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1.
采用在线LUXTM专业软件,根据BTV-NS3基因序列和EHDV-NS3基因序列,通过特异性单一引物序列3′末端的荧光标记,分别设计出两对BTV和EHDV的LUX荧光PCR引物,并采用BLAST软件对各引物进行匹配性和特异性分析,根据分析结果选择合适的引物合成。经过各反应条件的优化和特异性、敏感性试验,并对BTV、EHDV、VSV、PPRV、BVDV、AKV的BHK-21细胞培养物和临床样品检测,与常规RT-PCR进行对比检测,建立了能同时鉴别检测BTV和EHDV的二重LUXTM荧光PCR方法。该二重LUXTM荧光PCR的BTV和EHDV各自引物只对相应的病毒呈阳性反应,两者没有交叉反应现象,对健康牛、羊和猪基因组DNA、BKH-21细胞对照,以及其他几种相似疾病如VSV、PPRV、BVDV、AKV均呈阴性反应。该法对病毒的细胞培养液鉴别检测敏感性可达1TCID50C以上,比常规RT-PCR敏感性提高10倍以上,从样品核酸纯化到完成二重LUXTM荧光PCR反应和熔解曲线分析,仅需3h,在进出口动物检验检疫中快速鉴别BTV和EHDV具有实际应用价值。  相似文献   

2.
The median infectious dose (ID(50)) of porcine reproductive and respiratory syndrome (PRRS) virus isolate MN-184 was determined for aerosol exposure. In 7 replicates, 3-week-old pigs (n=58) respired 10l of airborne PRRS virus from a dynamic aerosol toroid (DAT) maintained at -4°C. Thereafter, pigs were housed in isolation and monitored for evidence of infection. Infection occurred at virus concentrations too low to quantify by microinfectivity assays. Therefore, exposure dose was determined using two indirect methods ("calculated" and "theoretical"). "Calculated" virus dose was derived from the concentration of rhodamine B monitored over the exposure sequence. "Theoretical" virus dose was based on the continuous stirred-tank reactor model. The ID(50) estimate was modeled on the proportion of pigs that became infected using the probit and logit link functions for both "calculated" and "theoretical" exposure doses. Based on "calculated" doses, the probit and logit ID(50) estimates were 1 × 10(-0.13)TCID(50) and 1 × 10(-0.14)TCID(50), respectively. Based on "theoretical" doses, the probit and logit ID(50) were 1 × 10(0.26)TCID(50) and 1 × 10(0.24)TCID(50), respectively. For each point estimate, the 95% confidence interval included the other three point estimates. The results indicated that MN-184 was far more infectious than PRRS virus isolate VR-2332, the only other PRRS virus isolate for which ID(50) has been estimated for airborne exposure. Since aerosol ID(50) estimates are available for only these two isolates, it is uncertain whether one or both of these isolates represent the normal range of PRRS virus infectivity by this route.  相似文献   

3.
Epizootic hemorrhagic disease virus (EHDV), an arthropod-borne orbivirus (family Reoviridae), is an emerging pathogen of wild and domestic ruminants that is closely related to bluetongue virus (BTV). The present study examines the outcome of an experimental EHDV-7 infection of Holstein cattle and East Frisian sheep. Apart from na?ve animals that had not been exposed to BTV, it included animals that had been experimentally infected with either BTV-6 or BTV-8 two months earlier. In addition, EHDV-infected cattle were subsequently challenged with BTV-8. Samples were tested with commercially available ELISA and real-time RT-PCR kits and a custom NS3-specific real-time RT-PCR assay. Virus isolation was attempted in Vero, C6/36 and KC cells (from Culicoides variipennis), embryonated chicken eggs and type I interferon receptor-deficient IFNAR(-/-) mice. EHDV-7 productively infected Holstein cattle, but caused no clinical signs. The inoculation of East Frisian sheep, on the other hand, apparently did not lead to a productive infection. The commercial diagnostic kits performed adequately. KC cells proved to be the most sensitive means of virus isolation, but viremia was shorter than 2 weeks in most animals. No interference between EHDV and BTV infection was observed; therefore the pre-existing immunity to some BTV serotypes in Europe is not expected to protect against a possible introduction of EHDV, in spite of the close relation between the viruses.  相似文献   

