Residual foci of Triatoma infestans infestation: Surveillance and control in Rio Grande do Sul, Brazil, 2001-2018

Abstract INTRODUCTION: This retrospective study conducted from 2001 to 2018 investigated the residual foci of Triatoma infestans infestation in Rio Grande do Sul, Brazil. METHODS: The data were obtained via entomological surveillance and the distribution of vector occurrence. The coverage of active research was mapped. RESULTS: The largest coverage rate for active research was observed in the northwest region of the total of 515,081 domiciles researched. Most T. infestans specimens were captured in the peridomicile. CONCLUSIONS: Infestation has decreased significantly since 2008, and T. infestans has not been captured since 2015.

Conocimientos sobre Enfermedad de Chagas y Triatoma infestans en Pobladores del Departamento de San Pedro, Paraguay 2019 / Knowledge about Chagas disease and Triatoma infestans in inhabitants of the Department of San Pedro, Paraguay 2019

La tripanosomiasis americana o enfermedad de Chagas, producida por el protozoo hemoflagelado Trypanosoma cruzi. En Paraguay el principal vector Triatoma infestans ("vinchuca" o "chichã guasu") es considerado, en términos sociales y económicos, una de las enfermedades parasitarias más importantes que pueden desencadenar complicaciones graves cardiológicas. Durante el Periodo 2014 al 2017 en el Departamento de San Pedro se registraron 302 casos de Enfermedad de Chagas detectados por serología. El objetivo del estudio estuvo dirigido a investigar el nivel de conocimiento de la población que, por su forma de vida, presentan factores de riesgo. Se realizó una investigación cualitativa exploratoria, con enfoque hermenéutico. La población de estudio estuvo conformada por 41 familias que residen en comunidades del Departamento de San Pedro, que se encuentran entre 15 km a 40 km de zonas urbanas, a quienes se le realizo una entrevista semi-estructurada en profundidad. Entre los resultados obtenidos se evidenció que: La mayoría de los pobladores de la zona conocen al triatoma y lo pudieron observar cuando eran niños y algunos afirman haber sido picados, pudiendo así describir la morfología y otras características del vector; la mayoría desconoce la sintomatología producida por el T. cruzi, pero tienen un conocimiento básico relacionado a la enfermedad.

The american trypanosomiasis, also known as Chagas disease, is caused by an hemophlagelated protozoo called Trypanosoma cruzi. In Paraguay, the most relevant vector is Triatoma infestans (vinchuca or "chichã guasu") is considered, in social and economic terms, one of the most important parasitic diseases which may cause severe cardiological complications. Since 2014 till 2017, in San Pedro´s department, have been registered 302 cases of Chagas disease, all detected by serology. The objective of this study was directed to investigate the degree of knowledge of the population that, because of their lifestyles, presents risk factors. It has been made a qualitative-exploratory investigation, with hermeneutic focus. The population studied was made up for 41 families which reside in communities of San Pedro´s department, that are located around 15/40 km of urban zones. They all had a deep semi-structured interview. The results showed that: most of the settlers know triatoma and could observe it when they were children and also some of them affirm have been chopped, being able to describe the morphology and other characteristics of the vector. Most of the interviewed unknown the symptomatology produced by T. cruzi, but have the basic knowledge related with this disease.

Revisión de más de 40 años de estudios en pacientes seropositivos para la enfermedad de Chagas en la provincia de Entre Ríos, Argentina / Review of more than 40 years of studies in seropositive patients for Chagas disease in the province of Entre Ríos, Argentina

El presente trabajo es una revisión de más de 40 años de investigación sobre los aspectos epidemiológicos, socioeconómicos y clínicos de la Enfermedad de Chagas en el Departamento Uruguay (Provincia de Entre Ríos). Se resumen las investigaciones sobre la presencia de vectores triatominos en viviendas urbanas y rurales donde se procedió a su identificación y búsqueda de Trypanosoma cruzi. Se describió la seroprevalencia de la enfermedad y su evolución a lo largo del tiempo. Se agregaron también aspectos cardiológicos y gastroenterológicos de pacientes en el período crónico de la enfermedad. La presencia de triatominos derivó en campañas de fumigación y de educación sanitaria, que provocaron un marcado descenso en el número de vectores capturados en los años siguientes. También se destacó el descenso de la seroprevalencia de la enfermedad de Chagas a través del tiempo, debido a las campañas de fumigación, educación sanitaria, controles en banco de sangre y embarazadas, mejora de las técnicas utilizadas y la aparición de tratamientos efectivos contra el parásito. Los estudios cardiológicos y gastroenterológicos de los pacientes crónicos mostraron alteraciones dentro de lo esperado para este estadio de la enfermedad. También se describió la detección de personas infectadas con acceso al tratamiento y los estudios cardiológicos y gastroenterológicos realizados en pacientes en estadio crónico. Por último, se considera que, globalmente, los estudios realizados en la zona han colaborado en lograr que la Provincia de Entre Ríos fuera declarada libre de transmisión vectorial en 2012.

