Abstract：
Breeding herds in the US are trending toward eradication of Mycoplasma hyopneumoniae (M. hyopneumoniae) due to the positive impact on welfare and downstream production. In an eradication program, \"Day 0″ is the time point when the last replacement gilts to enter the herd were exposed to M. hyopneumoniae and marks the beginning of a herd closure. However, no specific diagnostic protocols are available for confirmation of successful exposure to define Day 0. Therefore, the objective of this study was to develop diagnostic guidelines, including sample collection approaches, for two common gilt exposure methods to confirm an entire population has been infected with M. hyopneumoniae following purposeful exposure. Forty gilts, age 21-56 days, were ear-tagged for longitudinal sample collection at five commercial gilt developer units (GDUs) and were exposed to M. hyopneumoniae by natural contact or aerosolization. Study gilts originated from sources known to be negative to major swine pathogens, including M. hyopneumoniae, and were sampled prior to exposure to confirm negative status, then every two weeks. Blood samples were collected for antibody detection, while laryngeal and deep tracheal secretions and pen based oral fluids were collected for PCR, and sampling continued until at least 85% of samples were positive by PCR. Detection of M. hyopneumoniae varied greatly based on sample type. Oral fluids showed the lowest detection in groups of gilts detected positive by other sample types. Detection by PCR in deep tracheal secretions was higher than in laryngeal secretions. Seroconversion to and PCR detection of M. hyopneumoniae on oral fluids were delayed compared to PCR detection at the individual level. By two weeks post-exposure, at least 85% of study gilts in three GDUs exposed by aerosolization were PCR positive in deep tracheal secretions. Natural contact exposure resulted in 22.5% of study gilts becoming PCR positive by two weeks post-initial exposure, 61.5% at four weeks, and 100% at six weeks on deep tracheal secretions. Deep tracheal secretions required the lowest number of gilts to sample for the earliest detection compared to all other samples evaluated. As observed in one of the GDUs using aerosolization, demonstration of failure to expose gilts to M. hyopneumoniae allowed for early intervention in the exposure protocol and delay of Day 0, for accurate timing of the eradication protocol. Sampling guidelines proposed in this study can be used for verification of M. hyopneumoniae infection of gilts following exposure to determine Day 0 of herd closure.
摘要：
美国的种畜正倾向于根除猪肺炎支原体(M.猪肺炎）由于对福利和下游生产的积极影响。在根除计划中，“第0天”是最后一次进入牛群的替代后备母猪暴露于猪肺炎支原体并标志着牛群封闭开始的时间点。然而,没有特定的诊断方案可用于确认成功暴露以定义第0天。因此,这项研究的目的是制定诊断指南，包括样本收集方法，对于两种常见的小母猪暴露方法，以确认整个人群在有目的的暴露后感染了猪肺炎支原体。40只英国国债，年龄21-56天，在五个商业镀金开发者单位（GDU）处加耳标签以进行纵向样品收集，并通过自然接触或雾化暴露于猪肺炎支原体。研究母猪来自已知对主要猪病原体呈阴性的来源，包括猪肺炎支原体,并在暴露前取样以确认阴性状态，然后每两周.采集血样进行抗体检测,同时收集喉和深气管分泌物和笔基口腔液进行PCR，继续取样,直到至少85%的样品通过PCR为阳性。猪肺炎支原体的检测根据样品类型有很大差异。在其他样品类型检测为阳性的小母猪组中，口服液的检出率最低。通过PCR在气管深部分泌物中的检测高于在喉分泌物中的检测。与个体水平的PCR检测相比，口腔液中猪肺炎支原体的血清转化和PCR检测延迟。暴露后两周，通过雾化暴露的三个GDU中，至少有85％的研究母猪在深部气管分泌物中呈PCR阳性。自然接触暴露导致22.5%的研究后备母猪在初次暴露后两周出现PCR阳性，四周时61.5%，6周时100%的深度气管分泌物.与评估的所有其他样品相比，深层气管分泌物需要最低数量的后备母猪进行最早检测。正如在其中一个使用雾化的GDU中观察到的那样，未将小母猪暴露于猪肺炎支原体的证明允许在暴露方案中进行早期干预,并延迟第0天,以准确确定根除方案的时间.本研究中提出的采样指南可用于验证暴露后的猪肺炎支原体感染，以确定第0天的群关闭。
