Author Correction: Surveillance of vector-borne pathogens under imperfect detection: lessons from Chagas disease risk (mis)measurement.

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Surveillance of vector-borne pathogens under imperfect detection: lessons from Chagas disease risk (mis)measurement.

Vector-borne pathogens threaten human health worldwide. Despite their critical role in disease prevention, routine surveillance systems often rely on low-complexity pathogen detection tests of uncertain accuracy. In Chagas disease surveillance, optical microscopy (OM) is routinely used for detecting Trypanosoma cruzi in its vectors. Here, we use replicate T. cruzi detection data and hierarchical site-occupancy models to assess the reliability of OM-based T. cruzi surveillance while explicitly accounting for false-negative and false-positive results. We investigated 841 triatomines with OM slides (1194 fresh, 1192 Giemsa-stained) plus conventional (cPCR, 841 assays) and quantitative PCR (qPCR, 1682 assays). Detections were considered unambiguous only when parasitologists unmistakably identified T. cruzi in Giemsa-stained slides. qPCR was >99% sensitive and specific, whereas cPCR was ~100% specific but only ~55% sensitive. In routine surveillance, examination of a single OM slide per vector missed ~50-75% of infections and wrongly scored as infected ~7% of the bugs. qPCR-based and model-based infection frequency estimates were nearly three times higher, on average, than OM-based indices. We conclude that the risk of vector-borne Chagas disease may be substantially higher than routine surveillance data suggest. The hierarchical modelling approach we illustrate can help enhance vector-borne disease surveillance systems when pathogen detection is imperfect.

Synanthropic triatomines as potential vectors of Trypanosoma cruzi in Central Brazil

Abstract INTRODUCTION: Chagas disease surveillance requires current knowledge on synanthropic triatomines. We analyzed the occurrence and Trypanosoma cruzi infection rates of triatomine bugs in central Brazil, during 2012-2014. METHODS: Triatomines were collected inside or around houses, and T. cruzi infection was determined by optical microscopy and conventional/quantitative polymerase chain reaction. RESULTS: Of the 2706 triatomines collected, Triatoma sordida was the most frequent species in Goiás State, whereas Panstrongylus megistus predominated in the Federal District. Parasites identified were T. cruzi, T. rangeli, and Blastocrithidia sp. CONCLUSIONS: P. megistus and T. sordida sustained the risk of T. cruzi transmission to humans in central Brazil.

Synanthropic triatomines as potential vectors of Trypanosoma cruzi in Central Brazil.

INTRODUCTION: Chagas disease surveillance requires current knowledge on synanthropic triatomines. We analyzed the occurrence and Trypanosoma cruzi infection rates of triatomine bugs in central Brazil, during 2012-2014. METHODS: Triatomines were collected inside or around houses, and T. cruzi infection was determined by optical microscopy and conventional/quantitative polymerase chain reaction. RESULTS: Of the 2706 triatomines collected, Triatoma sordida was the most frequent species in Goiás State, whereas Panstrongylus megistus predominated in the Federal District. Parasites identified were T. cruzi, T. rangeli, and Blastocrithidia sp. CONCLUSIONS: P. megistus and T. sordida sustained the risk of T. cruzi transmission to humans in central Brazil.

Experimental infection of T4 Acanthamoeba genotype determines the pathogenic potential.

T4 is the Acanthamoeba genotype most related to cases of granulomatous amoebic encephalitis (GAE) in immunocompromised patients and of keratitis in contact lens wearers. The determination of the pathogenic potential of Acanthamoeba clinical and environmental isolates using experimental models is extremely important to elucidate the capacity of free-living organisms to establish and cause disease in hosts. The aim of this study was to compare and evaluate the histopathology and culture between two different routes of experimental infection of T4 Acanthamoeba isolated from environmental and clinical source in mice (intracranial and intraperitoneal). Swiss isogenic healthy mice were inoculated with 10(4) trophozoites by intracranial (IC) and intraperitoneal (IP) routes and observed during 21 days. The brains from animals inoculated by the IC route were collected and from the animals of the IP inoculation group, the brains, livers, kidneys, spleens, and lungs were removed. The organs were prepared and appropriately divided to be evaluated with histopathology and culture. There was no significant difference between the inoculation routes in terms of isolates recovery (χ(2) = 0.09; p = 0.76). In the IC group, isolate recovery rate was significantly higher in histopathology than the one achieved by culture (χ(2) = 6.45; p < 0.01). Experimental infection revealed that all isolates inoculated could be considered invasive because it was possible to recover evolutive forms of Acanthamoeba in both routes. This work represents the first in vivo pathogenicity assay of primary isolation source in Central region of Brazil showing in vivo pathogenicity and hematogenous spread capacity of these protozoa, improving the knowledge on free-living amoebae isolates.

