Molecular biology of pseudorabies (Aujeszky's disease) virus.

In this review, some of the aspects concerning the molecular biology of pseudorabies virus (PrV), the causative agent of Aujeszky's disease, will be discussed. It will mainly focus on new findings concerning viral glycoproteins, factors determining PrV virulence, the problem of PrV latency and the development regarding genetically engineered vaccines.     

Tonsillar changes in pigs given pseudorabies (Aujeszky's disease) virus

All of the eight 5-day-old pigs orally given pseudorabies (Aujeszky's disease) virus developed tonsillitis. The initial changes occurred in the subepithelial area between the lymphoid nodule and the crypt epithelium, showing a characteristic pattern of necrosis. The necrosis became more severe and gained access into the lymphoid nodule and crypt epithelium. Coincident with the histopathologic changes, numerous specific immunofluorescences were detected, first in the nucleus and in some parts of the cytoplasm of cells distributed in the subepithelial area. The fluorescence subsequently spread into adjacent lymphoid nodules and crypt epithelial cells. Ultrastructurally, many enveloped virus particles were detected in the center of the necrosis. Thereafter, the crypt epithelial cells also underwent degeneration, and a small number of virus particles were detected in the nucleus of the degenerating epithelial cells. In the more advanced stage, the enveloped virus particles were discharged into the crypt lumen.     

厦门市翔安区猪伪狂犬病流行病学调查

猪伪狂犬病是《国家中长期动物疫病防治规划(2012-2020年)》中优先防治的16种动物疫病之一,到2020年要达到规划设定的考核标准。为了有效控制猪场的猪伪狂犬病,对厦门市翔安区猪伪狂犬病感染状况进行流行病学调查,估计翔安区猪伪狂犬病的流行率。本研究使用猪伪狂犬病病毒g E-ELISA试剂盒,共检测1 411份血清样品,并实地调查20个猪场,了解猪场饲养管理和免疫情况。结果显示,翔安区猪伪狂犬病血清学场流行率为74.4%(95%CI:60.0%~88.7%),个体流行率为57.9%(95%CI:56.4%~59.4%)。     

Pathogenesis of ovine pseudorabies (Aujeszky''s disease) following intratracheal inoculation.

Pseudorabies virus was inoculated intratracheally into sheep to investigate the pathogenesis of pseudorabies virus infection. Clinical signs of pyrexia, depression, frequent swallowing, facial fasciculations, chorea, excessive salivation, mild tympanites, labored breathing and focal pruritus were followed by death Macroscopic lesions were severe focal facial trauma, petechiae in cervicothoracic ganglia and dilated esophaguses. The medulla oblongata and the trigeminal, cranial cervical, cervicothoracic and parabronchial ganglia contained pseudorabies virus and pronounced nonsuppurative inflammatory changes. The neural distribution of lesions and virus suggests that the virus travelled from the respiratory mucosa to the central and sympathetic nervous system by two routes: 1) in the vagus and glossopharyngeal nerves to the medulla oblongata and 2) in the postganglionic fibers to the sympathetic ganglia. The presence of virus in the nasal mucus indicated that horizontal transmission of pseudorabies virus may occur among sheep.     

厦门市同安区猪伪狂犬病流行病学调查

猪伪狂犬病是《国家中长期动物疫病防治规划（2012-2020年）》中优先防治的16种动物疫病之一,到2020年全国所有种猪场猪伪狂犬病都要达到规划设定的考核标准。厦门市同安区为了配合做好猪场净化工作,掌握全区猪群猪伪狂犬病的感染状况,对其进行流行病学调查,估计辖区内猪群猪伪狂犬病的血清学流行率。本研究使用猪伪狂犬病病毒gE-ELISA试剂盒,共检测991份血清样品,并实地调查20家猪场,了解猪场饲养管理和免疫情况。结果显示,同安区猪伪狂犬病血清学场流行率为65.0%,个体真实流行率为47.5%（44.5%~50.4%）。     

Antiviral effectiveness of butylated hydroxytoluene against pseudorabies (Aujeszky's disease) virus in cell culture, mice, and swine

Butylated hydroxytoluene (BHT) was evaluated for antiviral effectiveness on pseudorabies virus (PRV) in cell culture, mice, and swine. When relatively small amounts of BHT were mixed with PRV and incubated at 37 C for 30 or 60 minutes before inoculation into cell cultures, the cell cultures did not become infected with virus. The PRV was not infectious when the virus was treated with BHT and then inoculated intraperitoneally into mice, but was infectious when BHT and PRV were inoculated simultaneously or when BHT was inoculated either 30 or 60 minutes before PRV. Swine fed BHT-medicated feed for 10 days before they were intranasally exposed with virulent PRV did not have overt signs of pseudorabies, had a lower concentration of PRV in nasal mucus than did control swine, and had acceptable blood enzyme and cholesterol concentrations during the experiment. The BHT was detected in tissues of 2 swine after they were fed BHT-medicated feed for 10 days, and higher concentrations of BHT were detected in tissues of 3 swine given BHT feed for 29 days.     

