Monitoring antibodies to Mycoplasma hyopneumoniae in sow colostrum--a tool to document freedom of infection

In a survey in Finland in 1995, 14,919 colostral whey samples from 530 farrowing herds were analysed by a monoclonal blocking-ELISA to detect antibodies to Mycoplasma hyopneumoniae (M. hyopneumoniae). Antibodies were detected in 274 (1.8%) samples and in 42 herds (7.9%). The median prevalence of sows with antibodies in seropositive herds was 28.2% (range, 2.7-100%). According to clinical and pathological follow-up in finishing herds in 1996, all of the farrowing herds which were seronegative in 1995, were truly non-infected with M. hyopneumoniae. In acutely infected herds, samples collected earlier than 2 h after farrowing were 3 times more likely to contain antibodies than samples collected 2-12 h after farrowing (odds ratio, 3.0; 95% CI, 1.4-6.6). Repeated freezing or spoilage of the colostrum samples did not cause biologically relevant problems for the ELISA. Antibodies to M. hyopneumoniae were shown to persist up to 3 years in some sows. As a conclusion, colostrum samples were very sensitive samples for the screening of herds for M. hyopneumoniae infection and possibly also for a regular surveillance.     

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.     

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.     

Chronological study of Mycoplasma hyopneumoniae infection, seroconversion and associated lung lesions in vaccinated and non-vaccinated pigs

A field trial was conducted to study Mycoplasma hyopneumoniae (Mh) infection dynamics by nested polymerase chain reaction (nPCR) and serology in pigs of a farm affected by enzootic pneumonia (EP). Moreover, correlation of Mh detection at different respiratory tract sites with presence of EP gross and microscopic lung lesions was assessed. These parameters were studied and compared between vaccinated (two doses at 1 and 3 weeks of age versus one dose at 6 weeks of age) and non-vaccinated pigs. Animals were monitored from birth to slaughter by nPCR from nasal swabs and by serology. From 3 to 22 weeks of age, an average of three pigs per treatment and per batch were necropsied (n = 302). The remaining pigs were sent to the slaughter (n = 103). Nasal, bronchial and tonsillar swabs were taken from the necropsied/slaughtered pigs; gross and microscopic EP-suggestive lung lesions were also assessed. Single and double vaccination resulted in earlier seroconversion and higher percentage of Mh seropositive pigs compared to control group. At slaughter, double vaccinated pigs showed lower percentage of EP-compatible gross lung lesions and lower Mh prevalence at upper respiratory tract sites (nasal cavity and tonsil) than control pigs.     

Cell-mediated and humoral immune response to Mycoplasma hyopneumoniae in pigs enhanced by dextran sulfate

The effect of dextran sulfate (DS), known to be cytotoxic to macrophages, on the cell-mediated and humoral immune response to nonviable Mycoplasma hyopneumoniae in pigs was investigated. The cell-mediated immune response was determined by means of lymphocyte transformation a test, using uptake of [3H]thymidine in a microculture system and the humoral immune response by means of a microplate complement-fixation test. Peripheral blood lymphocytes from pigs vaccinated with nonviable M hyopneumoniae and DS incorporated substantially more [3H]thymidine than did those from pigs given Mycoplasma or DS alone. The transformation of lymphocytes from M hyopneumoniae-DS vaccinated pigs was enhanced when M hyopneumoniae cells used in the assay system were heated at 60 C for 30 minutes. Similarly prepared M flocculare and M hyorhinis cells also stimulated lymphocytes from M hyopneumoniae-DS vaccinated pigs, but not nearly as great as when M hyopneumoniae cells were used. The humoral antibody response and the cell-mediated immune response to nonviable M hyopneumoniae was markedly enhanced by DS. Pigs were vaccinated with nonviable M hyopneumoniae and/or DS 4 times and challenge exposed intratracheally with viable M hyopneumoniae. Pigs vaccinated with M hyopneumoniae and DS had less severe pneumonia than did nonvaccinated pigs.     

