The underestimated burden of placental schistosomiasis in endemic regions: Findings from a cross-sectional, diagnostic proof-of-concept study on placental schistosomiasis in Gabon.

BACKGROUND

Placental schistosomiasis (PS) is underdiagnosed and may compromise maternal and neonatal health. This study estimated the prevalence of PS in a rural Gabonese population of pregnant women with confirmed S. haematobium infection using light microscopy of macerated placental tissue.

METHODS

This is a cross-sectional, diagnostic proof-of-concept study which applied an improved placenta maceration technique in real-world conditions to diagnose PS. Performing light microscopic assessment of a single sample of 10 mL urine, we screened pregnant women for S. haematobium infection who sought antenatal care in Lambaréné (Gabon) between January 2022 and January 2023. Women positive for S. haematobium infection were followed up until delivery. Additionally, a subsample of women with negative urine samples was recruited as a non-infected control group (1:1 ratio infected and non-infected groups) and followed up until delivery. Only participants with available macerated placental samples were considered for final analysis. Placental samples were subjected to light-microscopy-based screening for S. haematobium eggs and PS was considered present if a least one S. haematobium egg was detected. Positive light microscopic placental samples were confirmed by qPCR.

RESULTS

Among 318 women screened for S. haematobium in urine, we found 40 (12.6%; 95% CI: 9.1-16.7%) to be positive. Together with 40 women in the non-infected control group all women were followed up until delivery. After loss-to-follow-up, 28 (70%; 28/40) women with S. haematobium infection and 20 (50%; 20/40) without infection provided placenta samples at delivery. In the group with S. haematobium infection, 14% (4/28; 95% CI: 4.0-32.7%) of women were positive for S. haematobium eggs in macerated placenta tissue. In the non-infected control group, one woman (5%; 1/20; 95% CI: 0.1-24.9%) had a positive microscopy result for PS. All five women with positive S. haematobium egg microscopy in placental tissue received a concordant qPCR result.

CONCLUSION

14% of women with S. haematobium infection also had PS. Notably, PS was also observed in 5% of women without detectable S. haematobium eggs in urine. This suggests that PS could be an underestimated phenomenon in highly endemic regions and warrants further investigations of its implications for mother-and-child health.