Jacobson Bryan Tegner, DeWit-Dibbert Jessica, Zanca LaShae, Sonar Sobha, Hardy Carol, Throolin Michael, Brewster Patricia C, Andujo Kaitlyn, Jones Kerri, Sago Jonathon, Smith Stephen, Bowen Lizabeth, Bimczok Diane
Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT, USA.
Department of Mathematical Sciences, Montana State University, Bozeman, MT, USA.
Vet Res. 2025 Jan 13;56(1):10. doi: 10.1186/s13567-024-01439-y.
M. ovipneumoniae is a respiratory pathogen that can cause mild to moderate pneumonia and reduced productivity in domestic lambs. However, studies on both natural and experimental M. ovipneumoniae infection have reported highly variable clinical signs and pathology. Here, we assessed the impact of administering M. ovipneumoniae to the upper respiratory tract (URT) or to the lower respiratory tract (LRT) of two-month-old specific pathogen-free lambs. Lambs were inoculated with PBS (control) or with ceftiofur-treated nasal wash fluid obtained from sheep with natural M. ovipneumoniae infection, monitored for eight weeks, and subsequently euthanized. All lambs in the URT and LRT groups developed a stable infection with M. ovipneumoniae. M. ovipneumoniae infection led to lower weight gains and mild respiratory disease, with significantly greater effects following LRT inoculation compared to URT inoculation. At necropsy, lambs inoculated via the LRT showed consolidation of the cranial lung lobes. In addition, histological signs of alveolar, bronchiolar, and interstitial inflammation were significantly more severe in the LRT compared to the URT group. M. ovipneumoniae loads in the trachea and bronchi also were significantly higher after LRT than URT inoculation. Interestingly, 9/10 inoculated lambs also tested positive for M. haemolytica in nasal swab but not in bronchial swab samples. In summary, our study suggests that bypassing protective mechanisms of the URT by delivering respiratory pathogens to the LRT leads to more severe respiratory disease and lung damage than delivery to the URT.
绵羊肺炎支原体是一种呼吸道病原体，可导致家养羔羊出现轻度至中度肺炎，并降低其生产力。然而，关于自然感染和实验性感染绵羊肺炎支原体的研究均报告了高度可变的临床症状和病理表现。在此，我们评估了将绵羊肺炎支原体接种到2月龄无特定病原体羔羊的上呼吸道（URT）或下呼吸道（LRT）的影响。给羔羊接种PBS（对照）或从自然感染绵羊肺炎支原体的绵羊获得的经头孢噻呋处理的鼻腔冲洗液，监测8周，随后实施安乐死。URT组和LRT组的所有羔羊均发生了稳定的绵羊肺炎支原体感染。绵羊肺炎支原体感染导致体重增加减缓以及轻度呼吸道疾病，与URT接种相比，LRT接种后的影响显著更大。尸检时，经LRT接种的羔羊出现颅侧肺叶实变。此外，与URT组相比，LRT组的肺泡、细支气管和间质炎症的组织学征象明显更严重。LRT接种后气管和支气管中的绵羊肺炎支原体载量也显著高于URT接种后。有趣的是，10只接种羔羊中有9只的鼻拭子检测到溶血支原体呈阳性，但支气管拭子样本中未检测到。总之，我们的研究表明，将呼吸道病原体输送到LRT从而绕过URT的保护机制，会导致比输送到URT更严重的呼吸道疾病和肺损伤。
