Detection and genetic characterization of Mamastrovirus 5 from Brazilian dogs

Alves, Christian D.B.T.; Budaszewski, Renata F.; Torikachvili, Marcela; Streck, André F.; Weber, Matheus N.; Cibulski, Samuel P.; Ravazzolo, Ana P.; Lunge, Vagner R.; Canal, Cláudio W.

Viruses belonging to the Astroviridae (AstV) family are spherical, non-enveloped, 28-30 nm in size, with a surface that forms a characteristic star-like structure. 1 The RNA genome of AstV ranges from 6.8 to 7.9-kb in size, polyadenylated at the 3 end, and contains three ORFs designated as ORF1a, ORF1b and ORF2. ORF1a encodes a protease, ORF1b encodes an RNA-dependent RNA-polymerase, 2,3 while ORF2 encodes the viral capsid structural polyprotein that is required for virion assembly. 4 The viral classification was previously based on the host and consisted of two genera, Avastrovirus and Mamastrovirus. However, recent characterization of novel astroviruses has taken in consideration that isolates from different animal species can be genetically similar, while genetically diverse viruses can be isolated from the same animal species. 2 Based on this analysis, the International Committee on Taxonomy of Viruses renamed canine astrovirus as Mamastrovirus 5 (MAstV5). 5 Astroviruses have been detected in fecal samples from a wide variety of mammals and birds that are associated with gastroenteritis. 2 In children, AstVs are the second most common cause of gastroenteritis after rotaviruses. 2, 6 Human AstVs can also cause significant disease in the elderly 7 and immune-compromised patients. 8, 9 In addition to enteric manifestations, AstVs have been associated with fatal hepatitis in ducks, 10 interstitial nephritis in young chickens, 11 stunting and pre hatching mortality in duck and goose embryos, 12 as well as shaking mink syndrome 13 . Recently, an AstV was also hypothesized to be the causative agent of nonsuppurative encephalitis in cattle. 14 Since the 1980s, astrovirus-like particles have been reported in dogs with and without diarrhea. [15] [16] [17] To date, canine astroviruses or astrovirus-like particles infecting dogs have been reported in several countries. [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] Despite the detection of MAstV5 in association with gastroenteritis in dogs, which suggests a possible role for MAstV5 as a canine enteric pathogen, the association of MAstV5 with clinical disease remains obscure in such reports. Here, we investigated the presence of MAstV5 using RT-PCR in fecal samples from dogs of different ages with and without diarrhea. The partial genomes of selected MAstV5 RNA-positive samples were also sequenced to perform a phylogenetic analysis comparing them with the MAstV5 sequences described in the literature as the cause of enteric disease. 18, 20, 23, 26 Additionally, MAstV5 was proposed to be classified in four putative genotypes.