Trypanosoma cruzi seroprevalence in pregnant women and screening by PCR and microhaematocrit in newborns from Guanajuato, Mexico

Chagas disease is caused by an infection with the protozoan hemoflagellate Trypanosoma cruzi, and it is a major endemic health problem in Latin America. The congenital route is one of the main non-vectorial pathways of transmission, which can arise either in the chronic or acute phase of maternal infection. Serological screening of T. cruzi infection was performed in 520 pregnant women and newborns at the Hospital General Regional de León, Guanajuato, Mexico, between 2014 and 2015. Anti-T. cruzi antibodies were detected in 20 mothers (4%) by ELISA and HIA with four PCR-positive newborn cases. Risk factors were identified according to an epidemiological survey, and the most significant (P<0.050) factors associated with T. cruzi infection were the building materials of dwellings, the presence of pets and dwellings located in rural areas. This study constitutes the first systematic study on congenital Chagas disease and the epidemiological risk factors in Guanajuato. Our results represent the probability of an incidence of 770 cases per 100,000 births during a period of 12 months, with a vertical transmission rate by 0.8%, which highlights the necessity to establish reliable serological and PCR tests in pregnant women to prevent vertical transmission. However, it is also important to follow-up the newborns from seropositive mothers for one year, which is necessary, as many children yielded negative results.

Development of a PCR Assay to Detect Low Level Trypanosoma cruzi in Blood Specimens Collected with PAXgene Blood DNA Tubes for Clinical Trials Treating Chagas Disease

Chagas disease is caused by the parasitic infection of Trypanosoma cruzi (T. cruzi). The STOP CHAGAS clinical trial was initiated in 2011 to evaluate posaconazole in treating Chagas disease, with treatment success defined as negative qualitative PCR results of detecting the parasites in blood specimens collected post-treatment. PAXgene Blood DNA tubes were utilized as a simple procedure to collect and process blood specimens. However, the PAXgene blood specimens challenged published T. cruzi PCR methods, resulting in poor sensitivity and reproducibility. To accurately evaluate the treatment efficacy of the clinical study, we developed and validated a robust PCR assay for detecting low level T. cruzi in PAXgene blood specimens. The assay combines a new DNA extraction method with a custom designed qPCR assay, resulting in limit of detection of 0.005 and 0.01 fg/μl for K98 and CL Brener, two representative strains of two of T. cruzi’s discrete typing units. Reliable qPCR standard curves were established for both strains to measure parasite loads, with amplification efficiency ≥ 90% and the lower limit of linearity ≥ 0.05 fg/μl. The assay successfully analyzed the samples collected from the STOP CHAGAS study and may prove useful for future global clinical trials evaluating new therapies for asymptomatic chronic Chagas disease.

Chagas disease is caused by the infection of the protozoan parasite Trypanosoma cruzi (T. cruzi) and carries a significant tropical disease burden in the Western Hemisphere. The STOP CHAGAS study was a global clinical trial evaluating therapies for Chagas disease. PAXgene blood DNA tubes used by the study simplified and standardized the sample collection and processing procedures, but challenged published PCR assays that detect circulating T. cruzi. In this study, we report our effort of developing and validating a robust, sensitive and specific PCR assay for detecting T. cruzi in PAXgene blood specimens. The efficacy outcome results of the STOP CHAGAS study that utilized our assay further support the use of the PCR assay as a marker of therapeutic response for patients with Chagas disease.

Bias due to methods of parasite detection when estimating prevalence of infection of Triatoma infestans by Trypanosoma cruzi

The study aimed to quantify the bias from parasite detection methods in the estimation of the prevalence of infection of Triatoma infestans by Trypanosoma cruzi, the agent of Chagas disease. Three common protocols that detect T. cruzi in a sample of 640 wild-caught T. infestans were compared: (1) the microscopic observation of insect fecal droplets, (2) a PCR protocol targeting mini-exon genes of T. cruzi (MeM-PCR), and (3) a PCR protocol targeting a satellite repeated unit of the parasite. Agreement among protocols was computed using Krippendorff Kα. The sensitivity (Se) and specificity (Sp) of each protocol was estimated using latent class models. The PCR protocols were more sensitive (Se > 0.97) than microscopy (Se = 0.53) giving a prevalence of infection of 17-18%, twice as high as microscopy. Microscopy may not be as specific as PCR if Trypanosomatid-like organisms make up a high proportion of the sample. For small T. infestans, microscopy is not efficient, giving a prevalence of 1.5% when PCR techniques gave 10.7%. The PCR techniques were in agreement (Kα = 0.94) but not with microscopy (Kα never significant with both PCR techniques). Among the PCR protocols, the MeM-PCR was the most efficient (Se=1; Sp=1).