Vector-borne transmission of Trypanosoma cruzi among captive Neotropical primates in a Brazilian zoo.

BACKGROUND: Neotropical primates are important sylvatic hosts of Trypanosoma cruzi, the etiological agent of Chagas disease. Infection is often subclinical, but severe disease has been described in both free-ranging and captive primates. Panstrongylus megistus, a major T. cruzi vector, was found infesting a small-primate unit at Brasília zoo (ZooB), Brazil. ZooB lies close to a gallery-forest patch where T. cruzi circulates naturally. Here, we combine parasitological and molecular methods to investigate a focus of T. cruzi infection involving triatomine bugs and Neotropical primates at a zoo located in the Brazilian Savannah. METHODS: We assessed T. cruzi infection in vectors using optical microscopy (n = 34) and nested PCR (n = 50). We used quantitative PCR (qPCR) to examine blood samples from 26 primates and necropsy samples from two primates that died during the study. We determined parasite lineages in five vectors and two primates by comparing glucose-6-phosphate isomerase (G6pi) gene sequences. RESULTS: Trypanosoma cruzi was found in 44 vectors and 17 primates (six genera and eight species); one Mico chrysoleucus and one Saguinus niger had high parasitaemias. Trypanosoma cruzi DNA was detected in three primates born to qPCR-negative mothers at ZooB and in the two dead specimens. One Callithrix geoffroyi became qPCR-positive over a two-year follow-up. All G6pi sequences matched T. cruzi lineage TcI. CONCLUSIONS: Our findings strongly suggest vector-borne T. cruzi transmission within a small-primate unit at ZooB - with vectors, and perhaps also parasites, presumably coming from nearby gallery forest. Periodic checks for vectors and parasites would help eliminate T. cruzi transmission foci in captive-animal facilities. This should be of special importance for captive-breeding programs involving endangered mammals, and would reduce the risk of accidental T. cruzi transmission to keepers and veterinarians.

Susceptibility of different Rhodnius species (Hemiptera, Reduviidae, Triatominae) to a Brazilian strain of Trypanosoma rangeli (SC58/KP1-).

INTRODUCTION: Specific host-parasite associations have been detected experimentally and suggest that triatomines of the genus Rhodnius act as biological filters in the transmission of Trypanosoma rangeli . OBJECTIVE: To analyze the susceptibility of four Rhodnius species ( Rhodnius robustus , Rhodnius neglectus , Rhodnius nasutus and Rhodnius pictipes ) to a Brazilian strain of T. rangeli (SC-58/KP1-). MATERIALS AND METHODS: We selected t hirty nymphs of each species, which were fed on blood infected with T. rangeli . Periodically, samples of feces and hemolymph were analyzed. Triatomines with T. rangeli in their hemolymph were fed on mice to check for transmission by bites. Later, the triatomines were dissected to confirm salivary gland infection. RESULTS: Specimens of R. pictipes showed higher rates of intestinal infection compared to the other three species. Epimastigotes and trypomastigotes were detected in hemolymph of four species; however, parasitism was lower in the species of the R. robustus lineage. Rhodnius robustus and R. neglectus specimens did not transmit T. rangeli by bite; after dissection, their glands were not infected. Only one specimen of R. nasutus and two of R. pictipes transmitted the parasite by bite. The rate of salivary gland infection was 16% for R. pictipes and 4% for R. nasutus . CONCLUSIONS: Both infectivity (intestinal, hemolymphatic and glandular) and transmission of T. rangeli (SC58/KP1-) were greater and more efficient in R. pictipes. These results reinforce the hypothesis that these triatomines may act as biological filters in the transmission of T. rangeli .