Experimental infection of SPF pigs with Actinobacillus pleuropneumoniae serotype 9 alone or in association with Mycoplasma hyopneumoniae

The purpose of this study was to compare in SPF pigs, the pathogenicity of an Actinobacillus pleuropneumoniae serotype 9 strain 21 (isolated from the palatine tonsils of a healthy gilt on a French nucleus pig farm, with no clinical signs or lung lesions but a highly positive reaction to A. pleuropneumoniae serotype 9 antibodies) with a pathogenic A. pleuropneumoniae strain 4915 serotype 9 (isolated in France from an outbreak of porcine pleuropneumonia). The pathogenicity of one Mycoplasma hyopneumoniae strain alone or associated with A. pleuropneumoniae strain 21 was also compared. Eight groups of 7 pigs were infected (at 6 or 10 weeks of age) and a control group was kept non-infected. Results showed that sensitivity to A. pleuropneumoniae was related to the age of the pig (6 weeks vs 10 weeks) whatever the strain. Surviving pigs infected at 6 weeks of age developed severe clinical signs, lung lesions typical of A. pleuropneumoniae and they seroconverted. In contrast, symptoms and lung lesions were almost non-existent in pigs infected with strain 21 at 10 weeks of age, but a seroconversion was observed with very high ELISA titres. These results were in accordance with those observed in the nucleus pig farm. Infection with M. hyopneumoniae alone induced typical mycoplasmal symptoms, pneumonia and seroconversion. Symptoms and lung lesions were the most noticeable in pigs infected with M. hyopneumoniae at 6 weeks of age and with A. pleuropneumoniae 4 weeks later. Our results show that the presence of A. pleuropneumoniae serotype 9 in a pig herd may be clinically unnoticed and that M. hyopneumoniae may potentiate A. pleuropneumoniae infection.     

Exploratory field study on Mycoplasma hyopneumoniae infection in suckling pigs

The present study focused on Mycoplasma hyopneumoniae (M. hyopneumoniae) detection by nPCR in nasal swabs of 507 suckling pigs. These animals came from 69 sows (from 1 to 8 parity number) of a farrow-to-finish herd with Enzootic Pneumonia (EP) problems at finishing stages. At 1 and 3 weeks of age (still in the farrowing units), nasal swabs and blood samples were taken from all piglets. Moreover, from these 507 animals, 37 randomly selected pigs were necropsied at 3 weeks of age. From those necropsied pigs, M. hyopneumoniae presence was tested in bronchial and tonsillar swabs. At 1 week post-farrowing, blood samples from sows were collected and used to detect M. hyopneumoniae antibodies. From the 69 analysed sows, 19 (27.5%) were seropositive. Global percentage of pigs with M. hyopneumoniae detection in nasal swabs at 1 and 3 weeks of age was 1.5% (8 out of 507) and 3.8% (19 out of 507), respectively. From these nPCR positive pigs, 89% (24 out of 27) were seronegative and 11% were seropositive. From necropsied animals, the pathogen DNA was detected in two pigs at bronchus level and in another pig at tonsil. In this study, sow parity was not statistically related with sow seropositivity and piglet colonization. These results confirm that M. hyopneumoniae infection may be detected not only in nasal cavities of naturally infected suckling piglets but also at their low respiratory tract airways. Our results suggest that M. hyopneumoniae detection in lower and upper respiratory tract could be an indicator that respiratory problems associated to EP may start relatively early in the production system. In consequence, sow-to-piglet and/or piglet-to piglet transmission in farrowing barns should not be underestimated.     

Serum antibody response to Mycoplasma hyopneumoniae measured by enzyme-linked immunosorbent assay after experimental and natural infection of pigs

Studies were conducted under experimental and field conditions to determine the effect of infection with M. hyopneumoniae on the immune response in serum as measured by ELISA. Following intratracheal challenge or contact exposure, serologically negative pigs derived from mycoplasma-free piggeries developed an immune response within 10 days. This response continued to rise for a further 50 days. In a field study in a commercial piggery, no animals (0/44) were observed to have M. hyopneumoniae antibodies at day 86 of life. However between day 86 and day 144, 97.7% (42/43) animals sero-converted. These results are discussed in terms of infection spread, particularly in the grower/finisher shed.     