Diversity of bats trypanosomes in hydroeletric area of Belo Monte in Brazilian Amazonia

The Trypanosoma comprises flagellates able to infect many mammalian species and is transmitted by several groups of invertebrates. The order Chiroptera can be infected by the subgenera Herpetosoma, Schizotrypanum, Megatrypanum and Trypanozoon. In this study, we described the diversity of bats trypanosomes, inferring the phylogenetic relationships among the trypanosomes from bats caught Belo Monte Hydroeletric area (Brazilian Amazonia). Trypanosomes from bats were isolated by haemoculture, and the molecular phylogeny based on small subunit rDNA (SSU rDNA) and glycosomal-3-phosphate dehydrogenase (gGAPDH) gene sequences. Morphological characterization included light and scanning electron microscopy. A total of 157 bats were caught in the area belonging 6 Families (Emballonuridae, Furipteridae, Mormoopidae, Natalidae, Phyllostomidae and Vespertilionidae) and 34 species. The bat trypanosome prevalence, as evaluated through haemoculture, was 5,7%. Phylogenetic trees grouped the isolates in T. cruzi branch (TCI and TCbat lineage), T. cruzi marinkellei and Trypanosoma wauwau from Pteronotus parnellii. This is the first isolate from T. wauwau in Para state. The occurrence of T. cruzi in the ​​ Belo Monte Hydroeletric area (UHE Belo Monte) in Amazon/Brazil attentive to the risk of migration human population required for the works of the dam and new cities that grow in the vicinity of these businesses, but it is a zoonosis already known to the Amazon region, and the presence of unclassified Trypanosoma species, attend to the large parasitic biodiversity still unknown.

Chagas Disease Diagnostic Applications: Present Knowledge and Future Steps

Chagas disease, caused by the protozoan Trypanosoma cruzi, is a lifelong and debilitating illness of major significance throughout Latin America and an emergent threat to global public health. Being a neglected disease, the vast majority of Chagasic patients have limited access to proper diagnosis and treatment, and there is only a marginal investment into R&D for drug and vaccine development. In this context, identification of novel biomarkers able to transcend the current limits of diagnostic methods surfaces as a main priority in Chagas disease applied research. The expectation is that these novel biomarkers will provide reliable, reproducible and accurate results irrespective of the genetic background, infecting parasite strain, stage of disease, and clinical-associated features of Chagasic populations. In addition, they should be able to address other still unmet diagnostic needs, including early detection of congenital T. cruzi transmission, rapid assessment of treatment efficiency or failure, indication/prediction of disease progression and direct parasite typification in clinical samples. The lack of access of poor and neglected populations to essential diagnostics also stresses the necessity of developing new methods operational in point-of-care settings. In summary, emergent diagnostic tests integrating these novel and tailored tools should provide a significant impact on the effectiveness of current intervention schemes and on the clinical management of Chagasic patients. In this chapter, we discuss the present knowledge and possible future steps in Chagas disease diagnostic applications, as well as the opportunity provided by recent advances in high-throughput methods for biomarker discovery.

Estimating the Burden of Chagas Disease in the United States

BACKGROUND

In recent years, there has been growing awareness of the significant burden of Chagas disease in the United States (US). However, epidemiological data on both prevalence and access to care for this disease are limited. The objective of this study is to provide an updated national estimate of Chagas disease prevalence, the first state-level estimates of cases of T. cruzi infection in the US and to analyze these estimates in the context of data on confirmed cases of infection in the US blood supply.

METHODS

In this study, we calculated estimates of the state and national prevalence of Chagas disease. The number of residents originally from Chagas disease endemic countries were computed using data on Foreign-Born Hispanic populations from the American Community Survey, along with recent prevalence estimates for Chagas disease in Latin America from the World Health Organization that were published in 2006 and updated in 2015. We then describe the distribution of estimated cases in each state in relation to the number of infections identified in the donated blood supply per data from the AABB (formerly American Association of Blood Banks).

FINDINGS

The results of this analysis offer an updated national estimate of 238,091 cases of T. cruzi infection in the United States as of 2012, using the same method as was used by Bern and Montgomery to estimate cases in 2005. This estimate indicates that there are 62,070 cases less than the most recent prior estimate, though it does not include undocumented immigrants who may account for as many as 109,000 additional cases. The state level results show that four states (California, Texas, Florida and New York) have over 10,000 cases and an additional seven states have over 5,000 cases. Moreover, since 2007, the AABB has reported 1,908 confirmed cases of T. cruzi infection identified through screening of blood donations.

CONCLUSIONS

This study demonstrates a substantial burden of Chagas disease in the US, with state variation that reflects the distribution of at risk Latin American immigrant populations. The study lends important new insight into the distribution of this disease in the US and highlights the need for further research quantifying prevalence and incidence to guide interventions for control of Chagas disease across the US.

One Health Interactions of Chagas Disease Vectors, Canid Hosts, and Human Residents along the Texas-Mexico Border

BACKGROUND

Chagas disease (Trypanosoma cruzi infection) is the leading cause of non-ischemic dilated cardiomyopathy in Latin America. Texas, particularly the southern region, has compounding factors that could contribute to T. cruzi transmission; however, epidemiologic studies are lacking. The aim of this study was to ascertain the prevalence of T. cruzi in three different mammalian species (coyotes, stray domestic dogs, and humans) and vectors (Triatoma species) to understand the burden of Chagas disease among sylvatic, peridomestic, and domestic cycles.

