HOUSEHOLD RISK FACTORS FOR TRYPANOSOMA CRUZI SEROPOSITIVITY IN TWO GEOGRAPHIC REGIONS OF ECUADOR

Human Trypanosoma cruzi infection in the Argentinean Chaco: risk factors and identification of households with infected children for treatment

BACKGROUND

Chagas disease is a neglected tropical disease (NTD). Cost-effective strategies for large-scale implementation of diagnosis and etiological treatment are urgently needed to comply with NTD control goals. We determined the seroprevalence of Trypanosoma cruzi infection and associated risk factors in a well-defined rural population of Pampa del Indio municipality including creole and indigenous (Qom) households and developed two indices to identify houses harboring infected children.

METHODS

We serodiagnosed and administered a questionnaire to 1337 residents (48.2% of the listed population) in two sections of the municipality (named Areas II and IV) 6-9 years after deploying sustained vector control interventions. Multiple logistic regression models were used to evaluate the relationship between human infection and a priori selected predictors. Two risk indices were constructed based on environmental and serostatus variables, and we used spatial analysis to test whether households harboring T. cruzi-seropositive children were randomly distributed.

RESULTS

The global seroprevalence of T. cruzi infection was 24.8%. Human infection was positively and significantly associated with exposure time to triatomines, the household number of seropositive co-inhabitants, maternal seropositivity for T. cruzi, recent residence at the current house and the presence of suitable walls for triatomine colonization in the domicile. The pre-intervention mean annual force of infection (FOI) was 1.23 per 100 person-years. Creoles from Area IV exhibited the highest seroprevalence and FOI; Qom people from both areas displayed intermediate ones and creoles from Area II the lowest. Three hotspots of infected children were spatially associated with hotspots of triatomine abundance at baseline and persistent house infestation. No child born after vector control interventions was T. cruzi seropositive except for one putative transplacental case. Two simple risk indices (based on self-reported inhabiting an infested house and suitable walls for triatomines or maternal serostatus) identified 97.3-98.6% of the households with at least one T. cruzi-seropositive child.

CONCLUSIONS

We showed strong heterogeneity in the seroprevalence of T. cruzi infection within and between ethnic groups inhabiting neighboring rural areas. Developed indices can be used for household risk stratification and to improve access of rural residents to serodiagnosis and treatment and may be easily transferred to primary healthcare personnel.

Identifying Barriers and Facilitators for Home Reconstruction for Prevention of Chagas Disease: An Interview Study in Rural Loja Province, Ecuador

BACKGROUND

Chagas disease (CD) is a tropical parasitic disease spread by triatomine bugs, which are bugs that tend to infest precarious housing in rural and impoverished areas. Reducing exposure to the bugs, and thus the parasite they can carry, is essential to preventing CD in these areas. One promising long-term sustainable solution is to reconstruct precarious houses. Implementing home reconstruction requires an understanding of how householders construct barriers and facilitators they might encounter when considering whether to rebuild their homes.

METHODS

To understand barriers and facilitators to home reconstruction, we performed in-depth qualitative interviews with 33 residents of Canton Calvas, Loja, Ecuador, a high-risk endemic region. Thematic analysis was used to identify these barriers and facilitators.

RESULTS

The thematic analysis identified three facilitators (project facilitators, social facilitators, and economic facilitators) and two major barriers (low personal economy and extensive deterioration of existing homes).

CONCLUSIONS

The study findings provide important loci for assisting community members and for agents of change in home reconstruction projects to prevent CD. Specifically, the project and social facilitators suggest that collective community efforts (minga) are more likely to support home reconstruction intentions than individualist efforts, while the barriers suggest that addressing structural issues of economy and affordability are necessary.

Evaluation of the Effectiveness of Chemical Control for Chagas Disease Vectors in Loja Province, Ecuador

The objective of this study was to evaluate the effectiveness of selective and community-wide house insecticide spraying in controlling triatomines in the subtropical areas of Loja Province, Ecuador. We designed a quasi-experimental pre-post-test without a control group to compare entomological levels before and after spraying. The baseline study was conducted in 2008. Second, third, and fourth visits were conducted in 2010, 2011, and 2012 in three rural communities. Out of the 130 domestic units (DU) visited, 41 domestic units were examined in each of the four visits. Selective and community-wide insecticide interventions included spraying with 5% deltamethrin at 25 mg/m2 active ingredient. At each visit, a questionnaire was administered to identify the characteristics of households, and DUs were searched for triatomine bugs. In addition, parasitological analysis was carried out in life triatomines. One and two rounds of selective insecticide spraying decreased the probability of infestation by 62% (pairwise odds ratios [POR] 0.38, 95% confidence interval [CI] 0.17-0.89, p = 0.024) and 51% (POR 0.49, 95% CI 0.23-1.01, p = 0.054), respectively. A similar effect was observed after one round of community-wide insecticide application in Chaquizhca and Guara (POR 0.55, CI 0.24-1.25, p = 0.155) and Bellamaria (POR 0.62, CI 0.22-1.79, p = 0.379); however, it was not statistically significant. Trypanosoma cruzi infection in triatomines (n = 483) increased overtime, from 2008 (42.9% and 8.5% for Rhodnius ecuadoriensis and Panstrongylus chinai, respectively) to 2012 (79.5% and 100%). Neither of the two spraying methodologies was effective for triatomine control in this area and our results point to a high likelihood of reinfestation after insecticide application. This underscores the importance of the implementation of physical barriers that prevent invasion and colonization of triatomines in households, such as home improvement initiatives, accompanied by a concerted effort to address the underlying socioeconomic issues that keep this population at risk of developing Chagas disease.

Chagas vectors Panstrongylus chinai (Del Ponte, 1929) and Panstrongylus howardi (Neiva, 1911): chromatic forms or true species?

Background

Chagas disease is a parasitic infection transmitted by “kissing bugs” (Hemiptera: Reduviidae: Triatominae) that has a huge economic impact in Latin American countries. The vector species with the upmost epidemiological importance in Ecuador are Rhodnius ecuadoriensis (Lent & Leon, 1958) and Triatoma dimidiata (Latreille, 1811). However, other species such as Panstrongylus howardi (Neiva, 1911) and Panstrongylus chinai (Del Ponte, 1929) act as secondary vectors due to their growing adaptation to domestic structures and their ability to transmit the parasite to humans. The latter two taxa are distributed in two different regions, they are allopatric and differ mainly by their general color. Their relative morphological similarity led some authors to suspect that P. chinai is a melanic form of P. howardi.

Methods

The present study explored this question using different approaches: antennal phenotype; geometric morphometrics of heads, wings and eggs; cytogenetics; molecular genetics; experimental crosses; and ecological niche modeling.

Results

The antennal morphology, geometric morphometrics of head and wing shape and cytogenetic analysis were unable to show distinct differences between the two taxa. However, geometric morphometrics of the eggs, molecular genetics, ecological niche modeling and experimental crosses including chromosomal analyses of the F1 hybrids, in addition to their coloration and current distribution support the hypothesis that P. chinai and P. howardi are separate species.