Aujeszky's disease (pseudorabies) virus: the virus and molecular pathogenesis--state of the art, June 1999

Considerable progress has been made during the last years in understanding the molecular basis of protein function in pseudorabies virus (PrV), the causative agent of Aujeszky's disease (AD). Major topics have been the identification and functional characterisation of viral envelope glycoproteins and cellular virus receptors, elucidation of viral proteins involved in neurovirulence and neuropathogenesis, detection and characterisation of attenuating mutations present in and leading to successful attenuated live vaccines, and the near completion of the genomic sequence of PrV DNA. This review, which follows an article prepared for the 1993 AD symposium in Budapest, Hungary, will briefly summarise those recent developments and update the reader on the current state of the art in PrV research.     

Study of the potential involvement of pseudorabies virus in swine respiratory disease.

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.     

Evidence of long distance airborne transmission of Aujeszky's disease (pseudorabies) virus

Aujeszky's disease has been the subject of an eradication campaign in Denmark since 1980. A detailed knowledge of the virus strains present in the country was provided by restriction fragment analyses of older clinical isolates, and of isolates from all the virologically confirmed outbreaks since 1985. The introduction of foreign strains into southern border areas was demonstrated during the winters of 1984/85, 1986/87 and 1987/88. An epizootic during the winter of 1987/88 was shown to correlate with an unusual predominance of southerly winds. Both conventional and specific pathogen free herds became infected. A herd level case-control analysis of the outbreaks during the winter of 1987/88 revealed that there was a positive correlation between the risk of infection and the size of the herd. The observations support the hypothesis of airborne transmission of the disease.     

猪伪狂犬病的诊断、防控及净化

伪狂犬病(Pseudorabies,PR)又名奥叶兹基氏病(Aujeszky disease,AD),该病由伪狂犬病病毒引起的多种家畜和野生动物均可感染的一种以发热、奇痒(猪很少发生)、脑脊髓炎及生产母猪繁殖障碍为特征的急性传染病。伪狂犬病在加拿大、英国、新西兰等西方国家已进行了很好的防控和净化,并宣布了根除,但在我国多个省市,该病仍频繁地发生,给养猪业造成了巨大的经济损失,制约了养猪业的健康发展。为此,本文根据病毒特征、发病机制、流行特点和临床症状等,对猪伪狂犬病的诊断、防控及净化措施进行简要综述。     

猪伪狂犬病的诊断

本文通过荧光抗体组织切片、细胞接种、兔子致病性等方法对临床怀疑为猪伪狂犬病的病猪进行了实验室诊断。结果如下:病猪脾脏和淋巴结制备的冰冻切片经PRV荧光抗体染色后,在荧光显微镜下见到特异性荧光;病料经处理后接种Vero细胞可致细胞圆缩和形成合胞体,具有疱疹病毒的培养特征;将病料上清和细胞培养毒分别皮下接种家兔均可引起奇痒、麻痹死亡,呈现典型的伪狂犬病临床特征,同时病死兔脏器的PRV免疫荧光试验也为阳性。根据上述结果证实了该病为猪伪狂犬病。     

猪伪狂犬病调查

这几年 ,猪伪狂犬病在我国不少地区呈流行或暴发流行 ,主要引起母猪的繁殖障碍 ,新生仔猪大量发病并死亡 ,给养猪业造成重大的经济损失。现将广西某瘦肉型猪场发生猪伪狂犬病的情况报告如下。1　基本情况该猪场为一家新办的小型瘦肉型猪场 ,场址选择在山边 ,不设围墙 ,鼠患相当     

Aujeszky's disease (pseudorabies) virus detection in cerebrospinal fluid in experimentally infected pigs

