Identification and genetic comparison of VP1 gene of Seneca Valley Virus in Brazil

Vesicular disease has been described recently in Brazil and was associated to Seneca Valley virus (SVV). The clinical presentations were characterized by vesicular lesions in sows and acute losses of neonatal piglets. SVV has been identified in swine herds from United States, Canada, Australia, Italy, China and New Zealand. Few reports in Brazil characterized the virus circulating in outbreaks in the country and performed the phylogenetic analysis to better understand the epidemiology of the virus. Based on that, the objective of this study was to identify the SVV circulating in Brazil and perform the phylogenetic comparison with other virus from Brazil, US and China.

Thirteen samples: vesicular fluid (n=1), lungs (n=5), lymph nodes + spleen (n=7), submitted to our laboratory from clinical vesicular disease had the total RNA extracted using RNeasy™ kits (Qiagen) The RNA (10 μl) was used as the template in a one-step RT-PCR with the primers SVV1C556F (5’-TCGGTTTACTCCGCTGATGGTTGG-3’) and SVV-2A22R (5’-AGGACCAGGATTGGTCTCGATATC-3’)destined from SVV VP1 gene and using the following cycling conditions: 30 min at 42 °C, 5 min at 94 °C, and then 35 cycles of 1 min at 94 °C, 1 min at 55 °C and 1.5 min at 72 °C, followed by 5 min at 72 °C and held at 4 °C. PCR products were analyzed by electrophoresis using 1.5% agarose gels, ran at 120 Volts for 40 min and visualized using a gel documentation system. The positive samples had the DNA sequencing performed and compared with other SVV sequence available at online public database. The RNA samples were also tested for vesicular stomatitis.

The vesicular fluid sample was PCR positive for SVV and all samples were PCR negative for vesicular stomatitis. The SVV positive sample shared 99% of identity with the Brazilian SVV strains: SVV/BRA/GO3/2015, SVV/BRA/MG2/2015 and SVV/BRA/MG1/2015 and 98% of identity with strains BRA/UEL-SVV-A1/15 and BRA/UEL-SVV-B2/15. To North American SVV strain USA/IA40380/2015 shared 97% of identity and to USA/SD41901/2015 and USA/IA46008/201 shared 96% of identity. And to a Chinese strain CH-01-2015 was observed 96% of identity.

A considerable sequence identity between our strain and the other Brazilian strains were found. Evidence of the introduction of the SVV and the distribution of this virus in the country still unclear, however, further studies are being made to better understand and identify the distribution of SVV in Brazil. The characterization of this virus could contribute to future control strategies, especially to avoid positive replacement animals.

Disclosure of Interest: None Declared.