Clinical Effect Of Chinese Herbal Compound "San Huang Lian" On Preventing Tilapia (Gift Oreochromis Niloticus) Streptococcus Disease And It’s Safety Evaluation

In this study,the clinical effect of Chinese herbal compound "San Huang Lian" on preventing tilapia(GIFT Oreochromis niloticus)streptococcus disease and it’s clinical safety was also evaluated.From the in vitro experiment,it was found that the Chinese herbal compound extract showed inhibition effect on all six tested streptococcus strains.The optimal dose of Chinese medicine compound extract on preventing tilapia from streptococcus disease was decided by adding a series dose of the extract to their daily feed.Firstly,using florfenicol as positive control,three dose of the extract,30 mL/kg,60 mL/kg,and 120 mL/kg,were employed to study the resistance of tilapia affected with Streptococcus agalactiaefrom streptococcus disease in this study.Further,tilapia was continuously fed with the Chinese herbal compound extract for 7 days and the relevant immune indices were analyzed to study the mechanism of Chinese herbal compound on preventing tilapia from streptococcus iniae.In addition,the acute toxicity and the maximum tolerated dose of the Chinese herbal compound extract was also evaluated in mice with the purpose of evaluating the clinical safety of this extract on target animal tilapia.Based on the in vitro bacteriostasis experiments,the MIC of this Chinese herbal compound for the six tested streptococcus strains were 62.5 mg/mL,125 mg/mL,125 mg/mL,125 mg/mL,125 mg/mL,and 62.5 mg/mL respectively.Doses of 40 mL/kg,60 mL/kg,and 120 mL/kg of the extract were able to reduce the mortality rate of tilapia,and the optimal dose was found to be 60 mL/kg.Further,studies on tilapia infected with streptococcus showed that 30 mL/kg,60 mL/kg,120 mg/mL Chinese herbal extract and florfenicol decrease the mortality rate of infected tilapia.It was found that the findings from 60 mL/kg and 120 mL/kg Chinese herbal extract showed better effects when compared to florfenicol.This San Huang Lian preparation also exhibited anti-immunosuppression effect on tilapia infected with streptococcus iniae.After 7 days feeding with the Chinese herbal extract with a dose of 30 mL/kg,60 mL/kg,and 120 mL/kg,the superoxide dismutase(SOD)level in tilapia was significantly increased.The level of serum complement C3 was also dramatically increased when 60 mL/kg of the extract was used.When comparing with tilapia infected with bacteria but without the Chinese herbal compound extract treatment,the fishes treated with the San Huang Lian extract showed a significantly increase of SOD activity,alkaline phosphatase activity,C3 level,and IgM level.From the acute tocixity test,Chinese herbal compound extract was proven to be actually non-toxic substance towards targeted animals with a maximum tolerance dose of 20 g/kg.Specifically,1 times,3 times,5 times,and 10 times of clinical recommended dose did not showed any side affects on the total weight,liver index,and spleen index of tilapia.However,when 5 times and 10 times of clinical recommended dose were used,certain blood biochemical indexes,such as the activity of glutamic-pyruvictransaminase and aspertate aminotransferase,as well as the level of total bilirubin and blood glucose was significantly increased.On the other hand,from the histopathological observation of the liver and spleen,it was found that the structure of liver cell was damage with blur cell interval and nuclue,indicating that the dose of San Huang Lian extract should not exceed 3 times of the clinical recommended dose.The obtained results indicated that Chinese herbal compound "San Huang Lian" had inhibitory effects on streptococcus agalactiae and streptococcusiniae.The optimal dose on preventing tilapia from streptococcal disease is defined as 60 mL/kg.A dose of 60 mL/kg and 120 mL/kg in feed was able to effectively reduce the mortality of Streptococcus agalactiae infected tilapia and enhance the related serum immune parameters of tilapia and thus their resistance to streptococcusiniae infection.Meanwhile,Chinese herbal compound "San Huang Lian" was proved to be non-toxic substance as no adverse effect has been observed when 180 mL/kg of this extract was added into the feed.Finally,a dose of 180 ml/kg was recommended to be added into the feed for clinical application on preventing tilapia from streptococcus iniae infection.