4.
Maedi-visna virus (MVV) spreads horizontally via the respiratory route. In order to establish an experimental mucosal infection route, we compared intranasal and intratracheal inoculation using the infectious MVV molecular clone KV1772-kv72/67. For intranasal infection 0.5 x 10(3)-0.5 x 10(7) TCID50 of virus was sprayed into the nostrils of the sheep. For the intratracheal infection 10(0)-10(6) TCID50 of virus was injected into the trachea. Successful infection was indicated by development of MVV specific antibodies and virus isolation over a period of 6 months. In the intranasal infection, only the sheep receiving the highest dose i.e., 0.5 x 10(7) TCID50, became infected, suggesting that intranasal application was not an efficient mode of infection. In the intratracheal infection, the sheep infectious dose 50% was 10(1) TCID50 and virus could be isolated from the central nervous system 4 months post infection with 10(4) TCID50. Therefore it is concluded that intratracheal infection is a very efficient route for experimental inoculation with MVV.  相似文献   

5.
Little information is known about infection, replication and transmission of porcine circovirus type 2 (PCV2) in species other than swine. Two sets of animal experiments were carried out to investigate the susceptibility of mice to PCV2 and to study their possible role in maintaining and transmitting the virus. In the first experiment 14 mice were inoculated with PCV2 by the intraperitoneal route with 5 x 10(2) TCID50 of the PCV2-ROM strain (Cadar et al., 2007). In a second experiment 24 mice were divided into two groups (A and B); mice in Group A (n = 18) were inoculated orally with 1 x 10(5) TCID50 PCV2-ROM and mice in Group B (n = 6) were left uninoculated until day 12 post inoculation (p.i.), when they were mixed with Group A. The animals were sacrificed at intervals for postmortem investigation and virus genome detection by polymerase chain reaction (PCR). The PCR results indicated that PCV2 could replicate in mice infected intraperitoneally or by the oral route, and that the virus can be transmitted directly from mouse to mouse.  相似文献   

6.
The temperature sensitive and host range mutant clone 147 of equine herpesvirus 1 (EHV-1) was assessed for its ability to protect conventional, susceptible adult horses against respiratory infection by EHV-1 and equine herpesvirus 4 (EHV-4).Intranasal (IN) vaccination with 5.2 log(10) TCID(50) did not cause adverse clinical reactions although a limited virus shedding and viraemia (leukocytes) was observed in 11 of 15 and 10 of 15 vaccinated horses respectively. All 15 vaccinated horses showed a significant seroresponse to both EHV-1 and EHV-4 for virus neutralising (VN) antibody. None of 14 control horses shed virus or became viraemic or seroconverted prior to challenge. EHV-1 challenge (dose 6.0 log(10)) 6 weeks after vaccination resulted in pyrexia in all eight control horses while eight vaccinated horses remained unaffected. Six control horses developed nasal discharge, five of which were mucopurulent nasal discharge (mean duration 3.2 days) which also occurred in four vaccinated horses for 1 day. All eight control horses shed challenge EHV-1 at a significantly higher level (group mean titre 2.6+/-0.4 log(10) TCID(50) per sample) and for much longer (mean duration 4.8+/-1.5 days) than that (group mean titre 1.4+/-0.8 log(10) TCID(50) per sample and mean duration 1.5+/-0.5 days) in six vaccinated horses. Furthermore, all eight control horses became viraemic (mean duration 2.9 days) but viraemia did not occur in eight vaccinated horses. Following EHV-1 challenge, all eight control horses showed a significant VN antibody rise to both EHV-1 and EHV-4 but this occurred in only one vaccinated horse and to EHV-4 only. In EHV-4 challenge (dose of 4.2 log(10) TCID(50)) of a separate pair of seven vaccinated and six control horses, 6 weeks after EHV-1 vaccination resulted in pyrexia (mean duration 2.3 days) and nasal discharge (mean duration 1.8 days) in three and five control horses respectively but the only reaction observed in the vaccinated group was nasal discharge for 1 day in one animal. All six control animals shed virus (mean titre 2.5+/-0.6 log(10) TCID(50) per sample and mean duration 2+/-0.6 days) compared to one vaccinated animal. Although EHV-4 viraemia is rare, 3 of 6 control horses became viraemic after EHV-4 challenge but this was not observed in vaccinated horses. After EHV-4 challenge 3 and 5 of 6 control horses seroconverted for VN antibody to EHV-1 and EHV-4 respectively; a non-responsive control horse had high level of pre-existing VN antibody to EHV-4. However, only 1 of 7 vaccinated horses showed a significant antibody rise and only to EHV-4.  相似文献   

