Detection of antibodies against membrane-glycoproteins of swine erythrocytes after experimental infection with Mycoplasma hyopneumoniae

During enzootic pneumonia of pig, antibodies against membrane glycoproteins of erythrocytes were detected with an enzyme-linked immunosorbent assay (ELISA). These antibodies arise simultaneously with the specific antibodies. They are not identical to cold agglutinins.     

A biological network describing infection with Mycoplasma hyopneumoniae in swine herds

We have made a biological model based on a Bayesian network for risk factors for infection with Mycoplasma hyopneumoniae (Mycoplasma) in slaughter pigs; prevalence of infection is based on veterinary examinations. The model is a probabilistic/stochastic determination based on the inherent biological uncertainty of the severity of infection with Mycoplasma and the derived stochastic effects on productivity for the herd. The conditional probabilities in the Bayesian network are based on published studies and expert opinions. We used the model to calculate how the risk factors and our evidence about the herd influenced our view on the severity of Mycoplasma, and how our view changed when we had more veterinary evidence. We also show how one can use the model to deal with conflicting examinations.     

Mycoplasma hyopneumoniae increases the susceptibility of pigs to experimental Pasteurella multocida pneumonia.

The interaction between Mycoplasma hyopneumoniae and Pasteurella multocida in experimental pneumonia was investigated in conventional pigs. The experimental animals were 49 days old when inoculated with M. hyopneumoniae; they were inoculated with P. multocida after 23 days, and killed 13 days later. In pigs inoculated only with P. multocida, clinical signs and lung lesions were not observed, and the agent was not recovered. Pigs inoculated with M. hyopneumoniae developed fever, moderate cough and dyspnea which tended to disappear, and small proliferative lung lesions from which M. hyopneumoniae was isolated. Pigs inoculated with both agents had higher fever, severe cough and dyspnea which tended to aggravate, and extensive exudative lung lesions from which organisms were isolated. All animals had similar growth rates, but the group infected with both agents consumed 60% more food. Therefore, M. hyopneumoniae causes mild pneumonia, whereas P. multocida is not pathogenic alone but aggravates the pneumonia initiated by M. hyopneumoniae.     

猪肺炎支原体对猪气管上皮细胞的黏附作用

采用气管结扎、链霉蛋白酶灌注冷消化法分离猪气管上皮细胞,并以对数生长期的猪肺炎支原体(Mhp)感染猪气管上皮细胞,通过间接免疫荧光技术定性定量研究不同滴度的猪肺炎支原体对猪气管上皮细胞的黏附及相同滴度的猪肺炎支原体随时间变化对猪气管上皮细胞的黏附。结果表明,分离的猪气管上皮细胞存活率为95%以上,广谱角蛋白染色阳性;Mhp野毒株XLW-1与猪气管上皮细胞37℃作用30min就能看到少量的支原体黏附,作用4h以上时黏附更明显,并且,二者作用1、2、4、6、10h,XLW-1对猪气管上皮细胞的黏附与阴性对照相比差异极显著(P0.01);1×107、2.5×106 CCU/mL的XLW-1与猪气管上皮细胞37℃作用6h,能看到支原体黏附于细胞表面,并且与阴性对照相比差异极显著(P0.01),而其他低滴度的XLW-1则看不到黏附。     

Mycoplasma hyopneumoniae infection in pigs immunosuppressed by thymectomy and treatment with antithymocyte serum

The effect of immunosuppression on Mycoplasma hyopneumoniae infection was evaluated by comparing data from infected, thymectomized, and antithymocyte serum-treated pigs (group 1) with data from infected (group 2) and noninfected (group 3) healthy pigs. After groups 1 and 2 pigs were inoculated intranasally with M hyopneumoniae, mycoplasmas tended to multiply slightly more in the lungs and bronchial lymph nodes of group 1 pigs than that of group 2 pigs. Organisms were also isolated from the spleen of 1 of 3 group 1 pigs. Pneumonia developed in group 2 pigs and was characterized by massive peribronchial, peribronchiolar, and perivascular lymphoid hyperplasia and exudate consisting mainly of polymorphonuclear leukocytes in the alveoli and lumina of the bronchioles and bronchi. In group 1 pigs, perivascular and peribronchiolar cuffings by lymphocytes were less prominent, and the extent of intraluminal exudate was severe and widespread. Bronchial lymph nodes from group 2 pigs had marked hyperplasia of germinal centers and paracortical areas. In group 1 pigs, germinal centers were hyperplastic, whereas in the paracortical areas, depletion of lymphocytes was evident. Seemingly, cell-mediated immune mechanisms are important in the development of pneumonic lesions in enzootic pneumonia of pigs.     

