Isolation And Identification Of Duck Tembusu Virus Tongling Strain

Duck tembusu virus(TMUV)is a new infectious disease which mainly caused ducklings neurologic death and laying drop break out on about 2010 in China.The outbreak quickly spread to Shanghai,Zhejiang,Fujian,Anhui,Jiangsu,Shandong and other places,bringing huge economic losses to duck industry.In recent years,the isolation and identification of TMUV have been reported.But researches about the pathogenesis,epidemiological characteristics and epidemic features of TMUV are continuing.And there is no vaccine or characteristic drug to the prevention and treatment.So it is very valuable to study DTMUV.In September 2015,a duck farm of TongLing appeared the laying rates droping of the laying duck,and appeared quite mortality.To find out the infectious agent,we took labotatory detection on the sick duck,then measured and analyzed the gene sequence,indicated the duck infected DTMUV.We collected illness ovarian etc tissues under aseptic condition,grinded to liquid,added double resistant and filtered to remove bacteria,then authenticated some common virus by PCR.The PCR detection showed the specificity strip of DTMUV,and no specificity strips of duck enteritis virus,duck circovirus,avian influenza virus,duck hepatitis virus,Newcastle disease virus and duck reovirus was appeared,indicated that their exist DTMUV infection in TongLing duck farm.The study innoculated the samples into 9 days SPF chiken embryos through allantioic cavity,and subcultured for 3 generations,the chiken embryos appeared chorioallantoic membrane thickened,liver splotchy oncosis and local liver appeared earthy yellow and swelling.And collected the allantonic fluid from 24h to 120h after the innoculation to isolate the virus.After then we took the preliminary study on the pathogenicity of the DTMUV,the allantoic was double diluted into 5 concentration gradient(100,10-1,10-2,10-3,104 and 10-5)solutions.The virulence of DTMUV was measured by the deaths of the chiken embryoes which were inoculated with the virus solutions.The ELD50 of the DTMUV-Tongling strain was 10-2.38/0.1ml according to Reed-Muench method.The animal regression test was proceeded subsequently.The feed intake and egg production of the ducks in treatment group were declined since challenged with DTMUV 3 days.On the 7th days,the dissection showed the ducks in the treatment group with the symptoms of ovarian atrophy,spleen swelling and pancreatic bleeding,while the control group did not appear similar symptoms.And the DTMUV was detected positive with the ovary,liver,pancreas brain and spleen of the ducks in the treatment group.We had the primary understanding of the epidemiological characteristics of DTMUV-Tongling strain according to the separation and identification assay of DTMUV.The study of virulence of DTMUV was provided a theoretical foundation for the pathological mechanisms studying and control measures exploring this virus.