Some pathological observations on the naturally infected dromedary camels (Camelus dromedarius) with the Middle East respiratory syndrome coronavirus (MERS-CoV) in Saudi Arabia 2018–2019

The natural MERS-CoV infection in dromedary camels is understudied. Recent experimental studies showed no obvious clinical signs in the infected dromedary camels. To study the pathological changes associated with natural MERS-CoV infection in dromedary camels. Tissues from three MERS-CoV positive animals as well as two negative animals were collected and examined for the presence of pathological changes. The screening of the animals was carried out first by the rapid agglutination test and then confirmed by the RT-PCR. The selected animals ranged from six to twelve months in age. The sensitivity of the latter technique was much higher in the detection of MERS-CoV than the Rapid test (14 out of 75 animals positive or 18% versus 31 out of 75 positive or 41%). MERS-CoV induced marked desquamation of the respiratory epithelium accompanied by lamina propria and submucosal mononuclear cells infiltration, epithelial hyperplasia in the respiratory tract, and interstitial pneumonia. Ciliary cell loss was seen in the trachea and turbinate. In addition, degeneration of glomerular capillaries with the complete destruction of glomerular tufts that were replaced with fibrinous exudate in renal corpuscles in the renal cortex were noticed. Expression of the MERS-CoV-S1 and MERS-CoV-N proteins was revealed in respiratory tract, and kidneys. To our knowledge, this is the first study describing the pathological changes of MERS-CoV infection in dromedary camels under natural conditions. In contrast to experimental infection in case of spontaneous infection interstitial pneumonea is evident at least in some affected animals.

单峰驼自然感染中东呼吸综合征冠状病毒（Middle East Respiratory Syndrome Coronavirus, MERS-CoV）的相关研究尚未得到充分开展。近期的实验研究表明，感染该病毒的单峰驼未出现明显临床症状。为探究单峰驼自然感染MERS-CoV相关的病理变化，本研究采集了3份MERS-CoV阳性及2份阴性的单峰驼组织样本，对其病理变化进行检测分析。研究对象首先通过快速凝集试验完成初筛，随后采用逆转录聚合酶链式反应（Reverse Transcription Polymerase Chain Reaction, RT-PCR）进行确认。受试单峰驼的年龄范围为6至12月龄。相较于快速凝集试验，后者（RT-PCR）检测MERS-CoV的灵敏度显著更高：75只受试动物中，RT-PCR检出阳性14只（占比18%），快速凝集试验检出阳性31只（占比41%）。MERS-CoV感染可引发显著的呼吸道上皮脱屑，伴随固有层及黏膜下层单核细胞浸润、呼吸道上皮增生以及间质性肺炎。在气管与鼻甲组织中可见纤毛细胞丢失现象。此外，还观察到肾皮质肾小体内的肾小球毛细血管发生变性，肾小球丛完全遭到破坏并被纤维蛋白渗出物所取代。在呼吸道及肾脏组织中可检测到MERS-CoV-S1蛋白与MERS-CoV-N蛋白的表达。据我们所知，本研究是首项针对单峰驼自然感染MERS-CoV后的病理变化展开的系统研究。与实验感染模型不同，自然感染状态下至少在部分受感染单峰驼中可观察到明确的间质性肺炎。