Conclusions

Based on the evidence provided here, P. howardi and P. chinai should not be synonymized. They represent two valid, closely related species.

Spatial analysis of dengue, cysticercosis and Chagas disease mortality in Ecuador, 2011-2016

Background

Neglected tropical diseases (NTDs) continue to be an important cause of disability and mortality in the poorest tropical and subtropical areas.

Methods

This is an ecological study. We included all death certificates with dengue, cysticercosis and Chagas disease in Ecuador from 2011 to 2016. The spatial autocorrelation was evaluated by GeoDa software through the Global Moran's I index and the formation of clusters by the local index of spatial association.

Results

The Global Moran's I index for the study period shows a positive spatial autocorrelation for dengue, cysticercosis and Chagas disease (0.25, p=0.001; 0.07, p=0.04; 0.45, p=0.001, respectively).

Conclusions

The clusters identified as higher risk in the country could be targeted by policymakers to adequately develop strategies to strengthen health promotion policies that break the cycle of these diseases.

Human Trypanosoma cruzi infection is driven by eco-social interactions in rural communities of the Argentine Chaco

The transmission of Trypanosoma cruzi to humans is determined by multiple ecological, socio-economic and cultural factors acting at different scales. Their effects on human infection with T. cruzi have often been examined separately or using a limited set of ecological and socio-demographic variables. Herein, we integrated the ecological and social dimensions of human infection risk with the spatial distribution patterns of human and vector (Triatoma infestans) infection in rural communities of the Argentine Chaco composed of indigenous people (90% Qom) and a creole minority. We conducted serosurveys in 470 households aiming at complete population enumeration over 2012–2015. The estimated seroprevalence of T. cruzi prior to the implementation of an insecticide spraying campaign (2008) was 29.0% (N = 1,373 in 301 households), and was twice as large in Qom than creoles. Using generalized linear mixed models, human seropositive cases significantly increased with infected triatomine abundance, having a seropositive household co-inhabitant and household social vulnerability (a multidimensional index of poverty), and significantly decreased with increasing host availability in sleeping quarters (an index summarizing the number of domestic hosts for T. infestans). Vulnerable household residents were exposed to a higher risk of infection even at low infected-vector abundances. The risk of being seropositive increased significantly with house infestation among children from stable households, whereas both variables were not significantly associated among children from households exhibiting high mobility within the communities, possibly owing to less consistent exposures. Human infection was clustered by household and at a larger spatial scale, with hotspots of human and vector infection matching areas of higher social vulnerability. These results were integrated in a risk map that shows high-priority areas for targeted interventions oriented to suppress house (re)infestations, detect and treat infected children, and thus reduce the burden of future disease.

Chagas disease is one of the main neglected tropical diseases (NTDs) affecting vulnerable communities in Latin America where transmission by triatomine vectors still occurs. Access to diagnosis and treatment is one of the remaining challenges for sustainable control of Chagas disease in endemic areas. In this study, we integrated the ecological and social determinants of human infection with the spatial component to identify individuals, households and geographic sectors at higher risk of infection. We found that human infection was more prevalent in indigenous people compared to creoles and increased with the abundance of infected vectors and with household social vulnerability (a multidimensional index of poverty). We also found that the social factors modulated the effect of the abundance of infected vectors: vulnerable-household residents were exposed to a higher risk of infection even at low infected-vector abundance, and human mobility within the area determined a lower and more variable exposure to the vector over time. These results were integrated in a risk map that showed high-priority areas, which can be used in designing cost-effective serological screening strategies adapted to resource-constrained areas.

Insights from quantitative and mathematical modelling on the proposed WHO 2030 goals for Chagas disease

Chagas disease (CD) persists as one of the neglected tropical diseases (NTDs) with a particularly large impact in the Americas. The World Health Organization (WHO) recently proposed goals for CD elimination as a public health problem to be reached by 2030 by means of achieving intradomiciliary transmission interruption (IDTI), blood transfusion and transplant transmission interruption, diagnostic and treatment scaling-up and prevention and control of congenital transmission. The NTD Modelling Consortium has developed mathematical models to study Trypanosoma cruzi transmission dynamics and the potential impact of control measures. Modelling insights have shown that IDTI is feasible in areas with sustained vector control programmes and no presence of native triatomine vector populations. However, IDTI in areas with native vectors it is not feasible in a sustainable manner. Combining vector control with trypanocidal treatment can reduce the timeframes necessary to reach operational thresholds for IDTI (<2% seroprevalence in children aged <5 years), but the most informative age groups for serological monitoring are yet to be identified. Measuring progress towards the 2030 goals will require availability of vector surveillance and seroprevalence data at a fine scale, and a more active surveillance system, as well as a better understanding of the risks of vector re-colonization and disease resurgence after vector control cessation. Also, achieving scaling-up in terms of access to treatment to the expected levels (75%) will require a substantial increase in screening asymptomatic populations, which is anticipated to become very costly as CD prevalence decreases. Further modelling work includes refining and extending mathematical models (including transmission dynamics and statistical frameworks) to predict transmission at a sub-national scale, and developing quantitative tools to inform IDTI certification, post-certification and re-certification protocols. Potential perverse incentives associated with operational thresholds are discussed. These modelling insights aim to inform discussions on the goals and treatment guidelines for CD.

Chagas Disease in Southern Coastal Ecuador: Coinfections with Arboviruses and a Comparison of Serological Assays for Chagas Disease Diagnosis

Occurrence of Chagas disease and arbovirus coinfections is unknown, despite the vast co-endemic areas throughout the Americas. This study examined the proportion of individuals positive for Trypanosoma cruzi and coinfections with dengue, chikungunya, and Zika viruses in Machala, Ecuador (January 2014-December 2015). Chagas seropositivity was evaluated with five commercially available assays. Dengue infections were identified by nonstructural protein 1 rapid test and enzyme linked immunosorbent assay (ELISA), immunoglobulin M ELISA, and reverse transcription PCR (RT-PCR); chikungunya and Zika infections were identified by RT-PCR. Of 658 individuals, six were positive for T. cruzi (0.91%), including one T. cruzi/dengue coinfection and one T. cruzi/chikungunya/dengue coinfection. The clinical manifestations of coinfected individuals corresponded to severe dengue and dengue with warning signs, respectively. We observed discrepant results by using the Hemagen Chagas kit and the rapid test Chagas Detect Plus (false positives: 3.9% and 15.4%), highlighting the need to assess diagnostic assays in geographic regions with distinct taxonomic units of T. cruzi.

Triatominae: does the shape change of non-viable eggs compromise species recognition?

Background

Eggs have epidemiological and taxonomic importance in the subfamily Triatominae, which contains Chagas disease vectors. The metric properties (size and shape) of eggs are useful for distinguishing between close species, or different geographical populations of the same species.

Methods

We examined the effects of egg viability on its metric properties, and the possible consequences on species recognition. Four species were considered: Panstrongylus chinai, P. howardi and Triatoma carrioni (tribe Triatomini), and Rhodnius ecuadoriensis (tribe Rhodniini). Digitization was performed on pictures taken when the viability of the egg could not clearly be predicted by visual inspection. We then followed development to separate viable from non-viable eggs, and the metric changes associated with viability status of the eggs were tested for species discrimination (interspecific difference).

Results

The shape of the complete contour of the egg provided satisfactory species classification (95% of correct assignments, on average), with improved scores (98%) when discarding non-viable eggs from the comparisons. Using only non-viable eggs, the scores dropped to 90%. The morphometric differences between viable and non-viable eggs were also explored (intraspecific comparison). A constant metric change observed was a larger variance of size and shape in non-viable eggs. For all species, larger eggs, or eggs with larger operculum, were more frequently non-viable. However, these differences did not allow for an accurate prediction regarding egg viability.

Conclusions

The strong taxonomic signal present in egg morphology was affected by the level of viability of the eggs. The metric properties as modified in non-viable eggs presented some general trends which could suggest the existence of an optimum phenotype for size and for shape. Globally, viable eggs tended to have intermediate or small sizes, and presented a less globular shape in the Triatomini, or a relatively wider neck in Rhodnius ecuadoriensis.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3104-1) contains supplementary material, which is available to authorized users.

Using the health belief model to identify communication opportunities to prevent Chagas disease in Southern Ecuador

Background

Chagas disease (CD) is a life-threatening illness caused by the protozoan parasite Trypanosoma cruzi, which is transmitted by triatomine bugs. Triatomine bugs inhabit poorly constructed homes that create multiple hiding spots for the bugs. Modifying the actual structure of a home, along with the homeowners’ practices, can reduce triatomine infestation. This research was designed to collect culturally-relevant information to develop a health campaign to decrease risk of CD transmission by promoting home maintenance and better hygiene in rural communities of southern Ecuador.

Methods and main findings

The Health Belief Model (HBM) guided focus group discussions and the interpretation of the results. Four focus groups ranging from 4 to 10 participants were conducted between May and June 2014 in three communities of Loja province in Southern Ecuador. A thematic analysis was used to identify within the data related to perceptions of susceptibility, severity, benefits, barriers and self-efficacy related to CD and its prevention. The results provide clear guidance for the development of Chagas-prevention messages.

Conclusion

Data obtained emphasize the importance of standardizing messages presented to the communities for CD prevention. Messages should provide more information on the protective nature of the behaviors promoted for CD prevention; overcoming barriers such as cost and convenience, and build on facilitating factors, including community members’ interest on quality of life, protection of their families, and relationship with the land.

This study focuses on Chagas disease (CD) prevention in southern Ecuador. This region has a high rate of triatomine infestation. We used the Health Belief Model (HBM) to understand why people do or do not engage in CD preventive behaviors, particularly those related to home improvement. Additionally, we wanted to learn how to communicate most effectively about CD prevention. We gathered information about community member’s perceptions of CD in four focus groups, with a total of 26 participants. Our results indicate that communities do not see triatomines and CD as a threat. Lack of structures, cost, and convenience were the three key barriers mentioned by research participants for implementing CD preventive behaviors. However, participants were open to work with prevention programs since they saw it as an opportunity for community members to work together under the motivation of improving their living conditions. Capitalizing on motivators and removing barriers will be important for subsequent communication campaigns. Messages evoking fear of triatomine bugs and CD will contradict participants’ personal experience; instead, messages focusing how these behaviors will improve communities’ quality of life, protect their families, and strengthen their relationship with the land, will be more acceptable and appealing.

Youth participatory research and evaluation to inform a Chagas disease prevention program in Ecuador

This qualitative study engaged a group of young people in participatory research and evaluation activities in order to study to what extent engaging youth in health interventions can inform research and evaluation processes. We applied a youth participatory research and evaluation approach (PRE) to inform research and evaluation on the impact of a Chagas disease control program in southern Ecuador. Our main interest was to examine the methodological contributions of PRE to knowledge sharing for health intervention planning in the context of global health and neglected tropical diseases. The results of this study suggest that by demystifying research and evaluation practices and rendering them accessible and relevant, marginalized youth can develop critical and reflexive thinking skills that could be useful for decision-making on health promotion. Our findings also reveal the potential of youth as active participants in project development in ways that enhance, validate, and improve health interventions. Young people are interested in learning about and sharing local knowledge that can benefit research and evaluation processes. Despite the numerous strengths demonstrated by PRE, the inherent complexities of international development, such as cultural differences, asymmetrical power relations, and the ongoing challenges of sustainability, remain.

Seroprevalence and risk factors for infection with Bartonella bacilliformis in Loja province, Ecuador

The seroprevalence and epidemiology of Bartonella bacilliformis infection in the Andean highlands of Ecuador is largely unknown. We conducted a sero-epidemiologic survey of 319 healthy children aged 1-15 years living in six rural, mountain communities in Loja Province, Ecuador. Blood was collected by finger stick onto filter paper and dried, and the eluted sera analyzed for antibodies to B. bacilliformis by rPap31 ELISA. Demographic, entomologic, and household variables were assessed to investigate associated risk factors for antibody seropositivity to B. bacilliformis. Seroprevalence of 28% was found among children in the study communities. Increased risk of seropositivity was associated with the presence of lumber piles near houses. Decreased risk of seropositivity was observed with the presence of animal waste and incremental 100 meter increases in elevation. Although investigation of clinical cases of Carrion's disease was not within the scope of this study, our serology data suggest that infection of children with B. bacilliformis is prevalent in this region of Ecuador and is largely unrecognized and undiagnosed. This study highlights the need to further investigate the prevalence, pathogenesis, epidemiology, and disease impact of this pathogen in Ecuador.

[Seroprevalence of Trypanosoma cruzi infection in the rural population of Sucre State, Venezuela]

The current study aimed to determine the seroprevalence of Trypanosoma cruzi infection in Sucre State, Venezuela, and its association with epidemiological risk factors. The cluster sampling design allowed selecting 96 villages and 576 dwellings in the State's 15 municipalities. A total of 2,212 serum samples were analyzed by ELISA, HAI, and IFI. Seroprevalence in Sucre State was 3.12%. Risk factors associated with T. cruzi infection were: accumulated garbage, flooring and wall materials, type of dwelling, living in a house with wattle and daub walls and/or straw roofing, living in a house with risky walls and roofing, risky buildings and wattle and daub outbuildings, poultry inside the human dwelling, and presence of firewood. Infection was associated with individual age, and three seropositive cases were found in individuals less than 15 years of age. Sucre State has epidemiological factors that favor the risk of acquiring T. cruzi infection.

Pioneer study of population genetics of Rhodnius ecuadoriensis (Hemiptera: Reduviidae) from the central coastand southern Andean regions of Ecuador

Effective control of Chagas disease vector populations requires a good understanding of the epidemiological components, including a reliable analysis of the genetic structure of vector populations. Rhodnius ecuadoriensis is the most widespread vector of Chagas disease in Ecuador, occupying domestic, peridomestic and sylvatic habitats. It is widely distributed in the central coast and southern highlands regions of Ecuador, two very different regions in terms of bio-geographical characteristics. To evaluate the genetic relationship among R. ecuadoriensis populations in these two regions, we analyzed genetic variability at two microsatellite loci for 326 specimens (n=122 in Manabí and n=204 in Loja) and the mitochondrial cytochrome b gene (Cyt b) sequences for 174 individuals collected in the two provinces (n=73 and=101 in Manabí and Loja respectively). The individual samples were grouped in populations according to their community of origin. A few populations presented positive F_IS, possible due to Wahlund effect. Significant pairwise differentiation was detected between populations within each province for both genetic markers, and the isolation by distance model was significant for these populations. Microsatellite markers showed significant genetic differentiation between the populations of the two provinces. The partial sequences of the Cyt b gene (578bp) identified a total of 34 haplotypes among 174 specimens sequenced, which translated into high haplotype diversity (Hd=0.929). The haplotype distribution differed among provinces (significant Fisher's exact test). Overall, the genetic differentiation of R. ecuadoriensis between provinces detected in this study is consistent with the biological and phenotypic differences previously observed between Manabí and Loja populations. The current phylogenetic analysis evidenced the monophyly of the populations of R. ecuadoriensis within the R. pallescens species complex; R. pallescens and R. colombiensis were more closely related than they were to R. ecuadoriensis.

Prevalence of Chagas Disease in the Latin American-born Population of Los Angeles

Background

According to an estimate from the Centers for Disease Control and Prevention (CDC), Chagas disease (CD) may affect 1.31% of Latin American immigrants in the United States, with >300 000 cases. However, there is a lack of real-world data to support this estimate. Little is known about the actual prevalence of this neglected tropical disease in the United States, and the bulk of those infected are undiagnosed.

Methods

From April 2008 to May 2014, we screened 4,755 Latin American-born residents of Los Angeles County. Blood samples were tested for serologic evidence of CD. We collected demographic data and assessed the impact of established risk factors on CD diagnosis, including sex, country of origin, housing materials, family history of CD, and awareness of CD.

Results

There were 59 cases of CD, for an overall prevalence of 1.24%. Prevalence was highest among Salvadorans (3.45%). Of the 3,182 Mexican respondents, those from Oaxaca (4.65%) and Zacatecas (2.2%) had the highest CD prevalence. Salvadoran origin (aOR = 6.2; 95% CI = 2.8-13.5; P < .001), prior knowledge of CD (aOR = 2.4; 95% CI = 1.0-5.8; P = .047), and exposure to all 3 at-risk housing types (adobe, mud, and thatched roof) (aOR = 2.5; 95% CI = 1.0-6.4; P = .048) were associated with positive diagnosis.

Conclusions

In the largest screening of CD in the United States to date outside of blood banks, we found a CD prevalence of 1.24%. This implies >30 000 people infected in Los Angeles County alone, making CD an important public health concern. Efficient, targeted surveillance of CD may accelerate diagnosis and identify candidates for early treatment.

Prevalence, Genetic Characterization, and 18S Small Subunit Ribosomal RNA Diversity of Trypanosoma rangeli in Triatomine and Mammal Hosts in Endemic Areas for Chagas Disease in Ecuador

Trypanosoma rangeli is a nonpathogenic parasite for humans; however, its medical importance relies in its similarity and overlapping distribution with Trypanosoma cruzi, causal agent of Chagas disease in the Americas. The genetic diversity of T. rangeli and its association with host species (triatomines and mammals) has been identified along Central and the South America; however, it has not included data of isolates from Ecuador. This study reports infection with T. rangeli in 18 genera of mammal hosts and five species of triatomines in three environments (domestic, peridomestic, and sylvatic). Higher infection rates were found in the sylvatic environment, in close association with Rhodnius ecuadoriensis. The results of this study extend the range of hosts infected with this parasite and the geographic range of the T. rangeli genotype KP1(-)/lineage C in South America. It was not possible to detect variation on T. rangeli from the central coastal region and southern Ecuador with the analysis of the small subunit ribosomal RNA (SSU-rRNA) gene, even though these areas are ecologically different and a phenotypic subdivision of R. ecuadoriensis has been found. R. ecuadoriensis is considered one of the most important vectors for Chagas disease transmission in Ecuador due to its wide distribution and adaptability to diverse environments. An extensive knowledge of the trypanosomes circulating in this species of triatomine, and associated mammal hosts, is important for delineating transmission dynamics and preventive measures in the endemic areas of Ecuador and Northern Peru.

Trypanosoma cruzi population dynamics in the Central Ecuadorian Coast

Chagas disease is the most important parasitic disease in Latin America. The causative agent, Trypanosoma cruzi, displays high genetic diversity and circulates in complex transmission cycles among domestic, peridomestic and sylvatic environments. In Ecuador, Rhodnius ecuadoriensis is known to be the major vector species implicated in T. cruzi transmission. However, across vast areas of Ecuador, little is known about T. cruzi genetic diversity in relation to different parasite transmission scenarios. Fifty-eight T. cruzi stocks from the central Ecuadorian coast, most of them derived from R. ecuadoriensis, were included in the study. All of them were genotyped as T. cruzi discrete typing unit I (DTU TcI). Analysis of 23 polymorphic microsatellite loci through neighbor joining and discriminant analysis of principal components yielded broadly congruent results and indicate genetic subdivision between sylvatic and peridomestic transmission cycles. However, both analyses also suggest that any barriers are imperfect and significant gene flow between parasite subpopulations in different habitats exists. Also consistent with moderate partition and residual gene flow between subpopulations, the fixation index (FST) was significant, but of low magnitude. Finally, the lack of private alleles in the domestic/peridomestic transmission cycle suggests the sylvatic strains constitute the ancestral population. The T. cruzi population in the central Ecuadorian coast shows moderate tendency to subdivision according to transmission cycle. However, connectivity between cycles exists and the sylvatic T. cruzi population harbored by R. ecuadoriensis vectors appears to constitute a source from which the parasite invades human domiciles and their surroundings in this region. We discuss the implications these findings have for the planning, implementation and evaluation of local Chagas disease control interventions.

