国家自然科学基金81171590,81572019;家畜疫病病原生物学国家重点实验室开放课题SKLVEB2013KFKT005;江苏高校优势学科建设工程资助项目PAPD联合资助 Funded by the National Natural Science Foundation of ChinaGrant .81171590,81572019;the Chinese Academy of Agricultural SciencesGrant SKLVEB2013KFKT005;a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions