Molecular Characterization and Typing of Chicken and Turkey Astroviruses Circulating in the United States: Implications for Diagnostics

Abstract

Avian astroviruses were detected by reverse transcriptase and polymerase chain reaction in intestinal contents collected from commercial chickens and turkeys from throughout the United States from 2003 through 2005. Astroviruses were detected in birds from both healthy and poorly performing flocks with or without enteric disease. Phylogenetic analysis was performed with sequence data from the polymerase (ORF-1b) genes of 41 turkey-origin astroviruses and 23 chicken-origin astroviruses. All currently available avian astrovirus sequence data and selected mammalian astrovirus sequence data were included in the analysis. Four groups of avian astroviruses were observed by phylogenetic analysis: turkey astrovirus type 1 (TAstV-1)-like viruses, turkey astrovirus type 2 (TAstV-2)-like viruses, both detected in turkeys; avian nephritis virus (ANV)-like viruses, detected in both chickens and turkeys; and a novel group of chicken-origin astroviruses (CAstV). Among these four groups, amino acid identity was between 50.1% and 73.8%, and was a maximum of 49.4% for all avian isolates when compared with the mammalian astroviruses. There were multiple phylogenetic subgroups within the TAstV-2, ANV, and CAstV groups based on 9% nucleotide sequence divergence. Phylogenetic analysis revealed no clear assortment by geographic region or isolation date. Furthermore, no correlation was observed between the detection of a particular astrovirus and the presence of enteric disease or poor performance. Based on these data, a revision of the present taxonomic classification for avian astroviruses within the genus Avastrovirus is warranted.

Identification of chicken enterovirus-like viruses, duck hepatitis virus type 2 and duck hepatitis virus type 3 as astroviruses

“…CAstVs were also detected in a recent study by Pantin-Jackwood et al (2006), who applied the Method 2 RT-PCR to faeces and gut content samples from chickens and turkeys obtained from problem and nonproblem US flocks. Nucleotide identities between 85.1% and 98.4% and amino acid identities between 92.4% and 100% were observed when 13 CAstV ORF 1b amplicon sequences were compared.…”

High-resolution melt curve analysis to confirm the presence of co-circulating isolates of avian nephritis virus in commercial chicken flocks

“…The viral RNA polymerase is considered to be one of the more conserved regions in the ANV genome. Nucleotide identities of 86-99% were found between the polymerase gene of ANV isolates in the United States (Pantin-Jackwood, 2006). The capsid gene on the other hand is the most variable with the capsid gene of European and Asian isolates having nucleotide identities of 56-100% (Todd et al, 2011).…”

Detection and characterization of avian nephritis virus in ducklings

“…Besides affecting mostly young mammals, astroviruses became a common finding in poultry after they were first reported in 1980 in turkey faeces (McNulty et al, 1980;Koci & Schultz-Cherry, 2002). Avian astroviruses are linked to poult enteritis and mortality syndrome (PEMS) in turkeys, runting and stunting syndrome (RSS) in chickens, fatal hepatitis in ducklings and enteritis in guinea fowl (Gough et al, 1984;Baxendale & Mebatsion, 2004;Catolli et al, 2005;Pantin-Jackwood et al, 2006;Spackman et al, 2010). They are classified as turkey astrovirus, chicken astrovirus, avian nephritis virus (ANV) and duck astrovirus (DAstV) (Wilcocks et al, 1992;Koci & Schultz-Cherry, 2002;Baxendale & Mebatsion, 2004;Fu et al, 2009).…”

“…Pantin-Jackwood et al (2006) identified and sequenced ANV for the first time from turkeys affected with PEMS; however, the role of ANV has not yet been clarified.…”

“…ANV is genetically and antigenically distinct from other known astroviruses, but turkey astrovirus-1 seems to be most closely related to ANV (Thouvenelle et al, 1995;Imada et al, 2000). Chicken astrovirus also shows some sequence identity with ANV; however, the isolates of this virus differ antigenically and serologically from ANV (Baxendale & Mebatsion, 2004 There are at least two reported serotypes of ANV (ANV-1, ANV-2) (Shirai et al, 1991;Pantin-Jackwood et al, 2006), and field strains of ANV show different degrees of pathogenicity in chickens varying from subclinical infection to death (Frazier et al, 1990;Shirai et al, 1991).…”