Epidemiological Investigation of Duck Hepatitis A Virus (DHAV) Isolated from Sichuan Basin by RT-PCR Disclose the Existence of Mixed Infection and the Feasibility of DHAV-A Evolved from C80 Strain

Thirty-five dhav field isolates from suspected ducklings in sichuan basin in 2002-2010 were rt-pcr confirmed by sequencing their vp1 gene. results demonstrated that dhav-a (22) and dhav-c (13) were dominant types. furthermore, dhav-a, dhav-c infection and their co-infection still exists to some degrees. gene analysis of vp1 disclosed that there are not obvious differences in nucleotides similarity and amino acid mutation except the v160 and g/n/d187 for reference strain was changed as g160 and s187 for dhav-a field strains and these two amino acid sites can be afterwards used as a beacon of molecular epidemiological investigation. besides, all dhav-a isolates possess nearest genetic relationship with reference strain c80 which was also previously isolated from china and used as vaccine strain. the feasibility that some variant strains were evolved from c80 strain may not be excluded.