Goose Parvovirus And Duck Circovirus Virus Induced Duck Big Tongue And Short Beak Syndrome

Since March 2015,a disease was named �duck big tongue and short beak syndrome'occurred in the Merchandise ducks of Shandong,Jiangsu,Anhui,Henan and other regions,which were characterised by slow-growing ducklings,duck beaks atrophy,duck tongues swelling,stiffness and the tongue was bending or leaning towards one side fell from beaks.Low lethality but the morbidity of this disease was 15%-45%.Feed intake was reduced or was not increased with the passing of time.The legs and wings would be fractured easily when the ducks was captured at late stage.In addition to generating huge economic losses for farmers,this disease also became the restricted factor of the creature cultivation sustainable developments.December 2015,some cases were send to Animal Molecuar Pathology Lab for histopathologic evaluation from farms in Shandong Heze and Shandong Feicheng where 6500 ducks were raised,which all developed duck big tongue and short beak syndrome symptoms.In this study,Methods Epidemiological,pathology with the methods of gross anatomy,routine paraffin section,blood smear and HE staining,Identification of bacterial culture,serum biochemistry,PCR detection,purification of related viruses,electronic microscopy,high-throughput sequencing and The establishment of the animal model were carried out.Significant gross lesions were noted at necropsy such as many necrosis in edge of the liver,congestion in the lungs,swelling of the tongue and shortening of the bill led to tongue sticking out.Showing a large number of heterophilic granulocytes and lymphocytes in the blood by blood smears.Histopathological observation found that the inflammatory infiltration of lymphocytes in tongue,beak and liver,many necrosis in liver,myocardium and pancreas,hemorrhage of lung and kidney,different degrees of pathological changes in other tissues.Duck tambus virus,duck virus hepatitis and duck reoviru were negative,both gooseparvovirus(GPV)and duck circoviru viru(DuCV)were double positive by PCR.Alanine aminotransferase,glutamyl transpeptidase,total bilirubin,direct bilirubin,total protein and other biochemical indicators content difference is enormous analyzed by blood biochemistry.Bacteriological test results were negative.The prevalence of GPV and DuCV in infected ducks was found to be 40% higher than that of GPV and DuCV.Liver and tongue specimens,which collected from these cases with diseases,were subjected to virus isolation by means of chick-embryo culture methods.Urinary allantoic fluid was collected at the age of 15 days after inoculation of 9-day-old duck embryos by 0.2ml inoculation.Diffuse hemorrhage was observed in pectorales,skin and myocardium of viral infection group while no significant gross lesions were noted in the controls.Histopathologic detection of the infected group showed that localized or diffuse bleeding in cardiomyocytes,slight vacuolar degeneration of the myocardial cells,diffuse eosinophil infiltration around the central vein of the liver,while no lesion in liver and heart of the normal group.GPV and DuCV in duck allantoic fluid was double positive by PCR.The virus was purified by ultracentrifugation of the virus in the duck capsule allantoic fluid by sucrose gradient.The virus consists of hexagonal,spherical or icosahedron was observed by electron microscopy negative staining.Some virions diameter were measured to be 20-22 nm or 14-20.5nm.Extract DNA of purified virus to amplify by whole genome sequencing,confirmed viral particles DuCV by high-throughput sequencing.The homology of the GPV strain was 99.8% with that of the Chinese GPV type QH15 strain,and 93.5% ~ 99.8% with the other strains by nucleotide sequence analysis.The whole gene of DuCV was obtained and named as SDFC12 strain(GenBank: KY328304.1)by high-throughput sequencing.The homology of SDFC12 strain DuCV was 99.3% with that of DU103 strain in China,the homology with other strains was 29.2% ~ 99.3%.The liver tissue of infected duck embryohe showed that there had a large number of hexagonal or spherical,14-22 nm diameter of the capsule-free virus particles exist by transmission electron microscopy.The gross anatomy of the model of infection by manual inoculation showed liver tissue necrosis,thymus hemorrhage,and Slightly long and curved duck tongue.The weight of spleen,bursa of fabricius and thymus were significantly lower than the control group,and the immune organ index was significantly decreased.The histopathological observation and blood smear observation of experimental animals were consistent with the clinical infection ofducks.The biochemical indexes such as alanine aminotransferase,glutamyl transpeptidase,alkaline phosphatase and total bilirubin total protein in the experimental group were significantly different from those in the control group.The GPV and DuCV of the experimental animals were double positive by PCR.These results indicate that duck big tongue and short beak syndrome associated with co-infection GPV and DuCV,the virus morphology of GPV and DuCV was observed by electron microscopy.Histopathological examination and serum biochemical indicators found that duck big tongue and short beak syndrome caused by duck liver bile duct epithelial swelling,sclerosing cholangitis,cirrhosis and liver necrosis and causing duck pancreatitis.Verify the presence of duck loop virus and obtain its whole gene sequence by High-throughput sequencing.Through this study,it is helpful to study and control the pathogenic mechanism of duck big tongue and short beak syndrome,and contribute to the healthy development of duck industry.