METHODOLOGY/PRINCIPAL FINDINGS

To determine prevalence of infection, we tested sera from coyotes, stray domestic dogs housed in public shelters, and residents participating in related research studies and found 8%, 3.8%, and 0.36% positive for T. cruzi, respectively. PCR was used to determine the prevalence of T. cruzi DNA in vectors collected in peridomestic locations in the region, with 56.5% testing positive for the parasite, further confirming risk of transmission in the region.

CONCLUSIONS/SIGNIFICANCE

Our findings contribute to the growing body of evidence for autochthonous Chagas disease transmission in south Texas. Considering this region has a population of 1.3 million, and up to 30% of T. cruzi infected individuals developing severe cardiac disease, it is imperative that we identify high risk groups for surveillance and treatment purposes.

The Type of Trypanosoma Cruzi Strain (Native or Non-Native) Used as Substrate for Immunoassays Influences the Ability of Screening Asymptomatic Blood Donors

BACKGROUND

The origin (native or non-native) of Trypanosoma cruzi strains used as substrate for immunoassays may influence their performance.

OBJECTIVE

To assess the performance of an immunoassay based on a native T. cruzi strain compared to another based on non-native T. cruzi strains, in asymptomatic blood donors from Mexico.

METHODS

Serum samples from a tertiary referral center were tested by both ELISA-INC9 (native) and Chagatest (non-native) assays. All reactive serum samples were further analyzed by indirect immunofluorescence.

RESULTS

Sera from 1,098 asymptomatic blood donors were tested. A 4.3 and 0.7% serum reactivity prevalence was observed using ELISA-INC9 and Chagatest, respectively (kappa = 0.13; -0.11 to 0.38). Subsequently, indirect immunofluorescence analyses showed higher positivity in serum samples reactive by ELISA-INC9 compared to those reactive by Chagatest (79 vs. 62.5%; p < 0.001). Furthermore, out of the 47 positive samples by both ELISA-INC9 and indirect immunofluorescence, only four (8.5%) were reactive in Chagatest assay. Meanwhile, four (80%) out of the five positive samples by both Chagatest and indirect immunofluorescence were reactive using ELISA-INC9.

CONCLUSION

Immunoassays based on a native T. cruzi strain perform better than those based on non-native strains, highlighting the need to develop and validate screening assays in accordance to endemic T. cruzi strains.

Chronic Chagas cardiopathy in Chile. Importance of Trypanosoma cruzi burden and clinical evaluation

Currently there are no biological markers to indicate which individuals with chronic indeterminate period of Chagas disease develop heart disease and who will remain all his life in this phase. The aim of this survey was to determine if Trypanosoma cruzi burden is related to the presence of heart disease in patients with chronic Chagas disease. 200 patients who had not been treated, 100 with cardiopathy and 100 without, groups A and B respectively, were submitted to clinical study and electrocardiogram, Echo-Doppler was performed for group A in which all important known causes of cardiopathy were discarded. In both groups xenodiagnosis, conventional PCR and quantitative PCR were undertaken. The 100 cardiopaths had 133 electrocardiographic alterations most of them in grade II of the New York Heart Association classification. 98 cardiopaths were classified in grade I by Echo-Doppler and only 2 cases were in grade III due to low ejection fraction. The difference in average parasitemia in patients of group A and B was not significant and no statistically differences were observed between average parasitemia of cardiopaths grade II versus grade I of NYHA. This results allow to characterize same clinical, electrocardiographical and parasitological features in chagasic cardiopaths of Chile.

Molecular Diagnosis of Chagas Disease in Colombia: Parasitic Loads and Discrete Typing Units in Patients from Acute and Chronic Phases

BACKGROUND

The diagnosis of Chagas disease is complex due to the dynamics of parasitemia in the clinical phases of the disease. The molecular tests have been considered promissory because they detect the parasite in all clinical phases. Trypanosoma cruzi presents significant genetic variability and is classified into six Discrete Typing Units TcI-TcVI (DTUs) with the emergence of foreseen genotypes within TcI as TcIDom and TcI Sylvatic. The objective of this study was to determine the operating characteristics of molecular tests (conventional and Real Time PCR) for the detection of T. cruzi DNA, parasitic loads and DTUs in a large cohort of Colombian patients from acute and chronic phases.

METHODOLOGY/PRINCIPAL FINDINGS

Samples were obtained from 708 patients in all clinical phases. Standard diagnosis (direct and serological tests) and molecular tests (conventional PCR and quantitative PCR) targeting the nuclear satellite DNA region. The genotyping was performed by PCR using the intergenic region of the mini-exon gene, the 24Sa, 18S and A10 regions. The operating capabilities showed that performance of qPCR was higher compared to cPCR. Likewise, the performance of qPCR was significantly higher in acute phase compared with chronic phase. The median parasitic loads detected were 4.69 and 1.33 parasite equivalents/mL for acute and chronic phases. The main DTU identified was TcI (74.2%). TcIDom genotype was significantly more frequent in chronic phase compared to acute phase (82.1% vs 16.6%). The median parasitic load for TcIDom was significantly higher compared with TcI Sylvatic in chronic phase (2.58 vs.0.75 parasite equivalents/ml).

