Figure 1. Duck model establishment and verification of infection with DHV-1.

A: No symptoms were evident in duckling organs without the specific bands of the conserved regions in the DHV-13D gene in the control group. B and C: Some symptoms were observed in duckling organs, including an enlarged liver with yellow or yellow-brown spots on kidneys, hyperemia and swelling, spleen enlargement with the specific bands of the conservative regions in the DHV-13D gene in the experimental ducklings (B: morbid group; C non-morbid group).