FETAL LOSS IN BALB C MICE INFECTED WITH NEOSPORA-CANINUM/

The suitability of mice as a model for reproductive loss due to Neospo ra caninum infection was investigated. Groups of mice were infected wi th 2 x 10(6) N. caninum before pregnancy (10 days) and during pregnanc y (days 5 and 10 of gestation). In mice infected before and during ear ly pregnancy, fetal loss was evaluated throughout gestation, and pregn ancy loss was evaluated by enumeration of fetal resorptions and total fetuses. In mice infected before pregnancy, no difference was present in resorptions between infected and control mice, although litter size was decreased in the infected mice (P < 0.05). In mice infected durin g early pregnancy (day 5 gestation) and examined temporally throughout gestation, resorptions were increased in the infected mice compared t o the control mice (P < 0.05). In mice infected at 5 days gestation an d examined at one time point (day 14 of gestation), the resorption rat e for infected mice was 33% and 12% for controls (P < 0.05). Routine h istopathologic examination and immunohistochemistry using N. caninum-s pecific antisera did not identify tachyzoites in placental and fetal t issues during the pre- and early pregnancy infections. In mice infecte d late midgestation (day 10), N. caninum tachyzoites were identified i n placenta and fetal muscle and neural tissue. In the placenta, there was multifocal necrosis and hemorrhage with intralesional tachyzoites. Tachyzoites in fetal tissues were not associated with pathologic chan ges. No reproductive loss was associated with mice infected late in ge station. These data demonstrate that mice can be used as a model for t he study of fetal resorption and congenital infection associated with N. caninum.