CONCLUSIONS/SIGNIFICANCE

The molecular tests are a precise tool to complement the standard diagnosis of Chagas disease, specifically in acute phase showing high discriminative power. However, it is necessary to improve the sensitivity of molecular tests in chronic phase. The frequency and parasitemia of TcIDom genotype in chronic patients highlight its possible relationship to the chronicity of the disease.

Over Six Thousand Trypanosoma cruzi Strains Classified into Discrete Typing Units (DTUs): Attempt at an Inventory

Trypanosoma cruzi, the causative agent of Chagas disease, presents wide genetic diversity. Currently, six discrete typing units (DTUs), named TcI to TcVI, and a seventh one called TcBat are used for strain typing. Beyond the debate concerning this classification, this systematic review has attempted to provide an inventory by compiling the results of 137 articles that have used it. A total of 6,343 DTU identifications were analyzed according to the geographical and host origins. Ninety-one percent of the data available is linked to South America. This sample, although not free of potential bias, nevertheless provides today's picture of T. cruzi genetic diversity that is closest to reality. DTUs were genotyped from 158 species, including 42 vector species. Remarkably, TcI predominated in the overall sample (around 60%), in both sylvatic and domestic cycles. This DTU known to present a high genetic diversity, is very widely distributed geographically, compatible with a long-term evolution. The marsupial is thought to be its most ancestral host and the Gran Chaco region the place of its putative origin. TcII was rarely sampled (9.6%), absent, or extremely rare in North and Central America, and more frequently identified in domestic cycles than in sylvatic cycles. It has a low genetic diversity and has probably found refuge in some mammal species. It is thought to originate in the south-Amazon area. TcIII and TcIV were also rarely sampled. They showed substantial genetic diversity and are thought to be composed of possible polyphyletic subgroups. Even if they are mostly associated with sylvatic transmission cycles, a total of 150 human infections with these DTUs have been reported. TcV and TcVI are clearly associated with domestic transmission cycles. Less than 10% of these DTUs were identified together in sylvatic hosts. They are thought to originate in the Gran Chaco region, where they are predominant and where putative parents exist (TcII and TcIII). Trends in host-DTU specificities exist, but generally it seems that the complexity of the cycles and the participation of numerous vectors and mammal hosts in a shared area, maintains DTU diversity.

Taxonomic and predicted metabolic profiles of the human gut microbiome in pre-Columbian mummies

Characterization of naturally mummified human gut remains could potentially provide insights into the preservation and evolution of commensal and pathogenic microorganisms, and metabolic profiles. We characterized the gut microbiome of two pre-Columbian Andean mummies dating to the 10-15th centuries using 16S rRNA gene high-throughput sequencing and metagenomics, and compared them to a previously characterized gut microbiome of an 11th century AD pre-Columbian Andean mummy. Our previous study showed that the Clostridiales represented the majority of the bacterial communities in the mummified gut remains, but that other microbial communities were also preserved during the process of natural mummification, as shown with the metagenomics analyses. The gut microbiome of the other two mummies were mainly comprised by Clostridiales or Bacillales, as demonstrated with 16S rRNA gene amplicon sequencing, many of which are facultative anaerobes, possibly consistent with the process of natural mummification requiring low oxygen levels. Metagenome analyses showed the presence of other microbial groups that were positively or negatively correlated with specific metabolic profiles. The presence of sequences similar to both Trypanosoma cruzi and Leishmania donovani could suggest that these pathogens were prevalent in pre-Columbian individuals. Taxonomic and functional profiling of mummified human gut remains will aid in the understanding of the microbial ecology of the process of natural mummification.

Chagas Disease Screening in Maternal Donors of Publicly Banked Umbilical Cord Blood, United States

To assess patterns of Chagas disease, we reviewed results of screening umbilical cord blood from a US public cord blood bank during 2007–2014. Nineteen maternal donors tested positive for Trypanosoma cruzi parasites (0.04%). Because perinatal transmission of Chagas disease is associated with substantial illness, targeted prenatal programs should screen for this disease.

Quantification by real-time PCR of Trypanosoma cruzi DNA in samples of Triatoma infestans used in xenodiagnosis of chronic Chagas disease patients

BACKGROUND

Trypanosoma cruzi multiplies and differentiates in the digestive tract of triatomine insects. Xenodiagnosis (XD) is a parasitological tool in which the insect vectors acts as a biological culture medium to amplify and detect T. cruzi infection in mammals. The sensitivity of XD has been overcome by the application of PCR in fecal samples (FS) of XD (PCR-XD). In this study, T. cruzi amplified in Triatoma infestans fed by XD on individuals with chronic Chagas disease (CChD) is quantified by real-time PCR (qPCR-XD).