The presence of Aujeszky's disease virus in cerebrospinal fluid of experimentally infected pigs was studied using the techniques of virus isolation and PCR. Pigs, some of which were previously vaccinated against Aujeszky's disease, were inoculated with different doses of the Aujeszky's disease NIA-3 strain. At the time of death or sacrifice, a sample of cerebrospinal fluid was taken and tested for the presence of virus using the mentioned techniques. Virus was isolated only from one sample, while it was detected by PCR in most of them. The higher sensitivity of the PCR technique and the possible presence of antiviral antibodies in the cerebrospinal fluid are reasons that can be argued to explain this fact. By PCR, the virus was detected more efficiently when digested cerebrospinal fluid cells were used as DNA source than when using whole cerebrospinal fluid, suggesting that the virus could be cell-associated. Aujeszky's disease virus could not be detected by PCR in pigs which survived the acute phase of the infection and were euthanased at 8 weeks post-inoculation, when they were latently infected. This indicated that the cerebrospinal fluid is not an adequate sample for the diagnosis of latency. Since Aujeszky's disease virus was detected from most of the tested samples, we believe that this could be an adequate procedure for the quick diagnosis of Aujeszky's disease.     

A necrotizing pneumonia in lambs caused by pseudorabies virus (Aujesky''s disease virus).

An outbreak of pseudorabies occurred in sheep housed with swine in the same building. Although the sheep and swine were not in physical contact, the lambs and ewes were exposed to air from the sows' section. Three dead lambs were submitted to the Iowa State University Veterinary Diagnostic Laboratory for necropsy. Grossly there were pulmonary congestion and multifocal pulmonary hemorrhages. Microscopic lesions were severe acute multifocal necrotizing bronchopneumonia with necrotizing vasculitis and intranuclear inclusion bodies within the neurons of the parabronchial ganglia. Bacterial cultures were negative for pathogenic agents; pseudorabies virus was isolated from ovine brain tissue. Viral antigen was demonstrated in the neurons of the parabronchial ganglia by immunoperoxidase staining. Electron microscopy revealed nucleocapsids in the parabronchial ganglionic neurons which contained basophilic intranuclear inclusion bodies. Viral DNA prepared from the ovine pseudorabies virus isolate was found by restriction endonuclease analysis to be related to the Indiana Funkhauser strain of pseudorabies virus.     

Antigens involved in vaccination of swine against Aujeszky's disease (pseudorabies) virus.

The polypeptide and glycopolypeptide composition of a local virulent Aujeszky's disease virus (suid herpesvirus 1, SHV-1) strain (E-974) was determined in order to characterize the individual SHV-1 antigens inducing the serological responses in immunized and non-immunized animals. A commercially available inactivated vaccine of known efficacy and three experimental immunogen preparations (whole inactivated SHV-1 particles, lectin-purified glycoproteins from SHV-1 culture, and a combination of both) were used for immunization. Sera of two-month old immunized and non-immunized animals were analyzed by ELISA, seroneutralization and Western immunoblotting prior to and following challenge with E-974. Sera of 7- to 30-day-old piglets littered by immunized and non-immunized sows were likewise analyzed by immunoblotting. The following variables were determined: the total level of anti-SHV-1 antibodies, the level of neutralizing antibodies, the IgG responses to individual SHV-1 antigens, and the clinical parameters and degree of protection of the animals. The whole-particle experimental immunogen conferred greatest protection, but correlation between antibody levels and the degree of protection was imperfect. Serological responses seemed to be directed against certain structural polypeptides and viral envelope glycoproteins. The glycoprotein immunogen caused a selective response to bands which closely resemble the glycopolypeptides gII and gIII. A 71 kDa component of uncertain location within the viral structure appeared to be one of the main antigens involved in porcine serological response to SHV-1 and colostral protection of piglets.     

The porcine humoral response to detergent extracted Aujeszky's disease (pseudorabies) virus antigens

Twenty Aujeszky's disease (AD) virus antigens were demonstrated by crossed immunoelectrophoresis in a Triton-X-100 detergent extract of virus-infected PK-1a cells. Eight of these antigens were shown to be glycosylated based on their ability to be specifically bound by the lectin Ricinus communis agglutinin II. Pigs nasally infected with AD virus showed a significant serum antibody titer to seven of the known glycosylated antigens and to four additional antigens. The antibody titer to these antigens persisted for at least 116 days. Pigs which were vaccinated parenterally with the whole detergent extract survived a nasal challenge of 10(8 . 5) PFU of virulent AD virus. The antibody response of these vaccinated pigs on the day of challenge was essentially identical to the recovery response previously observed in non-vaccinated nasally infected pigs. These results indicate that the optimum components of future AD virus subunit vaccines and their complementary diagnostic reagents should be selected from these 11 antigens.