7.
为了解近几年云南边境地区牛、羊流行性出血热病毒（EHDV）的感染和流行情况,本研究从2014年起连续3年在与老挝、越南接壤的江城县设置EHDV监测点,每年选择投放EHDV抗体阴性的10头牛和5只山羊作为哨兵动物进行跟踪监测。每年5~10月份对哨兵动物采血,每周1次,11、12月每月采集一次,进行EHDV抗体、抗原监测和病毒分离。针对致细胞病变的样品,采用EHDV群特异性S7基因片段引物进行RT-PCR方法检测,同时利用EHDV-1、-5、-6、-7、-10标准阳性血清对分离到的病毒进行中和试验鉴定。结果显示,2014－2016年江城县牛EHDV抗体阳性率分别为41.9%、58.6%和75.4%;3年期间共监测到15头EHDV抗体阳性黄牛,并从中分离到20个可致细胞病变样品,经RT-PCR确认为EHDV,遗传进化分析发现有11个毒株与1997和2003年日本分离的EHDV毒株亲缘关系较近,9个毒株与1977和1981年澳大利亚分离的EHDV毒株亲缘关系较近,5个毒株与2015年广西分离株的亲缘关系较近;3年期间在山羊体内未检测出抗体,未发现抗原阳性动物;经中和试验血清型鉴定,确定20株毒株包括EHDV-5、-6、-7、-10型4种血清型,感染时间均在5~9月之间。本研究发现,江城县长期存在多种血清型EHDV同时流行,2014－2016年EHDV抗体阳性率逐年增加,亟需加强对EHDV感染情况及活动规律的持续研究,提高流行性出血热的防控效率。  相似文献   

8.
In order to investigate the potential involvement of pseudorabies virus (PRV) in swine respiratory disease, nine week old pigs were intranasally inoculated with the PRV strain 4892. Two doses of infection were used: 10(4.5) median tissue culture infectious doses (TCID50)/pig and 10(3.5) TCID50/pig, with ten pigs per group. In the group of pigs inoculated with 10(4.5) TCID50, seven out of ten pigs died within six days after inoculation. The mortality rate in the group of pigs inoculated with the lower dose was only two out of ten and, there were several pigs in this group that showed signs of respiratory distress besides some mild nervous signs. Pseudorabies virus was isolated from various tissues collected postmortem, including alveolar macrophages. Virus localization in tissues was also detected by in situ hybridization. The histopathological examination of the respiratory tract tissues revealed a pathological process that was progressing from mild pneumonia to severe suppurative bronchopneumonia. The isolation of virus from alveolar macrophages provides support to the hypothesis that replication of PRV during the course of infection produces an impairment of the defense mechanisms in the respiratory tract.  相似文献   

