Epidemiological Survey Of Duck Hepatitis A Virusin Zhangqiu District Of Jinan City

Duck viral hepatitis(DVH)is an acute,highly lethal infectious disease in ducklings caused by duck hepatitis virus(DHV)infection.And duck hepatitis A virus(DHAV)infection is the main cause of the occurrence and prevalence of the disease.It mainly infects 1-3 weeks old ducklings with a mortality rate of 90%.DHAV is divided into three serotypes: DHAV-1,DHAV-2,and DHAV-3,and there is little cross-reactivity between the three serotypes.DHAV has two non-coding regions,located at both ends,an open reading frame(ORF region),located in the middle of the two non-coding regions,and finally able to form 12 mature different types of proteins,in turn VP0-VP3-VP1-2A1-2A2-2A3-2B-2C-3A-3B-3C-3D.Among them,VP1 is the main component of capsid protein,which can stimulate the body to produce protective antibodies.The nucleotide sequence of VP1 gene is a highly variable region in DHAV genome,which can be used as a marker for DHAV genotype research,and can be distinguished the serotype of the virus.In order to better understand the prevalence of DHAV in Zhangqiu District of Jinan City,Shandong Province,since 2018,a total of 26 batches of suspected DHAV materials have been collected from 8 towns of Zhangqiu District,such as Mingshui,Shuangshan,etc.Subsequently,we investigated the incidence of the disease,isolated and identified the viruses,and cloned,sequenced and analyzed the VP1 gene of these virus isolates.Through the investigation of the incidence of suspected DHAV cases collected from different areas of Zhangqiu District,it was found that DVH mainly concentrated in the ducklings below 4weeks of age,and the disease can occur all year round.There was no obvious seasonality to DVH,but the incidence rate of the disease was higher in autumn and winter.The main clinical symptoms of the ducklings with DHAV infection had neurological symptoms,depression,head tremors,unstable standing,sputum,etc.Dead ducks also show angular reflex symptom.There are spots or needle-like hemorrhage on the surface,and other organs also have different degrees of bleeding.The 26 batches of the disease materials were tested for virus,and 15 batches were detected as DHAV positive.The positive rate of DHAV was up to 57.7%.In them,5 batches were infected with DHAV-1,6 batches were infected with DHAV-3,and 4 batches were DHAV-1 and DHAV-3 were co-infection.,and DHAV was prevalent in 7 major duck-raising areas.The prevalence of DHAV-1 and DHAV-3 existed in most areas.According to the analysis of the results,the age of onset of DVH is tending to rise.According to the analysis of the results,the age of onset of DVH is tending to rise.If the ducks over 28 days of age are infected with DVH,they are mixed infection of DHAV-1 and DHAV-3.In this study,the VP1 gene was amplified from the DHAV strains isolated from Zhangqiu District of Jinan City.The sequence of VP1 gene of 9 DHAV-1 strains and the sequence of VP1 gene of 10 DAHV-3 were obtained.Compared with the VP1 gene of 17 DHAVs registered on NCBI,the corresponding phylogenetic tree was constructed for genetic analysis,and the homology of DHAV-1 and DHAV-3 was analyzed and compared.The results show that DHAV-1 and DHAV-3 were divided into two distinct branches on the phylogenetic tree.The VP1 gene nucleotide homology between the 9 DHAV-1 isolates was 90.6%-99.9%,and the homology with 8 DHAV-1 strains registered on NCBI was 94.6%-99.9%;The VP1 gene nucleotide homology between the 10 DHAV-3 isoltes was 93.1%-99.9%,and the homology with the 9 strains registered with NCBI was 89.3%-99.4%.Moreover,the VP1 of DHAV-3isolates have obvious regional characteristics.The epidemiological study on DHAV in Zhangqiu District of Jinan City provided a theoretical basis for the scientific prevention and control of duck viral hepatitis in this region.