Congenital transmission of Chagas disease by vector circulation zone in Bolivia.

Background: Bolivia has one of the highest burdens of Chagas disease. Transmission is most common through the triatomine bug vector carrying Trypanosoma cruzi infection, but a rising proportion of cases occurs through congenital transmission from mother to infant. Women living in endemic regions with high vector circulation are known to have an elevated risk of Chagas disease, but the relative risk of congenital transmission is unclear.

Methods: We performed a prospective observational study of pregnant women with Chagas disease and their infants at 11 hospitals in Bolivia from September 2020 to March 2023. High vector circulation zones were defined as having triatomine infestation in >3% of local homes. Congenital Chagas disease was diagnosed in infants using polymerase chain reaction (PCR) at birth, micromethod at birth and 1 month, or serology at 9 months.

Results: We enrolled 238 pregnant women, with a mean age of 28.7 years; 139 (58.4%) lived in high vector circulation areas. Of these, 19 women delivered infants who tested positive for T. cruzi infection (transmission rate 8.0%). Infants with congenital Chagas disease were significantly more likely to require hospitalization after birth (21.1% vs. 5.8%, p = 0.013). Women living in high vector circulation areas were more likely to have homes with mud walls (p < 0.001) and thatched roofs (p < 0.001) and to report having seen triatomine bugs in their home (p = 0.001). Congenital transmission rates did not significantly differ between women from low or high vector circulation zones (10.1% [9 of 139] vs. 6.5% [10 of 99], p = 0.31).

Conclusions: Congenital transmission of Chagas disease remains common through multiple regions of Bolivia, regardless of local vector circulation control, and is associated with markedly higher rates of infant hospitalization after birth.