Gerardo Sanchez

Trypanosoma cruzi-Infected Pregnant Women without Vector Exposure Have Higher Parasitemia Levels: Implications for Congenital Transmission Risk

Background Congenital transmission is a major source of new Trypanosoma cruzi infections, and as vector and blood bank control continue to improve, the proportion due to congenital infection will grow. A major unanswered question is why reported transmission rates from T. cruzi-infected mothers vary so widely among study populations. Women with high parasite loads during pregnancy are more likely to transmit to their infants, but the factors that govern maternal parasite load are largely unknown. Better understanding of these factors could enable prioritization of screening programs to target women most at risk of transmission to their infants. Methodology/Principal Findings We screened pregnant women presenting for delivery in a large urban hospital in Bolivia and followed infants of infected women for congenital Chagas disease. Of 596 women screened, 128 (21.5%) had confirmed T. cruzi infection; transmission occurred from 15 (11.7%) infected women to their infants. Parasite loads were significantly higher among women who transmitted compared to those who did not. Congenital transmission occurred from 31.3% (9/29), 15.4% (4/26) and 0% (0/62) of women with high, moderate and low parasite load, respectively (χx2 for trend 18.2; p<0.0001). Twin births were associated with higher transmission risk and higher maternal parasite loads. Infected women without reported vector exposure had significantly higher parasite loads than those who had lived in an infested house (median 26.4 vs 0 parasites/mL; p<0.001) with an inverse relationship between years of living in an infested house and parasite load. Conclusions/Significance We hypothesize that sustained vector-borne parasite exposure and repeated superinfection by T. cruzi may act as an immune booster, allowing women to maintain effective control of the parasite despite the down-regulation of late pregnancy.

Use of a Novel Chagas Urine Nanoparticle Test (Chunap) for Diagnosis of Congenital Chagas Disease

Background Detection of congenital T. cruzi transmission is considered one of the pillars of control programs of Chagas disease. Congenital transmission accounts for 25% of new infections with an estimated 15,000 infected infants per year. Current programs to detect congenital Chagas disease in Latin America utilize microscopy early in life and serology after 6 months. These programs suffer from low sensitivity by microscopy and high loss to follow-up later in infancy. We developed a Chagas urine nanoparticle test (Chunap) to concentrate, preserve and detect T. cruzi antigens in urine for early, non-invasive diagnosis of congenital Chagas disease. Methodology/Principal Findings This is a proof-of-concept study of Chunap for the early diagnosis of congenital Chagas disease. Poly N-isopropylacrylamide nano-particles functionalized with trypan blue were synthesized by precipitation polymerization and characterized with photon correlation spectroscopy. We evaluated the ability of the nanoparticles to capture, concentrate and preserve T. cruzi antigens. Urine samples from congenitally infected and uninfected infants were then concentrated using these nanoparticles. The antigens were eluted and detected by Western Blot using a monoclonal antibody against T. cruzi lipophosphoglycan. The nanoparticles concentrate T. cruzi antigens by 100 fold (western blot detection limit decreased from 50 ng/ml to 0.5 ng/ml). The sensitivity of Chunap in a single specimen at one month of age was 91.3% (21/23, 95% CI: 71.92%–98.68%), comparable to PCR in two specimens at 0 and 1 month (91.3%) and significantly higher than microscopy in two specimens (34.8%, 95% CI: 16.42%–57.26%). Chunap specificity was 96.5% (71/74 endemic, 12/12 non-endemic specimens). Particle-sequestered T. cruzi antigens were protected from trypsin digestion. Conclusion/Significance Chunap has the potential to be developed into a simple and sensitive test for the early diagnosis of congenital Chagas disease.