Bats, Trypanosomes, and Triatomines in Ecuador: New Insights into the Diversity, Transmission, and Origins of Trypanosoma cruzi and Chagas Disease

The generalist parasite Trypanosoma cruzi has two phylogenetic lineages associated almost exclusively with bats—Trypanosoma cruzi Tcbat and the subspecies T. c. marinkellei. We present new information on the genetic variation, geographic distribution, host associations, and potential vectors of these lineages. We conducted field surveys of bats and triatomines in southern Ecuador, a country endemic for Chagas disease, and screened for trypanosomes by microscopy and PCR. We identified parasites at species and genotype levels through phylogenetic approaches based on 18S ribosomal RNA (18S rRNA) and cytochrome b (cytb) genes and conducted a comparison of nucleotide diversity of the cytb gene. We document for the first time T. cruzi Tcbat and T. c. marinkellei in Ecuador, expanding their distribution in South America to the western side of the Andes. In addition, we found the triatomines Cavernicola pilosa and Triatoma dispar sharing shelters with bats. The comparisons of nucleotide diversity revealed a higher diversity for T. c. marinkellei than any of the T. c. cruzi genotypes associated with Chagas disease. Findings from this study increased both the number of host species and known geographical ranges of both parasites and suggest potential vectors for these two trypanosomes associated with bats in rural areas of southern Ecuador. The higher nucleotide diversity of T. c. marinkellei supports a long evolutionary relationship between T. cruzi and bats, implying that bats are the original hosts of this important parasite.

Comprehensive Survey of Domiciliary Triatomine Species Capable of Transmitting Chagas Disease in Southern Ecuador

BACKGROUND

Chagas disease is endemic to the southern Andean region of Ecuador, an area with one of the highest poverty rates in the country. However, few studies have looked into the epidemiology, vectors and transmission risks in this region. In this study we describe the triatomine household infestation in Loja province, determine the rate of Trypanosoma cruzi infection in triatomines and study the risk factors associated with infestation.

METHODOLOGY/PRINCIPAL FINDINGS

An entomological survey found four triatomine species (Rhodnius ecuadoriensis, Triatoma carrioni, Panstrongylus chinai, and P. rufotuberculatus) infesting domiciles in 68% of the 92 rural communities examined. Nine percent of domiciles were infested, and nymphs were observed in 80% of the infested domiciles. Triatomines were found in all ecological regions below 2,200 masl. We found R. ecuadoriensis (275 to 1948 masl) and T. carrioni (831 to 2242 masl) mostly in bedrooms within the domicile, and they were abundant in chicken coops near the domicile. Established colonies of P. chinai (175 to 2003 masl) and P. rufotuberculatus (404 to 1613 masl) also were found in the domicile. Triatomine infestation was associated with surrogate poverty indicators, such as poor sanitary infrastructure (lack of latrine/toilet [w = 0.95], sewage to environment [w = 1.0]). Vegetation type was a determinant of infestation [w = 1.0] and vector control program insecticide spraying was a protective factor [w = 1.0]. Of the 754 triatomines analyzed, 11% were infected with Trypanosoma cruzi and 2% were infected with T. rangeli.

CONCLUSIONS/SIGNIFICANCE

To date, only limited vector control efforts have been implemented. Together with recent reports of widespread sylvatic triatomine infestation and frequent post-intervention reinfestation, these results show that an estimated 100,000 people living in rural areas of southern Ecuador are at high risk for T. cruzi infection. Therefore, there is a need for a systematic, sustained, and monitored vector control intervention that is coupled with improvement of socio-economic conditions.

Positive deviance study to inform a Chagas disease control program in southern Ecuador

Chagas disease is caused by Trypanosoma cruzi, which is mainly transmitted by the faeces of triatomine insects that find favourable environments in poorly constructed houses. Previous studies have documented persistent triatomine infestation in houses in the province of Loja in southern Ecuador despite repeated insecticide and educational interventions. We aim to develop a sustainable strategy for the interruption of Chagas disease transmission by promoting living environments that are designed to prevent colonisation of rural houses by triatomines. This study used positive deviance to inform the design of an anti-triatomine prototype house by identifying knowledge, attitudes and practices used by families that have remained triatomine-free (2010-2012). Positive deviants reported practices that included maintenance of structural elements of the house, fumigation of dwellings and animal shelters, sweeping with "insect repellent" plants and relocation of domestic animals away from the house, among others. Participants favoured construction materials that do not drastically differ from those currently used (adobe walls and tile roofs). They also expressed their belief in a clear connection between a clean house and health. The family's economic dynamics affect space use and must be considered in the prototype's design. Overall, the results indicate a positive climate for the introduction of housing improvements as a protective measure against Chagas disease in this region.

Factors associated with the occurrence of Triatoma sordida (Hemiptera: Reduviidae) in rural localities of Central-West Brazil

This study estimates the factors of artificial environments (houses and peridomestic areas) associated with Triatoma sordida occurrence. Manual searches for triatomines were performed in 136 domiciliary units (DUs) in two rural localities of Central-West Brazil. For each DU, 32 structural, 23 biotic and 28 management variables were obtained. Multiple logistic regression analysis was performed in order to identify statistically significant variables associated with occurrence of T. sordida in the study areas. A total of 1,057 specimens (99% in peridomiciles, mainly chicken coops) of T. sordida were collected from 63 DUs (infestation: 47%; density: ~8 specimens/DU; crowding: ~17 specimens/infested DU; colonisation: 81%). Only six (0.6%) out of 945 specimens examined were infected with Trypanosoma cruzi. The final adjusted logistic regression model indicated that the probability of T. sordida occurrence was higher in DU with wooden chicken coops, presence of > 30 animals in wooden corrals, presence of wood piles and presence of food storeroom. The results show the persistence of T. sordida in peridomestic habitats in rural localities of Central-West Brazil. However, the observed low intradomestic colonisation and minimal triatomine infection rates indicate that T. sordida has low potential to sustain high rates of T. cruzi transmission to residents of these localities.

A national survey to determine prevalence of Trypanosoma cruzi infection among pregnant women in Ecuador

A nationwide survey was conducted to obtain an estimate of Chagas disease prevalence among pregnant women in Ecuador. As part of a national probability sample, 5,420 women seeking care for delivery or miscarriage at 15 healthcare facilities were recruited into the study. A small minority of participants reported knowing about Chagas disease or recognized the vector. A national seroprevalence of 0.1% (95% confidence interval [95% CI] = 0.0-0.2%) was found; cases were concentrated in the coastal region (seroprevalence = 0.2%; 95% CI = 0.0-0.4%). No cases of transmission to neonates were identified in the sample. Seropositive participants were referred to the National Chagas Program for evaluation and treatment. Additional studies are necessary to determine if areas of higher prevalence exist in well-known endemic provinces and guide the development of a national strategy for elimination of mother-to-child transmission of Chagas disease in Ecuador.

Repolarization Parameters Are Associated With Mortality In Chagas Disease Patients In The United States

Objective

The goal of this study was to examine the association between ECG repolarization parameters and mortality in Chagas disease (CD) patients living in the United States.

Methods

CD patients with cardiomyopathy (CM) and bundle branch block (BBB) or BBB alone were compared to age- and sex-matched controls. QT interval, QT dispersion (QTd), T wave peak to T wave end duration (Tp-Te) and T wave peak to T wave end dispersion ((Tp-Te)d) were measured. Presence of fractionated QRS (fQRS) was also assessed. The main outcome measure was the association between ECG parameters and mortality or need for cardiac transplant.

