A simple staining method for the identification of chlamydial elementary bodies in the fetal membranes of sheep affected by ovine enzootic abortion.

A dark-ground methylene blue (DGMB) staining method was used to demonstrate chlamydial elementary bodies in fetal membranes of sheep affected by Chlamydia psittaci. Before evaluation on material from clinically affected animals, the DGMB method was compared with modified Ziehl-Neelsen (MZN) and dark-ground Giemsa (DGG) staining methods for its ability to demonstrate chlamydial elementary bodies in hens' eggs which had been experimentally infected with C. psittaci. DGMB was more specific in its staining of chlamydial elementary bodies than DGG or MZN. The DGMB method was found to be a more reliable technique for the examination of fetal membranes from sheep affected with C. psittaci than DGG or MZN. Those samples diagnosed as positive using the DGMB showed a good correlation with those diagnosed as positive on macroscopic examination.     

Goat serums for fluorescent antibody conjugates to chlamydial antigens.

Serums from goats hyperimmunized with Chlamydia psittaci consistently produce antichlamydial fluorescent antibody conjugate of high titer. The titer of the fluorescent antibody conjugate prepared from a given serum correlated well with the titer obtained by agar gel precipitin, but not with the complement fixation. The agar gel precipitin test can be used to predict whether a given serum is satisfactory for use in production of a conjugate for direct fluorescent antibody tests. Serums with an agar gel precipitin titer of 1/8 or higher generally produce a usable fluorescent antibody conjugate. Labeling gamma globulins with fluorescein isothiocyanate at a ratio of 1/150 resulted in satisfactory fluorescent antibody conjugates. Cultures of Vero cells infected with chlamydiae were found to be suitable for titration of the fluorescent antibody conjugates.     

New challenges for vaccination to prevent chlamydial abortion in sheep

Ovine enzootic abortion (OEA) is caused by the obligate intracellular Gram-negative bacterium Chlamydia abortus. OEA remains a common cause of infectious abortion in many sheep-rearing countries despite the existence of commercially available vaccines that protect against the disease. There are a number of confounding factors that influence the uptake and use of these vaccines, which includes an inability to discriminate between infected and vaccinated animals (DIVA) using conventional serological diagnostic techniques. This suggests that the immunity elicited by current vaccines is similar to that observed in convalescent, immune sheep that have experienced OEA. The existence of these vaccines provides an opportunity to understand how protection against OEA is elicited and also to understand why vaccines can occasionally appear to fail, as has been reported recently for OEA. Interferon-gamma (IFN-γ), the cytokine that classically defines Th1-type adaptive immunity, is a strong correlate of protection against OEA in sheep and has been shown to inhibit the growth of C. abortus in vitro. Humoral immunity to C. abortus is observed in both vaccinated and naturally infected sheep, but antibody responses tend to be used more as diagnostic markers than targets for strategic vaccine design. A future successful DIVA vaccine against OEA should aim to elicit the immunological correlate of protection (IFN-γ) concomitantly with an antibody profile that is distinct from that of the natural infection. Such an approach requires careful selection of protective components of C. abortus combined with an effective delivery system that elicits IFN-γ-producing CD4+ve memory T cells.     

奶牛衣原体性流产病原分离及血清学调查

应用实验室病原分离、血清学检测技术对宁夏某规模化奶牛场流产牛进行衣原体病原分离及血清学调查.结果表明,多年以来,在宁夏奶牛场中流行的以孕牛流产、早产、死产或产无活力弱犊的繁殖障碍性疾病与衣原体感染有关.采集四家规模化奶牛场380份血清,IHA试验结果牛群平均阳性率28.4%.     

斑点酶联A蛋白免疫吸附试验(Dot-PPA-ELISA)检测猪衣原体抗体方法的建立

本研究建立了斑点酶联A蛋白免疫吸附试验（Dot-PPA-ELISA）,对猪衣原体IgG的最小检测量为1.21 ng。以间接血凝试验方法为对照,两种方法同时检测120头份猪血清样品,Dot-PPA-ELISA检出43头份（35.83%）,效价≥256;间接血凝试验检出26头份（21.67%）,效价≥64。诊断膜片与猪瘟、猪布氏杆菌病、猪口蹄疫和猪弓形体病标准阳性血清均不出现有意义的交叉反应。诊断膜片置室温、4℃和-20℃下至少保存3个月其抗原效价不变。试验表明本方法重复符合率为94.44%,且反应效果不受反应板质量和新旧的影响;试剂用量节省,各步骤均可做到严格定量,操作简便,3 h内可出结果,肉眼即可判断,不需要特殊检测仪器。由于辣根过氧化物酶标记的葡萄球菌A蛋白（PPA）是一种广谱诊断试剂,因此Dot-PPA-ELISA还可以用于其它哺乳动物衣原体抗体的检测。     

乳牛衣原体性流产的病原鉴定及免疫原性研究

对采自甘肃、陕西和宁夏奶牛场的发生不明原因流产乳牛病料进行了间接血凝试验（IHA）、PCR、病原分离鉴定和MOMP基因检测，证实病原为鹦鹉热衣原体（Chlamydia psittaci）。对分离株Sx5和Nx进行毒力稳定性和免疫原性测定，用鸡胚连传20代，SX5和NX株的毒力比较稳定，毒力效价分别为10^-11ELD50和10^-10ELD50；用这2株菌对小鼠和牛做免疫效力试验，结果显示，免疫鼠5／5和5／5保护，对照鼠0／5保护；免疫牛3／3和3／3保护，对照牛0／3保护。表明，SX5和NX株具有良好的免疫原性，可以作为疫苗研制的候选菌株。     

Microimmunodiffusion test for diagnosis of ovine progressive pneumonia.

Two microimmunodiffusion tests (MIDT) for detection and measurement of ovine progressive pneumonia antibody are described. Substrates of various salt concentrations and pH were used to determine the optimal conditions for the tests. In comparisons between two MIDT and one macroimmunodiffusion test, sera from cull ewes were used. The MIDT require less reagents and were more responsive than the macroimmunodiffusion test. After extended incubation of the test materials, results in all three tests were comparable.