This is a review of more than 40 years of research on the epidemiological, socioeconomic and clinical aspects of Chagas disease in the Department of Uruguay (Entre Ríos province). Research on the presence of triatomine vectors in urban and rural housing is summarized here.These vectors were identified and Trypanosoma cruzi was searched for. . The seroprevalence of the disease and its evolution over time were described. Cardiological and gastroenterological aspects of patients in the chronic period of the disease were also added. The presence of triatomines resulted in fumigation and health education campaigns, which caused a marked decrease in the number of vectors captured in the following years. The decrease in the seroprevalence of Chagas disease over time was also highlighted, due to fumigation campaigns, health education, blood bank and pregnant women controls, improvement of the techniques used and the development of effective treatments against the parasite. Cardiological and gastroenterological studies of chronic patients showed the abnormalities expected for this stage of the disease. The detection of infected persons with access to treatment and cardiological and gastroenterological studies performed in patients with chronic stage were also described. Finally, it is considered that, globally, the studies carried out in the area have helped to ensure that the Province of Entre Ríos be declared free of the vector transmission in 2012.

Este trabalho é uma revisão de mais de 40 anos de pesquisa sobre os aspectos epidemiológicos, socioeconômicos e clínicos da doença de Chagas no Departamento Uruguai (província de Entre Ríos). São resumidas as pesquisas sobre a presença de vetores de triatomíneos em moradias urbanas e rurais, onde foram identificados e pesquisados por Trypanosoma cruzi nelas. A soroprevalência da doença e sua evolução ao longo do tempo foram descritas. Também foram adicionados aspectos cardiológicos e gastroenterológicos dos pacientes no período crônico da doença. A presença de triatomíneos resultou em campanhas de fumigação e educação sanitária, o que causou uma redução acentuada no número de vetores capturados nos anos seguintes. Também foi destacada a diminuição da soroprevalência da doença de Chagas através do tempo, devido às campanhas de fumigação, educação sanitária, controles em bancos de sangue e gestantes, melhora das técnicas utilizadas e surgimento de tratamentos eficazes contra o parasita. Estudos cardiológicos e gastroenterológicos de pacientes crônicos mostraram alterações dentro do esperado para esse estágio da doença. Também foram descritas a detecção de pessoas infectadas com acesso ao tratamento e estudos cardiológicos e gastroenterológicos realizados em pacientes em estágio crônico. Por fim, consideramos que, globalmente, os estudos realizados na área ajudaram a garantir que a Província de Entre Ríos fosse declarada livre de transmissão vetorial em 2012.

Factors associated with the presence of triatomines in rural areas of south Argentine Chaco

Abstract INTRODUCTION: The domestic and peridomestic presence of Triatoma infestans depends on several factors, such as human behavior, vector behavior, ecology, and the environment. METHODS: This work was conducted in 139 domiciliary units, where triatomines were captured and risk factors in domiciles and peridomicilies were recorded. Household dwellers were interviewed to obtain information about practices regarding this disease and entomological indicators were calculated. RESULTS: Infestation indices were 59.7% for house compounds, 4.3% for domestic areas and 58.3% for the peridomestic areas. Intradomicile infestation was significantly associated with housing characteristics. The presence of chicken coops in peridomicilies was associated with an increased risk of infestation. Of the respondents, 80% did not recognize the importance of the peridomiciliary structures for triatomine control and had infested peridomicilies. CONCLUSIONS: The results show the importance of peridomiciles as refuge sites for Triatominae bugs; however, household dwellers do not perceive peridomiciles as areas that favor the presence of vectors. Actions for raising awareness about factors that favor the presence of triatomines are needed to improve the conditions of peridomiciliary environments.

