Prenatal treatment for serious neurological sequelae of congenital toxoplasmosis: an observational prospective cohort study

BACKGROUND

The effectiveness of prenatal treatment to prevent serious neurological sequelae (SNSD) of congenital toxoplasmosis is not known.

METHODS AND FINDINGS

Congenital toxoplasmosis was prospectively identified by universal prenatal or neonatal screening in 14 European centres and children were followed for a median of 4 years. We evaluated determinants of postnatal death or SNSD defined by one or more of functional neurological abnormalities, severe bilateral visual impairment, or pregnancy termination for confirmed congenital toxoplasmosis. Two-thirds of the cohort received prenatal treatment (189/293; 65%). 23/293 (8%) fetuses developed SNSD of which nine were pregnancy terminations. Prenatal treatment reduced the risk of SNSD. The odds ratio for prenatal treatment, adjusted for gestational age at maternal seroconversion, was 0.24 (95% Bayesian credible intervals 0.07-0.71). This effect was robust to most sensitivity analyses. The number of infected fetuses needed to be treated to prevent one case of SNSD was three (95% Bayesian credible intervals 2-15) after maternal seroconversion at 10 weeks, and 18 (9-75) at 30 weeks of gestation. Pyrimethamine-sulphonamide treatment did not reduce SNSD compared with spiramycin alone (adjusted odds ratio 0.78, 0.21-2.95). The proportion of live-born infants with intracranial lesions detected postnatally who developed SNSD was 31.0% (17.0%-38.1%).

CONCLUSION

The finding that prenatal treatment reduced the risk of SNSD in infected fetuses should be interpreted with caution because of the low number of SNSD cases and uncertainty about the timing of maternal seroconversion. As these are observational data, policy decisions about screening require further evidence from a randomized trial of prenatal screening and from cost-effectiveness analyses that take into account the incidence and prevalence of maternal infection. Please see later in the article for the Editors' Summary.

Disease burden of congenital toxoplasmosis

Although the outcomes of toxoplasmosis have been well documented, an integrated estimate of the impact of this infection on the health status of the population is not available. "Disability-adjusted life years" are the sum of years of life lost and years lived with disability, weighted for the severity of the illness. The estimated disease burden of congenital toxoplasmosis in The Netherlands is 620 (range, 220-1900) disability-adjusted life years per year, which is similar to that for salmonellosis and is mainly caused by fetal loss and chorioretinitis. However, there is considerable uncertainty in this estimate. Scenario analysis indicates that the true burden may be underestimated. In other countries, the disease burden is expected to vary with the incidence of congenital infection, but it may also depend on the health care system. In countries that actively screen for toxoplasmosis, such as France, there may be a lower burden of morbidity but a higher burden of mortality.

[Fatal toxoplasmosis in children]

Fatal cases of toxoplasmosis seen at the Hospital Infantil de México between 1943 and 1973, together with postmortem studies are reviewed. There were five postmortem studies where it was possible to identify toxoplasma in histologic lesions. Clinical manifestations were grouped in pictures; thus, the infectious picture, the intracranial hypertensive, the neurological and the meningeal pictures were made up. In all five cases of this small group, toxoplasma was identified within and without parasitized cells and was found specially abundant in the central nervous system. Considering the early initiation of neurological manifestations and the intensity of encephalic lesions, it may be assumed that all five cases of prenatal toxoplasmosis. The reason why an infection so usually light in the mother is able to cause a disease so severe in the fetus seems to have an explanation on the fact that toxoplasma increases in virulence when reaching the product as second-step infection. In all five cases, the intensity of the lesions agrees with the severeness of the clinical picture and with the early manifestations following birth. The parasite was identified in the brain in all cases and in some of them, in the liver and lungs.