Anses, Lyon Laboratory, UMR «Mycoplasmoses of Ruminants», Lyon cedex, France.
BMC Vet Res. 2012 Jul 9;8:109. doi: 10.1186/1746-6148-8-109.
Contagious agalactia (CA) of sheep and goats caused by Mycoplasma agalactiae is a widely occurring economically important disease that is difficult to control. The ELISA is commonly used for the serological detection of CA but it has some limitations and the performance of the available tests have not been properly evaluated.Two commercial ELISA kits are widely used, one involving a fusion protein as target antigen and the other a total antigen. The objectives were to compare these tests by evaluating:i. Their diagnostic sensitivity and specificity, the relevance of the recommended cut-off points, the correlation between the two tests, and, the correlation between serology data and the milk shedding of M. agalatiae;ii. The influence of extrinsic factors such as the targeted animal species, geographical origin of the samples, intra-specific variability of M. agalactiae and concurrent mycoplasma infections.A sample of 5900 animals from 211 farms with continuous CA monitoring for 20 years and no prior vaccination history was used. The infection status was known from prior bacteriological, epidemiological and serological monitoring with a complementary immunoblotting test.
The average diagnostic sensitivity was 56% [51.8-59.8] for the fusion protein ELISA and 84% [81.3-87.2] for the total antigen ELISA, with noteworthy flock-related variations. The average diagnostic specificity for the fusion protein ELISA was 100% [99.9-100], and for the total antigen ELISA differed significantly between goats and sheep: 99.3% [97.4-99.9] and 95.7% [93.8-97.2] respectively.Experimental inoculations with different M. agalactiae strains revealed that the ELISA kits poorly detected the antibody response to certain strains. Furthermore, test performances varied according to the host species or geographical origin of the samples.Finally, the correlation between milk shedding of M. agalactiae and the presence of detectable antibodies in the blood was poor.
These serological tests are not interchangeable. The choice of a test will depend on the objectives (early detection of infection or disease control program), on the prevalence of infection and the control protocol used. Given the variety of factors that may influence performance, a preliminary assessment of the test in a given situation is recommended prior to widespread use.
由无乳支原体引起的绵羊和山羊传染性无乳症（CA）是一种广泛存在的具有重要经济意义的疾病，难以控制。酶联免疫吸附试验（ELISA）常用于 CA 的血清学检测，但存在一些局限性，并且现有检测方法的性能尚未得到适当评估。目前有两种广泛使用的商业 ELISA 试剂盒，一种试剂盒使用融合蛋白作为靶抗原，另一种试剂盒使用全抗原。本研究的目的是通过评估以下内容来比较这两种试剂盒：i. 它们的诊断敏感性和特异性、推荐截断值的相关性、两种试剂盒之间的相关性，以及血清学数据与无乳支原体排乳之间的相关性；ii. 目标动物物种、样本的地理来源、无乳支原体的种内变异性和同时存在的支原体感染等外在因素的影响。本研究使用了 5900 只来自 211 个农场的动物样本，这些农场进行了 20 年的连续 CA 监测，且没有进行过疫苗接种。感染状态是通过之前的细菌学、流行病学和血清学监测以及补充免疫印迹试验来确定的。
融合蛋白 ELISA 的平均诊断敏感性为 56%（51.8-59.8），全抗原 ELISA 的平均诊断敏感性为 84%（81.3-87.2），并且存在显著的羊群相关差异。融合蛋白 ELISA 的平均诊断特异性为 100%（99.9-100），而全抗原 ELISA 在山羊和绵羊之间的差异显著：分别为 99.3%（97.4-99.9）和 95.7%（93.8-97.2）。用不同的无乳支原体菌株进行的实验性接种表明，ELISA 试剂盒对某些菌株的抗体反应检测能力较差。此外，测试性能还取决于样本的宿主物种或地理来源。最后，无乳支原体的排乳与血液中可检测抗体之间的相关性较差。
这些血清学检测方法不能互换使用。检测方法的选择将取决于目标（早期感染检测或疾病控制计划）、感染的流行程度以及使用的控制方案。鉴于可能影响性能的各种因素，建议在广泛使用之前，在特定情况下对检测方法进行初步评估。