Multiplex Real-Time PCR Assay Using TaqMan Probes for the Identification of Trypanosoma cruzi DTUs in Biological and Clinical Samples.

BACKGROUND: Trypanosoma cruzi has been classified into six Discrete Typing Units (DTUs), designated as TcI-TcVI. In order to effectively use this standardized nomenclature, a reproducible genotyping strategy is imperative. Several typing schemes have been developed with variable levels of complexity, selectivity and analytical sensitivity. Most of them can be only applied to cultured stocks. In this context, we aimed to develop a multiplex Real-Time PCR method to identify the six T. cruzi DTUs using TaqMan probes (MTq-PCR). METHODS/PRINCIPAL FINDINGS: The MTq-PCR has been evaluated in 39 cultured stocks and 307 biological samples from vectors, reservoirs and patients from different geographical regions and transmission cycles in comparison with a multi-locus conventional PCR algorithm. The MTq-PCR was inclusive for laboratory stocks and natural isolates and sensitive for direct typing of different biological samples from vectors, reservoirs and patients with acute, congenital infection or Chagas reactivation. The first round SL-IR MTq-PCR detected 1 fg DNA/reaction tube of TcI, TcII and TcIII and 1 pg DNA/reaction tube of TcIV, TcV and TcVI reference strains. The MTq-PCR was able to characterize DTUs in 83% of triatomine and 96% of reservoir samples that had been typed by conventional PCR methods. Regarding clinical samples, 100% of those derived from acute infected patients, 62.5% from congenitally infected children and 50% from patients with clinical reactivation could be genotyped. Sensitivity for direct typing of blood samples from chronic Chagas disease patients (32.8% from asymptomatic and 22.2% from symptomatic patients) and mixed infections was lower than that of the conventional PCR algorithm. CONCLUSIONS/SIGNIFICANCE: Typing is resolved after a single or a second round of Real-Time PCR, depending on the DTU. This format reduces carryover contamination and is amenable to quantification, automation and kit production.

Susceptibility of different Rhodnius species (Hemiptera, Reduviidae, Triatominae) to a Brazilian strain of Trypanosoma rangeli (SC58/KP1-) / Sensibilidad de diferentes especies de Rhodnius (Hemiptera, Reduviidae, Triatominae) a una cepa brasileña de Trypanosoma rangeli (SC58/KP1-)

Introduction: Specific host-parasite a ssociations have been detected experimentally and suggest that triatomines of the genus Rhodnius act as biological filters in the transmission of Trypanosoma rangeli . Objective: To analyze the susceptibility of four Rhodnius species ( Rhodnius robustus , Rhodnius neglectus , Rhodnius nasutus and Rhodnius pictipes ) to a Brazilian strain of T. rangeli (SC-58/KP1-). Materials and methods: We selected t hirty nymphs of each species, which were fed on blood infected with T. rangeli . Periodically, samples of feces and hemolymph were analyzed. Triatomines with T. rangeli in their hemolymph were fed on mice to check for transmission by bites. Later, the triatomines were dissected to confirm salivary gland infection. Results: Specimens of R. pictipes showed higher rates of intestinal infection compared to the other three species. Epimastigotes and trypomastigotes were detected in hemolymph of four species; however, parasitism was lower in the species of the R. robustus lineage. Rhodnius robustus and R. neglectus specimens did not transmit T. rangeli by bite; after dissection, their glands were not infected. Only one specimen of R. nasutus and two of R. pictipes transmitted the parasite by bite. The rate of salivary gland infection was 16% for R. pictipes and 4% for R. nasutus . Conclusions: Both infectivity (intestinal, hemolymphatic and glandular) and transmission of T. rangeli (SC58/KP1-) were greater and more efficient in R. pictipes. These results reinforce the hypothesis that these triatomines may act as biological filters in the transmission of T. rangeli .

