detection of active toxoplasma gondii (rh strain) in the different body tissues of experimentally infected rats

objectives: toxoplasma gondii is a coccidian protozoon which forms tissue cyst in different organs of infected intermediate host. the present study was conducted to demonstrate the active form of parasite in different tissues of rat, which was experimentally infected with rh strain of toxoplasma gondii using bioassay method inmice. materials & methods: in the experimental assay, 75 rats and 500 mice were used. the rats were infected experimentally with 40-50 thousands of tachyzoites intrapritoneally. three rats were killed every 24 h then with up to three days 3 days interval for 60 days and their different organs were searched biologically for presence of the parasite. in this regard, the organs were squeezed with mortar in normal saline, diluted and following adding streptomycin and penicillin injected intrapritoneally in three outbreed mice each. then the mice were followed up for 10 days. results: toxoplasma cyst was found in brain, liver and spleen of the rats within 5 to 9 post infection. the parasite was appeared in heart and muscles within 9-13 days after infection but not found in the kidney. the parasite was disappeared in spleen and liver following12 and 28 days of infection respectively but remain active in the brain, heart and muscles within 60 days of the study. implication: toxoplasma gondii could remain active in spleen and liver of infected rat for a short time. meanwhile brain and muscles (heart and skeletal muscles) of the infected animal can keep the parasite for a long time. kidney is not appropriate tissue for toxoplasma gondii localization.