FINDINGS

Under informed consent, 100 individuals were evaluated. In 21 of them XD, PCR-XD and qPCR-XD were positive. For the contrary, 79 were negative XD. In 58 (73.4 %) and 66 cases (83.5 %) of them, PCR-XD (Fisher's exact test P = 0.005) and qPCR-XD (Fisher's exact test: P = 0.037) respectively, were positive. In cases with positive XD, qPCR-XD allowed to establish that in 9/21 cases (42.9 %) the parasite burden fluctuated between 100 and 1,000 par. eq./ml. Otherwise, in 32/79 (40.5 %) cases with negative XD, a parasite burden between 1 and 10 par. eq./ml was determined. All samples showed amplification of exogenous internal control (X12, Ct average: 31.8), so problems in the DNA extraction (excess or loss of genetic material), unspecific amplification and/or inhibition in qPCR-XD reactions were ruled out. Additionally, in all the patients qPCR in blood (qPCR-B) was performed. In the cases with positive XD, the concordance between the positivity of qPCR-XD and qPCR-B was 100 %, nevertheless, the parasite burden in blood was lower and different than XD (Chi-square test: χ (2)  = 91.82, df = 5, P = 0.0001). In the cases with negative XD the ranges of qPCR-XD and qPCR-B were similar (Chi-square test: χ (2)  = 6.71, df = 5, P = 0.1520).

CONCLUSIONS

This study allowed the detection and quantification of T. cruzi by qPCR-XD in FS of Tr. infestans fed on patients with CChD. The highest parasite burden was observed in positive XD cases. qPCR-XD could be used in different studies related with the complex T. cruzi-vector-host interactions.

Trypanosoma cruzi Infection Prevalence and Bloodmeal Analysis in Triatomine Vectors of Chagas Disease From Rural Peridomestic Locations in Texas, 2013-2014

Protozoan pathogen Trypanosoma cruzi (Chagas, 1909) is the etiologic agent of Chagas disease, which affects millions of people in Latin America. Recently, the disease has been gaining attention in Texas and the southern United States. Transmission cycle of the parasite involves alternating infection between insect vectors and vertebrate hosts (including humans, wildlife, and domestic animals). To evaluate vector T. cruzi parasite burden and feeding patterns, we tested triatomine vectors from 23 central, southern, and northeastern counties of Texas. Out of the 68 submitted specimens, the majority were genetically identified as Triatoma gerstaeckeri (Stal, 1859), with a few samples of Triatoma sanguisuga (LeConte, 1855), Triatoma lecticularia (Stal, 1859), Triatoma rubida (Uhler, 1894), and Triatoma protracta woodi (Usinger, 1939). We found almost two-thirds of the submitted insects were polymerase chain reaction-positive for T. cruzi Bloodmeal sources were determined for most of the insects, and 16 different species of mammals were identified as hosts. The most prevalent type of bloodmeal was human, with over half of these insects found to be positive for T. cruzi High infection rate of the triatomine vectors combined with high incidence of feeding on humans highlight the importance of Chagas disease surveillance in Texas. With our previous findings of autochthonous transmission of Chagas disease, urgent measures are needed to increase public awareness, vector control in and around homes, and Chagas screening of residents who present with a history of a triatomine exposure.

Chagas Cardiomyopathy: Usefulness of EKG and Echocardiogram in a Non-Endemic Country

BACKGROUND

Chagas disease (CD) is a major cause of cardiomyopathy in Latin America, and migration movements have now spread the disease worldwide. However, data regarding Chagas cardiomyopathy (CC) and the usefulness of echocardiography in non endemic countries are still scarce.

METHODS AND RESULTS

We selected 485 patients in the chronic phase of CD from two Spanish settings. Data from physical examination, electrocardiogram (EKG), x-ray, and two dimensional transthoracic echocardiogram were recorded. Trypanosoma cruzi DNA was assessed by PCR in peripheral blood. Patients were stratified according to the Kuschnir classification and a combination of echocardiogram and electrocardiogram findings. Patients mainly came from Bolivia (459; 94.6%). One hundred and forty three patients (31.5%) had at least one electrocardiogram abnormality. Twenty seven patients (5.3%) had an abnormal echocardiography. Patients with abnormal echocardiography were older (47 (IQR 38-57) years vs 41 (IQR 38-57) years); p = 0.019) and there was a greater proportion of males (66.7% vs 29.7%); p<0.001). Among echocardiographic variables, diastolic dysfunction was associated with poor cardiac status. In the multivariate analysis, abnormal EKG and gender were associated with abnormal echocardiography. Echocardiography may be spared for males under 30 and females under 45 years old with normal EKG as the likelihood of having an abnormal echocardiography is minimal. Association between T. cruzi DNA in the peripheral blood and cardiac involvement was not observed.

CONCLUSION

CC rates in the studied population are low. Age and sex are important determinants for the development of CC, and with the EKG should guide echocardiogram performance.