9.
The use of gl deleted live vaccines against Aujeszky's disease (AD) facilitates to differentiate vaccinated from field-virus infected animals. In this study different modes of vaccination were tried to find out how sheep can be protected from a lethal infection with ADV. It could clearly be demonstrated that Aujeszky disease virus (ADV) is spread by horizontal transmission from infected pigs to sheep. The nasal discharges of infected pigs contained a maximum of 10(8.75)TCID50/g mucus at days 3 and 4 p.i. and those of the contact-pigs 10(8.5)TCID50/g mucus at days 6 and 7 after contact. Non-vaccinated contact sheep were infected horizontally by the pigs. The highest titres ranged from 10(6.25) to 10(7.5)TCID50/g mucus. These animals were sacrificed at day 5 p.i. exhibiting acute symptoms of AD. The nasal discharge of vaccinated sheep contained much lower amounts of ADV (maximum: 10(4.25)TCID50/g mucus). All surviving animals had developed antibodies. Following challenge with the ADV-strain NIA3, no febrile response or virus-shedding was observed in sheep vaccinated 2x s.c. or 2x i.m. with a gl deleted live vaccine, whereas sheep, vaccinated only 1x i.m. (4 out of 4 animals) or 1x i.m. (3 out of 4 animals) or 1x i.n. and 1x i.m. (1 out of 4 animals) had to be sacrificed after showing acute symptoms of AD. In conclusion it can be stated that a double parental vaccination with a gl deleted live vaccine protects sheep against a field-virus AD infection.  相似文献   

10.
A total of 457 nasal swab specimens from cases of respiratory disease in 2 feed lots were evaluated for the detection of bovine herpesvirus Type 1 (BHV-1) by ELISA. Thirty-three were found to be positive for BHV-1 by the recovery of infectious virus and 21 of these were positive by ELISA, yielding a sensitivity of 64%. Fifteen other virus isolations were made and included bovine viral diarrhea viruses, rhinoviruses and parainfluenza Type 3 viruses; none of these cases were positive with the BHV-1 ELISA. Specificity of the ELISA was 100%. Eighty percent of the specimens with BHV-1 titers greater than 10(5) TCID50 were detected by ELISA; the median amount of virus in positive specimens that were detected by ELISA was 7 X 10(5) TCID50 and the median amount of virus in specimens not detected was 1.5 X 10(4) TCID50. BHV-1 infection was most frequently diagnosed in feedlot cattle that had been in the feedlot for 40-80 days. Approximately half of the infected cattle were carrying virus-neutralizing antibodies in their serum.  相似文献   

11.
A comparison of intradermal (ID) versus intramuscular (IM) routes of pig vaccination with deleted Aujeszky's disease (AD) vaccine on the formation of specific postvaccinal and postchallenge humoral immune response was performed. The studies were carried out on 21 eight week-old piglets, divided into three groups--two experimental and one control of 7 piglets each. Animals of first two groups were vaccinated twice in 12 and 16 week of age with deleted, live attenuated AD vaccine Porcilis Begonia (Intervet). Group I was vaccinated with a dose of 2.0 ml (10(6.0) TCID50)) intramuscularly (IM) into neck muscles, and group II received 0.2 ml (10(5.0) TCID50) intradermally (ID) in neck area using needleless apparatus SERENA model SD 1-2 (Emplast, Italy). In group K (control) 2.0 ml PBS IM was used. Seventy days after the first vaccination all pigs were intranasally infected with a dose of 10(5.5) TCID50 of virulent Northern Ireland Aujeszky-3 (NIA-3) strain of Herpesvirus suis type 1 (SHV-1) by instilling 0.5 ml of virus suspension into each nostril. Specific humoral immune response was evaluated using seroneutralization (SN) test and gE-ELISA-Pseudorabies virus gpI Antibody Test Kit (Herd Chek Anti-PRV gpI), IDEXX Lab Inc (USA). It was found that challenge caused anamnestic reaction in both groups of vaccinated pigs, but postchallenge immune response was stronger in ID-vaccinated group--on 14 day post infection (dpi) SN antibody level was considerably higher than in IM-vaccinated group. The obtained results suggest that secondary immunological response after challenge is decidedly more effective in the range of evaluated parameters in animals vaccinated by ID route, which can be linked to, perhaps underestimated yet and seldom utilized, skin immunity mechanisms in specific prophylaxis of infectious diseases. Advantages and disadvantages of SN test and ELISA are also discussed.  相似文献   