Assessing the risk zones of Chagas' disease in Chile, in a world marked by global climatic change

BACKGROUND Vector transmission of Trypanosoma cruzi appears to be interrupted in Chile; however, data show increasing incidence of Chagas' disease, raising concerns that there may be a reemerging problem. OBJECTIVE To estimate the actual risk in a changing world it is necessary to consider the historical vector distribution and correlate this distribution with the presence of cases and climate change. METHODS Potential distribution models of Triatoma infestans and Chagas disease were performed using Maxent, a machine-learning method. FINDINGS Climate change appears to play a major role in the reemergence of Chagas' disease and T. infestans in Chile. The distribution of both T. infestans and Chagas' disease correlated with maximum temperature, and the precipitation during the driest month. The overlap of Chagas' disease and T. infestans distribution areas was high. The distribution of T. infestans, under two global change scenarios, showed a minimal reduction tendency in suitable areas. MAIN CONCLUSION The impact of temperature and precipitation on the distribution of T. infestans, as shown by the models, indicates the need for aggressive control efforts; the current control measures, including T. infestans control campaigns, should be maintained with the same intensity as they have at present, avoiding sylvatic foci, intrusions, and recolonisation of human dwellings.

El baúl de los recuerdos

El Dr. Salvador Mazza (Buenos Aires, Argentina, 6 de junio de 1886 - Monterrey, México, 9 de noviembre de 1946) fue un médico sanitarista y bacteriólogo argentino, que se destacó por haber dedicado casi toda su vida al estudio y a la lucha contra la tripanosomiasis americana (enfermedad de Chagas-Mazza) y otras enfermedades endémicas. Completó los estudios de Carlos Chagas sobre el agente etiológico (Trypanosoma cruzi) y sobre el vector de la enfermedad, la vinchuca (Triatoma infestans), además de perfeccionar el tratamiento de la misma. La "Misión de Estudios de Patología Regional Argentina" (MEPRA) fue fundada por la Universidad de Buenos Aires (UBA) en 1926, instalándose en la Provincia de Jujuy, el 25 de Agosto de 1929, en ella se escribieron 551 publicaciones, siendo 482 realizadas por Salvador Mazza. Durante 20 años, la MEPRA fue el centro científico más importante de la República Argentina, hasta que en 1946 fue trasladada a Buenos Aires, siendo el mismo año del fallecimiento de su fundador; estos dos hechos históricos fueron nefastos para la institución, que fue conducida posteriormente sin la dinámica de Don Salvador hasta su desaparición en 1959. En la sede de la MEPRA, se halló un baúl de cuero, repleto de fotografías viejas, más de 4.800 en las que se vislumbraba, el trabajo de Don Salvador durante su incansable tarea en el norte argentino; este baúl de los recuerdos fue rescatado, ordenado, clasificado y posteriormente digitalizado por la Universidad Nacional de Jujuy (UNJu) y depositado bajo la custodia del Archivo Histórico de la Provincia de Jujuy.

The trunk of memories Dr. Salvador Mazza (Buenos Aires, Argentina, June 6, 1886 - Monterrey, Mexico, November 9, 1946) was an Argentine sanitarist and bacteriologist, who stood out for having spent most of his life studying and fighting against american trypanosomiasis (Chagas-Mazza' disease) and other endemic diseases. He completed the studies of Carlos Chagas on the etiological agent (Trypanosoma cruzi) and on the vector of the disease, vinchuca (Triatoma infestans), besides perfecting the treatment of it. The "Mission of Studies of Regional Pathology in Argentina" (MEPRA) was founded by the University of Buenos Aires (UBA) in 1926 and settled in the province of Jujuy on August 25, 1929; 551 publications were written, 482 made by Salvador Mazza. During 20 years, the MEPRA was the most important scientific center of the Argentine Republic, until in 1946 it was transferred to Buenos Aires, being the same year of the death of its founder; these two historical events were harmful to the institution, which was later conducted without the dynamics of Don Salvador until his disappearance in 1959. In the headquarters of the MEPRA, a leather trunk was found, full of old photographs, more than 4,800 in which it was glimpsed, the work of Don Salvador during his tireless work in the Argentine north; this trunk of memories was rescued, sorted, classified and later digitized by the National University of Jujuy (UNJu) and deposited under the custody of the Historical Archive of the Province of Jujuy.

O baú de memórias O Dr. Salvador Mazza (Buenos Aires, Argentina, 6 de junho, 1886 - Monterrey, México, 09 de novembro de 1946) foi um médico e sanitarista bacteriologista argentino, que se destacou por ter dedicado a sua vida ao estudo eà luta contra a tripanossomíase americana (doença de Chagas) e outras doenças endêmicas. Completou os estudos de Carlos Chagas sobre o agente etiológico (Trypanosoma cruzi) e o barbeiro, vector da doença, o "vinchuca" (Triatoma infestans), além de melhorar o tratamento dos mesmos. A "Missão de Estudo da Patologia Regional Argentina" (MEPRA) foi fundada pela Universidade de Buenos Aires (UBA), em 1926, estabelecendo-se na província de Jujuy, em 25 de agosto de 1929, em suas foram escritas 551 publicações, sendo 482 feita por Salvador Mazza. Durante 20 anos, a MEPRA foi o mais importante centro científico da Argentina, até que em 1946 foi transferido para Buenos Aires, sendo o ano da morte de seu fundador; estes dois acontecimentos históricos foram desastrosos para a instituição, que foi conduzida mais tarde, sem a dinâmica de Don Salvador até seu desaparecimento em 1959. Na sede do MEPRA foi encontrado um baú de couro, cheio de fotografias antigas, mais de 4.800 apareceu em que assomava a obra de Don Salvador por seu trabalho incansável no norte da Argentina; este baú de memórias foi resgatado, classificado e após digitalizado pela Universidade Nacional de Jujuy (UNJU) e depositado sob a custódia do Arquivo Histórico da Província de Jujuy.

