Toxoplasmosis in pregnant women is a major issue in maternal and neonatal health. Primary infection with Toxoplasma gondii during pregnancy exposes the fetus to a risk of vertical transmission that increases with gestational age: about 2% at 6 weeks, 23% at 18 weeks, and up to 56% at 30 weeks of amenorrhea . The earlier the infection, the more severe the fetal consequences, including neurological involvement, intracranial calcifications, and chorioretinitis [2] [3] . Early European cohorts, notably those of Desmonts and Couvreur , established the relationship between gestational age and transmission risk. The introduction of early diagnostic and therapeutic strategies reduced the frequency and severity of congenital forms [4] - [6] . This approach involves several steps: immediate spiramycin therapy, infection dating by IgG avidity, recourse to amniocentesis with PCR, and, if positive, initiation of a combination therapy including pyrimethamine and sulfadiazine. The SYROCOT international meta-analysis confirmed that treatment effectiveness largely depends on earliness [7] . In the United States, the Chicago collaborative study followed more than 200 infected children and showed that prolonged treatments improved neurological and visual outcomes into adolescence [8] . Finally, the waterborne outbreak in British Columbia highlighted environmental exposures and the value of an integrated One Health approach [9] .

In Africa, seroprevalence ranges from 30% to 50% depending on the setting. In Senegal, a study at Le Dantec Hospital reported a 34.5% seroprevalence among 941 pregnant women [10] . More recently, Diop et al. (2022) confirmed a prevalence of 28.9% among more than 10,000 pregnant women in Dakar, reflecting low population immunity [11] . Data from Ghana [12] and Nigeria [13] show similar profiles, while work from Morocco and Egypt confirms this regional vulnerability [14] [15] . A substantial proportion of pregnant women in sub-Saharan Africa is therefore exposed to the risk of seroconversion.

The Senegalese legal framework is a major constraint: medical termination of pregnancy is not authorized for fetal anomaly, including congenital infections. The Penal Code only provides for termination to save the mother’s life [16] [17] . In this context, close ultrasound follow-up and neonatal surveillance are the main pillars of care. Moreover, while other maternal-fetal infections (HIV, syphilis, hepatitis B, tuberculosis) benefit from free national protocols and malaria is addressed by a proactive policy with free intermittent preventive treatment (sulfadoxine-pyrimethamine, SP) and management of severe forms [18] - [21] , toxoplasmosis is not included in national programs, reinforcing the importance of local studies to adapt international recommendations to Senegalese realities.

This multicenter descriptive observational study was conducted between January and December 2024 in sixteen public maternity units in the Diamniadio Health District, Dakar region, Senegal ( Figure 1 ), following a standardized local protocol.

The study population comprised pregnant women who were seronegative (IgG⁻/IgM⁻) at the first antenatal visit in the first trimester and who had a confirmed seroconversion during follow-up. Exclusion criteria were lack of biological confirmation or incomplete ultrasound follow-up.

Laboratory. Toxoplasma serology was systematically performed in the first trimester. Immune women (IgG⁺) were not subjected to additional surveillance, whereas non-immune women (IgG⁻/IgM⁻) were monitored monthly to detect early seroconversion. Any initial positivity was confirmed in a reference laboratory by a second sample with an IgG avidity test to date the infection. Rapid serology used an OnSite® Toxo IgG/IgM immunochromatographic test (turnaround 24 h - 48 h). In case of positivity, confirmation was performed by chemiluminescence (CMIA) on an Abbott Alinity i® analyzer, with a positivity threshold of 10 IU/mL for IgG and an index ≥ 1.1 for IgM. IgG avidity was interpreted using standard thresholds: low if < 0.3, intermediate 0.3 - 0.5 requiring repeat testing at 2 - 3 weeks, and high if > 0.5. When seroconversion was confirmed, amniocentesis was offered from 18 weeks’ gestation and at least four weeks after infection. Amniotic fluid was analyzed by real-time PCR (Sacace® kit, Applied Biosystems 7500® platform) with a detection limit of ten copies/µL and an average turnaround of fourteen days. Costs ranged from 6,000 FCFA for rapid serology to 118,000 - 152,000 FCFA for PCR, as detailed in the annex. Senegal’s guaranteed minimum wage (SMIG) is 64,000 FCFA (about 100 euros per month).

