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Open Access Research article

Incidence of maternal Toxoplasma infections in pregnancy in Upper Austria, 2000-2007

Ulrich Sagel123, Alexander Krämer1 and Rafael T Mikolajczyk14*

Author Affiliations

1 Department of Public Health Medicine, School of Public Health, University of Bielefeld, P.O. Box 10 01 31, D-33501 Bielefeld, Germany

2 analyse BioLab GmbH, Eisenhandstr. 4-6, A-4020 Linz, Austria

3 Institute of Hygiene and Mikrobiology, Lower Austria State Hospital of St. Pölten-Lilienfeld, Probst-Führer-Str. 4, A-3100 St. Pölten, Austria

4 Bremen Institute for Prevention Research and Social Medicine, Achterstr. 30, D-28359 Bremen, Germany

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BMC Infectious Diseases 2011, 11:348  doi:10.1186/1471-2334-11-348

Published: 14 December 2011

Abstract

Background

Despite three decades of prenatal screening program for toxoplasmosis in Austria, population-based estimates for the incidence of maternal infections with Toxoplasma gondii during pregnancy are lacking. We studied the incidence of primary maternal infections during pregnancy in the Federal State of Upper Austria.

Methods

Screening tests for 63,416 women and over 90,000 pregnancies (more than 84.5% of pregnancies in the studied region) in the time period between 01.01.2000 and 31.12.2007 were analysed. The incidence of toxoplasmosis was estimated indirectly by binomial and directly by interval censored regression.

Results

During the studied period, 66 acute infections (risk of 0.07% per pregnancy) were detected, but only 29.8% of seronegative women were tested at least three times during their pregnancies. The seroprevalence of Toxoplasma antibodies among all tested women was 31%. Indirectly estimated incidence (from differences in prevalence by age) was 0.5% per pregnancy, while directly estimated incidence (interval censored regression) was 0.17% per pregnancy (95% confidence interval: 0.13-0.21%).

Conclusions

Calculating incidence from observed infections results in severe underreporting due to many missed tests and potential diagnostic problems. Using statistical modelling, we estimated primary toxoplasmosis to occur in 0.17% (0.13-0.21%) of all pregnancies in Upper Austria.