Establishment of Infectious Model of Streptococccus suis Type 2 by Tibet Mini-pig

Three Streptococccus suis type 2 strains were selected to infect Tibet mini-pigs in order to evaluate an experimental model with Tibet mini-pigs.Twelve piglets were allotted in 4 separated groups.Group A consisted of negative control animals which received broth medium.Groups B,C,and D were intravenously challenged with 2 mL of S.suis,strains GZ06-122B,SH06-21D and HA9801,respectively.The strain GZ06-122B and SH06-21D were isolated from tonsils of slaughter pigs in south of China,and genetype were sly-/mrp-/ef-and sly+/mrp+/ef+.The strain HA9801 was isolated from dead pig in Jiangsu.Pigs inoculated with strain GZ06-122B did not present clinical signs of S.suis infection.Contamination in organs and bacterial blood circulation were rare and lesions were almost non-existent.Infection of pigs with S.suis strain SH06-21D(group C) and HA9801(group D) caused severe clinical problems,animals infected with S.suis HA9801 were the most affected.Pigs presented clinical signs such as high body temperature,lameness,nervous symptoms,and even death.One week after inoculation,1 pig died in group C and 2 pigs died in group D.It can be concluded that S.suis strain HA9801 is most virulent,followed by SH06-21D and GZ06-122B.The results demonstrated that an experimental model with Tibet mini-pigs can be used for discriminating the virulence of different S.suis type 2 strains.