Assessment of a complement fixation test to detect Mycoplasma hyopneumoniae infection in pigs

SUMMARY Serums from pigs slaughtered at abattoirs were tested for evidence of Mycoplasma hyopneumoniae infection using a complement fixation (CF) test which avoids the procomplementary effect of pig serum. To establish a diagnosis of enzootic pneumonia, the lungs from all sampled pigs were examined for pathological and histological changes consistent with the disease and cultures were made for mycoplasmas and bacteria. The study was carried out at Parkville and Bendigo 160 km apart at different times and all serums were tested at both laboratories. The results agreed closely. Thirty-six of 97 pigs at Parkville and 46 of 99 at Bendigo had enzootic pneumonia. About 80% were positive in the CF test. Sixteen per cent of porkers and 36% of baconers gave false negative reactors, that is, a negative test though lesions were present. About 18% to 36% gave false positive reactions but the level in the porkers in the Bendigo group was significantly higher (p<0.02). Possible explanations include, for the false negatives, loss of reactivity caused by circulating antigen and for the false positives, cross reacting antibody produced by another infection or failure to appreciate that lesions of EP were present in lungs because either they were not identified as such or they were not detected. The validity of any serological test for this disease cannot be established while there is a possibility that the present methods used for diagnosis, gross and microscopic examination and recovery of M. hyopneumoniae, fail to detect some infected animals. Other criteria may have to be adopted.     

环丙沙星在支原体肺炎猪体内的药动学

18头健康杜洛克×长白×大白杂交猪,分3组,每组6头,通过气管内接种含有猪肺炎支原体的病肺悬液复制疾病模型后,以5.0mg/kg静注、肌注及内服给药进行环丙沙星药物动力学研究.高效液相色谱法测定血浆中药物浓度.MCPKP药物动力学程序处理药时数据.结果显示感染猪静注给药的药时数据适合二室开放模型,t1/2α为0.59 h,t1/2β为3.52 h,Vd(area)为3.21 L/kg,ClB为0.645 L/(ks·h).感染猪肌注和内服给药后的药时数据则适合一级吸收一室模型,t1/2ka分别为0.09、0.31 h;tmax分别为0.46、1.41 h;Cmax分别为1.67、0.35 mg/L;F分别为97.30%、34.66%.上述结果表明,支原体性肺炎对环丙沙星静注给药在猪体内的分布有一定影响,但对其消除过程的影响不大;与健康猪比较,感染猪肌注给药的峰浓度、药时曲线下面积及生物利用度均显著提高,而内服给药的峰浓度、药时曲线下面积及生物利用度均显著降低.     

Antibody response in sows and piglets following vaccination against Mycoplasma hyopneumoniae, toxigenic Pasteurella multocida, and Actinobacillus pleuropneumoniae

The aim of the experimental study was to compare the humoral immune response and occurrence of adverse effects following single or multiple simultaneous vaccination of sows against Mycoplasma hyopneumonia, toxigenic Pasteurella multocida, and Actinobacillus pleuropneumoniae. In addition, passively transferred antibodies to piglets were studied until weaning at 3 weeks of age. Fever was seen in a few sows within the first 12 hours after the 1st and 2nd vaccination. No difference in the occurrence of other adverse effects was observed between groups. Antibody levels were significantly higher in vaccinated sows and their offspring compared with the control group. This was found to be independent of single or simultaneous vaccinations with the 3 vaccines. In conclusion, applying multiple vaccines simultaneously to sows appeared not to influence the occurrence of adverse effects or the sow’s serum levels of antibodies at the time of farrowing, nor the offspring’s serum levels up to 3 weeks of age.     