The eco-epidemiology of Triatoma infestans in the temperate Monte Desert ecoregion of mid-western Argentina

BACKGROUND The eco-epidemiological status of Chagas disease in the Monte Desert ecoregion of western Argentina is largely unknown. We investigated the environmental and socio-demographic determinants of house infestation with Triatoma infestans, bug abundance, vector infection with Trypanosoma cruzi and host-feeding sources in a well-defined rural area of Lavalle Department in the Mendoza province. METHODS Technical personnel inspected 198 houses for evidence of infestation with T. infestans, and the 76 houses included in the current study were re-inspected. In parallel with the vector survey, an environmental and socio-demographic survey was also conducted. Univariate risk factor analysis for domiciliary infestation was carried out using Firth penalised logistic regression. We fitted generalised linear models for house infestation and bug abundance. Blood meals were tested with a direct ELISA assay, and T. cruzi infection was determined using a hot-start polymerase chain reaction (PCR) targeting the kinetoplast minicircle (kDNA-PCR). FINDINGS The households studied included an aged population living in precarious houses whose main economic activities included goat husbandry. T. infestans was found in 21.2% of 198 houses and in 55.3% of the 76 re-inspected houses. Peridomestic habitats exhibited higher infestation rates and bug abundances than did domiciles, and goat corrals showed high levels of infestation. The main host-feeding sources were goats. Vector infection was present in 10.2% of domiciles and 3.2% of peridomiciles. Generalised linear models showed that peridomestic infestation was positively and significantly associated with the presence of mud walls and the abundance of chickens and goats, and bug abundance increased with the number of all hosts except rabbits. MAIN CONCLUSIONS We highlight the relative importance of specific peridomestic structures (i.e., goat corrals and chicken coops) associated with construction materials and host abundance as sources of persistent bug infestation driving domestic colonisation. Environmental management strategies framed in a community-based programme combined with improved insecticide spraying and sustained vector surveillance are needed to effectively suppress local T. infestans populations.

Insights from tissue-specific transcriptome sequencing analysis of Triatoma infestans

ABSTRACT Triatoma infestans is an insect of subfamily Triatominae (Hemiptera: Reduviidae) and an important vector of Trypanosoma cruzi, the etiologic agent of human Chagas disease. In this work we reported a transcriptome assembly and annotation of T. infestans heads obtained by Next Generation Sequencing (NGS) technologies.

Determinación del grado de infestación e infección de vectores de la enfermedad de Chagas en la comunidad de Huayhuasi (Mecapaca) / Determination of the degree of infestation and infection of vectors of Chagas disease in the community of Huayhuasi (Mecapaca)

Los trabajos realizados de trampeo y captura de triatominos (que son los insectos vectores de la enfermedad de Chagas) en zonas silvestres de los alrededores de la localidad de Huayhuasi, municipio de Mecapaca en el departamento de La Paz. Se colocaron 50 trampas en lugares estratégicos escogidos de acuerdo a las características del área de estudio. De las 50 trampas, en 9 trampas se lograron atrapar a los triatominos, lo que representa el 4.5% de infestación de la zona de estudio. Se capturaron a 13 insectos (7 ninfas de diferentes estadíos y 6 adultos). Las características morfológicas de los insectos fueron las típicas del Triatoma infestans. En el examen en fresco de las deyecciones de los 6 especímenes adultos capturados, en 4 de ellos se detectó presencia del parásito Trypanosoma cruzi, lo cual demuestra un 67% de infección, porcentaje bastante significativo en consideración a la cercanía de estos lugares infestados a las zonas urbanas del municipio de Mecapaca. Los parásitos que los especímenes portaban, fueron aislados y cultivados en medio de cultivo LIT (Liver Infusion Tryptose) suplementado con 10% de suero bovino fetal e incubados en estufa a 26°C. El análisis del ADN extraído de los parásitos, ha revelado la DTU (Discrete Typing Unit) correspondiente al linaje TcI.

