hours after the challenge. Vaccination with the commercial vaccine resulted in milder respiratory signs, but H1N2 virus replication was not prevented. Mean virus titres in the pigs vaccinated with the commercial vaccine were 1-5 log10 lower than in the controls at 24 hours but no different at 72 hours. In contrast, the H1N2-supplemented vaccine prevented respiratory disease in most pigs. There was a 4-5 log10 reduction in the mean virus titre at 24 hours in the pigs vaccinated with this vaccine, and no detectable virus replication at 72 hours. These data indicate that the commercial swine influenza vaccine did not confer adequate protection against the H1N2 subtype.  相似文献   

12.
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   

13.
The knowledge of the genome constellation in pandemic influenza A virus H1N1 2009 from different countries and different hosts is valuable for monitoring and understanding of the evolution and migration of these strains. The complete genome sequences of selected worldwide distributed influenza A viruses are publicly available and there have been few longitudinal genome studies of human, avian and swine influenza A viruses. All possible to download SIV sequences of influenza A viruses available at GISAID Platform (Global Initiative on Sharing Avian Influenza Data) were analyzed firstly through the web servers of the Influenza Virus Resource in NCBI. Phylogenetic study of circulating human pandemic H1N1 virus indicated that the new variant possesses a distinctive evolutionary trait. There is no one way the pandemic H1N1 have acquired new genes from other distinguishable viruses circulating recently in local human, pig or domestic poultry populations from various geographic regions. The extensive genetic diversity among whole segments present in pandemic H1N1 genome suggests that multiple introduction of virus have taken place during the period 1999-2009. The initial interspecies transmission could have occurred in the long-range past and after it the reassortants steps lead to three lineages: classical SIV prevalent in the North America, avian-like SIV in Europe and avian-like related SIV in Asia. This analysis contributes to the evidence that pigs are not the only hosts playing the role of "mixing vessel", as it was suggested for many years.  相似文献   

14.
Recently a commercial enzyme-linked immunosorbent assay (ELISA) kit for detecting antibody against H1N1 swine influenza virus (SIV) has been made available to diagnosticians and veterinary practitioners. Because the hemagglutination inhibition (HI) test has been considered the standard test for SIV serology, diagnostic performance of the new ELISA was evaluated using positive (n = 60) and negative (n = 188) serum samples from young pigs with known status of SIV infection and compared with that of the HI test. Both ELISA and HI test identified all negative animals correctly. None of the serum samples (n = 64) from pigs inoculated with H3N2 SIV was positive by ELISA for SIV antibody. The H1N1 SIV antibody detectable by ELISA appears to develop more slowly in comparison with antibody detectable by HI test. Although antibody was detected by HI test in all inoculated animals (n = 20) by day 7 postinoculation (PI), antibody was detected by ELISA in 0%, 75%, and 100% of the inoculated animals on days 7, 14, and 28 PI, respectively. Discrepancy in test results between the 2 serologic tests appeared to be because of differences in antibody isotypes detected by each test. Enzyme-linked immunosorbent assay mainly detected IgG antibody, whereas the HI test detects IgM antibody very efficiently as well as IgG antibody. Collectively, the commercial ELISA is highly specific for antibody to H1N1 SIV but may not identify positive animals at the early stage of infection as effectively as the HI test, particularly when SIV is introduced to a na?ve swine population.  相似文献   

15.
This study investigated the efficacy of a bivalent swine influenza virus (SIV) vaccine in piglets challenged with a heterologous H1N1 SIV isolate. The ability of maternally derived antibodies (MDA) to provide protection against a heterologous challenge and the impact MDA have on vaccine efficacy were also evaluated. Forty-eight MDA(+) pigs and 48 MDA(-) pigs were assigned to 8 different groups. Vaccinated pigs received two doses of a bivalent SIV vaccine at 3 and 5 weeks of age. The infected pigs were challenged at 7 weeks of age with an H1N1 SIV strain heterologous to the H1N1 vaccine strain. Clinical signs, rectal temperature, macroscopic and microscopic lesions, virus excretion, serum and local antibody responses, and influenza-specific T-cell responses were measured. The bivalent SIV vaccine induced a high serum hemagglutination-inhibition (HI) antibody titer against the vaccine virus, but antibodies cross-reacted at a lower level to the challenge virus. This study determined that low serum HI antibodies to a challenge virus induced by vaccination with a heterologous virus provided protection demonstrated by clinical protection and reduced pneumonia and viral excretion. The vaccine was able to prime the local SIV-specific antibody response in the lower respiratory tract as well as inducing a systemic SIV-specific memory T-cell response. MDA alone were capable of suppressing fever subsequent to infection, but other parameters showed reduced protection against infection compared to vaccination. The presence of MDA at vaccination negatively impacted vaccine efficacy as fever and clinical signs were prolonged, and unexpectedly, SIV-induced pneumonia was increased compared to pigs vaccinated in the absence of MDA. MDA also suppressed the serum antibody response and the induction of SIV-specific memory T-cells following vaccination. The results of this study question the effectiveness of the current practice of generating increased MDA levels through sow vaccination in protecting piglets against disease.  相似文献   

