Resumo

Bovine astrovirus (BoAstV) is a non-enveloped virus which has a single-stranded, positive sense RNA genome and belong to the genus Mamastrovirus of the family Astroviridae. Astroviruses were first identified in 1975 in children suffering from diarrhea and three years later astrovirus-like particles were described and reported in lambs and calves suffering from diarrhea. So far there is no report on the existence and diversity of BoAstV in cattle in Brazil. The goal of this study was to evaluate the presence and characterization of BoAstV in Brazilian herds by reverse transcription-polymerase chain reaction (RT-PCR) followed by nucleotide sequencing and phylogenetic analysis. A total of 122 diarrheic (n=97) and nondiarrheic (n=25) fecal specimens were collected from 114 calves (≤ 6 months old), 6 young cattle (≤ 2 years old), and 2 adults (> 2 years old). The fecal sampling was conducted in different farms from the states of São Paulo, Minas Gerais, Mato Grosso do Sul, Goiás, Rondônia, Paraná and Rio Grande do Sul. Fecal specimens of calves were obtained mainly from diarrheic animals (n=69) and dairy cattle contributed approximately 56.5% of all collected samples. The fecal samples were tested by RT-PCR with primers specific for pol gene of astroviruses. Twenty-eight (23%) out of 122 fecal samples tested positive. Positive samples were of diarrheic (n=21) and nondiarrheic (n=7) calves from dairy herds in São Paulo (n=17), Minas Gerais (n=10), and Mato Grosso do Sul (n=1) states. Five positive RT-PCR samples were submitted to nucleotide sequencing and phylogenetic analysis. Pairwise alignment and comparison revealed nucleotide sequence similarity >67.1% to other worldwide BoAstV. The phylogenetic data demonstrated that Brazilian bovine astroviruses clustered in a relative dispersal pattern to other worldwide BoAstV with three nucleotide sequences forming a monophyletic group and one nucleotide sequence being basal to other worldwide bovine and swine astroviruses. This finding is in compliance with other reports that indicate that single host species may be susceptible to infection by genetically distinct astroviruses. This is the first report of BoAstV detection in Brazil and it supports the assumption that BoAstV present a worldwide distribution. This work was financially supported by FAPESP (Proc. nº 2012/18441-0) and CNPq (Proc. nº 472509/2010-1).