Assessment of antibody response of swine infected with Mycoplasma hyopneumoniae by immunoblotting

An immunoblot procedure was used to evaluate porcine antibody response to inoculation with Mycoplasma hyopneumoniae. Mycoplasmas solubilized with sodium dodecyl sulfate were used as antigens. Antibodies to 5 antigens, estimated to be of molecular weight (mol wt) 110,000, 64,000, 50,000, 41,000, and 36,000, were detected in sera collected during the course of induced mycoplasmal pneumonia. Mycoplasma hyopneumoniae antigens, mol wt 110,000, 50,000, 41,000, and 36,000, cross-reacted with M flocculare when antigen prepared from M flocculare or hyperimmune serum against it were used in the immunoblot procedure. The 36,000-dalton (D) antigen reacted with M hyopneumoniae and M hyorhinis convalescent sera. The 64,000-D M hyopneumoniae antigen was the only antigen that did not cross-react with M flocculare or M hyorhinis. Exposure of immunoblot strips with antigens to trypsin before reacting them with the convalescent sera abolished binding ability of the 110,000-D and 36,000-D antigens, but had no effect on binding by 64,000-D, 50,000-D, or 41,000-D antigens. None of the 5 antigens bound to 11 lectins.     

猪肺炎支原体的研究进展

猪支原体肺炎是一直困扰养猪业发展的重要疾病之一。本文综合国内外对其病原一猪肺炎支原体的最新研究情况，从其对猪生长性能的影响、防治动向、检测、主要抗原的研究、基因工程疫苗研制等五个方面进行讨论。     

猪肺炎支原体的分离及PCR鉴定

猪喘气病(Mycop lasm a pneum on iae of Sw ine,M PS)是由猪肺炎支原体(Mycop lasm a hyopneum o-n iae,M hp)引起的慢性接触性呼吸道疾病,主要症状为咳嗽和气喘,以高发病率和低死亡率为特点。如果与其他肺部病原体(如猪繁殖与呼吸综合征病毒、放线杆菌、多杀性巴氏杆菌、猪流     

Fluorescence serological and culture detection of Mycoplasma hyopneumoniae and Mycoplasma hyorhinis in swine lungs

The present paper compares the fluorescence-serological detection of M. hyopneumoniae and M. hyorhinis in frozen sections with cultural procedures. In 161 lungs of swine the agent of enzootic pneumonia, M. hyopneumoniae, was found almost exclusively in frozen sections (22 times). Only one strain was cultivable. M. hyorhinis was detected 59 times by culture but only 18 times in the sections. For the detection of M. hyopneumoniae therefore the fluorescence-serological investigation of lung sections is the preferable method.     

Evaluation of virulence of Mycoplasma hyopneumoniae field isolates

The course of enzootic pneumonia, caused by Mycoplasma hyopneumoniae, is strongly influenced by management and housing conditions. Other factors, including differences in virulence between M. hyopneumoniae strains, may also be involved. The aim of this study was to evaluate the virulence of six M. hyopneumoniae field isolates and link it to genetic differences as determined by randomly amplified polymorphic DNA (RAPD) analysis. Ninety, conventional M. hyopneumoniae-free piglets were inoculated intratracheally with the field isolates, a virulent reference strain or sterile culture medium. Animals were examined daily for the presence of disease signs and a respiratory disease score (RDS) was assessed per pig. Twenty-eight days post infection, pigs were euthanized, blood sampled and a lung lesion score was given. Lung samples were processed for histopathology, immunofluorescence testing for M. hyopneumoniae and isolation of M. hyopneumoniae. RAPD analysis was performed on all M. hyopneumoniae strains. Significant differences between isolates were found for the RDS, lung lesion score, histopathology, immunofluorescence and serology. Based on the results of the different parameters, isolates were divided into three "virulence" groups: low, moderately and highly virulent strains. Typically, a 5000 bp RAPD fragment was associated with the highly and moderately virulent strains whereas it was absent in low virulent strains. It was concluded that high variation in virulence exists between M. hyopneumoniae strains isolated from different swine herds. Further studies are required to determine whether the 5000 bp fragment obtained in the RAPD analysis can be used as a virulence marker.     

Evaluation of tiamulin for treatment of mycoplasmal pneumonia in swine

During 3 trials, using affected pigs of various ages, tiamulin was evaluated for treatment of experimentally induced mycoplasmal pneumonia. Pneumonia was induced in respiratory tract disease-free swine by intratracheal inoculation of a lung homogenate containing Mycoplasma hyopneumoniae. Eleven days after inoculation, when more than 20% of pigs were coughing, pigs were allotted to 3 or 4 groups (n = 8 pigs each) and were given regimens of no medication or 60 mg, 120 mg, or 180 mg of tiamulin/L of drinking water for 10 days. Twenty-one days after cessation of medication, pigs were euthanatized and then were necropsied. Results obtained from the 3 trials did not indicate significant difference among treatment groups in severity of macroscopic or microscopic lesions induced by M hyopneumoniae or in detection of M hyopneumoniae by use of immunofluorescent technique. Clinical evaluations, daily gain, and feed efficiency did not differ significantly among treatment groups. In this study, tiamulin administration did not have beneficial effects in swine with mycoplasmal pneumonia.     

