Toxoplasma gondii strains are remarkably clonal, and virulence in the mouse model is strongly influenced by the genotype of the parasite. Toxoplasma gondii infection in mice after immunohistochemical staining of various organs. Is the percentage of stained positive of the organs of the mice infected with the virulent strains less than the Intermediate strains can be happen? Isolates were previously reported to have different virulence and pathogenicity in mice(ToxoDB#9). (Chen, Z. W., Gao, J. M., Huo, X. X., Wang, L., Yu, L., Halm-Lai, F., et al. 2011.Genotyping of Toxoplasma gondii isolates from cats in different geographic regions of China. Vet. Parasitol. 183, 166–170. doi: 10.1016/j.vetpar.2011.06.013)