Background: Toxoplasmosis is an important zoonotic disease that can cause abortion in human and sheep. T.gondii is generally transmitted by infective oocysts excreted by the definitive host, the cat, Ingestion of undercooked meat and relatively rare by congenital transmission. In the present study, the effect of T.gondii strain isolate that was obtained from sheep was examined to produce congenital infection in the mouse model by IFAT and PCR. Materials and Methods: Twenty pregnant Swiss breed mice were divided four groups. The groups 1 to 3 were orally infected with 20 sporulated oocysts of T.gondii on day 5, 10 and 15 pregnancy, respectively. The group 4 was determined as control negative. The Fertility, litter size and mortality rate were monitored within two generations of consecutive pregnancies. Results: During a three months period of the study, all infected females showed antibodies against T.gondii, while the non- infected control mice remained seronegative. There was no difference in the fertility rate of the dams, or in the litter size of infected and control mice. Mortality of offspring of the first and second generations of the infected dams was observed within the first week of life. The vertical transmission was analyzed by serology and PCR methods in dam and offspring. In this study , the rate of vertical transmission in group 1, 2 and 3 were 100% , 60% and %50 in first generation ,respectively . In second generation, 82% of offspring were infected with T.gondii and the vertical transmission in Group1, 2 and 3 were were 100%, 100% and 50%, respectively. Conclusion: Based on the results, it is concluded that a non-virulent T.gondii isolate from sheep could be congenitally transmitted through successive generation of mice

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