Experimental studies on vertical infection of mice with Japanese encephalitis virus. II. Effect of inoculation route on placental and fetal infection.

Studies were made on the effect of the route of inoculation on the establishment of experimental vertical infection of mice with Japanese encephalitis virus. Mice of the three strains, CFW, C3H/He, and C57BL/6, were inoculated with a field strain of the virus by the intravenous, intraperitoneal, or subcutaneous route. An attempt was made on them to recover the virus from the placenta and fetus. As a result, there were differences in rate of plancental and fetal infection among the route of inoculation. It was dependent the establishment of vertical infection. In general, the rates of placental and fetal infection were the highest in the case of intravenous inoculation, the second highest in the case of intraperitoneal inoculation, and the lowest in the case of subcutaneous inoculation, although there were small differences in this tendency among the mouse strains used. The differences in the rates of placental and fetal infection were presumed to be derived not from the difference in the severity of infection of the respective mothers, but from the degree of direct approach of virus to the placenta as one of the factors.