Vector capacity of members of Triatoma brasiliensis species complex: The need to extend Chagas disease surveillance to Triatoma melanica

We conducted a lab-based comparative study on vector capacity features of two species of triatomines: Triatoma brasiliensis and T. melanica. Both are members of the T. brasiliensis species complex. The former is the most important Chagas disease vector in the northeastern region of Brazil. To date, no transmission via T. melanica has been recorded. Immature insects exhibited distinct intermoult periods without a direct relationship to a given species. Females of T. brasiliensis consumed an average of 1.9 times more meals (mean = 12.92 vs 6.63) and survived for a shorter period (mean =330.8 days) than T. melanica (mean = 365.2 days), probably due to the cost of reproduction (all significant at P<0.05). These data support the idea that T. brasiliensis is more adapted to lab conditions and is more able to infest domiciles than T. melanica. We also found significant distinctions in other features between these species, such as the elapsed time without eating before molting, which was higher for the second, third, and fifth nymph stages of T. melanica. Regarding features analyzed related to vector capacity, insects of all life stages of both species were considered competent to transmit Trypanosoma cruzi because they needed many feedings (mean =1.5-3.82) to moult and because a high proportion (>39%) of insects defecated rapidly (<30 s) after feeding. Overall, results highlight the need to extend vector surveillance to T. melanica.

Detection and Quantification of Viable and Nonviable Trypanosoma cruzi Parasites by a Propidium Monoazide Real-Time Polymerase Chain Reaction Assay

Molecular techniques based on real-time polymerase chain reaction (qPCR) allow the detection and quantification of DNA but are unable to distinguish between signals from dead or live cells. Because of the lack of simple techniques to differentiate between viable and nonviable cells, the aim of this study was to optimize and evaluate a straightforward test based on propidium monoazide (PMA) dye action combined with a qPCR assay (PMA-qPCR) for the selective quantification of viable/nonviable epimastigotes of Trypanosoma cruzi PMA has the ability to penetrate the plasma membrane of dead cells and covalently cross-link to the DNA during exposure to bright visible light, thereby inhibiting PCR amplification. Different concentrations of PMA (50-200 μM) and epimastigotes of the Maracay strain of T. cruzi (1 × 10(5)-10 parasites/mL) were assayed; viable and nonviable parasites were tested and quantified by qPCR with a TaqMan probe specific for T. cruzi. In the PMA-qPCR assay optimized at 100 μM PMA, a significant qPCR signal reduction was observed in the nonviable versus viable epimastigotes treated with PMA, with a mean signal reduction of 2.5 logarithm units and a percentage of signal reduction > 98%, in all concentrations of parasites assayed. This signal reduction was also observed when PMA-qPCR was applied to a mixture of live/dead parasites, which allowed the detection of live cells, except when the concentration of live parasites was low (10 parasites/mL). The PMA-qPCR developed allows differentiation between viable and nonviable epimastigotes of T. cruzi and could thus be a potential method of parasite viability assessment and quantification.

Genomic African and Native American Ancestry and Chagas Disease: The Bambui (Brazil) Epigen Cohort Study of Aging

BACKGROUND

The influence of genetic ancestry on Trypanosoma cruzi infection and Chagas disease outcomes is unknown.

METHODOLOGY/PRINCIPAL FINDINGS

We used 370,539 Single Nucleotide Polymorphisms (SNPs) to examine the association between individual proportions of African, European and Native American genomic ancestry with T. cruzi infection and related outcomes in 1,341 participants (aged ≥ 60 years) of the Bambui (Brazil) population-based cohort study of aging. Potential confounding variables included sociodemographic characteristics and an array of health measures. The prevalence of T. cruzi infection was 37.5% and 56.3% of those infected had a major ECG abnormality. Baseline T. cruzi infection was correlated with higher levels of African and Native American ancestry, which in turn were strongly associated with poor socioeconomic circumstances. Cardiomyopathy in infected persons was not significantly associated with African or Native American ancestry levels. Infected persons with a major ECG abnormality were at increased risk of 15-year mortality relative to their counterparts with no such abnormalities (adjusted hazard ratio = 1.80; 95% 1.41, 2.32). African and Native American ancestry levels had no significant effect modifying this association.

CONCLUSIONS/SIGNIFICANCE

Our findings indicate that African and Native American ancestry have no influence on the presence of major ECG abnormalities and had no influence on the ability of an ECG abnormality to predict mortality in older people infected with T. cruzi. In contrast, our results revealed a strong and independent association between prevalent T. cruzi infection and higher levels of African and Native American ancestry. Whether this association is a consequence of genetic background or differential exposure to infection remains to be determined.

Host-Feeding Sources and Infection With Trypanosoma cruzi of Triatoma infestans and Triatoma eratyrusiformis (Hemiptera: Reduviidae) From the Calchaqui Valleys in Northwestern Argentina