A field evaluation of two vaccines against Mycoplasma hyopneumoniae infection in pigs

Background

A field trial was carried out with two Mycoplasma hyopneumoniae vaccines in order to investigate the benefit of vaccination under field conditions in modern Danish pig production facilities with pigs being positive for M. hyopneumoniae. The M. hyopneumoniae infection of the herd was confirmed through blood samples that were positive for antibodies against M. hyopneumoniae combined with gross lesions of the lungs related to M. hyopneumoniae at slaughter and detection of M. hyopneumoniae by polymerace chain reaction in these lesions.

Results

A total of 2,256 pigs from two herds were randomly divided into three groups. Group 1 received 2 mL ThoroVAX^®VET, Group 2 received 1 mL Ingelvac^®MycoFLEX, and Group 3 was a non-vaccinated control group. The vaccination was performed by a person who was not involved in the rest of the trial and vaccination status thereby blinded to the evaluators.The prevalence of lung lesions related to M. hyopneumoniae were significantly lower for pigs vaccinated with ThoroVAX^®VET but not for pigs vaccinated with Ingelvac^®MycoFLEX^®, when compared to non-vaccinated pigs. There was no significant effect of vaccination on growth rate, antibiotic consumption or mortality.

Conclusion

This trial demonstrated that vaccination with Thoro^®VAX VET was effective in reducing the prevalence of lung lesion in pig units infected with M. hyopneumoniae.     

Comparison of two swine Mycoplasma hyopneumoniae enzyme-linked immunosorbent assays for detection of antibodies from vaccinated pigs and field serum samples.

Mycoplasma hyopneumoniae (Mhyo) causes mycoplasmal pneumonia, an economically important disease of swine. Serodiagnosis of Mhyo is based on the current available commercial enzyme immunoassays for detection of swine antibodies against Mhyo, which are the indirect enzyme-linked immunosorbent assay (ELISA) and the blocking ELISA (B-ELISA). Because of the limited information available for these ELISAs, these 2 assays were compared by testing 347 serum samples collected from vaccinated pigs at 0, 13, 28, 43, and 62 days postimmunization (DPI), 50 samples from nonvaccinated pigs, and 1,013 field serum samples. The results of comparison study showed that the specificity for both ELISAs was 99.2% generated from 139 non-vaccinated negative samples. The sensitivities for indirect ELISA generated from samples collected from animals that received the vaccine at DPI 13, 28, 43, and 62 were 0%, 95.7%, 88.4%, and 92.6%, respectively, whereas the sensitivities for B-ELISA were 0%, 98%, 100%, and 97%, respectively. The overall agreement of 96.7% and 80.3% was generated between 2 ELISAs from negative and vaccinated pigs and from field samples, respectively.     

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.     

Polyserositis in pigs caused by infection with Mycoplasma

A bovine adenovirus was isolated from a yearling heifer with systemic adenovirus infection. The virus was characterized as a subgroup 2 bovine adenovirus but could not be typed with reference antisera to the 10 known bovine adenovirus serotypes. A serological survey of cattle in the northern half of the North Island showed the prevalence of precipitating antibodies to bovine adenoviruses to be 43.3%.     

Effectiveness of treatment with lincomycin hydrochloride and/or vaccination against Mycoplasma hyopneumoniae for controlling chronic respiratory disease in a herd of pigs

A herd of pigs infected with Mycoplasma hyopneumoniae was used in a double-blind randomised trial to assess the effectiveness of three control strategies against chronic respiratory disease in growing-finishing pigs. One group of 61 pigs received 220 ppm lincomycin hydrochloride in the feed from day 71 to day 91, a second group was vaccinated against M. hyopneumoniae at four and 28 days of age, and a third group received both treatments; a fourth group was left untreated as a control. Throughout the nursery-finishing period (day 29 to slaughter) the average daily weight gain and feed conversion rate of all the treated groups were slightly better than in the controls, but there were no significant differences between them. There were no significant differences between the treated groups in terms of clinical signs, serology, pathology or mortality, which was very low throughout the trial.