engleski

Molecular analysis and phylogenetic relationship of astroviruses detected in domestic waterfowl

Avian astroviruses (AAstV) are the members of the Astroviridae family, and are classified upon the host in turkey, chicken and duck-origin astroviruses. Here we describe the molecular and phylogenetic analysis of chicken (chicken astrovirus ; CAstV, and avian nephritis virus ; ANV) and turkey-origin (turkey astrovirus 1 and 2 ; TAstV-1, TAstV-2) identified by reverse-transcription PCR (RT-PCR) and sequencing in commercial duck and goose flocks in Croatia. The aim of this study was to reveal phylogenetic diversity of AAstV newly identified in domestic waterfowl. The partial polymerase gene sequences from 14 ANVs detected in ducks and 2 in geese, 1 CAstV, 2 TAstV-1 and 3 TAstV-2 isolates from ducks were aligned together and analysed. Nucleotide sequences were phylogenetically analysed using Neighbour-joining method, based on the p-distance, while deduced amino acids were analysed by Poisson correction method. The highest level of nucleotide (67.1%) and amino acid (53.6%) conservation between compared astroviruses was observed among CAstV and TAstV-2 sequences. Conversely, the ANV group of sequences showed the highest genetic diversity of the polymerase gene fragment compared between chicken and turkey-origin astroviruses. On the molecular level, ANV sequences were more similar to both turkey-origin astroviruses (34.8-40.9%) than to CAstV (34.8%). Similarity among nucleotide ANV sequences (82.9-100%) was lower than in deduced amino acids (88.6-100%). The analysed sequences of turkey astroviruses detected in ducks showed genetic parity. Evolutionary distances between astroviruses were greater on amino acid, than on nucleotide level. The results showed that the relationship of different types of astroviruses detected in domestic waterfowl was consistent with analyses of astroviruses isolated from chicken and turkeys (Pantin-Jackwood et al., 2006). Phylogenetic analysis and both constructed trees showed that ANV was evolutionary distant astrovirus, while TAstV-1, TAstV-2 and CAstV formed more related group of sequences. The cluster of ANV sequences was divided in three subgroups, suggesting that different ANV genotypes were detected to circulate in duck and goose flocks, but no host-related genotypes were observed. ANV appeared to be the most frequently found and genetically diverse astrovirus in waterfowl. By knowing the fact that recombination can occure in astrovirus genome, further analyses are required to determine genotypes and serotypes of newly identified chicken and turkey-origin astroviruses identified in domestic waterfowl.

astroviruses; domestic waterfowl

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