Co-circulation of distinct genetic lineages of astroviruses in turkeys and guinea fowl

Abstract

Viruses belonging to the genus Astrovirus have been increasingly associated with enteritis in mammalian and avian species, including turkeys. More recently, astroviruses have also been detected in diseased guinea fowl. In turkeys, two genetically distinct types of astrovirus have been reported, namely turkey astrovirus 1 and 2 (TAstV1 and TAstV2). The prevalence and the pathogenesis of astrovirus infections in this species is currently unknown, with the exception of data generated in the USA. In the present report, we have demonstrated the co-circulation of distinct genetic lineages of astroviruses infecting turkeys and guinea fowl. The predominant lineage infecting turkeys is genetically related to the American TAstV2, but genetic variability within this lineage was demonstrated. Other isolates appeared to be either TastV1-related or unrelated to any other known isolate. Astroviruses infecting guinea fowl were more closely related to TAstV2, and interspecies transmissions between turkeys and guinea fowl is suggested as a possible mechanism by which these viruses may have evolved, based on the genetic data available. This investigation provides genetic and epidemiological information contributing to a better understanding of enteric viral infections in turkeys and guinea fowl.

Experimental infection of poults and guinea fowl with genetically distinct avian astroviruses

“…Two genetically distinct viruses were used in this study: one TAstV2 (TK-6363) detected in 2003 in a commercial turkey farm (Cattoli et al, 2007); and one GFAstV (GF-5497), detected in 2009 in a commercial guinea fowl farm in Italy. Birds in these farms showed depression, severe enteritis and increased mortality (up to 30%), and from both farms the laboratory diagnosis of astrovirus infection was made based on electron microscopy examinations and confirmed by astrovirus-specific reverse transcriptase-polymerase chain reaction (RT-PCR) performed as previously described (Cattoli et al, 2007). Based on the phylogenetic analysis of the ORF1b sequence, the turkey virus TK-6363 and the guinea fowl virus GF-5497 are grouped into two separate clusters according to the distinction made by Cattoli et al (2007).…”

“…A genetically and antigenically distinct type of turkey astrovirus was then identified in 1996 (Turkey astrovirus type 2 [TAstV2]) by Koci et al (2000a). Since these first detections, enteritis in turkey has been increasingly associated with the presence of astroviruses (Cattoli et al, 2007;Pantin-Jackwood et al, 2007, 2008aDa Silva et al, 2008;Jindal et al, 2010a), although high astrovirus prevalence has also been reported in apparently healthy turkey flocks (PantinJackwood et al, 2007(PantinJackwood et al, , 2008aJindal et al, 2010b;Domanska-Blicharz et al, 2011). TAstV2 appears to be the most common among the identified turkey astroviruses, while TAstV1 and avian nephritis virus* an astrovirus first described as responsible for nephritis in chicken (Imada et al, 2000)*have only been detected sporadically in turkey flocks (Pantin-Jackwood et al, 2007, 2008aDomanska-Blicharz et al, 2011).…”

“…More recently, astroviruses have also been detected in diseased guinea fowl in Italy by Cattoli et al (2005Cattoli et al ( , 2007, but whether or not astroviruses were the causative agents of the clinical disease is still to be demonstrated. Although grouped separately in phylogenetic trees based on the open reading frame (ORF) 1b (viral RNAdependent RNA polymerase, RdRp) gene sequences, the guinea fowl astrovirus (GFAstV) appeared closely related to TAstV2, and for this reason the possibility of interspecies transmission between turkey and guinea fowl was proposed (Cattoli et al, 2007;De Battisti et al, 2012).…”

“…Although grouped separately in phylogenetic trees based on the open reading frame (ORF) 1b (viral RNAdependent RNA polymerase, RdRp) gene sequences, the guinea fowl astrovirus (GFAstV) appeared closely related to TAstV2, and for this reason the possibility of interspecies transmission between turkey and guinea fowl was proposed (Cattoli et al, 2007;De Battisti et al, 2012). On the other hand, sequences of the ORF2 gene, coding for the capsid protein of TAstV2 and GFAstV, imply a high level of divergence between these two viruses (De Battisti et al, 2012).…”

“…This is true especially for Avastroviruses, such as TAstV1 and TAstV2 (Tang et al, 2006;Cattoli et al, 2007;Pantin-Jackwood et al, 2008a), since data available to date have been generated only by few studies using the turkey as a model (Thouvenelle et al, 1995a, b;Behling-Kelly et al, 2002;Tang et al, 2006;Pantin-Jackwood et al, 2008b). These studies are insufficient for the complete understanding of the course of the disease.…”