Trapping and capture of triatomines (which are the insect's vectors of Chagas' disease) were carried out in wild areas around the town of Huayhuasi, municipality of Mecapaca, in the department of La Paz. 50 traps were placed in strategic places chosen according to the characteristics already established. Of the 50 traps, nine traps managed to trap the triatomines, representing 4.5% of infestation in the study area. 13 insects (7 nymphs of different stages and 6 adults) were captured. The morphological characteristics of the insects were typical of Triatoma infestans. In the fresh examination of the excrement of the six captured adult specimens, in 4 of them the presence of the parasite Trypanosoma cruzi was detected, which shows a 67% infection, a very significant percentage considering the proximity of these infested places to the Urban areas of the municipality of Mecapaca. The parasites that the specimens carried were isolated and cultured in LIT (Liver Infusion Triptose) medium supplemented with 10% fetal bovine serum and incubated in an oven at 26 °C. Analysis of the DNA extracted from the parasites has revealed the DTU corresponding to the Tc I lineage.

Chagas disease: national survey of seroprevalence in children under five years of age conducted in 2008

BACKGROUND Since the early 1990s, programs to control Chagas disease in South America have focused on eradicating domiciliary Triatoma infestans, the main vector. Seroprevalence studies of the chagasic infection are included as part of the vector control programs; they are essential to assess the impact of vector control measures and to monitor the prevention of vector transmission. OBJECTIVE To assess the interruption of domiciliary vector transmission of Chagas disease by T. infestans in Paraguay by evaluating the current state of transmission in rural areas. METHODS A survey of seroprevalence of Chagas disease was carried out in a representative sample group of Paraguayans aged one to five years living in rural areas of Paraguay in 2008. Blood samples collected on filter paper from 12,776 children were tested using an enzyme-linked immunosorbent assay. Children whose serology was positive or undetermined (n = 41) were recalled to donate a whole blood sample for retesting. Their homes were inspected for current triatomine infestation. Blood samples from their respective mothers were also collected and tested to check possible transmission of the disease by a congenital route. FINDINGS A seroprevalence rate of 0.24% for Trypanosoma cruzi infection was detected in children under five years of age among the country’s rural population. Our findings indicate that T. cruzi was transmitted to these children vertically. The total number of infected children, aged one to five years living in these departments, was estimated at 1,691 cases with an annual incidence of congenital transmission of 338 cases per year. MAIN CONCLUSION We determined the impact of vector control in the transmission of T. cruzi, following uninterrupted vector control measures employed since 1999 in contiguous T. infestans-endemic areas of Paraguay, and this allowed us to estimate the degree of risk of congenital transmission in the country.

Where do these bugs come from? Phenotypic structure of Triatoma infestans populations after control interventions in the Argentine Chaco

House re-invasion by native triatomines after insecticide-based control campaigns represents a major threat for Chagas disease vector control. We conducted a longitudinal intervention study in a rural section (Area III, 407 houses) of Pampa del Indio, northeastern Argentina, and used wing geometric morphometry to compare pre-spray and post-spray (re-infestant bugs) Triatoma infestans populations. The community-wide spraying with pyrethroids reduced the prevalence of house infestation by T. infestans from 31.9% to < 1% during a four-year follow-up, unlike our previous studies in the neighbouring Area I. Two groups of bug collection sites differing in wing shape variables before interventions (including 221 adults from 11 domiciles) were used as a reference for assigning 44 post-spray adults. Wing shape variables from post-spray, high-density bug colonies and pre-spray groups were significantly different, suggesting that re-infestant insects had an external origin. Insects from one house differed strongly in wing shape variables from all other specimens. A further comparison between insects from both areas supported the existence of independent re-infestation processes within the same district. These results point to local heterogeneities in house re-infestation dynamics and emphasise the need to expand the geographic coverage of vector surveillance and control operations to the affected region.

