Some factors influencing transmission of Toxoplasma in pregnant rats fed cysts

An overall 44% transplacental transmission rate was observed in 221 rats fe d cysts of 12 Toxoplasma strains at 15 days of pregnancy, with a range of 0 -90% transmission. Considerable variability in the transmission rate was se en among different groups of rats that received similar Toxoplasma inocula. this is attributed to genetically based susceptibility to Toxoplasma among individuals of the outbred Wistar strain of rats. Transplacental transmiss ion was more frequent in Long Evans than in Wistar rats. Significant differ ences in the rate of transmission were not found between rats that were fed similar Toxoplasma inocula 6-8 days or 15 days after conception. The frequ ency of transmission was not affected by the strain or dose of Toxoplasma u sed.