Imaging and fetal follow-up. A standard mid-trimester morphology scan (22 -24 weeks) was systematically performed, in line with ISUOG and CNEOF standards. In case of seroconversion, targeted ultrasounds were scheduled every 2 - 3 weeks, with particular focus on the central nervous system, abdomen, and middle cerebral artery Doppler. Examinations were performed by obstetrician-gynecologists specialized in ultrasound using Mindray and SonoScape P9 devices with convex (2 MHz - 5 MHz) and endovaginal (5 MHz - 9 MHz) probes. Any suspicious finding was second-read by a specialist to ensure diagnostic reliability.

Therapy. Upon confirmation of seroconversion, spiramycin was started immediately. When amniocentesis was not performed or PCR was negative, this treatment was continued with close ultrasound surveillance. If PCR was positive, a triple therapy combining pyrimethamine, sulfadiazine, and folinic acid was introduced with weekly hematologic monitoring.

Data. Maternal data included age, gravidity, parity, obstetric history, and socio-epidemiological context (residence, cat exposure, gardening, dietary habits). Pregnancy follow-up included number of antenatal visits, serology schedule, and access conditions for tests. Each seroconversion was characterized by the date of the first negative sample, date of diagnosis, technique used, and quantitative values obtained. Obstetric management recorded spiramycin prescription and tolerance, amniocentesis and its results, ultrasound abnormalities (ventriculomegaly, calcifications, growth restriction, ascites, hepatosplenomegaly), and mode of delivery with indication. The Senegalese medico-legal context—absence of authorization for medical termination—was integral to the care pathway.

Neonatal. Parameters included gestational age at birth, weight, length, head circumference, Apgar score, and any resuscitation. Initial investigations comprised serology (IgG, IgM, IgA), PCR on blood or CSF, cranial ultrasound, and ophthalmologic exam. Short-term follow-up (1 - 3 months) assessed serologic dynamics, growth, neuroclinical progress, and complementary test results; at six months it evaluated psychomotor development, growth, potential complications (seizures, developmental delay, macrocrania), ophthalmologic exam, serology, and, if needed, EEG or MRI.

Outcomes. Primary endpoints were amniotic fluid PCR result, presence of significant ultrasound anomalies, 6-month neonatal outcome, and definitive confirmation of absence of infection by IgG negativization at 12 months.

Ethics. Data were anonymized and written consent was obtained for any invasive procedure. Management complied with national standards. The study adhered to the Declaration of Helsinki and was validated by the scientific committee of the Diamniadio Health District.

In 2024, a total of 22,691 antenatal consultations were recorded in the Diamniadio Health District, including 5,249 first-trimester first visits at which initial toxoplasma serology was systematically performed. Seven confirmed seroconversions were identified (incidence 0.13%).

This multicenter experience conducted in 2024 in the Diamniadio Health District shows that even in a resource-limited setting, it is possible to implement a pragmatic and reproducible protocol for managing toxoplasma seroconversion during pregnancy.

The strategy combining immediate spiramycin, serologic dating by IgG avidity, close ultrasound follow-up, selective amniocentesis, and triple therapy in case of positive PCR proved safe and adapted to local realities where medical termination for fetal anomaly is not authorized.

Several key lessons emerge:

1) most pregnant women remain vulnerable due to low seroprevalence, likely influenced by Sahelian environmental conditions (high sunlight, drought) that reduce oocyst survival;

2) economic (PCR and avidity costs) and sociocultural constraints (refusal of amniocentesis, absence of legal termination) limit optimal management;

3) serial ultrasound is central to distinguishing transient anomalies from persistent involvement and supports parental counseling;

4) limited availability of antiparasitics remains a major obstacle: in our series, treatment of the infected newborn could only be initiated thanks to family purchase of drugs abroad—illustrating both inequity of access and the decisive role of family solidarity.

Prevention should now be framed within an integrated One Health approach combining human, animal, and environmental health. Despite its limitations, this work underscores the urgency of integrating congenital toxoplasmosis into national maternal-fetal health programs alongside HIV, syphilis, hepatitis B, and malaria, to ensure test accessibility, treatment availability, and ultimately sustainably improve neonatal prognosis.

Costs of biological investigations related to toxoplasmosis in pregnancy.

1) Rapid serology test (On Site® IgG/IgM): 6,000 FCFA (≈ 9 €).

2) IgG avidity test: 67,000 FCFA (≈ 100 €).

3) Confirmatory serology (CMIA, Abbott Alinity i®): 12,000 FCFA (≈ 18 €).

4) Amniotic fluid PCR (Sacace® kit, Applied Biosystems 7500® platform): 118,000 - 152,000 FCFA (≈ 180 €- 230 €).

5) Minimum interprofessional guaranteed wage (SMIG, Senegal 2024): 64,000 FCFA/month (≈ 100 €).