Susceptibility characterization of residual Brazilian populations of Triatoma infestans Klug, 1834 (Hemiptera: Reduviidae) to deltamethrin pyrethroid

INTRODUCTION: Despite years of efforts towards the elimination of Triatoma infestans in Brazil, residual foci still persist in some areas of the States of Bahia and Rio Grande do Sul. The persistence of these T. infestans populations in the country has two different origins of equal concern: operational failures or insecticide resistance. Thus, the objective of this study was to characterize the susceptibility profile of the residual Brazilian populations of T. infestans to deltamethrin. METHODS: The susceptibility reference lineage was derived from Cipein/Argentina. The populations studied were manually collected using a dislodging agent in peridomiciles in the States of Bahia (Novo Horizonte) and of Rio Grande do Sul (Santa Rosa and Doutor Maurício Cardoso). Serial dilutions of deltamethrin were prepared and applied at the dorsal abdomen of first instar nymphs. The control group received only pure acetone. Mortality was evaluated after 72h. Qualitative tests assessed the mortality of a diagnostic dose of 1xLD99 (2.76ng a.i./nymph) determined for the susceptibility reference lineage. RESULTS: The susceptibility profile characterization of the T. infestans populations revealed an RR50 ranging from 1.73 to 3.26. The mortality percentage in response to a diagnostic dose was 100%. The results obtained in the quantitative and qualitative assays corresponded for all populations. CONCLUSIONS: The results of this study indicate that the persistence of residual foci of T. infestans in Bahia and Rio Grande do Sul is not related to insecticide resistance but may be associated with operational failures. In Rio Grande do Sul, we must consider the possibility of continuous reinfestation by Argentinian individuals, which justifies active and efficient epidemiological surveillance. .

Eficacia in vitro de tres endectocidas frente a Triatoma infestans / In vitro efficacy of three endectocides against Triatoma infestans

Introducción: distintos estudios han demostrado el papel preponderante que el peridomicilio cumple en la reinfestación de las viviendas por Triatoma infestans (vinchucas). Con el objetivo de eliminar focos residuales de T. infestans que habitan alrededor de los hogares se han desarrollado distintas estrategias. La administración de diferentes compuestos que tengan actividad contra T. infestans a los animales que habitan zonas cercanas a los domicilios y sirvan como fuente de alimentación a estos insectos, podría ser una buena manera de disminuir el riesgo de reinfestación domiciliaria. Objetivo: evaluar la eficacia in vitro de tres agentes antiparasitarios, doramectina (DRM), ivermectina (IVM) y eprinomectina (EPR) frente a ninfas de quinto estadio de Triatoma infestans. Métodos: se diseñaron alimentadores artificiales en donde se colocó sangre heparinizada y fortificada con distintas concentraciones de los tres endectocidas (100-0,4 ng/mL). Se utilizaron 600 ninfas de quinto estadio de T. infestans durante el experimento. Un grupo de vinchucas fue alimentada con sangre sin tratar (control). Luego de realizada la alimentación se observó el estado de los insectos cada 24 hs. durante el transcurso de una semana. Resultados: los tres endectocidas demostraron actividad frente a ninfas de quinto estadio de T. infestans. Comparando la actividad de las tres moléculas, DRM fue la que exhibió una mayor potencia contra los insectos, inclusive mantuvo su actividad frente T. infestans a 0,4 ng/mL (menor concentración evaluada). En el caso de IVM y EPR comenzaron a perder eficacia a concentraciones por debajo de los 6,25 y 3,15 ng/mL respectivamente, siendo totalmente inactivas a 0,4 ng/mL. Conclusiones: en base a estos resultados podemos aseverar que bajo nuestras condiciones experimentales, tanto IVM, EPR como DRM poseen una alta eficacia in vitro contra T. infestans, siendo la última la más efectiva de las tres evaluadas(AU)

Introduction: various studies have demonstrated the role that areas around the houses play in domiciliary re-infestation by Triatomainfestans (kissing bugs). With the aim of removing residual foci of T. infestans that inhabit in neighboring areas of houses, different strategies have been developed. The administration of different anti-T. infestans compounds to animals living in areas around the houses might be a good way to reduce the risk of domiciliary re-infestation. Objective: to evaluate the in vitro efficacy of three antiparasitic agents, doramectin (DRM), ivermectin (IVM) and eprinomectin (EPR) against fifth instar nymphs of Triatomainfestans. Methods: artificial feeders were designed , which contained heparinized and fortified blood with various concentrations of the three endectocides (100-0.4 ng/mL). We used 600 fifth instar nymphs of T. infestans during the experiment. A group of insects were fed with untreated blood (control). After feeding they were under observation to check their condition every 24 hours for a week. Results: the three molecules showed activity against T. infestans. In comparing the activity of the three molecules, DRM exhibited greater potency against insects, it even kept its activity against T. infestans at 0.4 ng/mL (lowest concentration tested). In the case of EPR and IVM, their efficacy began to lower at concentrations below 6.25 and 3.15 ng/mL respectively, being totally inactive at 0.4 ng/mL concentration. Conclusions: Based on these results, we can assert that under our experimental conditions, IVM, EPR and DRM show in vitro high efficacy against T. infestans, being the latter more effective than the other two molecules(AU)

The peri-urban interface and house infestation with Triatoma infestans in the Argentine Chaco: an underreported process?