12.
Intranasal infection of Getah virus in experimental horses.   总被引：1，自引：0，他引：1  
Aerosol transmission in equine Getah virus (GV) infection was examined by intranasal inoculation with 10(3.0) to 10(7.0) TCID50 of the MI-110 strain in 7 experimental horses. The establishment of intranasal infection of GV was confirmed in all these horses by detecting serum neutralizing antibody against the MI-110 strain. Horses inoculated with more than 10(4.0) TCID50 of the virus manifested mild pyrexia, eruptions, serous nasal discharge, lymphopenia or monocytosis. Viremia ranging from 10(1.0) to 10(3.5) TCID50/0.2 ml occurred in horses inoculated with 10(5.0) TCID50, or more. Virus recovery from the nasal cavity was observed only in horses inoculated with 10(7.0) TCID50, and the viral titers recorded were 10(3.0) TICD50/ml or less. From these results, it is assumed that GV disseminated from the nasal cavity of naturally infected horses, except for intranasal infection with a lot of the virus, is probably very low in titer. So it seems to be rare that GV in natural cycles is spread from horse to horse by aerosol transmission.  相似文献   

13.
Immunisation of mice with recombinant VP7 antigen of epizootic hemorrhagic disease virus of deer (EHDV) induced serum antibody responses to EHDV. However, from the 19 monoclonal antibodies (Mab) produced from these mice, 15 were specific for EHDV and four for bluetongue virus (BTV). No Mabs were identified with the specificity for an epitope of VP7 shared by both EHDV and BTV in spite of the fact that they share a large portion of homology in VP7 amino acids composition. These Mabs were divided into five groups based on their specificity and interaction with each other. Group II Mabs, consisting of 13 Mabs, recognises a potential serogroup specific, linear epitope of EHDV VP7 antigen. One of the Mabs to BTV (Group V) was identified as BTV VP7 specific with the possibility of being the serogroup specific and recognizes a potential conformational epitope. Two Mabs from these VP7 specific groups were further analysed and found to be useful in a competitive enzyme-linked immunosorbent assay (C - ELISA) for detection of specific antibodies against EHDV and BTV in bovine sera.  相似文献   

14.
The efficacy of several povidone-iodine (PVP-I) products, a number of other chemical agents, and various physical conditions were evaluated for their ability to inactivate the severe acute respiratory syndrome coronavirus (SARS-CoV). Treatment of SARS-CoV with PVP-I products for 2 min reduced the virus infectivity from 1.17 x 10(6) TCID50/ml to below the detectable level. The efficacy of 70% ethanol was equivalent to that of PVP-I products. Fixation of SARS-CoV-infected Vero E6 cells with a fixative including formalin, glutaraldehyde, methanol, and acetone for 5 min or longer eliminated all infectivity. Heating the virus at 56 degrees C for 5 min dramatically reduced the infectivity of the virus from 2.6 x 10(7) to 40 TCID50/ml, whereas heating the virus for 60 min or longer eliminated all infectivity. Irradiation with ultraviolet light at 134 microW/cm2 for 15 min reduced the infectivity from 3.8 x 10(7) to 180 TCID50/ml; however, prolonged irradiation (60 min) failed to eliminate the remaining virus, leaving 18.8 TCID50/ml. We believe that these findings will be useful for the implementation of infection control measures against SARS, and for the establishment of effective guidelines for the prevention of SARS outbreaks.  相似文献   

