| The study was carried out to evaluate the protective effect of the new dosage forms of Chinese herbal medicine Maxing Shigan powder on Infectious Bronchitis Virus (IBV) through artificial infection in chickens,and initially discuss its possible function mechanism. The result of this study will provided a novel thought and method for studying Chinese herbal medicine to prevent and treat Animal diseases.Method: Determine the EID50 of IBV-M41 strain after rejuvenation on embryo at 5 generation, then 15-day-old chicks were inoculated intranasally with IBV-M41 refer to 100 EID50, the clinical symptom were observed and chicks were diagnosed by empirical method at 24h post infection. Two hundred and forty 15-day-old chicks were randomly divided into eight groups of 30 each: blank control group, model group,low, middle and high dose of Maxingshigan soluble powder groups and Maxingshigan coarse powder groups. Except for blank control group, chickens in other groups were inoculated intranasally with 0.2 ml inoculum of IBV-M41 respectively. Birds in the two kinds of drug therapeutic groups were intervened with 0.5%, 1% and 1.5% dose of Maxingshigan soluble powder and 0.12%, 0.24% and 0.36% dose of Maxingshigan coarse powder respectively at 48h post infection, successive administration for 3 days. Clinical signs were recorded daily before or after drug usage and serum was collected at 18,21,24,27,30 days of age with six chicks from each group randomly; the IBV antibody titers in serum were determined by ELISA; pathological sections of lung and bronchus were observed; the changes of IgA-secreting cells per unit area of bronchus were measured by immunohistochemistry; the weights of whole body, spleen and bursa of Fabricius were weighed for the calculation of immune organ index. For evaluating the toxicity of Maxingshigan soluble powder, the index of acute toxicity intensity was evaluated by LD50, forty mouses were randomly divided into four groups of 10 each, the route of administration was orally. The test period was 7d, clinical manifestation and death was observed.Result: (1)IBV infected model could be replicated successfully by inoculating with 0.2 ml inoculum of IBV-M41 and under the physical environment of low temperature and high moisturization. It could be confirmed by the clinical symptoms and signs, the pathological appearances of lung and bronchus tissue; (2)The total efficiency of Maxingshigan soluble powder on IBV infection was 90%-93.5%, the cure rate was 86.7%-90%, it was confirmed that the therapeutic effect of Maxingshigan soluble powder on IBV infection was significantly better than Maxingshigan coarse powder and the optimum therapeutic concentration was 0.1%-0.15%; (3)Compared with model group, Maxingshigan soluble powder groups could rapidly induce tissue regeneration through promotion of cell activation, and could improve the pathological changes of the bronchus and lung tissues of the IBV infected model which was better than Maxingshigan coarse powder groups; (4)After administrated with Chinese herb medicine, the serum level of IBV antibody rised obviously, high and middle dose of Maxingshigan soluble powder groups showed positive which was significantly higher than Maxingshigan coarse powder groups; (5) at 3 days postinfection, the areas of IgA secreting cells in the groups challenged with virus continued to increase, but at 9 days postinfection, the increase extent of IgA secreting cells in model group and Maxingshigan coarse powder groups was not obviously, but in high and middle dose of Maxingshigan soluble powder groups,it still maintained upward trend,especially in the rehabilitative period of the body,it still secreted antibody at a high level,therefore enhanced the chicken's ability of resisting the virus; (6)The result of acute toxicity test was LD50>60000mg/kg, explained that Maxingshigan soluble powder is non-toxic, which was safe to take.Conclusion: Maxingshigan soluble powder had significant therapeutic effect on IBV infection, meanwhile reparation effect on pathology injury caused by IBV infection, and immune regulation. It could increase serum antibody against IBV, improve the cellular immunity and humoral immunity, which would eventually kill the pathogenic microorganism and speed up the chick's recovery from IBV infection; it also had the ability of enhancing the function of Mucosal immunity, enhanced the chicken's ability of resisting the virus. The effects aboved of Maxingshigan soluble powder were significantly higher than the traditional coarse powder, moreover it without toxic and side-effect, thereby protect the chickens with IBV infection. |
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