Introducción. Se han detectado asociaciones biológicas huésped-parásito específicas que sugieren que los triatominos del género Rhodnius podrían actuar como filtros biológicos en la transmisión de Trypanosoma rangeli . Objetivo. Estudiar la sensibilidad de cuatro especies de Rhodnius ( Rhodnius robustus , Rhodnius neglectus , Rhodnius nasutus y Rhodnius p ictipes ) frente a la cepa de T. rangeli (SC-58/KP1-). Materiales y métodos. Se seleccionaron treinta ninfas de cada especie después de xenodiagnóstico artificial en sangre infectada con T. rangeli. Se examinaron periódicamente m uestras de heces y hemolinfa. Los insectos con hemolinfas infectadas fueron alimentados en ratones a fin de comprobar la transmisión por picadura y posteriormente disecados para confirmar la infección de las glándulas salivales . Resultados . En Rhodnius pictipes se encontró un mayor porcentaje de infección intestinal que en las otras especies . Se detectaron epimastigotes y tripomastigotes en la hemolinfa de las cuatro especies , y se encontró que el parasitismo fue menor en las especies del linaje R. robustus . Rhodnius robustus y R. neglectus no transmitían T. rangeli a ratones por picadura: después de la disección , sus glándulas no estaban infectadas. Solo un espécimen de R. nasutus y dos de R. pictipes transmitieron el parásito por la picadura . La tasa de infección glandular fue de 16 % para R. pictipes y de 4 % para R. nasutus . Conclusiones . La capacidad infecciosa ( hemolinfática, intestinal y glandular ) y la transmisión de T. rangeli (SC-58/KP1-) fueron mayores y más eficientes en R. pictipes . Estos resultados refuerzan la hipótesis de que estos triatominos actúan como filtros biológicos en la transmisión de T. rangeli .

Occurrence and characterization of Acanthamoeba similar to genotypes T4, T5, and T2/T6 isolated from environmental sources in Brasília, Federal District, Brazil.

Species of Acanthamoeba can cause keratitis and brain infections. The characterization of environmental isolates is necessary to analyze the risk of human infection. We aimed at identifying and genotyping Acanthamoeba isolates from soil, swimming pools, and water features in Brasília, Federal District, Brazil, as well as determining their physiological characteristics and pathogenic potential. Among the 18 isolates studied, eight were similar to genotype T5, five to T4, and one to T2/T6, classified by the sequence analysis of 18S rDNA. Genotypes of four isolates were not determined. Ten isolates (55%) grew at 37 °C and seven (39%) grew in media with 1.5M mannitol, which are the physiological parameters associated with pathogenic Acanthamoeba; also, four isolates from swimming pools presented high pathogenic potential. Our results indicate a widespread distribution of potentially pathogenic Acanthamoeba T4, T5, and T2/T6 in different environmental sources in Brasília, revealing the potential risk of human infection and the need of preventive measures.

Adaptabilidad de cepas argentinas de Trypanosoma cruzi en Dipetalogaster maxima (Uhler, 1894) / Adaptability of Argentine strains of Trypanosoma cruzi in Dipetalogaster maxima

Dipetalogaster maxima habita el sur de la península de Baja California, México. La adaptabilidad de las cepas argentinas de Trypanosoma cruzi a vectores propios de otras latitudes podría tener importancia epidemiológica y para su uso en xenodiagnóstico. El objetivo principal del presente estudio fue investigar si existía buena adaptación de cepas de T. cruzi (circulantes en Santiago del Estero, Argentina) en D. maxima, comparativamente con Triatoma infestans. Se utilizaron ninfas I de D. maxima y ninfas III de T. infestans, criadas en laboratorio. Se realizaron diez xenodiagnósticos sobre pacientes chagásicos crónicos no tratados, con serología positiva para cada especie, en paralelo. El peso promedio de sangre ingerida por cada ejemplar fue 61.4 mg para T. infestans y 63.8 mg para D. maxima. A los 30 días, la materia fecal de los insectos fue examinada al microscopio óptico. Se encontró que el 30% de los ejemplares de T. infestans y el 20% de los de D. maxima estaban infectados. Todos los pacientes que mostraron positividad en el xenodiagnóstico con D. maxima también fueron positivos con T. infestans. Comparados los resultados de infectividad, existió significación estadística válida para afirmar que las cepas de T. cruzi argentinas estudiadas se adaptaban a D. maxima. Consideramos importante este primer registro de infectividad de D. maxima con T. cruzi de pacientes chagásicos crónicos de la Argentina debido a la adaptabilidad significativa demostrada, ya que posibilitaría su utilización para xenodiagnóstico. Además, y a pesar del hábitat y la distribución actual de D.maxima, podría tener repercusiones epidemiológicas futuras, como consecuencia de los procesos de globalización y cambios climáticos que se observan en el planeta.

