Congenital toxoplasmosis: late pregnancy infections detected by neonatal screening and maternal serological testing at delivery

Abstract

The first aim of this study was to determine the prevalence of congenital toxoplasmosis in newborn infants treated by the public health system in Porto Alegre, a city in southern Brazil, using neonatal screening for Toxoplasma gondii-specific IgM. The second aim was to investigate whether the cases detected by this approach could have been identified by the prenatal screening for antibodies to T. gondii that was performed in the same population. A fluorometric assay was used to analyse T. gondii-specific IgM in filter paper specimens obtained from newborn infants for routine screening for metabolic diseases. When the specific IgM was positive, serum samples from the infant and the mother were requested for confirmatory serological testing, and the infant underwent clinical examination. Among 10 000 infants screened for T. gondii-specific IgM, seven filter paper samples were positive, and congenital toxoplasmosis was confirmed in six patients. The prevalence of IgM specific for T. gondii was 6/10 000 [95% CI 2/10 000, 13/10 000]. One infected infant had already been identified in the maternity ward before birth, three had been identified by maternal serology at delivery, and two infants with congenital toxoplasmosis were identified solely through neonatal screening. Although four mothers of the patients with congenital toxoplasmosis received prenatal care, and three mothers had one or two serological tests for T. gondii-specific antibodies (one at first trimester, one at first and second trimesters, and the other at second and third trimesters), they were not identified during pregnancy as infected. Neonatal screening identified cases of infection not detected by obtaining only one or two serum samples from pregnant women for T. gondii serology, mainly when infection was acquired and transmitted in late pregnancy. Maternal serology at delivery and neonatal screening were especially useful in the identification of infants with congenital toxoplasmosis when the mother did not receive regular prenatal serological testing or prenatal care.

Prevalence of acute toxoplasmosis infection among 41,112 pregnant women and the mother-to-child transmission rate in a public hospital in South Brazil

“…The prevalence of CTox by the end of the first year of life in our study (0.9/1,000 newborns) was comparable to that found at birth in other areas of Southern Brazil (Glasner et al 1992, Mozzatto & Procianoy 2003, Lago et al 2007. A prevalence of 5.0/1,000 newborns reported in Minas Gerais, Brazil, could partially be explained by the use of cord blood samples (Segundo et al 2004).…”

“…In the Southern region, the prevalence of congenital infection based on cord blood samples reached 0.8/1,000 births (95% CI: 0.02-4.45) (Mozzatto & Procianoy 2003). Other studies using blood samples adsorbed onto filter paper found prevalences from 0.3/1,000 (Neto et al 2000) to 0.6/1,000 newborns (Lago et al 2007). In Ribeirão Preto, São Paulo, another cross-sectional study also using blood samples adsorbed onto filter paper (Carvalheiro et al 2005) found a prevalence of 0.3/1,000 births.…”

Profile of pregnant women and children treated at a reference center for congenital toxoplasmosis in the northern state of Minas Gerais, Brazil

“…In fact, this has been one of the major dilemmas for studies such as ours, because a routine protocol has not been established, and it is difficult to define the parasitemia phase accurately 8,[18][19][20][21][22] . However, this finding is significant in relation to the large percentage of pregnant women with postnatal diagnosis, because of the presence of sequelae in their children.…”

Incidence of congenital toxoplasmosis in the city of Belém, state of Pará, northern Brazil, determined by a neonatal screening program: preliminary results

“…In addition, these states are performing toxoplasmosis diagnosis in newborns by measuring the levels of anti-T. gondii IgM or IgA antibodies in dry blood samples on filter paper obtained as part of the neonatal screening program for metabolic disorders 7,8 .…”