Fig. 1. In vitro and in vivo analysis of the infectivity of cluster 3 Tembusu virus SD strain in ducks. (a) The replication kinetics of TMUV SD in DEF cells. Cells were infected at an MOI of 0.0001, and virus-containing supernatants were collected at different time points post-infection. Viral litres were subsequently determined by titration on BHK cells. (b) Viremia levels in ducks infected i.m. with 10^3.5 TCID₅₀ of TMUV SD strain. Virus litres in the blood collected at 2, 3 and 4 dpi were determined by titration on BHK cells. (c) Viral shedding was assessed via throat and cloacal swabs collected from infected ducks at 2, 3 and 4 dpi. Virus litres were determined by titration on BHK cells. (d) Detection of TMUV-specific antibodies in serum samples of inoculated ducks, contact ducks and non-infected ducks using ELISA. Seroconversion was defined by a PI value of ≥18.4%, indicating a positive antibody response to the virus.