Abstract
6 guinea-pigs were inoculated intraperitoneally at 4-54 days of pregnancy with 60 or 100 Toxoplasma cysts in mouse-brain saline suspension. All foetuses were infected. 3 sows died on 17-19th post-inoculation day, with signs of meningo-encephalitis, and displayed focal lymphocytic inflammation and, in 2, Toxoplasma rosette formation in the cerebral hemisphere. 6 Sows previoulsy inoculated with 100-200 cysts were followed in later pregnancy: 5 of 17 foetuses were found to be infected when delivered-a further 4, and 3 carneous moles, were not examined. 4 non-pregnant sows died at 12-14 days after inoculation with 100-200 cysts, with similar clinical signs to those in the first group.
Antibody titres of 256 were found at 2½ weeks, rising to a maximum of 16 384 at 6 weeks. Levels were consistently falling by 12-14 weeks.
Transmission across the placenta could not wholly be prevented by the presence of antibody except in high titre, and the important factor was concluded to be the parasitaemia.
The strain RB is midway in virulence in guinea-pigs between strains RH and 76.