Protective effects of an oral microencapsulated Mycoplasma hyopneumoniae vaccine against experimental infection in pigs.

Oral microencapsulated Mycoplasma hyopneumoniae vaccines were tested for their ability to prevent mycoplasmal pneumonia in pigs. Eighteen four-week-old specific pathogen free pigs were divided into six groups of three. Each pig of groups 1 to 4 was inoculated intramuscularly with formalin-inactivated M hyopneumoniae in adjuvant and boosted orally 14 days later with four different microencapsulated vaccine microspheres. Group 5 was used as a positive control. All 15 pigs of groups 1 to 5 were challenged at 28 days after the first vaccination by an intratracheal inoculation of pneumonic lung suspension. The three pigs of group 6 were used as a negative control. All four vaccinated groups showed some protection when challenged, but the protection was more solid in pigs boosted with vaccine D (group 4) which contained less porcine serum in the microsphere. The study indicates that oral vaccination with M hyopneumoniae could play a role in prevention and eradication of mycoplasmal pneumonia in the pig.     

Dynamics and persistence of Mycoplasma hyopneumoniae infection in pigs

The purpose of this study was to describe the dynamics (shedding and transmission) of Mycoplasma hyopneumoniae infection within a population of swine and to determine the duration of the infection (persistence) through the identification of the agent in bronchial samples. Sixty-three 2-month-old pigs were used in this study. The pigs (n = 28) were experimentally infected by the intratracheal route with M. hyopneumoniae and considered as seeder pigs. The remaining pigs (n = 32) were not inoculated and randomly allocated to 2 different groups: direct contact exposure pigs (n = 12) and indirect contact exposure pigs (n = 20). Blood samples and nasal swabs were collected throughout the study on days 0, 28, 35, 42, 49, 63, 91, and 119 postinfection. To assess the duration of M. hyopneumoniae infection, 9 seeder and 6 contact exposure pigs were slaughtered at days 155 (group 1), 170 (group 2), and 185 (group 3) postinfection. Direct contact pigs showed evidence of infection on day 28 by polymerase chain reaction (PCR) and on day 35 by serology. The indirect contact exposure pigs presented a very delayed and slow seroconversion pattern; they did not present evidence of transmission until 42 d after the infection of seeder pigs. Identification of M. hyopneumoniae in bronchial swabs was confirmed by nested-PCR from days 155 to 185 postinfection. At the last slaughter date, 77.7% and 100% of the seeders and contact exposure pigs, respectively, tested positive. The results of this study reconfirmed direct infection of M. hyopneumoniae and suggest that indirect transmission can occur in a population. Finally, duration of the infection in this study was longer than previously described.     

Genotype distribution of Mycoplasma hyopneumoniae in swine herds from different geographical regions

Genetic heterogeneity of Mycoplasma hyopneumoniae in pigs has been reported, however there has been limited reproducibility on the molecular methods employed so far. The aim of this study was to modify and standardize a high-resolution multiple locus variable number tandem repeat analysis (MLVA), to investigate the genetic variability of M. hyopneumoniae circulating in the United States of America (USA), Brazil, Mexico and Spain. The MLVA was standardized on the basis of the number of tandem repeats in two Mycoplasma adhesins, P97 and P146, which are proteins involved in the adherence of the pathogen to cilia. A total of 355 samples obtained from the four countries were analyzed. The Simpson's diversity index for the assay was D = 0.976 when samples from all countries were combined. A large number of MLVA types (n = 139) were identified, suggesting that multiple M. hyopneumoniae variants are circulating in swine. The locus P97 had 17 different types with 2–18 repeats. The P146 locus showed higher heterogeneity, with 34 different types, ranging from 7 to 48 repeats. MLVA types that presented more than 30 repeats in P146 were found in Spain and Brazil, while shorter repeats were observed in the USA and Mexico. This simplified MLVA method proved to be an efficient tool for typing M. hyopneumoniae with a high degree of stability, repeatability, and discriminatory power. In conclusion, M. hyopneumoniae showed a high variable number tandem repeat heterogeneity and this assay can be applied in molecular epidemiology investigations within farms and productions systems.     

无需全群淘汰从肥育猪群中根除猪肺炎支原体

利用疫苗和药物,不需要将猪群全部淘汰将猪肺炎支原体从肥育猪群中根除。对3 243头来自猪肺炎支原体阴性猪群的保育猪在被转入猪肺炎支原体阳性肥育猪群前一次性注射灭活疫苗。在第1群已免疫的猪肺炎支原体阴性猪群被转入猪肺炎支原体阳性猪群时,对阳性猪群使用抗生素类药物。所有猪群按猪舍采用全进全出方法进行管理,猪舍内通风和清粪采用单独的处理系统。之后猪场只从猪肺炎支原体阴性母猪群所生产且没做疫苗免疫的仔猪群引猪。血清学调查结果显示,5年半无猪肺炎支原体抗体阳性。结论:这项无需使用全部淘汰方法建立无猪肺炎支原体猪群的根除计划已经获得成功。