Prevalence and Transmission of Trypanosoma cruzi in People of Rural Communities of the High Jungle of Northern Peru

Background Vector-borne transmission of Trypanosoma cruzi is seen exclusively in the Americas where an estimated 8 million people are infected with the parasite. Significant research in southern Peru has been conducted to understand T. cruzi infection and vector control, however, much less is known about the burden of infection and epidemiology in northern Peru. Methodology A cross-sectional study was conducted to estimate the seroprevalence of T. cruzi infection in humans (n=611) and domestic animals [dogs (n=106) and guinea pigs (n=206)] in communities of Cutervo Province, Peru. Sampling and diagnostic strategies differed according to species. An entomological household study (n=208) was conducted to identify the triatomine burden and species composition, as well as the prevalence of T. cruzi in vectors. Electrocardiograms (EKG) were performed on a subset of participants (n=90 T. cruzi infected participants and 170 age and sex-matched controls). The seroprevalence of T. cruzi among humans, dogs, and guinea pigs was 14.9% (95% CI: 12.2 – 18.0%), 19.8% (95% CI: 12.7- 28.7%) and 3.3% (95% CI: 1.4 – 6.9%) respectively. In one community, the prevalence of T. cruzi infection was 17.2% (95% CI: 9.6 - 24.7%) among participants < 15 years, suggesting recent transmission. Increasing age, positive triatomines in a participants house, and ownership of a T. cruzi positive guinea pig were independent correlates of T. cruzi infection. Only one species of triatomine was found, Panstrongylus lignarius, formerly P. herreri. Approximately forty percent (39.9%, 95% CI: 33.2 - 46.9%) of surveyed households were infested with this vector and 14.9% (95% CI: 10.4 - 20.5%) had at least one triatomine positive for T. cruzi. The cardiac abnormality of right bundle branch block was rare, but only identified in seropositive individuals. Conclusions Our research documents a substantial prevalence of T. cruzi infection in Cutervo and highlights a need for greater attention and vector control efforts in northern Peru.

Etiological Role and Repeated Infections of Sapovirus among Children Aged Less than 2 Years in a Cohort Study in a Peri-urban Community of Peru

ABSTRACT Human sapovirus has been shown to be one of the most important etiologies in pediatric patients with acute diarrhea. However, very limited data are available about the causative roles and epidemiology of sapovirus in community settings. A nested matched case-control study within a birth cohort study of acute diarrhea in a peri-urban community in Peru from 2007 to 2010 was conducted to investigate the attributable fraction (AF) and genetic diversity of sapovirus. By quantitative reverse transcription–real-time PCR (qPCR) sapovirus was detected in 12.4% (37/299) of diarrheal and 5.7% (17/300) of nondiarrheal stools (P = 0.004). The sapovirus AF (7.1%) was higher in the second year (13.2%) than in the first year (1.4%) of life of children. Ten known genotypes and one novel cluster (n = 5) within four genogroups (GI, GII, GIV, and GV) were identified by phylogenetic analysis of a partial VP1 gene. Further sequence analysis of the full VP1 gene revealed a possible novel genotype, tentatively named GII.8. Notably, symptomatic reinfections with different genotypes within the same (n = 3) or different (n = 5) genogroups were observed in eight children. Sapovirus exhibited a high attributable burden for acute gastroenteritis, especially in the second year of life, of children in a Peruvian community. Further large-scale studies are needed to understand better the global burden, genetic diversity, and repeated infections of sapovirus.

Toward Improving Early Diagnosis of Congenital Chagas Disease in an Endemic Setting