Adaptabilidad de cepas argentinas de Trypanosoma cruzi en Dipetalogaster maxima (Uhler, 1894) / Adaptability of Argentine strains of Trypanosoma cruzi in Dipetalogaster maxima

Dipetalogaster maxima habita el sur de la península de Baja California, México. La adaptabilidad de las cepas argentinas de Trypanosoma cruzi a vectores propios de otras latitudes podría tener importancia epidemiológica y para su uso en xenodiagnóstico. El objetivo principal del presente estudio fue investigar si existía buena adaptación de cepas de T. cruzi (circulantes en Santiago del Estero, Argentina) en D. maxima, comparativamente con Triatoma infestans. Se utilizaron ninfas I de D. maxima y ninfas III de T. infestans, criadas en laboratorio. Se realizaron diez xenodiagnósticos sobre pacientes chagásicos crónicos no tratados, con serología positiva para cada especie, en paralelo. El peso promedio de sangre ingerida por cada ejemplar fue 61.4 mg para T. infestans y 63.8 mg para D. maxima. A los 30 días, la materia fecal de los insectos fue examinada al microscopio óptico. Se encontró que el 30% de los ejemplares de T. infestans y el 20% de los de D. maxima estaban infectados. Todos los pacientes que mostraron positividad en el xenodiagnóstico con D. maxima también fueron positivos con T. infestans. Comparados los resultados de infectividad, existió significación estadística válida para afirmar que las cepas de T. cruzi argentinas estudiadas se adaptaban a D. maxima. Consideramos importante este primer registro de infectividad de D. maxima con T. cruzi de pacientes chagásicos crónicos de la Argentina debido a la adaptabilidad significativa demostrada, ya que posibilitaría su utilización para xenodiagnóstico. Además, y a pesar del hábitat y la distribución actual de D.maxima, podría tener repercusiones epidemiológicas futuras, como consecuencia de los procesos de globalización y cambios climáticos que se observan en el planeta.(AU)

Infestation of Mauritia flexuosa palms by triatomines (Hemiptera: Reduviidae), vectors of Trypanosoma cruzi and Trypanosoma rangeli in the Brazilian savanna.

To determine the infestation and trypanosome infection of triatomines captured in Mauritia flexuosa palm trees across its geographic distribution in the Brazilian savanna (Cerrado), we sampled 42 localities in eight states and in the Federal District, Brazil, between July 2005 and January 2010. Overall, 2154 specimens of the species Rhodnius neglectus, Psammolestes tertius, Triatoma sordida, and Microtriatoma borbai, were collected. Among the 341 palms sampled, 182 (53.3%) were infested with R. neglectus, which resulted in the capture of 1639 specimens (9.0 insects per infested palm). P. tertius occurred in 26 palms (8%), which resulted in the capture of 484 specimens (19 insects per infested palm). T. sordida (n=30) and M. borbai (n=1) occurred in only one location. From 537 R. neglectus examined, 44 were infected (8%) with Trypanosoma rangeli and/or Trypanosoma cruzi (Tc Id). M. flexuosa was previously recognized as a suitable breeding ecotope for R. neglectus in the Brazilian states of Minas Gerais, Goiás, Tocantins and the Federal District. Our results expand this distribution to other states (São Paulo, Bahia, Mato Grosso, Maranhão and Piauí), and also show that this particular palm tree harbors other triatomine species. Finally, we show that R. neglectus plays an important role in maintaining the enzootic circulation of T. cruzi and T. rangeli in the Brazilian savanna.