Results

A total of 18 CM and 13 BBB CD patients were studied with 97% originating from Mexico or Central America. QTd (60.0±15.0 ms vs 43.5±9.8 ms, P=0.0002), Tp-Te (102.6±29.3 ms vs 77.1±11.0 ms, P=0.0002) and (Tp-Te)d (39.5±9.4 ms vs 22.7±7.6 ms, P<0.0001) were prolonged in CD CM patients compared to CM controls. Chagas CM patients had more fQRS then controls (84.2±0.10% vs 33.3±0.11%, p=0.0005). QTd (59.9±15.0 ms vs 29.5±6.9 ms, P=0.0001) and (Tp-Te)d (40.0±15.9 ms vs 18.5±5.4 ms, p<0.0001) were longer in the CD BBB group compared to BBB controls. Univariate analysis showed QTd (56.9±15.0 ms vs 46.5±17.3 ms, p=0.0412) and (Tp-Te)d (36.8±13.5 ms vs 28.5±13.3 ms, p=0.0395) were associated with death and/or need for cardiac transplant.

Conclusion

Our results indicate that P-max and PD are useful electrocardiographic markers for identifying the β-TM-high-risk patients for AF onset, even when the cardiac function is conserved.

Dynamics of sylvatic Chagas disease vectors in coastal Ecuador is driven by changes in land cover

Background

Chagas disease is a serious public health problem in Latin America where about ten million individuals show Trypanosoma cruzi infection. Despite significant success in controlling domiciliated triatomines, sylvatic populations frequently infest houses after insecticide treatment which hampers long term control prospects in vast geographical areas where vectorial transmission is endemic. As a key issue, the spatio-temporal dynamics of sylvatic populations is likely influenced by landscape yet evidence showing this effect is rare. The aim of this work is to examine the role of land cover changes in sylvatic triatomine ecology, based on an exhaustive field survey of pathogens, vectors, hosts, and microhabitat characteristics' dynamics.

Methodology and Principal Findings

The study was performed in agricultural landscapes of coastal Ecuador as a study model. Over one year, a spatially-randomized sampling design (490 collection points) allowed quantifying triatomine densities in natural, cultivated and domestic habitats. We also assessed infection of the bugs with trypanosomes, documented their microhabitats and potential hosts, and recorded changes in landscape characteristics. In total we collected 886 individuals, mainly represented by nymphal stages of one triatomine species Rhodnius ecuadoriensis. As main results, we found that 1) sylvatic triatomines had very high T. cruzi infection rates (71%) and 2) densities of T. cruzi-infected sylvatic triatomines varied predictably over time due to changes in land cover and occurrence of associated rodent hosts.

Conclusion

We propose a framework for identifying the factors affecting the yearly distribution of sylvatic T. cruzi vectors. Beyond providing key basic information for the control of human habitat colonization by sylvatic vector populations, our framework highlights the importance of both environmental and sociological factors in shaping the spatio-temporal population dynamics of triatomines. A better understanding of the dynamics of such socio-ecological systems is a crucial, yet poorly considered, issue for the long-term control of Chagas disease.

Globally, more than 10 million people are infected with Trypanosoma cruzi. The emergence and perpetuation of Chagas disease in some endemic countries, such as Ecuador, depends largely on sylvatic populations of T. cruzi-infected vectors that frequently infest houses after insecticide treatment thereby hampering long-term control prospects in vast geographical areas. Our study describes, for the first time in an agricultural landscape, how the temporal dynamics of sylvatic vector, host, and pathogen populations interact spatially in a farming community of coastal Ecuador. In particular, we found that land cover changes due to both farming activities and vegetation phenology affect rodent host distribution and consequently the relative abundance of vectors involved in the transmission cycle of T. cruzi.

In vivo imaging of mice infected with bioluminescent Trypanosoma cruzi unveils novel sites of infection

Background

The development of techniques that allow the imaging of animals infected with parasites expressing luciferase opens up new possibilities for following the fate of parasites in infected mammals.

Methods

D-luciferin potassium salt stock solution was prepared in phosphate-buffered saline (PBS) at 15 mg/ml. To produce bioluminescence, infected and control mice received an intraperitoneal injection of luciferin stock solution (150 mg/kg). All mice were immediately anesthetized with 2% isofluorane, and after 10 minutes were imaged. Ex vivo evaluation of infected tissues and organs was evaluated in a 24-well plate in 150 μg/ml D-luciferin diluted in PBS. Images were captured using the IVIS Lumina image system (Xenogen). Dissected organs were also evaluated by microscopy of hematoxylin-eosin stained sections.

Results

Here we describe the results obtained using a genetically modified Dm28c strain of T. cruzi expressing the firefly luciferase to keep track of infection by bioluminescence imaging. Progression of infection was observed in vivo in BALB/c mice at various intervals after infection with transgenic Dm28c-luc. The bioluminescent signal was immediately observed at the site of T. cruzi inoculation, and one day post infection (dpi) it was disseminated in the peritoneal cavity. A similar pattern in the cavity was observed on 7 dpi, but the bioluminescence was more intense in the terminal region of the large intestine, rectum, and gonads. On 14 and 21 dpi, bioluminescent parasites were also observed in the heart, snout, paws, hind limbs, and forelimbs. From 28 dpi to 180 dpi in chronically infected mice, bioluminescence declined in regions of the body but was concentrated in the gonad region. Ex vivo evaluation of dissected organs and tissues by bioluminescent imaging confirmed the in vivo bioluminescent foci. Histopathological analysis of dissected organs demonstrated parasite nests at the rectum and snout, in muscle fibers of mice infected with Dm28c-WT and with Dm28c-luc, corroborating the bioluminescent imaging.

Conclusion

Bioluminescence imaging is accurate for tracking parasites in vivo, and this methodology is important to gain a better understanding of the infection, tissue inflammation, and parasite biology regarding host cell interaction, proliferation, and parasite clearance to subpatent levels.

Seroprevalence and risk factors of Crimean-Congo hemorrhagic fever in selected seven provinces in Turkey

Turkey has been one of the most endemic regions since 2002, when Crimean-Congo hemorrhagic fever emerged worldwide. The aim of the present study was to estimate the seroprevelance of CCHF virus in humans who reside in rural and urban areas of known endemic and nonendemic selected provinces of Turkey by using commercial ELISA kit. CCHFV IgG antibodies were detected in 2.3% of the population. The most important risk factors for CCHF seropositivity, were older age, male gender, illiterate, farmer, animal husbandry, living in rural residence in adobe houses, and a previous tick bite history.

IFN-γ plays a unique role in protection against low virulent Trypanosoma cruzi strain

Background

T. cruzi strains have been divided into six discrete typing units (DTUs) according to their genetic background. These groups are designated T. cruzi I to VI. In this context, amastigotes from G strain (T. cruzi I) are highly infective in vitro and show no parasitemia in vivo. Here we aimed to understand why amastigotes from G strain are highly infective in vitro and do not contribute for a patent in vivo infection.

