Abstract: 【Objective】 The aim of this study was to investigate the preventive and therapeutic effects of the compound traditional Chinese medicine preparation Chushi Lifei Xiaodusan (XDS) on chickens artificially infected with Infectious bronchitis virus (IBV). 【Method】 Twenty-five 9-day-old SPF chicken embryos were randomly divided into five groups and inoculated via the allantoic cavity with different doses of XDS (1.33, 0.665, 0.332, 0.166, and 0 g/0.1 mL) mixed with IBV virus solution (10³ EID₅₀). The control group received sterile PBS instead of XDS. After incubation at 37 ℃ for 36 hours, allantoic fluid was collected for viral quantification. Sixty experimental chickens were randomly divided into prevention,treatment,model and control groups,with 15 chickens in each group.Chickens in the first three groups were inoculated intranasally and intraocularly with 0.1 mL of IBV (gx2021/12-z strain) at 15 days old at a dose of 10⁵ EID₅₀/0.1 mL,while chickens in control group received an equal volume of sterile PBS.Chickens in prevention group received XDS in drinking water at a dose of 2.66 g/d per chicken starting from 12 days old for 3 days.Chickens in treatment group received XDS in the same manner and dose for 5 days starting from 1 day post-infection.Chickens in control and model groups did not receive XDS.Throughout the experiment,the mortality rate,weight gain and clinical symptoms of the chickens were monitored.Trachea and kidney tissues were collected 3,7 and 14 days post-infection to stain with hematoxylin and eosin for histopathological observation, measure the expression of immune-related genes (TLR7,IRF7,IFN-α and IFN-β) and pro-inflammatory cytokine genes (TNF-α,IL-1β,IL-6 and IL-8) using Real-time quantitative PCR,and to determine the viral load in trachea and kidney. 【Result】 The viral loads in the allantoic fluid of chicken embryos in the 0.332, 0.665, and 1.33 g/0.1 mL dosage groups were significantly lower than those in the control group (P＜0.05), and the viral loads decreased with increasing dosage. All chickens in prevention and treatment groups survived,while the chickens in model group had a mortality rate of 20%.In terms of clinical symptoms,compared to model group,XDS effectively alleviated clinical symptoms such as tracheal rales and open-mouth breathing in prevention and treatment groups. 14 days post-infection,the body weight of chickens in model group was significantly lower than that in control group (P＜0.05),whereas no significant differences were observed among the other groups (P＞0.05).HE staining results showed that 7 days post-infection,tracheal ciliated epithelial cells of chickens in model group exhibited shedding and necrosis,while chickens in treatment group maintained better tracheal mucosal integrity. 14 days post-infection,chickens in model group displayed damaged renal tubule structures,whereas chickens in treatment group showed no obvious pathological changes. The extent of tracheal and renal damage in prevention group was intermediate between that of model group and treatment group. In terms of viral load,Real-time quantitative PCR results indicated that the viral load in the trachea and kidneys of chickens in prevention group was significantly lower than that of model group 3 and 14 days post-infection (P＜0.05).The viral load of chickens in treatment group was consistently lower than that of model group throughout the observation period (P＜0.05).The expression levels of immune-related genes TLR7 and IFN-α of chicken trachea were significantly higher in prevention and treatment groups than that in model group 3 days post-infection (P＜0.05). 7 days post-infection,TLR7 gene expression level of chicken trachea were significantly higher in prevention group,and TLR7,IRF7,IFN-α and IFN-β gene expression levels of chicken trachea were significantly higher in treatment group compared to model group (P＜0.05).The expression levels of pro-inflammatory cytokine genes TNF-α,IL-1β, IL-6 and IL-12 of chicken trachea were significantly lower in prevention and treatment groups than that in model group 3 and 7 days post-infection (P＜0.05). 【Conclusion】 XDS effectively alleviated clinical symptoms,enhanced weight gain,reduced viral load in the trachea and kidney,mitigated pathological damage in trachea and kidneys of chicken,and maintained immune homeostasis in chickens infected with IBV.It had good preventive and therapeutic effect on infectious bronchitis of chicken.

Key words: infectious bronchitis; Chushi Lifei Xiaodusan; prevention; treatment