Chagas disease control-surveillance in the Americas: the multinational initiatives and the practical impossibility of interrupting vector-borne Trypanosoma cruzi transmission

Chagas disease (CD) still imposes a heavy burden on most Latin American countries. Vector-borne and mother-to-child transmission cause several thousand new infections per year, and at least 5 million people carry Trypanosoma cruzi. Access to diagnosis and medical care, however, is far from universal. Starting in the 1990s, CD-endemic countries and the Pan American Health Organization-World Health Organization (PAHO-WHO) launched a series of multinational initiatives for CD control-surveillance. An overview of the initiatives' aims, achievements, and challenges reveals some key common themes that we discuss here in the context of the WHO 2030 goals for CD. Transmission of T. cruzi via blood transfusion and organ transplantation is effectively under control. T. cruzi, however, is a zoonotic pathogen with 100+ vector species widely spread across the Americas; interrupting vector-borne transmission seems therefore unfeasible. Stronger surveillance systems are, and will continue to be, needed to monitor and control CD. Prevention of vertical transmission demands boosting current efforts to screen pregnant and childbearing-aged women. Finally, integral patient care is a critical unmet need in most countries. The decades-long experience of the initiatives, in sum, hints at the practical impossibility of interrupting vector-borne T. cruzi transmission in the Americas. The concept of disease control seems to provide a more realistic description of what can in effect be achieved by 2030.

II Consenso Brasileiro em Doença de Chagas, 2015 / Brazilian Consensus on Chagas Disease, 2015

A doença de Chagas é uma condição crônica negligenciada com elevada carga de morbimortalidade e impacto dos pontos de vista psicológico, social e econômico. Representa um importante problema de saúde pública no Brasil, com diferentes cenários regionais. Este documento traduz a sistematização das evidências que compõe o Consenso Brasileiro de Doença de Chagas. O objetivo foi sistematizar estratégias de diagnóstico, tratamento, prevenção e controle da doença de Chagas no país, de modo a refletir as evidências científicas disponíveis. Sua construção fundamentou-se na articulação e contribuição estratégica de especialistas brasileiros com conhecimento, experiência e atualização sobre diferentes aspectos da doença. Representa o resultado da estreita colaboração entre a Sociedade Brasileira de Medicina Tropical e o Ministério da Saúde. Espera-se com este documento fortalecer o desenvolvimento de ações integradas para enfrentamento da doença no país com foco em epidemiologia, gestão, atenção integral (incluindo famílias e comunidades), comunicação, informação, educação e pesquisas.

Chagas disease is a neglected chronic condition that presents high morbidity and mortality burden, with considerable psychological, social, and economic impact. The disease represents a significant public health issue in Brazil, with different regional patterns. This document presents the evidence that resulted in the Brazilian Consensus on Chagas Disease. The objective was to review and standardize strategies for diagnosis, treatment, prevention, and control of Chagas disease in the country, based on the available scientific evidence. The consensus is based on collaboration and contribution of renowned Brazilian experts with vast knowledge and experience on various aspects of the disease. It is the result of close collaboration between the Brazilian Society of Tropical Medicine and the Ministry of Health. This document shall strengthen the development of integrated control measures against Chagas disease in the country, focusing on epidemiology, management, comprehensive care (including families and communities), communication, information, education, and research.

Certifying the interruption of Chagas disease transmission by native vectors: cui bono?

Certifying the absence of Chagas disease transmission by native vectors lacks scientific grounds and weakens long-term control-surveillance systems to the detriment of people living under risk conditions. Instead, a regular "certification of good practice" (including vector control-surveillance, case detection/patient care and blood safety) could help achieve sustained disease control.

Rhodnius barretti, a new species of Triatominae (Hemiptera: Reduviidae) from western Amazonia

Rhodnius barretti , a new triatomine species, is described based on adult specimens collected in rainforest environments within the Napo ecoregion of western Amazonia (Colombia and Ecuador). R. barretti resembles Rhodnius robustus s.l. , but mitochondrial cytochrome b gene sequences reveal that it is a strongly divergent member of the “robustus lineage”, i.e., basal to the clade encompassing Rhodnius nasutus , Rhodnius neglectus , Rhodnius prolixus and five members of the R. robustus species complex. Morphometric analyses also reveal consistent divergence from R. robustus s.l. , including head and, as previously shown, wing shape and the length ratios of some anatomical structures. R. barretti occurs, often at high densities, in Attalea butyracea and Oenocarpus bataua palms. It is strikingly aggressive and adults may invade houses flying from peridomestic palms. R. barretti must therefore be regarded as a potential Trypanosoma cruzi vector in the Napo ecoregion, where Chagas disease is endemic.

Attraction of Chagas disease vectors (Triatominae) to artificial light sources in the canopy of primary Amazon rainforest

Adult triatomines occasionally fly into artificially lit premises in Amazonia. This can result in Trypanosoma cruzi transmission to humans either by direct contact or via foodstuff contamination, but the frequency of such behaviour has not been quantified. To address this issue, a light-trap was set 45 m above ground in primary rainforest near Manaus, state of Amazonas, Brazil and operated monthly for three consecutive nights over the course of one year (432 trap-hours). The most commonly caught reduviids were triatomines, including 38 Panstrongylus geniculatus, nine Panstrongylus lignarius, three Panstrongylus rufotuberculatus, five Rhodnius robustus, two Rhodnius pictipes, one Rhodnius amazonicus and 17 Eratyrus mucronatus. Males were collected more frequently than females. The only month without any catches was May. Attraction of most of the known local T. cruzi vectors to artificial light sources is common and year-round in the Amazon rainforest, implying that they may often invade premises built near forest edges and thus become involved in disease transmission. Consequently, effective Chagas disease prevention in Amazonia will require integrating entomological surveillance with the currently used epidemiological surveillance.

Biogeography and evolution of Amazonian triatomines (Heteroptera: Reduviidae): implications for Chagas disease surveillance in humid forest ecoregions

An ecological-evolutionary classification of Amazonian triatomines is proposed based on a revision of their main contemporary biogeographical patterns. Truly Amazonian triatomines include the Rhodniini, the Cavernicolini, and perhaps Eratyrus and some Bolboderini. The tribe Rhodniini comprises two major lineages (pictipes and robustus). The former gave rise to trans-Andean (pallescens) and Amazonian (pictipes) species groups, while the latter diversified within Amazonia (robustus group) and radiated to neighbouring ecoregions (Orinoco, Cerrado-Caatinga-Chaco, and Atlantic Forest). Three widely distributed Panstrongylus species probably occupied Amazonia secondarily, while a few Triatoma species include Amazonian populations that occur only in the fringes of the region. T. maculata probably represents a vicariant subset isolated from its parental lineage in the Caatinga-Cerrado system when moist forests closed a dry trans-Amazonian corridor. These diverse Amazonian triatomines display different degrees of synanthropism, defining a behavioural gradient from household invasion by adult triatomines to the stable colonisation of artificial structures. Anthropogenic ecological disturbance (driven by deforestation) is probably crucial in the onset of the process, but the fact that only a small fraction of species effectively colonises artificial environments suggests a role for evolution at the end of the gradient. Domestic infestation foci are restricted to drier subregions within Amazonia; thus, populations adapted to extremely humid rainforest microclimates may have limited chances of successfully colonising the slightly drier artificial microenvironments. These observations suggest several research avenues, from the use of climate data to map risk areas to the assessment of the synanthropic potential of individual vector species.

Chagas disease in the Amazon Region

The risk that Chagas disease becomes established as a major endemic threat in Amazonia (the world's largest tropical biome, today inhabited by over 30 million people) relates to a complex set of interacting biological and social determinants. These include intense immigration from endemic areas (possibly introducing parasites and vectors), extensive landscape transformation with uncontrolled deforestation, and the great diversity of wild Trypanosoma cruzi reservoir hosts and vectors (25 species in nine genera), which maintain intense sylvatic transmission cycles. Invasion of houses by adventitious vectors (with infection rates > 60 percent) is common, and focal adaptation of native triatomines to artificial structures has been reported. Both acute (~ 500) and chronic cases of autochthonous human Chagas disease have been documented beyond doubt in the region. Continuous, low-intensity transmission seems to occur throughout the Amazon, and generates a hypoendemic pattern with seropositivity rates of ~ 1-3 percent. Discrete foci also exist in which transmission is more intense (e.g., in localized outbreaks probably linked to oral transmission) and prevalence rates higher. Early detection-treatment of acute cases is crucial for avoiding further dispersion of endemic transmission of Chagas disease in Amazonia, and will require the involvement of malaria control and primary health care systems. Comprehensive eco-epidemiological research, including prevalence surveys or the characterization of transmission dynamics in different ecological settings, is still needed. The International Initiative for Chagas Disesae Surveillance and Prevention in the Amazon provides the framework for building up the political and scientific cooperation networks required to confront the challenge of preventing Chagas disease in Amazonia.

