The Incubation Period, Dynamics Of Viral Shedding And Dynamic Distribution In Blood And Diverse Tissues Of Ducklings Challenged With Tembusu Virus

In 2010, Tembusu virus infection was first reported by Cao Zhenzhen and Zhang Dabing.The disease was first defined as duck hemorrhagic ovaritis(DHO), but further study proved that the causative agent is a new kind of flavivirus--Tembusu virus(TMUV). The outbreak quickly spread to Fujian, Shanghai, Jiangsu, Zhejiang, Shandong, and the emergence of TMUV has significantly affected the duck industry and resulted in huge economic losses in China.Currently, there are many methods of detecting Tembusu virus have been established,like Nested RT-PCR, RT-LAMP, ELISA, DIG-labeled probe, RTFQ-PCR and so on. Among those methods, quantitative RT-PCR is fast, accurate, high sensitivity, good reproducibility,and have a widely used in many areas. We recorded both the clinical signs and the incubation period of the ducklings which have infected the TMUV. Furthermore, SYBR Green Ⅰfluorescence quantitative RT-PCR analysis of viral shedding, detection in blood and diverse tissues were also performed. This study provided a theoretical basis for a better study of TMUV and also offered essential data for prevention and control this disease.110 ducklings were inoculated with the duck-origin Tembusu virus(TMUV) AHQY strain each duckling 3.5mL virus allantoic fluid intravenously, intranasally at 10-day-old. We break the ducklings into groups of three: 70 ducklings for intravenous injection group, 20 ducklings for intraocular-nasal injection group and 20 ducklings for group naturally infected.We fed the group infected naturally with intravenous injection ducklings, without any other treatment. After the ducklings infected the TMUV, cloaca swabs and blood samples were collected and 3 ducklings were killed at random every two days. We used the fluorescence quantitative RT-PCR assay to detect TMUV of the infected ducklings’ viral shedding,detection in blood and diverse tissues.The results show that the incubation period of 3 groups ducklings is consistent, average24 h. We found that Viral RNA can detected in cloacal swabs from the first day to 25 th day and the content of Tembusu virus in cloacal swabs is higher on the 5th day, 11 th day and 17 th day, and it reached the peak on the 5th day, changes of ducklings infected naturally were twodays later than other two groups. It is significantly lower than the other two groups that the detection of Tembusu virus in blood of the intravenous injection group, and it reached the peak on the 7th and 19 th day, the group intraocular-nasal injection also reached the peak on the 7th and 19 th day. The content of Tembusu virus in blood reached its highst value on 9th day and 21 th day in ducklings infected naturally. Higher viral copy numbers in the tissues,especially in vital organs such as the brain, thymus, bursa of Fabricius, pancreas and the heart,were reduced after increased at the 5th day and climbed to the highest at day 13. The experiment results indicated that Tembusu virus has a very strong infectivity and short incubation period, virus can shed into the environment through cloaca for a long time and quickly invaded all major organs with blood circulation.