We assessed the prevalence of infection with Trypanosoma cruzi, parasite genotypes (discrete typing units, DTUs), and the host-feeding sources of domestic and peridomestic Triatoma infestans Klug and Triatoma eratyrusiformis Del Ponte in eight rural communities of the subandean Calchaqui valleys in northwestern Argentina. We sought to analyze their epidemiological role in the context of routine vector surveillance and control actions. Infection with T. cruzi was determined by optic microscopy or polymerase chain reaction (PCR) amplification of the hypervariable region of kinetoplast DNA minicircles. Parasite genotypes were identified through a multi PCR-based strategy. Bloodmeal contents were tested with a direct ELISA assay against nine antisera. Human sleeping quarters (domiciles) and peridomestic dry-shrub fences concentrated most of the T. infestans and T. eratyrusiformis infected with T. cruzi, respectively. The most frequent host-feeding sources of T. infestans were chickens (73.1%) in peridomiciles and humans (73.3%) in domiciles, whereas T. eratyrusiformis fed more often on cavid rodents (92.6%), which thrived in the dry-shrub fences. The main T. cruzi DTU identified in both vectors was T. cruzi I (TcI). Triatoma eratyrusiformis was implicated in the local circulation of TcI among cavies and perhaps mice, but infection with other typically domestic DTUs (TcVI and TcII/TcV/TcVI) indicated overlap between (peri)domestic transmission cycles in both vector species. Because dry-shrub fences were not targeted for routine insecticide spraying, they may act as sources of (peri)domestic reinfestation. Triatoma eratyrusiformis is an emergent secondary vector of T. cruzi and plays a significant role in the local transmission of T. cruzi.

Genotyping of Trypanosoma cruzi DTUs and Trypanosoma rangeli genetic groups in experimentally infected Rhodnius prolixus by PCR-RFLP

The specific detection and genetic typing of trypanosomes that infect humans, mammalian reservoirs, and vectors is crucial for diagnosis and epidemiology. We utilized a PCR-RFLP assay that targeted subunit II of cytochrome oxidase and 24Sα-rDNA to simultaneously detect and discriminate six Trypanosoma cruzi discrete typing units (DTUs) and two genetic groups of Trypanosoma rangeli (KP1+/KP1-) in intestinal contents of experimentally infected Rhodnius prolixus. The PCR assays showed that in 23 of 29 (79.4%) mixed infections with the six T. cruzi DTUs and mixed infections with individual DTUs and/or groups KP1+ and KP1-, both parasites were successfully detected. In six mixed infections that involved TcIII, the TcI, TcII, TcV, and TcVI DTUs predominated to the detriment of TcIII, indicating the selection of genetic groups. Interactions between different genetic groups and vectors may lead to genetic selection over TcIII. The elimination of this DTU by the immune system of the vector appears unlikely because TcIII was present in other mixed infections (TcIII/TcIV and TcIII/KP1+). Both molecular markers used in this study were sensitive and specific, demonstrating their usefulness in a wide geographical area where distinct genotypes of these two species are sympatric. Although the cellular and molecular mechanisms that are involved in parasite-vector interactions are still poorly understood, our results indicate a dynamic selection toward specific T. cruzi DTUs in R. prolixus during mixed genotype infections.

Shelter dogs as sentinels for Trypanosoma cruzi transmission across Texas

Chagas disease, an infection with the parasite Trypanosoma cruzi, is increasingly diagnosed among humans in the southern United States. We assessed exposure of shelter dogs in Texas to T. cruzi; seroprevalence across diverse ecoregions was 8.8%. Canine serosurveillance is a useful tool for public health risk assessment.

Cost-Effectiveness of Blood Donation Screening for Trypanosoma cruzi in Mexico

An estimated 2 million inhabitants are infected with Chagas disease in Mexico, with highest prevalence coinciding with highest demographic density in the southern half of the country. After vector-borne transmission, Trypanosoma cruzi is principally transmitted to humans via blood transfusion. Despite initiation of serological screening of blood donations or donors for T. cruzi since 1990 in most Latin American countries, Mexico only finally included mandatory serological screening nationwide in official Norms in 2012. Most recent regulatory changes and segmented blood services in Mexico may affect compliance of mandatory screening guidelines. The objective of this study was to calculate the incremental cost-effectiveness ratio for total compliance of current guidelines from both Mexican primary healthcare and regular salaried worker health service institutions: the Secretary of Health and the Mexican Institute for Social Security. We developed a bi-modular model to analyze compliance using a decision tree for the most common screening algorithms for each health institution, and a Markov transition model for the natural history of illness and care. The incremental cost effectiveness ratio based on life-years gained is US$ 383 for the Secretary of Health, while the cost for an additional life-year gained is US$ 463 for the Social Security Institute. The results of the present study suggest that due to incomplete compliance of Mexico’s national legislation during 2013 and 2014, the MoH has failed to confirm 15,162 T. cruzi infections, has not prevented 2,347 avoidable infections, and has lost 333,483 life-years. Although there is a vast difference in T. cruzi prevalence between Bolivia and Mexico, Bolivia established mandatory blood screening for T.cruzi in 1996 and until 2002 detected and discarded 11,489 T. cruzi -infected blood units and prevented 2,879 potential infections with their transfusion blood screening program. In the first two years of Mexico’s mandated program, the two primary institutions failed to prevent due to incomplete compliance more potential infections than those gained from the first five years of Bolivia’s program. Full regulatory compliance should be clearly understood as mandatory for the sake of blood security, and its monitoring and analysis in Mexico should be part of the health authority’s responsibility.

