Large-Scale Field Evaluation of a Chicken Embryo Fibroblast Adapted Live Attenuated Vaccine Against Duck Viral Enteritis

Duck viral enteritis (DVE) causes significant economic losses to duck industries in endemic regions, and existing control measures, including embryonated-egg-based vaccines, are limited by batch variability and restricted scalability. In this context, the present study reports the development of a cell culture-based live attenuated duck enteritis virus (DEV) vaccine and its evaluation under both experimental and field conditions. The Holland strain of DEV was adapted to chicken embryo fibroblast (CEF) cells and cultured through 60 serial passages, achieving a titer of 10⁶^.⁸⁸ 50% tissue culture-infective dose (TCID₅₀)/mL. Evaluation in seronegative ducklings demonstrated the safety and immunogenicity of the vaccine, with no adverse clinical signs. Field evaluation in 9,000 ducklings across diverse farming systems showed consistent humoral immune responses under varying conditions. The vaccine's efficacy was further assessed under controlled-challenge conditions, where it conferred complete protection against a virulent field isolate of DEV (DP/As/Km/19). Overall, the findings indicate that the CEF-adapted live attenuated vaccine is safe, highly immunogenic, and suitable for large-scale production, highlighting its potential as a practical and scalable strategy for controlling DVE in endemic regions.