Methodology/Principal Findings

Our in vitro studies demonstrated the first evidence that IFN-γ would be associated to the low virulence of G strain in vivo. After intraperitoneal amastigotes inoculation in wild-type and knockout mice for TNF-α, Nod2, Myd88, iNOS, IL-12p40, IL-18, CD4, CD8 and IFN-γ we found that the latter is crucial for controlling infection by G strain amastigotes.

Conclusions/Significance

Our results showed that amastigotes from G strain are highly infective in vitro but did not contribute for a patent infection in vivo due to its susceptibility to IFN-γ production by host immune cells. These data are useful to understand the mechanisms underlying the contrasting behavior of different T. cruzi groups for in vitro and in vivo infection.

Trypanosoma cruzi, an obligate intracellular protozoan, is the etiological agent of Chagas disease that represents an important public health burden in Latin America. The infection with this parasite can lead to severe complications in cardiac and gastrointestinal tissue depending on the strain of parasite and host genetics. Currently, six genetic groups (T. cruzi I to VI) have been identified in this highly genetic and diverse parasite.The majority of published data concerning host immune response has been obtained from studying T. cruzi II to VI-infected mice, and the genetic differences between T. cruzi II to VI and T. cruzi I strains are large. Here we aimed to understand how amastigotes from T. cruzi I G strain are highly infective in vitro and do not contribute for a patent parasitemia in vivo. Our results showed that amastigotes from G strain are highly susceptible to IFN-γ treatment in vitro and secretion by immune cells in vivo. This information may represent important findings to design novel immune strategies to control pathology that may be caused by different strains in the same host.

[Seroprevalence for Trypanosoma cruzi infection and associated factors in an endemic area of Venezuela]

This study investigated risk factors associated with positive serological status for Trypanosoma cruzi antibodies in 26 rural communities including 905 households, 2,156 humans, and 333 dogs in Lara State, Venezuela. Serology was performed with ELISA and MABA. Data were obtained from entomological, demographic, and clinical surveys. Risk factors were determined through binary logistic regression. Seroprevalence was 7.24% in humans and 6.9% in canines. Positive serological status was positively associated with the Rhodnius prolixus vector, age, maternal history of Chagas disease, tobacco chewing, presence of mammals and birds in the household, household disarray, mud-and-wattle outbuildings, and animal nests and burrows in the peridomicile, and negatively associated with tobacco and alcohol consumption, history of cancer, and storage deposits in the peridomile. In conclusion, Chagas disease in this rural area is an old phenomenon transmitted by R. prolixus or by the transplacental route, associated with socio-cultural habits related to poverty, sylvatic surroundings, and the host's medical history.

Retracing micro-epidemics of Chagas disease using epicenter regression

Vector-borne transmission of Chagas disease has become an urban problem in the city of Arequipa, Peru, yet the debilitating symptoms that can occur in the chronic stage of the disease are rarely seen in hospitals in the city. The lack of obvious clinical disease in Arequipa has led to speculation that the local strain of the etiologic agent, Trypanosoma cruzi, has low chronic pathogenicity. The long asymptomatic period of Chagas disease leads us to an alternative hypothesis for the absence of clinical cases in Arequipa: transmission in the city may be so recent that most infected individuals have yet to progress to late stage disease. Here we describe a new method, epicenter regression, that allows us to infer the spatial and temporal history of disease transmission from a snapshot of a population's infection status. We show that in a community of Arequipa, transmission of T. cruzi by the insect vector Triatoma infestans occurred as a series of focal micro-epidemics, the oldest of which began only around 20 years ago. These micro-epidemics infected nearly 5% of the community before transmission of the parasite was disrupted through insecticide application in 2004. Most extant human infections in our study community arose over a brief period of time immediately prior to vector control. According to our findings, the symptoms of chronic Chagas disease are expected to be absent, even if the strain is pathogenic in the chronic phase of disease, given the long asymptomatic period of the disease and short history of intense transmission. Traducción al español disponible en Alternative Language Text S1/A Spanish translation of this article is available in Alternative Language Text S1.

Absence of domestic triatomine colonies in an area of the coastal region of Ecuador where Chagas disease is endemic

Rhodnius ecuadoriensis is considered the second most important vector of Chagas disease in Ecuador. It is distributed across six of the 24 provinces and occupies intradomiciliary, peridomiciliary and sylvatic habitats. This study was conducted in six communities within the coastal province of Guayas. Triatomine searches were conducted in domestic and peridomestic habitats and bird nests using manual searches, live-bait traps and sensor boxes. Synantrhopic mammals were captured in the domestic and peridomestic habitats. Household searches (n = 429) and randomly placed sensor boxes (n = 360) produced no live triatomine adults or nymphs. In contrast, eight nymphs were found in two out of six searched Campylorhynchus fasciatus (Troglodytidae) nests. Finally, Trypanosoma cruzi DNA was amplified from the blood of 10% of the 115 examined mammals. Environmental changes in land use (intensive rice farming), mosquito control interventions and lack of intradomestic adaptation are suggested among the possible reasons for the lack of domestic triatomine colonies.

Limitations of selective deltamethrin application for triatomine control in central coastal Ecuador

Background

This year-long study evaluated the effectiveness of a strategy involving selective deltamethrin spraying and community education for control of Chagas disease vectors in domestic units located in rural communities of coastal Ecuador.

Results

Surveys for triatomines revealed peridomestic infestation with Rhodnius ecuadoriensis and Panstrongylus howardi, with infestation indices remaining high during the study (13%, 17%, and 10%, at initial, 6-month, and 12-month visits, respectively), which indicates a limitation of this strategy for triatomine population control. Infestation was found 6 and 12 months after spraying with deltamethrin. In addition, a large number of previously vector-free domestic units also were found infested at the 6- and 12-month surveys, which indicates new infestations by sylvatic triatomines. The predominance of young nymphs and adults suggests new infestation events, likely from sylvatic foci. In addition, infection with Trypanosoma cruzi was found in 65%, 21% and 29% at initial, 6-month and 12-month visits, respectively. All parasites isolated (n = 20) were identified as TcI.

Conclusion

New vector control strategies need to be devised and evaluated for reduction of T. cruzi transmission in this region.

Mexican Trypanosoma cruzi T. cruzi I strains with different degrees of virulence induce diverse humoral and cellular immune responses in a murine experimental infection model

It is has been shown that the majority of T. cruzi strains isolated from Mexico belong to the T. cruzi I (TCI). The immune response produced in response to Mexican T. cruzi I strains has not been well characterized. In this study, two Mexican T. cruzi I strains were used to infect Balb/c mice. The Queretaro (TBAR/MX/0000/Queretaro)(Qro) strain resulted in 100% mortality. In contrast, no mortality was observed in mice infected with the Ninoa (MHOM/MX/1994/Ninoa) strain. Both strains produced extended lymphocyte infiltrates in cardiac tissue. Ninoa infection induced a diverse humoral response with a higher variety of immunoglobulin isotypes than were found in Qro-infected mice. Also, a stronger inflammatory TH1 response, represented by IL-12p40, IFNγ, RANTES, MIG, MIP-1β, and MCP-1 production was observed in Qro-infected mice when compared with Ninoa-infected mice. We propose that an exacerbated TH1 immune response is a likely cause of pathological damage observed in cardiac tissue and the primary cause of death in Qro-infected mice.

