通过人工授精传播的猪疾病

(上接2012年第6期92页)2.2.1非洲猪瘟病毒非洲猪瘟病毒第1次在病毒进入点的临近淋巴结的单核细胞和巨噬细胞内复制,随后就随着体内的血液和/或淋巴系统扩散。有人假设,在公猪感染后,有可能在精液里会发现病毒,甚至传播给受精的母猪。但是,没有公开的证据来支持这个假设。还不能得到对这病毒的处理方法或有效的疫苗。     

经人工授精传播的猪病及其预防措施

猪人工授精技术（Artificial insemination,AI）已在集约化养猪生产国中得到了广泛应用。人工授精是一种将优秀基因引入母猪群中的非常有效的工具,并能够将疾病传播的风险降至最小。然而,受到病原体污染的精液对生产实际的危害是巨大的。在已经从公猪精液中检测到的微生物中,大部分是非致病性的,但有一些是有名的病原体,如猪繁殖与呼吸综合症病毒,这部分病原体能给养猪业造成重大的经济损失。精液受到微生物的污染可能是由于公猪全身性感染和/或泌尿生殖道感染所致,或可能发生在精液采集、处理和存储过程中。这会导致精液品质下降,胚胎或胎儿死亡,以及受体母猪的子宫内膜炎和全身性感染和/或发病。用于从精液中分离细菌和病毒的常规技术因受多种原因的影响并不总是能获得理想的结果,这些原因包括所用技术缺乏敏感性和检测速度慢、对检测结果难以进行解释。近年来,PCR技术得到了普遍的应用,它们具有很高的敏感性,能很快获得检测结果,并且适合对大样本的检测。防止通过人工授精传播疾病的最佳方法是使用无特定病原体的公猪、对它们及其精液进行定期检测以及维持极高的生物安全水平。其它方法则应该侧重于利用合适的抗菌剂对精液进行处理,以及重点减少在采集、处理和存储过程中精液所受到的污染。     

放牧型合作猪生态特性的初步研究

对放牧型合作猪品种特性及其生物学特性和生态环境适应性进行研究,并探讨了放牧型合作猪品种形成与生态环境的关系.结果表明,放牧型合作猪是适应特殊生态环境的产物;不同性别生理生化指标无显著性(P＞0.05)差异;不同生长阶段部分指标有显著(P＜0.05)或极显著(P＜0.01)差异.研究显示放牧型合作猪对高寒草原气候具有较强的适应性.     

Diseases of the extremities of swine in relationship to the floor condition with special reference to bursitis

In 2 pig farms, 102 sows kept in single ranging on plain concrete floor, 168 sows kept in single ranging on cast-iron grates and 27 fattening pigs kept in group penning on concrete slatted floors were repeatedly examined for the incidence of auxiliary synovial bursae (ASB). The clinical examination was completed by radiological, patho-anatomical and histological examinations of the rear legs. In sows, ASB were found on two prominences of the bones: on the latero-plantar area of the calcaneum and the fourth tarsal bone as well as on the plantar tarsal sesamoid bone. ASB on the rear legs were found in 41.2% of the sows kept on plain concrete floor and in 59.5% of the sows kept on cast-iron grates. The ASB of the sows kept on cast-iron grates were larger than those of the sows kept on plain concrete floor. In 49% of the sows kept on plain concrete floor the skin covering the ASB was reddened, in 45% of the sows kept on cast-iron grates it was covered with scab. Injury and necrosis of the skin as well as injury of the ASB themselves were found only in animals kept on cast-iron grates and made up 5% of the cases. In 30% of the cases, palpation of the ASB induced defensive movement. The palpation of ball-shaped, soft bursae more often caused defensive movement than did the palpation of flat-shaped, hard bursae. The occurrence of ASB was combined with kyphosis of the spine, false posture of the rear legs, dystasia, hyperextension of the fetlock, arthrosis of the ankle joint, and anomalies of the claws. In fattening pigs, the ASB were localized at the lateroplantar area of the calcaneum and the fourth tarsal bone as well as at the posterior surface of the calcaneum. At the end of the fattening period, ASB were detected in 26 out of 27 fattening pigs. All of the 48 ASB that were examined histologically showed signs of inflammation. In 30 cases the inflammation was chronic, in 18 cases it turned out to be florid. The results indicate that ASB cause pain during the developing phase and also in the chronic stage.     

猪A型产气荚膜梭菌病研究

家畜A型产气荚膜梭菌病是我省首先发现的一种多种家畜共患的传染病。目前全国许多省市都有发生。由于该病往往没有任何前驱症状，突然发病死亡，在没有确定该病病原之前，人们通常称之家畜“猝死症”。我省该病最初见于1985年河南周口市某县，当时呈零星散发，患病家畜以犊牛和仔猪为主。近几年来，仔猪对该病的感染率呈上升趋势，为了有效控制该病，笔者曾系统参与了我省A型产气荚膜梭菌病的研究，现将其研究结果报告于后。     

Comparison of type I and type II bovine viral diarrhea virus infection in swine.

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.     