16.
The H1N1, H3N2 and, more recently, H1N2 subtypes of influenza A virus are presently co‐circulating in swine herds in several countries. The objectives of this study were to investigate the pathogenesis of Sw/Italy/1521/98 (H1N2) influenza virus, isolated from respiratory tissues of pigs from herds in Northern Italy, and to evaluate its potential cross‐protection against the Sw/Fin/2899/82 (H1N1) strain. In the pathogenesis test, eight pigs were intranasally infected with H1N2 virus; at pre‐determined intervals, these animals were killed and necropsied, along with eight uninfected animals. In the cross‐protection test, sixteen pigs were infected by intranasal (i.n.) and intratracheal (i.t.) routes with either H1N2 or H1N1 virus. Twenty days later, all pigs were challenged (by the same route), with either the homologous H1N2 or heterologous H1N1 virus strains. Control group was inoculated with culture medium alone. On post‐challenge days (PCD) 1 and 3, two pigs from each infected group, along with one control pig, were killed. Clinical, virological, serological and histopathological investigations were performed in both the pathogenicity and cross‐protection tests. In the pathogenicity test, mild clinical signs were observed in two pigs during 3 and 4 days, respectively. Virus was isolated from two pigs over 6 days and from lung samples of pigs killed on post‐infection days 2 and 4. Seroconversion was detected in the two infected animals killed 15 days after infection. In the cross‐protection study, mild clinical respiratory signs were detected in all pigs infected with either the H1N2 or H1N1 virus. The virus was isolated from nasal swabs of almost all pigs till 6 days. After the challenge infection, the pigs remained clinically healthy and virus isolation from the nasal secretions or lung samples was sporadic. Antibody titres in H1N1 or H1N2 infected groups were similar, whereas the H1N2 sub‐type induced less protection against re‐infection by homologous and heterologous virus than H1N1 sub‐type. The controls had no signs of the disease. In the H1N2 infected pigs, a reduced number of goblet cells in nasal and tracheal mucosa and small foci of lymphomononuclear cell infiltrates in the submucosa were detected. Furthermore, the goblet cell reduction was related to the time of infection. Diffuse mild interstitial pneumonia was also recorded in pigs infected with the H1N2 virus and challenged with either H1N1or H1N2 pigs. These studies showed the moderate virulence of the H1N2 virus and a partial cross‐protection against heterologous infection.  相似文献   

17.
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   

18.
中国类禽型H1N1亚型猪流感病毒的发现和遗传分析   总被引：1，自引：0，他引：1  
采用禽流感病毒通用引物,对2006年发现的1株H1N1亚型的类禽型猪流感病毒的全基因组进行了测序,并进行了遗传学分析。序列分析表明它的8个片段与欧洲的类禽型猪流感病毒A/swine/Ile et Vilaine/1455/99(H1N1)病毒和A/swine/Cotes d'Armor/1488/99(H1N1)病毒的相应基因具有高度的同源性,同源性可达97%~99%,表明类禽型猪流感病毒已在中国出现。其血凝素基因的190E→D和225G→E的突变使得其结合NeuAc-a2,6Gal受体的能力高于NeuAca2,3Gal受体。欧洲的类禽型猪流感病毒可以直接感染人,并且可导致人的肺炎和死亡。中国类禽型猪流感病毒的发现及其的NeuAca2,6Gal受体结合特性使其成为一个潜在可感染人的病毒。  相似文献   

19.
Intratracheal inoculation of a field isolate of influenza A H1N1 caused high fever, anorexia and dyspnoea in unvaccinated pigs. In a limited study, it was shown that animals vaccinated once with an inactivated influenza A H1N1 strain showed partial protection at challenge, indicated by mild or absent clinical signs and by the suppression of viral replication. There appeared to be a correlation between the hemagglutination-inhibition titers of the serum of vaccinated pigs and the degree of protection. Animals vaccinated with two spaced injections were completely protected at challenge. Viral replication was inhibited in their respiratory tract since no virus was isolated from animals at slaughter and no increase in antibody titer was observed in challenged vaccinates followed serologically. It was concluded that vaccination of swine against influenza with an inactivated vaccine can result in a protective immunity in the respiratory tract. The New Jersey vaccine strain could protect against swine influenza strains (H1N1) currently prevalent in several European countries.  相似文献   

20.
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   

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