Molecular characterization of chicken astrovirus from high embryonic mortality, based on the capsid protein (ORF2) gene, in Brazil

Abstract

ABSTRACT In recent years, reports of chicken astrovirus (CAstV) infections in commercial birds have increased, affecting the poultry industries in Brazil and worldwide. The objective of this study was to use molecular methods to characterize the CAstV found in one breeding and three different incubation companies that reported increased embryonic mortality and the appearance of birds with white chick syndrome. RT-qPCR with SYBR green chemistry was used to determine the presence of the virus in the faeces of breeders, organs of neonatal chickens, and unhatched embryos. By sequencing the ORF2 gene that codes for the viral capsid, the strains responsible for these clinical signs were characterized using strains previously reported in Brazil, North America, Europe, and Asia. The percentage of identity of the amino acid sequences compared with those from group A was less than 41% (37.01% to 40.52%) and the identity with those from subgroups Bi, Bii, and Biii was less than 90% (81.81% to 89.85%). Therefore, the sequences were characterized within subgroup Biv with identity greater than 95% (95.26% to 99.59%), together with CAstV strains previously found in Brazil, Canada, and the United States. Using antigenicity prediction tools, 14 highly conserved peptides located on the surface of the capsid protein were considered potentially responsible for inducing the immune response in the host. Our data provide important information related to the increase in embryo mortality in vertically-infected birds, reinforcing the potential association of white chick syndrome with CAstV Biv subgroup. RESEARCH HIGHLIGHTS CAstV infections were found in farms and incubators with increased embryo mortality. Brazilian CAstV Biv strains were associated with white chick syndrome. Antigenic peptides were predicted on the surface of the capsid protein.