Effect of Plant Essential Oil on Prevention and Treatment of Chicks Artificially Infected with Infectious Bronchitis Virus
The aim was to investigate the efficacy of plant essential oil(Commercial name:Shu-ning 500)on chicks artificially infected with avian infectious bronchitis virus(IBV).A total of 260 1-day-old non-immunized healthy chicks were divided into 13 groups,including blank group,model control groups(A,B,C),preventive groups(A,B,C),treatment groups(A,B,C),and positive drug groups(A,B,C),with 20 chicks in each group.Except the blank group,all the chicks in group A were mono-infected with IBV strain GX-QZ20181028(LX4 type)at 8-day-old,and all the chicks in group B were mono-infected with IBV strain GX-NN20200723(Taiwan type)at 8-day-old.All group C chicks were co-infected with IBV strains GX-QZ20181028(LX4)and GX-NN20200723(Taiwan type)at 8-day-old.The preventive groups were given the drug(es-sential oil,1 mL·L-1 water)in drinking water from 3-day-old(5 days before infection).Both the treatment groups and the positive drug group(Shuanghuanglian Oral Liquid,0.7 mL·L-1 water)were administered when more than half of the chicks showed clinical symptoms,and the drug was administered continuously for 5 days.Clinical symptoms and efficacy were evaluated at 8,9,13,14,15,16,17,18,19,and 20 days old,while pathological histopathological changes,im-mune organ indexes,and viral loads in trachea and kidneys were observed at 19 and 22 days old.IBV-specific antibodies,as well as cytokines IFN-γ,IL-4,and IL-6 in sera were detected at 8,9,15,17,19,and 22 days old.The results showed that the protection rates of prevention group A,Band C were 75.00％,85.00％and 70.00％,respectively.The effective rates of treatment group A,B and C were 92.31％,78.57％and 77.78％,respectively.In the model control groups,cilia of a large number of epithelial cells in the tracheal mucosa decreased or disappeared,and degeneration and necrosis occurred,and lymphocytes were infiltrated in the renal mesen-chyme,and no obvious lesions were observed in other groups.The viral loads of trachea and kid-ney in the prevention,treatment and positive drug groups were significantly lower than those in the model control groups(P＜0.05).The thymus and bursa indices in the model control groups were significantly lower than those in the remaining groups(P＜0.05).At 17 days old(the 5th day after administration),the antibody levels of prevention,treatment and positive drug groups increased,and at 22 days old(the 5th day after withdrawal),the antibody levels were significant-ly higher than those in the model control groups(P＜0.05).The levels of IL-4 and IFN-γ in the model control groups were significantly lower than those in other groups from pre-administration to the 5th day after withdrawal(P＜0.05)at 13 to 22 day-old(5 days before treatment to 5 days after withdrawal),and the contents of IL-6 were significantly higher than those in other groups(P＜0.05).In conclusion,under the condition of the current study,the plant essential oil has good preventive and therapeutic effects on chicks both mono-infected and co-infected with IBV,and the preventive and curative effects are mainly exerted through inhibiting viral replication,promoting immune organ development and antibody production,and regulating cytokines.The present study provides a new idea for the prevention and treatment of avian infectious bronchitis(IB),and also provides a reference for the effective treatment and prevention of coronavirus dis-eases in other animals.
万方数据
维普
