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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.

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  • Authors

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

    Institution

    Istituto Zooprofilattico della Lombardia e dell'Emilia Romagna (IZSLER), via Bianchi 9, 25124 Brescia (BS), Italy. elena.canelli@izsler.it

    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