Colostral transfer of Clostridium perfringens type C beta antitoxin in swine

Nine bred gilts were vaccinated with 2 doses of a Clostridium perfringens type C toxoid at a 5-week interval. Time of vaccination during gestation differed among the gilts. Clostridium perfringens beta antitoxin in colostral samples and in serum samples was titrated in mice. Blood was collected from 2 to 5 neonatal pigs from each dam (total = 32 pigs) when the pigs were 36 to 48 hours old. Antitoxin titers in colostrum were 123 to 4.5 IU/ml, indicating considerable variation in individual responses of the gilts to toxoid. Serum titers of neonatal pigs reflected colostrum titers of their dams. This colostrum-to-serum titer correlation was essentially a straight-line fit by least-squares linear regression analysis, establishing a direct proportional relationship between colostrum titers and serum titers of neonatal pigs. In the dams, a correlation was not found between colostral titers and serum titers of blood samples collected 2 weeks after collection of colostrum.     

新型猪瘟疫苗研究现状

猪瘟(classical swine fever,CSF)是由猪瘟病毒(classical swine fever virus,CSFV)引起的一种以急性出血和发热为主要特征的烈性传染病,死亡率极高,对养猪业危害极大,已被国际兽疫局(OIE)列为A类动物传染病.许多国家已经针对该病施行了控制和根除措施,但因为生猪及其产品贸易的全球化、养猪业的集约化和野猪群中CSFV的持久性等原因,CSF仍然对世界养猪业构成很大威胁.     

Bacterial lipopolysaccharide induces porcine circovirus type 2 replication in swine alveolar macrophages

Monocyte/macrophage lineage cells are major target cells of porcine circovirus type 2 (PCV2). From tissues of field pigs suffering from postweaning multisystemic wasting syndrome (PMWS), both intracytoplasmic and intranuclear PCV2 signals, including antigens and nucleic acid, were easily detected in the monocyte/macrophage lineage cells. However, there was a high incidence of intracytoplasmic PCV2-positive signals, but lack of intranuclear signals and PCV2 replication in these cells in vitro. Concurrent infection with bacteria and activation of immune system are suggested to promote viral replication. In this study, lipopolysaccharide (LPS) and phorbol-12-myristate-13-acetate (PMA) were used to stimulate PCV2-inoculated alveolar macrophages (AMs). A decrease in intracytoplasmic but increase in intranuclear PCV2-positive signals, including antigens and nucleic acid, were detected in LPS-treated PCV2-inoculated AMs, but not in PMA-treated cells. Additionally, the replication product corresponding to PCV2 spliced major capsid protein (Cap) mRNA and a significant elevation in PCV2 titer were demonstrated in the LPS-treated PCV2-inoculated AMs. The results imply that Gram-negative bacterial co-infection in PCV2-infected pigs may be an important factor in promoting PCV2 replication and contributing, at least partially, to the full development of PMWS.     

猪亚洲Ⅰ型口蹄疫免疫程序试验

口蹄疫是世界动物卫生组织（OIE）规定的A类烈性动物传染病，我国列为一类动物传染病。口蹄疫共有7种血清型，亚洲Ⅰ型是其中一种。目前国内还没有猪亚洲Ⅰ型口蹄疫免疫程序，通过对105头猪进行亚洲Ⅰ型口蹄疫母源抗体和免疫抗体的检测，观察其抗体消长规律，以制定比较符合实际的、科学的猪亚洲Ⅰ型口蹄疫免疫程序。     

Epidemiologic assessment of porcine circovirus type 2 coinfection with other pathogens in swine

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.     

Seroprevalence of porcine circovirus type 2 in swine populations in Canada and Costa Rica

Porcine circovirus (PCV) was recently divided into 2 antigenically distinct types that differ (65% amino acid identity) in the protein encoded by open reading frame 2 (ORF2). Porcine circovirus 1 is apparently non-pathogenic and, in contrast, PCV2 is associated with porcine multisystemic wasting syndrome (PMWS). Our objective was to determine the extent of exposure of normal pigs in Canada and Costa Rica to PCV2. Recombinant DNA techniques were used to produce an antigen from ORF2 of PCV2 that was suitable for the detection of antibody in swine sera. The presence of PCV2 nucleotide sequences was detected using polymerase chain reaction (PCR) techniques. Using these tests, specific antibody and nucleotide sequences were demonstrated in sera from a cohort of pigs during a PMWS outbreak. Antibody was detected in normal, healthy hogs slaughtered in Canada (82.4% of 386) and in Costa Rica (14.6% of 322). This is the first report indicating the presence of PCV2 in Latin America. More than 50% of these sera also contained PCV2 nucleotide sequence. Although these hogs were healthy when slaughtered, they were infected with PCV2 and may have previously been ill. The widespread occurrence of PCV2 in swine suggests that this virus is adapted to replication in porcine tissue.     

Antibody responses of swine to type A influenza viruses in the most recent several years.

A serological survey was conducted on 4,080 swine sera collected for the years 1985-90. The swine sera positive to A/New Jersey/8/76 (swine type H1N1) strain were observed in annual (10-20%) and monthly (20-40%) incidences during the observation period except for occasional months. Antibodies to recent human H1N1 viruses in swine were recognized in relation to the human H1N1 influenza epidemics. Antibody responses of swine to human H3N2 strains appeared irrespective of human epidemics with the virus in the years 1985-87. However, in 1988 almost no antibodies to three human H3N2 isolates of 1983-88 were observed for this year except a few months though the human epidemic occurred in the area. Although in 1989-90 many swine had antibodies to the three strains in the percentage of 3 to 35, no antibody to the latest isolate, A/Hokkaido/20/89 (H3N2), was found for almost all the months of both years. These findings differed markedly from the possible relationship between the prevalence of H3N2 virus-antibodies in swine and the human influenza epidemics, which were described previously in many reports including our studies.