PHYLOGENETIC ANALYSES OF PORCINE ENTERIC CALICIVIRUS (SAPOVIRUS) REVEALS HIGHER FREQUENCY OF NON-COWDEN STRAINS IN BRAZILIAN PIG HERDS

Aline Fernandes Barry (UEL); Thaís Neris da Silva Medeiros (UEL); Alice Fernandes Alfieri (UEL); Amauri Alcindo Alfieri (UEL)

Sapoviruses are an important cause of gastroenteritis in children and elderly. In swine, a few studies associated the presence of the sapovirus (SaV) infection and diarrhea episodes. Sapovirus (SaV) is a positive sense ssRNA virus that belongs to Caliciviridae family. Based on the polymerase gene, this genus is divided into eight genogroups (G). Porcine sapoviruses are classified in GIII, GVI, GVII, and the more recently described, GVIII genogroups. The prototypes of these genogroups are Cowden, JJ681, K7/JP, and BRA04 strains. In the present study thirteen polymerase gene sequences of SaV were obtained by RT-PCR assay with primers p289/290. Stool samples were collected from 1 to 4 week-old piglets. The herds were situated in six (Mato Grosso, Mato Grosso do Sul, Minas Gerais, Paraná, Rio Grande do Sul, and Santa Catarina) Brazilian states from the main pig raising regions of the country (South, Southeast, and Center-West). The sequences were obtained in MegaBACE^TM 1000 using Thermo Sequenase™ II DNA Polymerase and DYEnamic™ ET Dye Terminator Kit with the forward and reverse primers. Molecular and phylogenetic analyses were performed in BioEdit v7.0.5.3 and MEGA4. Prototype strains for the dendrogram reconstruction were obtained at GenBank. The Cowden strain is the most frequently porcine SaV strain described. In the present study, based on phylogenetic analysis of a 151 bp polymerase fragment, only five sequences were classified in the GIII genogroup. One sequence was classified in GVII and the others six in GVIII genogroup. It was previously described that the SaV Cowden strain induced diarrhea in experimentally inoculated gnotobiotic piglets, and is the only strain associated with the disease yet. In Brazil, previous studies did not associate SaV infection with porcine diarrhea. Since most (61.5%) of the strains identified are not Cowden-like, the results herein presented suggest that the non-Cowden strains may induce more frequently asymptomatic infection justifying the negative correlation between the SaV and diarrhea. Furthermore, primers designed exclusively on Cowden strain, may underestimate the real SaV infection rate in pig herds and not detect the most circulating SaV genogroups.