1967 Volume 20 Issue 6 Pages 255-260,240
The sows used were divided into five groups and treated as follows: 3 doses of 2 ml of Ap-purified vaccine at a tissue concentration (TC) of 100% in group A, 3 doses of 2 ml of 1: 20 dilution of the same vaccine (at a TC of 5%) in group B, 3 doses of 2ml of commercial high-titer vaccine at a TC of 10% in group C, 2 doses of 10 ml of commercial ordinary vaccine at a TC of 1% in group D, and no doses in group E as untreated control.
These sows were also classified into four sections. Section I: those in which more than a month of the gestation period had been included in the prevailing period of Japanese encephalitis, or a 3-month period beginning with July. Section II: those which did not fall under this category. Section III: those which were highly suspected of having a history of natural infection in the previous year, since they were proved to have serum antibody before the present inoculation, or they were born earlier than June of the previous year. Section IV: those for which it was highly possible to be free from spontaneous infection, since they were proved to be negative for serum antibody before the present inocula tion, or they were born later than September of the previous year.
I. The rate of stillbirth was higher in section I than in section II.
2. There was no great difference in the rate of stillbirth between sections III and IV in group E (23.7 and 24.7% respectively). This rate was reduced remarkably in section III in groups A, B, and C (0, 0, and 6. 7% respectively). In section IV, however, it showed a significant decrease only in group A (16.2%).
