Data and serum samples collection

With the owners consents, a total of 1995 serum samples were collected from 6 chicken flocks in 6 districts (Yantai, Qingdao, Weifang, Linyi, Jinan and Heze) of Shandong Province and 8 flocks in 6 districts (Yulin, Tongchuan, Weinan, Xianyang, Xian and Ankang) of Shaanxi Province. The flocks from Shandong Province showed the egg production decreasing by 30–45% and mortality increasing by 5–8%. And the flocks from Shaanxi Province showed the egg production decreasing by 10–13% and mortality increasing by 1–3%. The incidence of hepatitis syndrome, including hepatomegaly, hepatic necrosis and hemorrhage, were 92% and 67% in the dead chickens in Shandong and Shaanxi provinces. All of the serum samples were collected from 7 broiler breeder flocks and 7 layer flocks and were divided into the following 6 groups based on the age of the chickens: 10 to 19 weeks, 20 to 29 weeks, 30 to 39 weeks, 40 to 49 weeks, 50 to 59 weeks and 60 to 69 weeks. These serum samples were stored at -20 ^oC until tested. In addition, total of 323 liver samples were collected from these diseased birds in Shandong (n = 203) and Shaanxi provinces (n = 120) for detection of avian HEV RNA and ALV-J cDNA. These samples were stored at -80 ^oC until tested.

Shandong Province is located on the east coast of China, has a semi-humid continental climate, and lies in the warm temperate zone with four distinct seasons. The annual average temperature is 11–14 ^oC and the average rainfall is 710 mm per year. Shandong is the province with the largest poultry industry in China. In 2011, the output of poultry meat and eggs in Shandong totaled 2.55 and 4 million tons, respectively, accounting for nearly 15% of China’s total output. Therefore, poultry farming in Shandong makes up a large portion of overall Chinese poultry production.

Shaanxi Province is located in central China and also has a warm temperate semi-humid climate with a continental monsoon system and four distinct seasons. Its annual average temperature is 12–14 ^oC and the average rainfall is 576.9 mm per year. Shaanxi generally lags behind Shandong Province in poultry industry output and thus manages smaller chicken populations.

The animal experiments were approved by the Animal Care and Use Committee of Northwest Agricultural & Forestry University (NWSUAF, Permit Number: AE189056) with adherence to NWSUAF guidelines during handling of all experimental animals.