Isolation and genotyping of Toxoplasma gondii from domestic rabbits in China to reveal the prevalence of type III strains

In this study, Toxoplasma gondii antibodies in 77 free domestic rabbits from a rural area surrounding Shanghai, China were analyzed via ELISA, which identified 18 seropositive rabbits. One strain of T. gondii (designated SHR) was successfully isolated from one seropositive rabbit using a mouse bioassay. The isolated T. gondii killed all BALB/c mice inoculated with 104 tachyzoites, indicating its virulence in mice. Mn-PCR-RFLP analysis was used to type parasites recovered from cell cultures. Further analysis based on sequencing of a polymorphic intron revealed that the isolated strain contained a clonal type III genome, a rare finding in any host in China. This is the first reported isolation of T. gondii genotype III from rabbits in China. Our results suggested that type III strains are circulating in rabbits in China, which act as potential reservoirs of T. gondii transmission.