El-Nahass El-Shaymaa, Abdelhamid Mohamed Kamal, Ali Ahmed, Shalaby Adel A, Shaalan Mohamed
Department of Pathology, Faculty of Veterinary Medicine, Beni-Suef University, Beni-Suef, 62511 Egypt.
Department of Poultry Diseases, Faculty of Veterinary Medicine, Beni-Suef University, Beni-Suef, 62511 Egypt.
Virusdisease. 2023 Sep;34(3):410-420. doi: 10.1007/s13337-023-00842-x. Epub 2023 Sep 17.
Avian infectious bronchitis is one of the most common viral infections in chickens affecting all ages. The tropism of infectious bronchitis virus (IBV) strains became broader and more variable posing major implications for the effective control of IBV infection. In this study, two IBV viruses representing classic and variant strains were inoculated intranasally into day-old SPF chicks (10 EID/0.2 ml/bird). Clinical signs were observed for 15 days post-infection (DPI). Five chicks from each group were euthanized at 2, 4, 6, 8, 10, 12, and 15 DPI for histopathology and virus antigen detection by IHC and quantitative rRT-PCR. Results revealed that both classic and variant IBV strains induced mild clinical signs with no mortalities and fewer various histopathological lesions in infected SPF chickens. Although the viruses were detected by rRT-PCR up to 12 DPI, the affected tissues showed regeneration after 10 DPI with IHC revealing no IBV antigen. In summary, no differences were found in the behaviour of both IBV isolates in chickens. The broad tissue tropism for both IBV strains as indicated by viral antigen detection in various organs with no clinical or gross lesion suggest that the main cause of death in IBV infection under field conditions occurs as a result of complication with secondary infections rather single IBV infection. Due to positive immunostaining in the bursa, it is thought that IBV infection has immunosuppressive consequences, hence further study is required to validate this impact.
禽传染性支气管炎是鸡群中最常见的病毒感染之一，可感染各个年龄段的鸡。传染性支气管炎病毒（IBV）毒株的嗜性变得更广且更具变异性，这对有效控制IBV感染构成了重大影响。在本研究中，将代表经典毒株和变异毒株的两种IBV病毒经鼻接种到1日龄的SPF雏鸡中（每只鸡接种10个鸡胚感染剂量/0.2毫升）。感染后15天观察临床症状。每组5只雏鸡在感染后2、4、6、8、10、12和15天安乐死，用于组织病理学检查以及通过免疫组化和定量逆转录聚合酶链反应（rRT-PCR）检测病毒抗原。结果显示，经典毒株和变异毒株在感染的SPF鸡中均引起轻度临床症状，无死亡情况，且各种组织病理学损伤较少。虽然通过rRT-PCR在感染后12天仍能检测到病毒，但感染组织在10天后显示出再生迹象，免疫组化显示无IBV抗原。总之，两种IBV分离株在鸡体内的表现没有差异。在各种器官中通过病毒抗原检测表明两种IBV毒株均具有广泛的组织嗜性，且无临床或肉眼可见病变，这表明在野外条件下，IBV感染导致死亡的主要原因是继发感染并发症，而非单纯的IBV感染。由于法氏囊中存在阳性免疫染色，推测IBV感染具有免疫抑制后果，因此需要进一步研究来证实这种影响。