Peri-urban infestations with triatomine bugs, their sources and their dynamics have rarely been investigated. Here, we corroborated the reported occurrence of Triatoma infestans in a peri-urban area and in neighbouring rural houses in Pampa del Indio, in the Argentine Chaco, and identified its putative sources using spatial analysis and demographic questionnaires. Peri-urban householders reported that 10% of their premises had triatomines, whereas T. infestans was collected by timed manual searches or community-based surveillance in only nine (3%) houses. Trypanosoma cruzi-infected T. infestans and Triatoma sordida were collected indoors only in peri-urban houses and were infected with TcV and TcI, respectively. The triatomines fed on chickens, cats and humans. Peri-urban infestations were most frequent in a squatter settlement and particularly within the recently built mud houses of rural immigrants, with large-sized households, more dogs and cats and more crowding. Several of the observed infestations were most likely associated with passive bug transport from other sources and with active bug dispersal from neighbouring foci. Thus, the households in the squatter settlement were at a greater risk of bug invasion and colonisation. In sum, the incipient process of domestic colonisation and transmission, along with persistent rural-to-urban migratory flows and unplanned urbanisation, indicate the need for active vector surveillance and control actions at the peri-urban interface of the Gran Chaco.

Is imidacloprid an effective alternative for controlling pyrethroid-resistant populations of Triatoma infestans (Hemiptera: Reduviidae) in the Gran Chaco ecoregion?

The prevention of Chagas disease is based primarily on the chemical control of Triatoma infestans (Klug) using pyrethroid insecticides. However, high resistance levels, correlated with control failures, have been detected in Argentina and Bolivia. A previous study at our laboratory found that imidacloprid could serve as an alternative to pyrethroid insecticides. We studied the delayed toxicity of imidacloprid and the influence of the blood feeding condition of the insect on the toxicity of this insecticide; we also studied the effectiveness of various commercial imidacloprid formulations against a pyrethroid-resistant T. infestans population from the Gran Chaco ecoregion. Variations in the toxic effects of imidacloprid were not observed up to 72 h after exposure and were not found to depend on the blood feeding condition of susceptible and resistant individuals. Of the three different studied formulations of imidacloprid on glass and filter paper, only the spot-on formulation was effective. This formulation was applied to pigeons at doses of 1, 5, 20 and 40 mg/bird. The nymphs that fed on pigeons treated with 20 mg or 40 mg of the formulation showed a higher mortality rate than the control group one day and seven days post-treatment (p < 0.01). A spot-on formulation of imidacloprid was effective against pyrethroid-resistant T. infestans populations at the laboratory level.

Analysing deltamethrin susceptibility and pyrethroid esterase activity variations in sylvatic and domestic Triatoma infestans at the embryonic stage

The aim of the present work was to study the deltamethrin susceptibility of eggs from Triatoma infestans populations and the contribution of pyrethroid esterases to deltamethrin degradation. Insects were collected from sylvatic areas, including Veinte de Octubre and Kirus-Mayu (Bolivia) and from domiciliary areas, including El Palmar (Bolivia) and La Pista (Argentina). Deltamethrin susceptibility was determined by dose-response bioassays. Serial dilutions of deltamethrin (0.0005-1 mg/mL) were topically applied to 12-day-old eggs. Samples from El Palmar had the highest lethal dose ratio (LDR) value (44.90) compared to the susceptible reference strain (NFS), whereas the Veinte de Octubre samples had the lowest value (0.50). Pyrethroid esterases were evaluated using 7-coumaryl permethrate (7-CP) on individually homogenised eggs from each population and from NFS. The El Palmar and La Pista samples contained 40.11 and 36.64 pmol/min/mg protein, respectively, and these values were statistically similar to NFS (34.92 pmol/min/mg protein) and different from Kirus-Mayu and Veinte de Octubre (27.49 and 22.69 pmol/min/mg protein, respectively). The toxicological data indicate that the domestic populations were resistant to deltamethrin, but no statistical contribution of 7-CP esterases was observed. The sylvatic populations had similar LDR values to NFS, but lower 7-CP esterase activities. Moreover, this is the first study of the pyrethroid esterases on T. infestans eggs employing a specific substrate (7-CP).

