Study Of Experimental Animal Models Of Infection And Immunity Of Rabbits With Streptococcus Suis Serotype 2

Streptococcus suis serotype 2 is an important cause of meningitis, arthritis, endocarditis, septicemia, and sudden death in pigs. It is also increasingly becoming human health concern due to its zoonotic capabilities. In China, there were two epidemic outbreaks in 1998 and in 2005. S. suis 2 infection could not only lead to enormously economic loss but also severely threat to human.Molecular basis of infection and immunity of Streptococcus suis serotype 2 had not been deeply studied so far. Morbility and mechanism of transmission of the disease had not been clear, which made it hard to prevent and control the disease. Consequently, it is greatly essential to set up an animal model of infection and immunity of Streptococcus suis 2, for a further study on virulence factors and pathogenic mechanism of S. suis 2 infection.Rabbit was selected as the experimental animal in this study. Rabbits were inoculated with Streptococcus suis 2 virulent strain 458# and low virulent strain 5# and avirulent strain 1330# for effectiveness of infection and immunity. The results indicated that strain 458# can artificially infect rabbits. In the initial stage of morbility, rabbit infected strain 458# presented with clinical signs such as decreased food appetite and absolute diet, ophthalmia, nasal mucus and so on; in the advanced stage, they presented caput obliquum, nystaxis and ecphysesis et al. The results of pathoanatomical examination showed engorgement and haemorrhage of many organs, swelling of spleen, vascular engorgement on the surface of meninges. The histopathological lesion was disseminated intravascular coagulopathy(DIC) of mult-tissues. The clinical symptom and pathological changes of infected rabbits were similar with that of naturally infected pigs. Rabbit infected with low virulent strain 5# only manifested very slight clinical symptom, such as low-grade fever and depression. The histopathological lesion was slight disseminated intravascular coagulopathy(DIC) of mult-tissues. The results showed rabbit might be the experimental animal model for studying on the disease of S. suis 2 infection and evaluating virulence of S. suis 2.Rabbits immunized with avirulent strain 1330# didn't appear any pathological changes. The histopathological lesion was not obvious. The results of the examination was increment of splenic corpuscle and concentration of leukomonocyte. The investigative results indicated rabbit could be the experimental animal model for evaluating effectiveness of S. suis 2 vaccine.The experimental animal model of S. suis serotype 2 infection and immunity of rabbits, which would be helpful for further study on pathogenesis of S. suis and prevention of S. suis infection.