Curso de Enfermedades Vectoriales. Módulo 3 Dengue / Vector Diseases Course. Module 3 Dengue

Este módulo les propone conocer con más detalle el Dengue. Les presenta con detalle cómo es el insecto que participa en la transmisión del Dengue, qué características tiene el virus que lo produce, cómo se desarrolla la enfermedad y de qué manera pueden participar ustedes en su prevención. Para comprender estos puntos, es muy importante que tengan presente lo que se trabajó en el módulo anterior acerca de la concepción de salud, la organización del sistema de atención de salud, las herramientas que aporta la Epidemiología, las generalidades sobre vectores y las enfermedades que ellos transmiten, y los cuidados a tener al manipular los residuos.

[Comparative biology and feeding behavior of Rhodnius neglectus and Rhodnius robustus (Triatominae) under laboratory conditions]. / Biologia comparativa e comportamento alimentar de Rhodnius neglectus e Rhodnius robustus (Triatominae) sob condições de laboratório.

INTRODUCTION: The vector competence of triatomine insects is determined by studying their biology and feeding behavior under field and/or laboratory conditions. Factors including the number of bites, the amount of blood ingested and defecation time have implications for trypanosome transmission. The biological and behavioral parameters of Rhodnius neglectus and R. robustus were compared under experimental conditions to estimate differences in the potential transmission of trypanosomes. METHODS: The insects were observed daily to determine the period of nymphal development, mortality, detection of food source, number of bites, time of blood meal intake, amount of blood ingested, time elapsed between the end of the meal and the first defecation and the frequency of defecation. RESULTS: Although the nymphal development of R. neglectus (156.4 ± 25.05d) was lower than that of R. robustus (204.7 ± 13.22d), the mortality between species was similar (63.8 and 65% respectively).R. robustus and R. neglectus quickly located the food source, especially in the first instar (2.5 and 1.6 min, respectively). Although the time of blood meal intake was similar between the species, R. robustus ingested a larger amount of blood on average at all stages and exhibited higher values for the fifth instar. Nymphs of R. neglectus bit more frequently, and they defecated faster and more often than those of R. robustus. CONCLUSIONS: Under laboratory conditions, R. neglectus has a greater potential for transmission of Trypanosoma cruzi and T. rangeli than does R. robustus, an attribute that should be further evaluated in experimental infections.

Biologia comparativa e comportamento alimentar de Rhodnius neglectus e Rhodnius robustus (Triatominae) sob condições de laboratório / Comparative biology and feeding behavior of Rhodnius neglectus and Rhodnius robustus (Triatominae) under laboratory conditions

INTRODUÇÃO: A competência vetorial de triatomíneos é determinada a partir de estudos sobre biologia e comportamento alimentar em condições de campo e/ou laboratório. Fatores como número de picadas, quantidade de sangue ingerido e tempo de defecação têm implicações na transmissão de tripanosomatídeos. Parâmetros biológicos e comportamentais de Rhodnius neglectus e R. robustus foram comparados experimentalmente para estimar diferenças no potencial de transmissão de tripanosomatídeos. MÉTODOS: Os triatomíneos foram observados diariamente para determinar o período de desenvolvimento ninfal, mortalidade, detecção da fonte alimentar, número de picadas, tempo do repasto sanguíneo, quantidade de sangue ingerido, tempo entre o final do repasto e a primeira defecação e frequência de defecação. RESULTADOS: Apesar do período ninfal de R. neglectus (156,4 ± 25,05d) ter sido menor que o de R. robustus (204,7 ± 13,22d), a mortalidade foi similar entre as espécies (63,8 e 65%, respectivamente). R. robustus e R. neglectus detectaram rapidamente a fonte alimentar, especialmente no primeiro estádio (2,5 e 1,6min, respectivamente). Apesar do tempo de repasto sanguíneo ter sido similar entre as espécies, R. robustus ingeriu em média uma maior quantidade de sangue em todos os estádios, com maiores valores para as ninfas V. As ninfas de R. neglectus picaram mais vezes as fontes alimentares, defecaram mais rápido e mais frequentemente que as de R. robustus. CONCLUSÕES: Sob as condições de laboratório usadas, R. neglectus possui um maior potencial para transmissão de Trypanosoma cruzi e T. rangeli que R. robustus, atributo que deve ser avaliado em infecções experimentais.