Toxicological and biochemical analysis of the susceptibility of sylvatic Triatoma infestans from the Andean Valley of Bolivia to organophosphate insecticide

To increase our knowledge of the natural susceptibility of Triatoma infestans to an organophosphate insecticide, we performed toxicological and biochemical studies on three sylvatic populations from Bolivia and two populations from domestic dwellings from Bolivia and Argentina. Fifty-per-cent lethal doses (LD50) were determined based on the topical application of fenitrothion on first instar nymphs and mortality was assessed at 24 h. Both type of populations exhibited LD50ratios significantly higher than 1 with a range of the values (1.42-2.47); the maximum value were found in a sylvatic (-S) population, Veinte de Octubre-S. Samples were biochemically analysed using a glutathione S-transferase activity assay. The highest significant activity was obtained for Veinte de Octubre-S and the lowest activity was obtained for the reference population (102.69 and 54.23 pmol per minute per mg of protein respectively). Two out of the three sylvatic populations (Veinte de Octubre-S and Kirus Mayu-S) exhibited significantly higher glutathione S-transferase activity than that of the reference population. Based on this analysis of the natural susceptibility of this organism to organophosphate insecticides, continental and focal surveys of organophosphate susceptibility should be conducted to evaluate the evolution and distribution of this phenomenon.

New structures for goat corrals to control peridomestic populations of Triatoma infestans (Hemiptera: Reduviidae) in the Gran Chaco of Argentina

Goat production is an important economic activity for rural communities in the Gran Chaco of Argentina. Goat corrals are important for the survival of peridomestic populations of Triatoma infestans. This study evaluated the impact of modifying the traditional structure of goat corrals on T. infestans populations and goat productivity in the region of Los Llanos (La Rioja). Thirty-nine experimental corrals were constructed and 57 traditional corrals were used as controls. We evaluated the infestations of the control and experimental corrals for five years following construction of the structures. The results showed that the new structures did not prevent the colonization, although it enhanced the detection of infestation at low densities of T. infestans. No significant difference was found in T. infestans population abundance between control and experimental corrals, probably because of the different detectability in the two types of structures, especially among the small nymphs. Although goat productivity average was higher in experimental than in control corrals, no significant difference was found because of high variability. The new structures can be used as a complement to promote the development of rural communities. Acceptability and adoption of the new corrals by the owners was high, as the enclosures offered better protection for the goats, increased growth of kids and facilitated herd handling.

Potential sources of Triatoma infestans reinfesting peridomiciles identified by morphological characterization in Los Llanos, La Rioja, Argentina

The presence of Triatoma infestans in habitats treated with insecticides constitutes a frequent problem in endemic areas. Basing our study on the hypothesis that descendants of a residual population should be more similar to the pre-treatment population than to any other, we compared the indications of two quantitative morphological approaches. This study seeks to find the origin of 247 T. infestans from three populations found in two chicken coops and a goat corral after treatment with insecticides. The results obtained by quantitative morphology suggest that the T. infestans found between three-34 months after the application of insecticides formed mixed populations with insects derived from residual foci and neighbouring habitats. Our analyses also showed the presence of a phenotype which does not resemble neither the pre-treatment phenotype nor the one from neighbouring populations, suggesting the presence of a particular post-treatment phenotype. The heads size showed some variations in males from different populations and remained unchanged in females, which reinforces the hypothesis of an intraspecific competition for food with priority for females. This article presents, for the first time, the combined analysis of geometric morphometry of heads and antennal phenotypes to identify the composition of reinfesting populations.

Chronic Chagas disease: PCR-xenodiagnosis without previous microscopic observation is a useful tool to detect viable Trypanosoma cruzi

We evaluate the elimination of the microscopic stage of conventional xenodiagnosis (XD) to optimize the parasitological diagnosis of Trypanosoma cruzi in chronic Chagas disease. To this purpose we applied under informed consent two XD cages to 150 Chilean chronic chagasic patients. The fecal samples (FS) of the triatomines at 30, 60 and 90 days post feeding were divided into two parts: in one a microscopic search for mobile trypomastigote and/or epimastigote forms was performed. In the other part, DNA extraction-purification for PCR directed to the conserved region of kDNA minicircles of trypanosomes (PCR-XD), without previous microscopic observation was done. An XD was considered positive when at least one mobile T. cruzi parasite in any one of three periods of incubation was observed, whereas PCR-XD was considered positive when the 330 bp band specific for T. cruzi was detected. 25 of 26 cases with positive conventional XD were PCR-XD positive (concordance 96.2%), whereas 85 of 124 cases with negative conventional XD were positive by PCR-XD (68.5%). Human chromosome 12 detected by Real-time PCR used as exogenous internal control of PCR-XD reaction allowed to discounting of PCR inhibition and false negative in 40 cases with negative PCR-XD. Conclusion: PCR-XD performed without previous microscopic observation is a useful tool for detection of viable parasites with higher efficiency then conventional XD.