Chagas disease continues to be a neglected disease in Mexico and Latin-American. Although an estimated 96% of Trypanosoma cruzi transmission to humans occurs via 32 triatomine vector species, the only transmission prevention in Mexico has been sparse and based on heterogeneous blood donation screening. Despite mandating serological screening of blood donations or donors for T. cruzi since 1990 in most Latin American countries, Mexico only finally included mandatory serological screening nationwide in official Norms in 2012. In 2005, a survey of blood donor centers in Mexico was conducted to compare T. cruzi prevalence in donations with that of Mexican migrants in the US. Since there was little coincidence between data from that survey and official screening or confirmed case rates, and screening for the social security system only initiated in 2010, the objective of this study was to calculate the incremental cost-effectiveness ratio for total compliance of current guidelines from both Mexican primary healthcare (the Secretary of Health) and regular salaried worker health services (the Mexican Institute for Social Security). A bi-modular model to analyze compliance was developed using a decision tree for the most common documented screening algorithms for the two principal health institution, and a Markov transition model for the natural history of illness and care. The incremental cost effectiveness ratio based on life-years gained is US$ 383 for the Secretary of Health (MoH), while the cost for an additional life-year gained is US$ 463 for the Social Security Institute (IMSS). Using survey compliance data for MoH, and that published by IMSS, failure to detect current infections, to avoid new infections, and life-years lost were calculated for 2013 and 2014 for both institutions. The MoH has failed to confirm 15,162 T. cruzi infections, did not prevent 2,347 avoidable infections, and lost 333,483 life-years over the two year period. Full regulatory compliance should be mandatory and timely monitoring should be part of the health authority’s responsibilities for the sake of blood security in Mexico.

Molecular Diversity of Trypanosoma cruzi Detected in the Vector Triatoma protracta from California, USA

BACKGROUND

Trypanosoma cruzi, causative agent of Chagas disease in humans and dogs, is a vector-borne zoonotic protozoan parasite that can cause fatal cardiac disease. While recognized as the most economically important parasitic infection in Latin America, the incidence of Chagas disease in the United States of America (US) may be underreported and even increasing. The extensive genetic diversity of T. cruzi in Latin America is well-documented and likely influences disease progression, severity and treatment efficacy; however, little is known regarding T. cruzi strains endemic to the US. It is therefore important to expand our knowledge on US T. cruzi strains, to improve upon the recognition of and response to locally acquired infections.

METHODOLOGY/PRINCIPLE FINDINGS

We conducted a study of T. cruzi molecular diversity in California, augmenting sparse genetic data from southern California and for the first time investigating genetic sequences from northern California. The vector Triatoma protracta was collected from southern (Escondido and Los Angeles) and northern (Vallecito) California regions. Samples were initially screened via sensitive nuclear repetitive DNA and kinetoplast minicircle DNA PCR assays, yielding an overall prevalence of approximately 28% and 55% for southern and northern California regions, respectively. Positive samples were further processed to identify discrete typing units (DTUs), revealing both TcI and TcIV lineages in southern California, but only TcI in northern California. Phylogenetic analyses (targeting COII-ND1, TR and RB19 genes) were performed on a subset of positive samples to compare Californian T. cruzi samples to strains from other US regions and Latin America. Results indicated that within the TcI DTU, California sequences were similar to those from the southeastern US, as well as to several isolates from Latin America responsible for causing Chagas disease in humans.

CONCLUSIONS/SIGNIFICANCE

Triatoma protracta populations in California are frequently infected with T. cruzi. Our data extend the northern limits of the range of TcI and identify a novel genetic exchange event between TcI and TcIV. High similarity between sequences from California and specific Latin American strains indicates US strains may be equally capable of causing human disease. Additional genetic characterization of Californian and other US T. cruzi strains is recommended.

Detection of Trypanosoma cruzi and Treatment Monitoring by PCR from Dried Blood Spot Samples in Children

BACKGROUND

Parasitic infections by Trypanosoma cruzi (T. cruzi) are frequent in children from endemic areas. Specific therapies have been successfully used in pediatric populations to treat this disease. T. cruzi diagnosis should be optimized and become available for any clinical environment.

OBJECTIVE

To study T. cruzi prevalence in children from an area of active transmission and carry out a posttreatment follow-up. To verify the feasibility of detecting DNA of T. cruzi from dried blood spot.

METHODS

We analyzed presence of T. cruzi in 78 Aboriginal children (Toba community) that attended to a rural school of Chaco province, Argentina. Serum and whole blood (dried blood spot) were assessed by means of serological techniques and PCR. Positive children received Benznidazole. Diagnosis and post treatment follow-up of T. cruzi infection were performed.

RESULTS

The serology assay showed infection in 34 of 78 (43.5%) children studied; PCR was positive in 5/34, displaying parasitemia. Serology remained positive in 28/28 children 120 days post-treatment, while PCR was positive in 18/28 (6/34 children were lost in follow-up). No adverse effects during the treatment were reported.

CONCLUSIONS

We were able to establish T. cruzi prevalence in the studied population and also to prove the usefulness of dried blood spot for T. cruzi detection using PCR in isolated areas. This method allowed us to verify early treatment failure. Possible causes of this failure are discussed below.