Turkey coronavirus (TCoV) can cause a highly contagious enteric disease in turkeys with severe economic losses in the global turkey industry. To date, no commercial vaccines are available for control of the disease. In the present study, we isolated a field strain (NC1743) of TCoV and evaluated its pathogenicity in specific-pathogen-free (SPF) turkey poults to establish a TCoV disease model. The results showed that the TCoV NC1743 isolate was pathogenic to turkey poults with a minimal infectious dose at 10⁶ EID₅₀/bird. About 50 % of one-day-old SPF turkeys infected with the virus’s minimal infectious dose exhibited typical enteric disease signs and lesions from 6 days post-infection (dpi) to the end of the experiment (21 dpi). In contrast, fewer than 20 % of older turkeys (1- or 2-week-old) infected with the same amount of TCoV displayed enteric disease signs, which disappeared after 15–18 dpi. Although all infected turkeys, regardless of age, shed TCoV, the older turkeys shed less virus than the younger birds, and 50 % of the 2-week-old birds even cleared the virus at 21 dpi. Furthermore, the viral infection caused day-old turkeys more body-weight-gain reduction than older birds. The overall data demonstrated that the TCoV NC1743 isolate is a highly pathogenic strain and younger turkeys are more susceptible to TCoV infection than older birds. Thus, one-day-old turkeys infected with the minimal infectious dose of TCoV NC1743 could be used as a TCoV disease model to study the disease pathogenesis, and the TCoV NC1743 strain could be used as a challenge virus to evaluate a vaccine protective efficacy.

土耳其冠状病毒 (TCoV) 可在火鸡中引起高度传染性的肠道疾病，给全球火鸡产业带来严重的经济损失。迄今为止，尚无商业疫苗可用于控制该疾病。在本研究中，我们分离了 TCoV 的田间菌株 (NC1743) 并评估了其在无特定病原体 (SPF) 火鸡幼禽中的致病性，以建立 TCoV 疾病模型。结果表明，TCoV NC1743 分离株对火鸡幼禽具有致病性，在 10 ⁶ EID _{50 时}的最小感染剂量/鸟。从感染后 6 天 (dpi) 到实验结束 (21 dpi)，大约 50% 的一天龄 SPF 火鸡感染了病毒的最小感染剂量，表现出典型的肠道疾病迹象和病变。相比之下，感染相同数量 TCoV 的年长火鸡（1 或 2 周大）中只有不到 20% 出现肠道疾病症状，并在 15-18 dpi 后消失。尽管所有受感染的火鸡，无论年龄大小，都会排出 TCoV，但年长的火鸡比年轻的火鸡排出的病毒更少，而且 50% 的 2 周龄鸡甚至在 21 dpi 时清除了病毒。此外，病毒感染导致日龄火鸡比年长的火鸡体重增加更多。总体数据表明，TCoV NC1743 分离株是一种高致病性菌株，年轻的火鸡比年长的火鸡更容易感染 TCoV。因此，