A naturally isolated symbiotic bacterium enhances Tembusu virus thermostability, enabling its fecal-oral transmission in ducks

Notably, the cloaca serves as the primary and persistent site of viral shedding for up to 28 days; significantly higher viral titers here than in pharyngeal swabs indicate a risk of long-term environmental contamination. Even at low infection doses (10³ TCID50), ducklings remain susceptible, with viral replication primarily localized to the duodenum. Furthermore, although maternal antibodies prevent mortality, they cannot entirely block viral replication.

To elucidate the molecular mechanisms underlying this transmission, we utilized single round infection particles (SRIPs) and E-swapped chimeric viruses (CQ/MM-E and MM/CQ-E). We confirmed that specific interactions between duck gut commensal microbiota and the viral envelope (E) protein enhance the thermostability of the duck-origin TMUV strain (CQW1), enabling the virus to maintain infectivity within the gastrointestinal tract and environment.

In summary, this study elucidates TMUV's transmission characteristics—including high susceptibility, intestinal tropism, and persistent shedding—and reveals the molecular mechanism of stability mediated by the viral E protein, providing a critical basis for understanding TMUV's natural transmission cycle in duck populations and optimizing disease control strategies.