Animal Science, School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia,
School of Veterinary Medicine, Wolaita Sodo University, Wolaita Sodo, Ethiopia.
Avian Dis. 2021 Mar;65(1):30-39. doi: 10.1637/aviandiseases-D-20-00073.
Infectious laryngotracheitis virus (ILTV) is thought to exit the host in respiratory aerosols and enter by inhalation of these. High levels of ILTV DNA have been detected in excreta, raising the possibility of alternative routes of shedding from the host. However, it is not known whether or not the ILTV DNA in excreta represents infective virus. This study investigated transmission of wild type and vaccinal ILTV from infected to susceptible commercial meat chickens. Airborne- and excreta-mediated transmission of two field isolates of ILTV (Classes 9 and 10) and three vaccine strains (SA2, A20, and Serva) were tested. To test airborne transmission, air from isolators containing infected birds was ducted through a paired isolator containing uninfected chickens. To test excreta transmission, aliquots were prepared from excreta containing a high level of ILTV DNA within the first week after infection. Chicks were infected bilaterally by eye drop. Clinical signs were monitored daily and choanal cleft swab samples for ILTV detection by quantitative PCR were collected at 4, 8, 15, 22, and 28 days postinfection (DPI) in the airborne transmission study and at 7 and 14 DPI from the excreta transmission studies. There was no transmission of ILTV from excreta, suggesting that ILTV is inactivated during passage through the gut. All strains of ILTV were transmitted by the airborne route but only to a limited extent for the vaccine viruses. The field viruses induced clinical signs, pathology, and greatly elevated ILTV genome copies in swabs. In summary, these findings confirm the suspected airborne transmission of ILTV, demonstrate differential transmission potential between wild type and vaccine strains by this route, and indicate that excreta is unlikely to be important in the transmission of ILTV and the epidemiology of ILT.
传染性喉气管炎病毒（ILTV）被认为通过呼吸飞沫离开宿主，并通过吸入这些飞沫进入宿主。在排泄物中检测到高水平的 ILTV DNA，这增加了从宿主中排出的替代途径的可能性。然而，尚不清楚排泄物中的 ILTV DNA 是否代表感染性病毒。本研究调查了从感染的商业肉用鸡向易感鸡传播野生型和疫苗型 ILTV。检测了两种 ILTV 田间分离株（9 类和 10 类）和三种疫苗株（SA2、A20 和 Serva）的空气传播和排泄物介导的传播。为了检测空气传播，将含有感染鸟类的空气通过管道输送到含有未感染鸟类的配对隔离器中。为了检测排泄物传播，从感染后第一周排泄物中含有高水平 ILTV DNA 的部分制备样本。鸡通过滴眼进行双侧感染。临床症状每天监测，在空气传播研究中，于感染后 4、8、15、22 和 28 天，以及排泄物传播研究中于感染后 7 和 14 天，采集鼻后腔拭子样本，通过定量 PCR 检测 ILTV。未从排泄物中传播 ILTV，表明 ILTV 在通过肠道时失活。所有 ILTV 株均通过空气传播途径传播，但疫苗病毒的传播程度有限。田间病毒引起临床症状、病理学，并大大增加了拭子中的 ILTV 基因组拷贝数。总之，这些发现证实了 ILTV 的疑似空气传播，证明了野生型和疫苗株通过该途径传播的潜力不同，并表明排泄物不太可能在 ILTV 的传播和 ILT 的流行病学中起重要作用。
