Researchers at Department of Avian Infectious Diseases, Shanghai Veterinary Research Institute (SHVRI) of Chinese Academy of Agricultural Sciences (CAAS) have published a research paper on Journal of Virology about the molecular basis on the pathogenicity of TMUV in Ducks.

Since 2010, novel duck Tembusu virus (TMUV) disease has spread widely in China, causing huge economic losses in the duck breeding industry. TMUV is a member the genus Flavivirus, family Flaviviridae. Duck TMUV, like other zoonotic mosquito-borne flaviviruses such as Japanese encephalitis virus (JEV) and West Nile virus (WNV), can be transmitted vector-independently. To date, why these flaviviruses can be transmitted without mosquito vectors remains poorly understood. 

To explore the key molecular basis of TMUV transmissibility, they compared virus replication and transmissibility of an early and a recent TMUV in ducks. The recent TMUV strain FX2010 replicated systemically and transmitted efficiently in ducks while the replication of early strain MM1775 was limited and did not transmit among ducks. They found the TMUV envelope protein and its domain I were responsible for tissue tropism and transmissibility. Further, they prove the mutation S156P in the domain I resulted in disruption of N-linked glycosylation at amino acid 154 of the E protein and changed the conformation of "150 loop" of the E protein, which reduced virus replication in lungs and abrogated transmission in ducks. These data indicate that the 156S in the envelope protein is critical for TMUV tissue tropism and transmissibility in ducks in the absence of mosquitos. The findings provided novel insights on understanding TMUV transmission among ducks. More details are available on the bellow links:
http://jvi.asm.org/content/early/2018/06/07/JVI.00427-18.full.pdf