Congenital Trypanosoma cruzi transmission in Santa Cruz, Bolivia

Abstract

Background: We conducted a study of congenital Trypanosoma cruzi infection in Santa Cruz, Bolivia. Our objective was to apply new tools to identify weak points in current screening algorithms, and find ways to improve them.

Methods: Women presenting for delivery were screened by rapid and conventional serological tests. For infants of infected mothers, blood specimens obtained on days 0, 7, 21, 30, 90, 180, and 270 were concentrated and examined microscopically; serological tests were performed for the day 90, 180, and 270 specimens. Maternal and infant specimens, including umbilical tissue, were tested by polymerase chain reaction (PCR) targeting the kinetoplast minicircle and by quantitative PCR.

Results: Of 530 women, 154 (29%) were seropositive. Ten infants had congenital T. cruzi infection. Only 4 infants had positive results of microscopy evaluation in the first month, and none had positive cord blood microscopy results. PCR results were positive for 6 (67%) of 9 cord blood and 7 (87.5%) of 8 umbilical tissue specimens. PCR-positive women were more likely to transmit T. cruzi than were seropositive women with negative PCR results (P < .05). Parasite loads determined by quantitative PCR were higher for mothers of infected infants than for seropositive mothers of uninfected infants P < .01). Despite intensive efforts, only 58% of at-risk infants had a month 9 specimen collected.

Conclusions: On the basis of the low sensitivity of microscopy in cord blood and high rate of loss to follow-up, we estimate that current screening programs miss one-half of all infected infants. Molecular techniques may improve early detection.

Figure 1

Flow chart of the study design, with the number of mothers and infants completing each step of the follow-up plan. The rapid diagnostic tests (RDTs) used for maternal specimens were the InBios Trypanosoma Detect test (InBios International) and the indirect hemagglutination assay (IHA); a subset of specimens were tested by Stat Pak (Chembio Diagnostic Systems). One woman had a false-positive IHA result. Specimens from 16 confirmed seropositive women yielded false-negative RDT results; follow-up was significantly less complete for the infants of these women than for infants of women with true-positive RDT results.

Figure 2

A, Nest of Trypanosoma cruzi amastigotes in hematoxylin-and-eosin–stained section of proximal umbilical cord tissue from infant 203. B, Nest of T. cruzi showing forms intermediate between amastigotes and trypomastigotes in hematoxylin-and-eosin–stained section of proximal umbilical cord tissue from infant 120. (Original magnification, ×1000). No inflammatory response was seen in infected umbilical cord tissue specimens.

Figure 3

Mean absorbance (optical density minus cutoff) for the whole epimastigote lysate enzyme-linked immunosorbent assay in specimens from uninfected infants of seropositive mothers at 3, 6, and 9 months of age. Error bars represent 1 standard deviation above and below the mean. The curve demonstrates the elimination of passively transferred maternal immunoglobulin G (IgG) antibodies over the first 9 months of life and confirms that conventional IgG serology should not be applied for infant diagnosis until at least 9 months of age.