Background Congenital Trypanosoma cruzi transmission is now estimated to account for 22% of new infections, representing a significant public health problem across Latin America and internationally. Treatment during infancy is highly efficacious and well tolerated, but current assays for early detection fail to detect >50% of infected neonates, and 9-month follow-up is low. Methods Women who presented for delivery at 2 urban hospitals in Santa Cruz Department, Bolivia, were screened by rapid test. Specimens from infants of infected women were tested by microscopy (micromethod), quantitative PCR (qPCR), and immunoglobulin (Ig)M trypomastigote excreted-secreted antigen (TESA)-blots at birth and 1 month and by IgG serology at 6 and 9 months. Results Among 487 infants of 476 seropositive women, congenital T. cruzi infection was detected in 38 infants of 35 mothers (7.8%). In cord blood, qPCR, TESA-blot, and micromethod sensitivities/specificities were 68.6%/99.1%, 58.3%/99.1%, and 16.7%/100%, respectively. When birth and 1-month results were combined, cumulative sensitivities reached 84.2%, 73.7%, and 34.2%, respectively. Low birthweight and/or respiratory distress were reported in 11 (29%) infected infants. Infants with clinical signs had higher parasite loads and were significantly more likely to be detected by micromethod. Conclusions The proportion of T. cruzi-infected infants with clinical signs has fallen since the 1990s, but symptomatic congenital Chagas disease still represents a significant, albeit challenging to detect, public health problem. Molecular methods could facilitate earlier diagnosis and circumvent loss to follow-up but remain logistically and economically prohibitive for routine screening in resource-limited settings.

Regional Variation in the Correlation of Antibody and T-Cell Responses to Trypanosoma cruzi

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, is a major cause of morbidity and mortality in Central and South America. Geographic variations in the sensitivity of serologic diagnostic assays to T. cruzi may reflect differences in T. cruzi exposure. We measured parasite-specific T-cell responses among seropositive individuals in two populations from South America with widely varying antibody titers against T. cruzi. Antibody titers among seropositive individuals were significantly lower in Arequipa, Peru compared with Santa Cruz, Bolivia. Similarly, the proportion of seropositive individuals with positive T-cell responses was lower in Peru than Bolivia, resulting in overall lower frequencies of interferon-γ (IFNγ)-secreting cells from Peruvian samples. However, the magnitude of the IFNγ response was similar among the IFNγ responders in both locations. These data indicate that immunological discrepancies based on geographic region are reflected in T-cell responses as well as antibody responses.

Field Evaluation of the InBios Chagas Detect Plus Rapid Test in Serum and Whole-Blood Specimens in Bolivia

ABSTRACT Trypanosoma cruzi causes Chagas disease, which affects an estimated 7 million to 8 million people. Chagas disease is endemic throughout Latin America, with the highest prevalence in Bolivia. Conventional diagnosis requires a well-equipped laboratory with experienced personnel. We evaluated the Chagas Detect Plus (CDP) (InBios, Seattle, WA), a rapid immunochromatographic assay for IgG antibodies to T. cruzi. CDP performance was compared to infection status based on results obtained by indirect hemagglutination assay, immunofluorescent-antibody test, and enzyme-linked immunosorbent assay. Confirmed infection required positive results by at least 2 conventional assays. We used specimens from adults of both sexes in a general hospital in the city of Santa Cruz and from pregnant women in a hospital and children in villages in the Bolivian Chaco, an area of hyperendemicity. CDP was performed in paired whole-blood and serum specimens from 385 individuals in the two hospital studies and in 200 serum specimens from the community study. CDP showed sensitivities/specificities of 96.2% (95% confidence interval, 92.7 to 98.4)/98.8% (95.9 to 99.9) in whole blood and 99.3% (97.5 to 99.9)/96.9% (94.2 to 98.6) in serum, with no differences by sex, age group, or study site. CDP showed excellent sensitivity and specificity in our study population, comparable to those of conventional serology. The test is reliable for field surveys, requires no laboratory equipment, and performed well in serum and whole blood. The CDP could also be used for accurate maternal screening to identify neonates at risk of congenital transmission. CDP performance data in diverse geographic areas are needed to strengthen the evidence base for its use.

Severity of Chagasic Cardiomyopathy Is Associated With Response To A Novel Rapid Diagnostic Test For Trypanosoma cruzi TcII/V/VI.

We describe a novel, point-of-care, rapid diagnostic test for Trypanosoma cruzi TcII/V/VI infection. Positive test response is associated with severity of Chagas cardiomyopathy. Repeated T. cruzi infection may exacerbate disease and boost immune response to this TSSApep-II/V/VI epitope.