Vector Competence of Culex quinquefasciatus  for Tembusu Virus and Viral Determinants for Virus Transmission by Mosquitoes

The recent pandemic of flaviviruses all over the world has underscored the importance of studying flavivirus vector competence, as the evolutionary enhancement of mosquito transmission played a significant role in its spread. Tembusu virus is an avian-related mosquito-borane flavivirus, which is mainly epidemic in China and Southeast Asia since 2010. However, the reason for the outbreak of Tembusu virus in 2010 remains unclear, and it is unknown whether changes in vector transmission played an essential role in this process. To address these questions, we conducted a study using Culex quinquefasciatus as a model for Tembusu virus infection, employing both oral infection and microinjection methods. Our findings confirmed that both vertical and horizontal transmission collectively contribute to the cycle of Tembusu virus within the mosquito population, with persistent infection observed. Importantly, our data revealed that the prototypical Tembusu virus MM_1775 strain exhibited significantly higher infectivity and transmission rates in mosquitoes compared to a duck Tembusu virus (CQW1 strain). Furthermore, we identified that the viral E protein and 3' untranslated region are key elements responsible for these differences. In conclusion, our study sheds light on the mosquito transmission of Tembusu virus and provides valuable insights into the factors influencing its infectivity and transmission rates. These findings contribute to a better understanding of Tembusu virus epidemiology and can potentially aid in the development of strategies to control its spread.