N130, N175 and N207 are N-linked glycosylation sites of duck Tembusu virus NS1 that are important for viral multiplication, viremia and virulence in ducklings

•Asn 130, Asn 175 and Asn 207 are the N-linked glycosylation sites of duck Tembusu virus nonstructural protein 1.•N130A, N175A, N207A or N130A/N175A/N207A substitution in nonstructural protein 1 impaired viral multiplication in vitro.•Nonglycosylated duck Tembusu virus was highly attenuated in ducklings.