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Astroviruses as causative agents of poultry enteritis: genetic characterization and longitudinal studies on field conditions.

Abstract

Astroviruses (AstVs) are nonenveloped RNA small round viruses (SRVs) with a genome of 6.8-7.9 kb. Known avian AstVs are spread worldwide; they have been associated with poult enteritis and mortality syndrome in the United States and reported in Italy in intensive turkey and guinea fowl flocks. Nevertheless, their real prevalence and their pathogenic role in avian enteritis affecting Italian flocks is far from clear. Negative staining electron microscopy (nsEM) is used for the routine diagnosis of avian enteric SRVs, although it cannot distinguish morphologically similar particles. Enzyme-linked immunosorbent assay (ELISA), reverse-transcription PCR (RT-PCR), and genomic sequencing are now used for this specific purpose. We analyzed 329 samples of chicken, turkey, and guinea fowl intestinal contents from Italian poultry flocks. Most samples were from enteritis outbreaks, but we also included samples from three longitudinal studies (one on 11 broiler flocks and the other two on a guinea fowl flock). We first examined the samples with nsEM. SRVs, including AstVs, are often associated with rotaviruses and were the most commonly detected morphotypes in avian enteric diseases. We then analyzed 124 of the samples with an RT-PCR targeting the open reading frame (ORF)-1b of AstV. This gene codes for an RNA-dependent polymerase. We then sequenced and genetically analyzed the RT-PCR positive samples. Phylogenetic analysis distinguished three defined clusters: the first included guinea fowl AstVs and turkey AstVs-2; the second, chicken AstVs; and the third was formed by avian nephritis viruses (ANVs). No strains clustered with turkey AstVs-1. The results indicate that ORF-1b presents certain genetic variability, even among AstVs from the same species. In longitudinal studies, samples retrieved from the same shed were homogeneous, with some exceptions suggesting possible coexistence of different genetic types in the same unit. The finding of ANV-like viruses in commercial guinea fowls underlines the genetic variability of AstVs and strengthens the hypothesis of a varied intraherd situation.

Authors

Canelli E, Cordioli P, Barbieri I, Catella A, Pennelli D, Ceruti R, Moreno A, Lavazza A

Source

Avian diseases 56:1 2012 Mar pg 173-82

MeSH

Amino Acid Sequence
Animals
Astroviridae Infections
Avastrovirus
Chickens
DNA, Viral
Enteritis
Feces
Galliformes
Italy
Microscopy, Electron
Molecular Sequence Data
Phylogeny
Poultry Diseases
RNA, Viral
Reverse Transcriptase Polymerase Chain Reaction
Sequence Analysis, RNA
Species Specificity
Turkeys

Pub Type(s)

Journal Article

Language

eng

PubMed ID

22545544