15.
伪狂犬病病毒弱毒株LY株的分离鉴定   总被引：2，自引：1，他引：2  
从辽阳某猪场的10日龄仔猪中分离到1株病毒,经纯化后测得其毒价为107.29TCID50/mL.细胞中和试验表明,该病毒能被猪伪狂犬病病毒标准阳性血清所中和.电镜下可见到典型的疱疹病毒粒子,具有囊膜及外周纤突.所分离的病毒对氯仿、胰蛋白酶、乙醚敏感,在pH5.0～9.0下稳定,56℃ 30 min可以灭活.应用特异性引物,通过PCR能扩增出伪狂犬病病毒1 240 bp的gD基因.分离病毒对3日龄乳鼠有一定的致病力,但对家兔、3～5日龄仔猪及妊娠母猪都有很高的安全性.用不同剂量的病毒培养液肌肉注射于3～5日龄仔猪,14 d后用105.7TCID50伪狂犬病病毒强毒攻击,所有试验仔猪均可得到有效保护.用分离毒免疫母猪,其后代可获高滴度的母源抗体,15日龄的仔猪能抵抗105.7TCID50强毒的攻击.试验的结果初步说明,所分离的病毒为伪狂犬病病毒(命名为PRV LY株),并可能是一株弱毒株,而且具有很好的免疫保护作用.  相似文献   

16.
To investigate the pathogenicity of A/Hero/Guangdong/C1/2013(H5N6), an AIV strain isolated from Heron on ducks and mice, pathogenicity of this new virus strain and changing of histopathology as well as a preliminary study on its biological characteristics were studied by virus challenges test via intranasal and eye-drop and in chicken via jugular vein injection.Results showed that the EID50 of this strain of virus was 10-8.16/0.1 mL in embryonated chicken eggs and the intravenous inoculation of pathogenic index (IVPI) was 2.76.In ducks and mice, the 50% lethal doses (LD50) of it were determined to be 10-4.0/0.2 mL and 10-4.67/0.05 mL, respectively.Symptoms of infection included loss of appetite, depression, swollen head and tears after being infected with 106 EID50 per duck by intranasal and eye-drop administration.Most of ducks died 4 to 7 days post-infection, liver, lung and kidney still eliminated toxicants at day 7 post-infection.Anatomy showed symptoms of pericardial effusion, pulmonary congestion and kidney enlargement, while pathological section showed pathological change like karyopycnosis and inflammatory cell infiltration in heart, liver, kidney and spleen.Mice developed symptoms of infection like loss of appetite, depression, shaggy coat and ruffled coat after being infected with 5×105 EID50 per mouse by intranasal and eye-drop administration.Most of the infected mice died 5 to 7 days post-infection and only liver still eliminated toxicants at day 7 post-infection.Although organ anatomy showed no obvious pathological changes, pathological section showed pathological changes like karyopycnosis and inflammatory cell infiltration in heart, kidney and lung.Our research demonstrated that this H5N6 subtype AIV had a strong pathogenicity and could be defined as a highly pathogenic AIV strain as its IVPI was greater than 1.2.Our work laid a theory foundation for study, prevention and control of H5N6 subtype AIV.  相似文献   

17.
为了研究一株从鹭中分离到的禽流感病毒(AIV)A/Heron/Guangdong/C1/2013(H5N6)对鸭和小鼠的致病力,本研究通过对鸭和小鼠滴鼻点眼和鸡的颈静脉注射进行攻毒试验,观察其致病力和组织病理学等变化,对其生物学特性进行初步研究。结果显示,该毒株的鸡胚半数感染量(EID50)为10-8.16/0.1 mL,静脉接种致病指数(IVPI)为2.76。对鸭的半数致死量(LD50)为10-4.0/0.2 mL,对小鼠的LD50为10-4.67/0.05 mL。以106 EID50/只滴鼻点眼感染鸭,主要表现为食欲下降、精神萎靡、肿头流泪等症状,大多数鸭在感染后4~7 d死亡,感染后第7 天肝脏、肺脏、肾脏仍在排毒,解剖可见心包积液、肺脏淤血、肾脏肿大等症状,病理切片可见心脏、肝脏、脾脏、肾脏炎性细胞浸润,脑细胞核固缩等病变。以5×105 EID50/只滴鼻感染小鼠,主要表现为食欲下降、精神萎靡、被毛粗乱、聚堆等症状,大部分小鼠在感染后5~7 d死亡,第7天时只有肺脏仍在排毒,各脏器解剖学病变不明显,病理切片可见心脏、肾脏、肺脏炎性细胞浸润,脑细胞核固缩等病变。研究结果表明,该H5N6亚型AIV毒株对鸭和小鼠具有很强的致病力,IVPI大于1.2,为高致病性AIV,本研究为H5N6亚型AIV研究和防控提供了理论基础。  相似文献   

