Toxoplasmosis: Experimental Vaginal Infection in NMRI Mice and Its Effect on Uterin, Placenta and Fetus Tissues

BACKGROUND Toxoplasma gondii is an important zoonotic pathogen. Vertical transmission of the parasite occurs when females were infected primarily during gestation. This parasite is transmitted to the fetus through the placenta and may cause miscarriage, permanent neurological damage, premature birth and visual impairment. It has been found that mouse is susceptible to Toxoplasma and is particularly an interesting model to the study of congenital infection but whether the entry of T. gondii through vagina route is involved in transmission of the parasite to the placenta and fetus or not. OBJECTIVES The current study aimed to find a route of infection which perhaps carried the parasite under natural conditions in human. MATERIALS AND METHODS In the current experimental study, two 6-8 week NMRI female mice were crossed with one male. The pregnant mice were divided into 2 groups: experimental group that was infected by parasite via intra-vaginal (IV) and control group that received the same volume of normal saline via IV. One mouse from each group was killed on the fifth day after infection. The peritoneal fluid, ovary and uterus of mouse samples were taken and divided into two parts. One part used for DNA extraction and the other was kept in formalin and sent for histological study. These steps were repeated seven times and at least 10 mice in each group (case and control) were studied by molecular and histological methods. RESULTS PCR using DNA extracted from the experimental group showed that the parasite existed in tissues of the uterus and placenta but not in the embryos and peritoneal fluid. PCR using DNA extracted from the control group was negative. CONCLUSIONS Tachyzoite of Toxoplasma and DNA of this parasite were observed in sub mucosa and muscles of the uterus and in the villis of placenta, but not in histological sections of the fetus. Therefore, histological and molecular results were consistent.