INTRODUCTION: The vector competence of triatomine insects is determined by studying their biology and feeding behavior under field and/or laboratory conditions. Factors including the number of bites, the amount of blood ingested and defecation time have implications for trypanosome transmission. The biological and behavioral parameters of Rhodnius neglectus and R. robustus were compared under experimental conditions to estimate differences in the potential transmission of trypanosomes. METHODS: The insects were observed daily to determine the period of nymphal development, mortality, detection of food source, number of bites, time of blood meal intake, amount of blood ingested, time elapsed between the end of the meal and the first defecation and the frequency of defecation. RESULTS: Although the nymphal development of R. neglectus (156.4 ± 25.05d) was lower than that of R. robustus (204.7 ± 13.22d), the mortality between species was similar (63.8 and 65% respectively).R. robustus and R. neglectus quickly located the food source, especially in the first instar (2.5 and 1.6 min, respectively). Although the time of blood meal intake was similar between the species, R. robustus ingested a larger amount of blood on average at all stages and exhibited higher values for the fifth instar. Nymphs of R. neglectus bit more frequently, and they defecated faster and more often than those of R. robustus. CONCLUSIONS: Under laboratory conditions, R. neglectus has a greater potential for transmission of Trypanosoma cruzi and T. rangeli than does R. robustus, an attribute that should be further evaluated in experimental infections.

Sequence analysis of the spliced-leader intergenic region (SL-IR) and random amplified polymorphic DNA (RAPD) of Trypanosoma rangeli strains isolated from Rhodnius ecuadoriensis, R. colombiensis, R. pallescens and R. prolixus suggests a degree of co-evolution between parasites and vectors.

Spliced leader intergenic region (SL-IR) sequences from 23 Trypanosoma rangeli strains isolated from the salivary glands of Rhodnius colombiensis, R. ecuadoriensis, R. pallescens and R. prolixus and two human strains revealed the existence of 4 genotypes with CA, GT, TA, ATT and GTAT microsatellite repeats and the presence of insertions/deletions (INDEL) and single nucleotide polymorphism (SNP) characterizing each genotype. The strains isolated from the same vector species or the same Rhodnius evolutionary line presented the same genotypes, even in cases where strains had been isolated from vectors captured in geographically distant regions. The dendrogram constructed from the SL-IR sequences separated all of them into two main groups, one with the genotypes isolated from R. prolixus and the other group containing three well defined sub-groups with the genotypes isolated from R. pallescens, R. colombiensis and R. ecuadoriensis. Random amplified polymorphic DNA (RAPD) analysis showed the same two main groups and sub-groups supporting strict T. rangeli genotypes' association with Rhodnius species. Combined with other studies, these results suggest a possible co-evolutionary association between T. rangeli genotypes and their vectors.

Trypanosoma cruzi I genotypes in different geographical regions and transmission cycles based on a microsatellite motif of the intergenic spacer of spliced-leader genes.

