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.

Here, in a screening of dog fecal samples, 26% (71/269) of the dogs with and without diarrhea were MAstV5 positive, as determined using RT-PCR. Likewise, non-viral agents and factors such as bacteria, intestinal parasites, malnutrition and intoxications are able to promote enteric disease mainly in the young dog population. The search for other enteric viruses in the MAstV5-positive samples from dogs with gastroenteritis showed that the dogs were also infected with other known pathogens. Moreover, we found that single MAstV5 infection was associated only with the asymptomatic state, although there is a risk that the results will be biased, since the analyzes were conducted on the basis of convenience sampling and we can not exclude the possibility that the long term of viral shedding could be an explanation for the MAstV5-positive samples detected in asymptomatic dogs, based on previous study that demonstrated the comparison between virus load and clinical manifestation 26 (Fig. 1 and Table 3 ). These findings were not unexpected, as mixed infections are common, but more studies will be necessary to real deduce the role of MAstV5 in the cases reported here. [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] Several reports of MAstV5 suggest a clinical association of virus molecular detection and diseased dog clinical samples. 18, [20] [21] [22] [23] 26, 33 Furthermore, studies of the prevalence of MAstV5 in China showed that 12% (22/183) of the puppies displaying clinical signs of diarrhea were positive for MAstV5, as determined using RT-PCR, compared to none of 138 healthy dogs, although these studies did not look for other viruses that may be associated with diarrhea. 19 In a study conducted in Italy, 24% of 110 stool samples collected from dogs with clinical signs tested positive for the presence of MAstV5 RNA, and 9% (10/110) of the samples showed an MAstV5single infection, although other asymptomatic animals (9% of 75) were also positive for MAstV5 33 . Therefore, the association with clinical signs and the shedding of the virus was described only in a case study of 2 animals, which is apparently an isolated case. 26 A prevalence study in France found that 21% (66/316) of the puppies in 42% (14/33) of the breeding kennels surveyed were MAstV5 positive, as determined using RT-PCR. 21 In the same report, the authors observed that puppies that were less than 7 weeks old were especially susceptible to MAstV5 infection, although a direct association with clinical signs was not possible. 21 Lastly, recent studies found a MAstV5 prevalence of 6% in the United Kingdom and an infection rate of 33% in puppies under three months in Japan. 22, 23 The partial genomic sequencing and characterization of selected samples revealed a remarkable genetic heterogeneity of MAstV5 of Brazilian origin. Because it was hypothesized that two strains of human AstV with less than 95% identity at the nucleotide level are serologically distinguishable, 34 the lower identities (<85%) shown between the capsid gene sequences analyzed here may reflect the need for a novel species classification into four genotypes -MAstV5a to MAstV5d. Additionally, phylogenetic analysis indicated that the four MAstV5 strains reported here represent a lineage that is more closely related to the Chinese strains than to the others strains, based on the high sequence identity (97%) of ORF2, according to the species demarcation criteria established by the ICTV 5 ( Table 2) .