Experimental congenital infection of Toxoplasma gondii in Macaca arctoides.

: Congenital toxoplasmosis was studied in Macaca arctoides as a model for primates. Time-mated female monkeys were assigned to 5 experimental groups and inoculated with 4 different strains of Toxoplasma gondii before pregnancy and during various stages of gestation. All monkeys showed a rise in indirect hemagglutination antibody (IHA) titers following infection, and some had demonstrable parasitemia. Of the 23 progeny, 2 were stillbirths and 2 died soon after birth, but only the one neonate born of a mother inoculated intrauterally succumbed to acute toxoplasmosis. No physical anomalies were observed in any of the progeny. The toxoplasms organism was not isolated from any of the placentas obtained nor from the cord blood. None of the tissues from the stillborn or infant monkeys that died were positive for toxoplasmosis by mouse inoculation. The live progeny were usually born with high IHA antibody titers which were usually soon lost, indicating presence of passively acquired maternal antibody. However, 2 babies, born of mothers infected with tissue cysts on day 79 and 149 of gestation, maintained moderate to high titers for about 8 and 19 months respectively, indicating that an active infection had taken place but no clinical disease was detected. Data obtained suggest that although certain developmental stages of the toxoplasma organism and of the fetus may favor the occurrence of congenital infection, very little neonatal disease results in this primate model.