18.
We observed 15 goats for 9 days after subcutaneous infection with 10(3) TCID(50) with isolates of peste-des-petits ruminants virus from Africa and India and five concurrent, uninfected control goats. Typical clinical signs of the infection were present in all 15 infected goats by day 8 and in most by day 6 and some signs were present by day 4. However, 6 out of 15 goats already have detectable virus shedding by day 3 and four more were shedding by day 4 and every goat had virus shedding for at least 1 day before the recognition of clinical signs. This experiment indicates that incubatory carriers therefore might play a role in the transmission of PPRV among small ruminants.  相似文献   

19.
Some isolates of type II bovine viral diarrhea virus (BVDV) are capable of causing severe clinical disease in cattle. Bovine viral diarrhea virus infection has been reported in pigs, but the ability of these more virulent isolates of type II BVDV to induce severe clinical disease in pigs is unknown. It was our objective to compare clinical, virologic, and pathologic findings between type I and type II BVDV infection in pigs. Noninfected control and BVDV-infected 2-month-old pigs were used. A noncytopathic type I and a noncytopathic type II BVDV isolate were chosen for evaluation in feeder age swine based upon preliminary in vitro and in vivo experiments. A dose titration study was performed using 4 groups of 4 pigs for each viral isolate. The groups were inoculated intranasally with either sham (control), 10(3), 10(5), or 10(7) TCID50 of virus. The pigs were examined daily and clinical findings were recorded. Antemortem and postmortem samples were collected for virus isolation. Neither the type I nor type II BVDV isolates resulted in clinical signs of disease in pigs. Bovine viral diarrhea virus was isolated from antemortem and postmortem samples from groups of pigs receiving the 10(5) and the 10(7) TCID50 dose of the type I BVDV isolate. In contrast, BVDV was only isolated from postmortem samples in the group of pigs receiving the 10(7) TCID50 dose of the type II BVDV isolate. Type I BVDV was able to establish infection in pigs at lower doses by intranasal instillation than type II BVDV. Infection of pigs with a type II isolate of BVDV known to cause severe disease in calves did not result in clinically apparent disease in pigs.  相似文献   

20.
Two experiments were performed to compare the severity of encephalomyocarditis virus (EMCV) infection in pigs. The pigs were challenged with the Greek myocardial strain, at different ages and with different doses. In the first experiment, nineteen susceptible pigs, 40 days old, were divided into three groups and were experimentally infected with 10(6) TCID(50), 10(4) TCID(50) or 10(2) TCID(50) of the Greek EMCV strain. In the second experiment, 10 susceptible pigs, of either 20 or 105 days, were divided into two groups according to age and were experimentally infected with 10(6) TCID(50) of the Greek EMCV strain. In addition, five piglets, each one the same age as its experimental group, were used as uninfected controls. No clinical signs were observed after infection, except a transient temperature rise in some pigs. Another important observation was the difference in mortality between groups. The survival rate of the 40-day-old pigs was inversely related to the viral dose. In these pigs, a positive association between the viral dose and the severity of macroscopical and histopathological lesions of the heart was also evident. Viral isolations from various organs of the challenged 40-day-old pigs increased with the increasing dose level. When challenged with 10(6) TCID(50) of EMCV, there was no difference in the fatality rate of the 20- and 40-day-old pigs, but none of the 105-day-old pigs died. The severity of the macroscopical and the histopathological heart lesions was inversely related to the age of the pigs. Furthermore, viral isolations from the various organs were higher in 20- and 40-day-old pigs than in the older ones. In 40-day-old pigs, neutralizing antibodies linearly increased as the dose increased. These antibodies were consistently lower in 20-day-old pigs. Viraemia, and nasal and faecal excretions were detected in all groups and lasted 1-3 days, except for the 105-day-old pigs whose symptoms lasted for an additional day.  相似文献   

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