Prevalence Of Avian Hepatitis E Virus Infection In Laying Farms From Yangling,Shannxi Province

Avian hepatitis E virus(HEV), the causative agent of big liver and spleen(BLS) disease or hepatitis-splenomegaly(HS) syndrome, mainly causes 30-72 weeks old aged broiler breeder hens and laying hens,which showed increasing mortality, egg reduction(20-40%), red fluid in the abdomen, regressive ovaries and enlarged liver and spleen in chickens. The diseases caused heavy economic losses of in Australia poultry. There were also few case reports in China. In 2014-2015, many laying hen flocks in Yangling of Shaanxi province occurred a decrease in egg production(10%-40%) in laying hens. Some necropsied laying hens showed liver hemorrhage and enlarged. To determine the causative agent of the disease, the 337 serum and 268 fecal samples were collected from 6 laying hen flocks. Subsequently, anti-avian hepatitis E virus(HEV) IgG antibodies in serum samples by indirect ELSIA and avian HEV RNA by nested RT-PCR(RT-nPCR) were tested. The results of indirect ELISA showed that the 168 serum samples were positive for anti-avian HEV IgG antibodies and the positive rate was 49.85%. The results of RT-nPCR showed that the 63 fecal samples were positive for avian HEV RNA and the total positive rate was 23.51%. Comparisons of the sequences from the positive fecal samples showed that they shared 93.0-99.2% identities with the isolates from other provinces of China. Phylogenetic analysis showed that these strains were located in the same branch with other isolates in China and they all belonged to genotype 3 avian HEV.