关键词: 鸭坦布苏病毒病, 灭活疫苗, 雏鸭, 免疫保护, 病毒载量, 组织病理学

Abstract: Objective　To investigate the efficacy of the inactivated Duck Tembusu Virus vaccine (HB strain) on the immune organs of ducklings infected with Duck Tembusu virus (DTMUV).Methods Fourteen-day-old Peking ducks were randomly divided into three groups: immunized group, non immunized control group, and negative control group. The immunized group was inoculated with the inactivated DTMUV vaccine at a dose of 0.3 mL per duck, and a booster immunization after 14 days. The challenge test was conducted at 21 days after the second immunization. Two days post-challenge, vaccine efficacy was evaluated via virus isolation. At five- and seven-days post-challenge, spleens, thymuses, and bursa of ducklings in each group were collected for viral load quantification and histopathological examination to assess the protective effects of the vaccine on immune organs of ducklings. Results　Virus isolation result showed that all 10 ducks in the immunized group were protected, whereas all 10 ducks in the non-immunized control group were infected. The result of virus load determination indicated that, on day 5 post-challenge, the viral load in the immune organs of the non-immunized control group was significantly higher than that of the immunized group. The result of histopathological observation revealed that on day 5 and 7 post-challenge, a large number of lymphocyte depletion and an increase in reticular cells in the immune organs of the non-immunized control group were observed. In the immunized group, aside from mild fatty degeneration in the liver, no significant pathological changes were observed in other tissues. Immunohistochemical analysis showed that on day 5 post-challenge, numerous positive antigen particles were detected in the immune organs of the non immunized control group, whereas no significant positive particles were found in the immunized group. The transcriptional level analysis of cytokines and granzyme A revealed that the immunized group of ducks maintained low expression levels of TNF-α, IL-6, IL-10, and granzyme A throughout the entire post challenge period.Conclusion　The inactivated Duck Tembusu virus vaccine effectively protects the immune organs of ducklings against DTMUV, maintaining their normal immune function.

Key words: duck Tembusu virus, inactivated vaccine, ducklings, immune protection, viral load, histopathology