Pathogenicity comparison between porcine G9P[23] and G5P[23] RVA in piglets.

Rotavirus Group A (RVA) is a primary pathogen that causes viral diarrhea in humans and animals. Porcine rotaviruses (PoRVs) are widely epidemic in pig farms in China, causing great economic losses to the swine industry. In the past 30 years, the G5 RVA had been the main epidemic genotype in pig farms worldwide. However, G9 RVA is an emerging genotype that is gradually becoming prevalent in humans and animals. To explore its potential mechanism, we isolated G9P[23] and G5P[23] rotaviruses, named 923 H and NG523 respectively, from diarrheal samples and compared the growth curves and virulence of two strains. In vitro experiments revealed that pig small intestine epithelial cells were more susceptible to 923 H strain. In vivo experiments showed that 923 H strain was more virulent than NG523 strain, causing more severe damage to piglets. The viral load of G9 infection groups in intestinal and extra-intestinal tissues was higher than that of G5 infection group. Histopathological examination showed cell degeneration, necrosis and nuclear condensation in the jejunum of G9 RVA infection group as well as more inflammatory cell infiltration and tissue destruction in the lung of G9 RVA infection group. Our results indicate that 923 H strain is more pathogenic than NG523 strain, which provides new insights into the widespread epidemic of G9 RVA in pig farms.