Congenital toxoplasmosis: an experimental study in rhesus monkeys for transmission and prenatal diagnosis

This paper describes a rhesus monkey model to study congenital transmission and the prenatal diagnosis of Toxoplasma gondii infection. Transmission to the fetus was investigated after maternal infection in the second (Day 90) or third trimester (Day 130) of pregnancy. A parasitemia was induced and lasted for about 10 days as proven by mouse inoculation and nested PCR on whole blood samples and peripheral blood mononuclear cells. Transmission of T. gondii was proven in 4 of 9 (44%) fetuses in the second trimester and in 3 of 9 fetuses in the third trimester of gestation. Six of the 7 proven fetal infections could be diagnosed antenatally. Postnatally, 4 additional fetuses that most likely were congenitally infected were found, although this could not formally be proven. The mothers of these 4 fetuses were infected in the third trimester. If we accept this group as being antenatally infected, an overall transmission rate is found of 11 of 18 cases (61%). This rate is similar to that found in humans. This is the first description of a monkey model for congenital toxoplasmosis, that is suitable to study the approach of antenatal diagnosis and the effectivity of treatment, with obvious relevance for Toxoplasma infections in humans.