High genetic diversity in RdRp gene of Brazilian porcine sapovirus strains.

Sapovirus is one genus within Caliciviridae family that causes diarrhea in humans and animals. Sapovirus (SaV) has been classified into seven genogroups (GI to GVII). The GIII, GVI, and GVII, which prototype is Cowden, JJ681, and K7/JP strains, respectively, infect pigs. The objective of this study was to characterize wild-type Brazilian SaV strains from piglet stool samples and determine SaV infection frequency, age distribution and association with diarrheic disease. Stool samples from 113 piglets up to 28-days-old were collected from 34 pig farms located in the States of Minas Gerais (MG), Mato Grosso do Sul (MS), Paraná (PR), Santa Catarina (SC), and Rio Grande do Sul (RS), during 2004 and 2005. The specimens were evaluated for enteric calicivirus by RT-PCR assay with primers p289/290, designed to detect the polymerase gene of SaV and norovirus. Thirty four (30.1%) samples were positive for SaV and five amplicons were sequenced. Phylogenetic analyses placed BRA29-MS/04 and BRA52-PR/05 sequences into the GIII of SaV genus. BRA04-SC/04, BRA21-RS/04, and BRA37-MG/05 demonstrated low identity with the Cowden strain but were closely related (up to 86.3%) to the Japanese and Dutch SaV strains, grouping together in a new cluster (GVIII?) in the phylogenetic tree. SaV infection was detected more frequently (p=0.0001) in animals between 22 and 28 days of age, in equal frequencies in piglets with and without diarrhea (p=0.59), and in the five Brazilian States. In this study, such as other unclassified worldwide SaVs, the Brazilian strains showed high genetic variability. Furthermore, the distribution and frequency of SaV infection provides evidence that the virus is circulating in Brazilian pig herds.