The intergenic region of spliced-leader (SL-IR) genes from 105 Trypanosoma cruzi I (Tc I) infected biological samples, culture isolates and stocks from 11 endemic countries, from Argentina to the USA were characterised, allowing identification of 76 genotypes with 54 polymorphic sites from 123 aligned sequences. On the basis of the microsatellite motif proposed by Herrera et al. (2007) to define four haplotypes in Colombia, we could classify these genotypes into four distinct Tc I SL-IR groups, three corresponding to the former haplotypes Ia (11 genotypes), Ib (11 genotypes) and Id (35 genotypes); and one novel group, Ie (19 genotypes). Genotypes harbouring the Tc Ic motif were not detected in our study. Tc Ia was associated with domestic cycles in southern and northern South America and sylvatic cycles in Central and North America. Tc Ib was found in all transmission cycles from Colombia. Tc Id was identified in all transmission cycles from Argentina and Colombia, including Chagas cardiomyopathy patients, sylvatic Brazilian samples and human cases from French Guiana, Panama and Venezuela. Tc Ie gathered five samples from domestic Triatoma infestans from northern Argentina, nine samples from wild Mepraia spinolai and Mepraia gajardoi and two chagasic patients from Chile and one from a Bolivian patient with chagasic reactivation. Mixed infections by Tc Ia+Tc Id, Tc Ia+Tc Ie and Tc Id+Tc Ie were detected in vector faeces and isolates from human and vector samples. In addition, Tc Ia and Tc Id were identified in different tissues from a heart transplanted Chagas cardiomyopathy patient with reactivation, denoting histotropism. Trypanosoma cruzi I SL-IR genotypes from parasites infecting Triatoma gerstaeckeri and Didelphis virginiana from USA, T. infestans from Paraguay, Rhodnius nasutus and Rhodnius neglectus from Brazil and M. spinolai and M. gajardoi from Chile are to our knowledge described for the first time.

Predicting the potential geographical distribution of Rhodnius neglectus (Hemiptera, Reduviidae) based on ecological niche modeling.

Rhodnius neglectus is frequently found in palm trees and bird nests in sylvatic environments. However, adult specimens infected by Trypanosoma cruzi have been invading houses in central Brazil. Analyzing and predicting the geographical distribution of this species may improve vector surveillance strategies for Chagas disease. Ecological niche modeling using the genetic algorithm for rule-set production (GARP) was applied to predict the geographical distribution of R. neglectus from occurrence records and a set of 23 predictor variables (e.g., temperature, precipitation, altitude, and vegetation). Additionally, the geographical distribution of R. neglectus was compared with the geographical distribution of four species of palm trees and two species of birds from the study region. The models were able to predict, with high probability, the occurrence of R. neglectus as a regular (although nonendemic) species of the Cerrado biome in central Brazil. Caatinga, Amazonian savanna, Pantanal, and the Bolivian Chaco appear as areas with lower probabilities of potential occurrence for the species. A great overlap was observed between the distribution of R. neglectus, palm trees (Acrocomia aculeata and Syagrus oleracea), and birds (Phacellodomus ruber and Pseudoseisura cristata). By including new records for R. neglectus (from both sylvatic and domestic environments), our study showed a distribution increase toward the west and northeast areas of Brazil in the "diagonal of open/dry ecoregions of South America". These results should aid Chagas disease vector surveillance programs, given that household invasion by Rhodnius species maintains the risk of disease transmission and limits control strategies.

Is Rhodnius prolixus (Triatominae) invading houses in central Brazil?

Sylvatic triatomines of the genus Rhodnius commonly fly into houses in Latin America, maintaining the risk of Chagas disease transmission in spite of control efforts. In the recent past, adult bugs collected inside houses in central Brazil were identified as R. prolixus, a primary disease vector whose natural geographical range excludes this region. Three nearly sibling species (R. neglectus, R. nasutus, and R. robustus), secondary vectors with limited epidemiological significance, occur naturally south of the Brazilian Amazon. The specific status of Rhodnius specimens found inside houses in central Brazil is therefore an epidemiologically important (and still debated) issue. We used wing and head geometric morphometrics to investigate the taxonomic status of 230 adult specimens representing all four 'R. prolixus group' species (19 populations from palm trees, domiciles, and reference laboratory colonies). Discriminant analyses of shape variation allowed for an almost perfect reclassification of individuals to their putative species. Shape patterning revealed no consistent differences between most specimens collected inside houses in central Brazil and R. neglectus, and showed that R. robustus and R. neglectus occur sympatrically (and fly into houses) in southern Amazonia. Furthermore, all Brazilian specimens clearly differed from our reference R. prolixus population. Using geometric morphometrics, we confidently ascribed individual triatomines to their species within the problematic 'R. prolixus group', illustrating the potential value of this approach in entomological surveillance. Our results strongly support the idea that R. neglectus, and not R. prolixus, is the species invading houses in central Brazil.