The complexity of social mobilization in health communication: top-down and bottom-up experiences in polio eradication

The Polio Eradication Initiative (PEI) has been one of the most ambitious global health efforts in recent times. Social mobilization (SM) has been a strategic component of the PEI. Yet, a close-up analysis of SM dynamics seems to be lacking in the health communication literature. We examine critical aspects of the PEI experience in an attempt to move from dominant informational perspectives to a focus on emerging challenges in polio eradication efforts and new levels of complexity to SM. We examine available literature on communication and public health, available data on SM experiences that support polio eradication in Africa and Asia, and field work conducted by the authors where polio eradication efforts are ongoing. Our analysis suggests that (1) SM should not be casually approached as a top-down informational strategy to advance pre-established health goals; (2) centralized strategies hardly amount to SM; and (3) hybrid options that combine both activist and pragmatic SM are concrete possibilities for global health initiatives. In the context of renewed global democratization and persistent conflicts rooted in ethnicity, religion, and economics, it cannot be assumed that communities will either diligently espouse global goals or necessarily oppose them. Communication and SM strategies should rely on a clear understanding of the motives and agendas of involved actors. Resistance or opposition are important analytical dimensions as they may uncover new opportunities for effective health interventions. Further studies using these perspectives should be a priority for global health programs, including studies of the trust level, or lack thereof, among social actors.

Life cycle, feeding and defecation patterns of Rhodnius ecuadoriensis (Lent & León 1958) (Hemiptera: Reduviidae: Triatominae) under laboratory conditions

Rhodnius ecuadoriensis is the second most important vector of Chagas Disease (CD) in Ecuador. The objective of this study was to describe (and compare) the life cycle, the feeding and defecation patterns under laboratory conditions of two populations of this specie [from the provinces of Manabí (Coastal region) and Loja (Andean region)]. Egg-to-adult (n = 57) development took an average of 189.9 +/- 20 (Manabí) and 181.3 +/- 6.4 days (Loja). Mortality rates were high among Lojan nymphs. Pre-feeding time (from contact with host to feeding initiation) ranged from 4 min 42 s [nymph I (NI)] to 8 min 30 s (male); feeding time ranged from 14 min 45 s (NI)-28 min 25 s (male) (Manabí) and from 15 min 25 s (NI)-28 min 57 s (nymph V) (Loja). The amount of blood ingested increased significantly with instar and was larger for Manabí specimens (p < 0.001). Defecation while feeding was observed in Manabí specimens from stage nymph III and in Lojan bugs from stage nymph IV. There was a gradual, age-related increase in the frequency of this behaviour in both populations. Our results suggest that R. ecuadoriensis has the bionomic traits of an efficient vector of Trypanosoma cruzi. Together with previous data on the capacity of this species to infest rural households, these results indicate that control of synanthropic R. ecuadoriensis populations in the coastal and Andean regions may have a significant impact for CD control in Ecuador and Northern Peru.

Prognostic impact of Chagas disease in the United States

A prior publication from our group reported the fact that Chagas disease is underdiagnosed. This review will summarize several aspects of Chagas disease in the United States including modes of transmission, which will demonstrate that clinicians should be more aware of the disease and its consequences. Trypanosoma cruzi is present in many animal species spread throughout most of the United States. Chagas disease also reaches the North American continent through immigration, making it more frequent than expected. Apart from immigration, non-endemic countries should be aware of transmissions through blood transfusions, organ transplantations, or mother-to-child infections. In conclusion, it is possible that many chagasic cardiomyopathies are being misdiagnosed as "primary dilated idiopathic cardiomyopathies." Recognizing that there is an evident threat of Chagas disease present in the United States will allow an increase of clinician's awareness and hence will permit to correctly diagnose and treat this cardiomyopathy. Health authorities should guarantee a generalized screening of T cruzi of blood donors, before organ donations, and of pregnant women who were born or have lived in endemic areas.

Geographical clustering of Trypanosoma cruzi I groups from Colombia revealed by low-stringency single specific primer-PCR of the intergenic regions of spliced-leader genes

A low-stringency single-primer polymerase chain reaction (LSSP-PCR) typing procedure targeted to the intergenic regions of spliced-leader genes (SL) was designed to profile Trypanosoma cruzi I stocks from endemic regions of Colombia. Comparison between SL-LSSP-PCR profiles of parasite DNA from vector faeces and cultures isolated from those faeces showed more conservative signatures than profiles using LSSP-PCR targeted to the minicircle variable regions (kDNA). This was also observed by analysing 15 parasite clones from one stock as well as serial samples of a same stock after in vitro culturing or inoculation into mice. Thus, SL-LSSP-PCR appears more appropriate than kDNA-LSSP-PCR for reliable typing of major T. cruzi I groups from in vitro cultured stocks and triatomine faeces. SL-LSSP-PCR grouped 46 of 47 T. cruzi I Colombian stocks according to their geographical procedences in four clusters: Cluster Cas from Casanare Department, Cluster Mg from Northern Magdalena department, Cluster Mom from Momposina Depression in Southern Magdalena and finally Cluster NW from northwestern Colombia, including Sucre, Chocó, Córdoba and Antioquia departments. Sequence analysis identified punctual mutations among amplicons from each cluster. Within Cluster Mg, sequence polymorphism allowed association with different sylvatic vector species. Novel SL sequences and LSSP-PCR profiles are reported from T. cruzi I infecting Eratyrus cuspidatus, Panstrongylus geniculatus and Rhodnius pallescens vectors.

Chagas disease transmission in periurban communities of Arequipa, Peru

BACKGROUND

Chagas disease, caused by Trypanosoma cruzi infection, is an urban problem in Arequipa, Peru, and the epidemiology of Chagas disease is likely to be quite different in this area, compared with in rural zones.

METHODS

We conducted a serosurvey of 1615 children <18 years old in periurban districts that included hillside shantytowns and slightly more affluent low-lying communities. In addition, 639 adult residents of 1 shantytown were surveyed to provide data across the age spectrum for this community.

RESULTS

Of 1615 children, 75 (4.7%) were infected with Trypanosoma cruzi. Infection risk increased by 12% per year of age, and children living in hillside shantytowns were 2.5 times as likely to be infected as were those living in lower-lying communities. However, age-prevalence data from 1 shantytown demonstrated that adults were no more likely to be seropositive than were teenagers; the results of maximum likelihood modeling suggest that T. cruzi transmission began in this community <20 years ago.

CONCLUSIONS

The problem of Chagas disease in periurban settings, such as those around Arequipa, must be addressed to achieve elimination of vector-borne T. cruzi transmission. Identification of infected children, vector-control efforts, and education to avoid modifiable risk factors are necessary to decrease the burden of Chagas disease.