Molecular research and the control of Chagas disease vectors

Programas destinados ao controle da doença de Chagas vêm apresentando resultados positivos. Estudos moleculares têm auxiliado programas de controle exitosos através da identificação e caracterização de populações de vetores introduzidas, além da definição precisa das espécies a serem combatidas. Contudo, pesquisadores e autoridades da área de saúde estão enfrentando novos desafios, no âmbito da América Latina. Vetores nativos estão continuadamente re-infestando habitações previamente tratadas com inseticidas, e triatomíneos silvestres estão mantendo ciclos de transmissão da doença em regiões de floresta tropical úmida (incluíndo a Amazônia), sem colonizar habitações humanas. Nessas situações, estudos detalhados dos vetores são essenciais na definição de padrões de risco epidemiológico e no esclarecimento do envolvimento de espécies de triatomíneos pouco conhecidas, na transmissão da doença. Investigações eco-epidemiológicas dessa natureza, assim como o planejamento e monitoramento de intervenções de controle, dependem fortemente de identificações taxonômicas precisas. Problemas decorrentes de especiação críptica e da plasticidade fenotípica, ilustram essa necessidade - e de como a sistemática molecular pode contribuir na geração das respostas necessárias. A análise de dados moleculares também auxilia no entendimento de aspectos básicos da evolução e tendências adaptativas dos vetores. Neste artigo, fazemos uma revisão da aplicação de marcadores moleculares (concentrando em isoenzimas e sequenciamento de ADN) no estudo de triatomíneos. Analisamos também a aplicabilidade, vantagens e desvantagens dos métodos mais utilizados, nas investigações em diferentes níveis sistemáticos (populações, espécies e categorias taxonômicas mais elevadas).

Enzootic transmission of Trypanosoma cruzi and T. rangeli in the Federal District of Brazil

O Distrito Federal (DF) do Brasil está localizado no bioma Cerrado, um complexo de fisionomias savânicas incluindo matas de galeria e campos úmidos permanentes (veredas). Triatomíneos silvestres infectados por Trypanosoma cruzi ocorrem na área, mas a transmissão enzoótica de tripanossomatídeos permanece insuficientemente caracterizada. Um estudo parasitológico envolvendo triatomíneos silvestres (166 Rhodnius neglectus coletados em palmeiras da espécie Mauritia flexuosa) e pequenos mamíferos (98 marsupiais e 70 roedores, totalizando 18 espécies) foi conduzido em 18 áreas, principalmente matas de galeria e veredas. Os parasitas foram isolados, identificados morfologicamente e caracterizados por PCR do DNA do cinetoplasto (kDNA) e núcleo (gene mini-exon). Seis R. neglectus, sete Didelphis albiventris e um Akodon cursor estavam infectados por tripanossomatídeos; a infecção em reservatórios silvestres é documentada pela primeira vez no DF. O PCR do kDNA detectou T. cruzi em cinco R. neglectus e o PCR do gene mini-exon revelou T. cruzi I nos isolados de D. albiventris. Um dos insetos mostrou estar infectado por T. rangeli KP1+. Apesar da ocorrência de D. albiventris (um importante reservatório silvestre e peridoméstico) e R. neglectus (um vetor secundário capaz de invadir domicílios) infectados por T. cruzi, um baixo risco de transmissão da doença de Chagas humana seria esperado no DF, considerando a baixa prevalência da infecção apresentada neste trabalho. A evidência molecular apresentada neste trabalho confirma a circulação de T. rangeli KP1+ com R. neglectus como vetor, amplia a distribuição geográfica deste parasita no Brasil e reforça a hipótese de adaptação de populações de T. rangeli (KP1+ e KP1-) a diferentes linhagens evolutivas de espécies de Rhodnius.

The triatomines of northern Peru, with emphasis on the ecology and infection by Trypanosomes of Rhodnius ecuadoriensis (Triatominae)

Information on the distribution and synanthropic behaviour of triatomines is essential for Chagas disease vector control. This work summarises such information from northern Peru, and presents new data on Rhodnius ecuadoriensis - an important local vector infesting 10-35 percent of dwellings in some zones. Three species are strongly synanthropic and may be suitable targets for chemical control of domestic/peridomestic bug populations. Panstrongylus herreri, the main domestic vector in the area, is probably present in sylvatic ecotopes in the Marañón river system. R. ecuadoriensis and Triatoma dimidiata seem exclusively domestic; biogeographical and ecological data suggest they might have spread in association with humans in northern Peru. Confirmation of this hypothesis would result in a local eradication strategy being recommended. Presence of trypanosome natural infection was assessed in 257 R. ecuadoriensis; Trypanosoma rangeli was detected in 4 percent of bugs. Six further triatomine species are potential disease vectors in the region (T. carrioni, P. chinai, P. rufotuberculatus, P. geniculatus, R. pictipes, and R. robustus), whilst Eratyrus mucronatus, E. cuspidatus, Cavernicola pilosa, Hermanlentia matsunoi, and Belminus peruvianus have little or no epidemiological significance. A strong community-based entomological surveillance system and collaboration with Ecuadorian public health authorities and researchers are recommended

Trapping Triatominae in silvatic habitats

Large-scale trials of a trapping system designed to collect silvatic Triatominae are reported. Live-baited adhesive traps were tested in various ecosystems and different triatomine habitats (arboreal and terrestrial). The trials were always successful, with a rate of positive habitats generally over 20 percent and reaching 48.4 percent for palm trees of the Amazon basin. Eleven species of Triatominae belonging to the three genera of public health importance (Triatoma, Rhodnius and Panstrongylus) were captured. This trapping system provides an effective way to detect the presence of triatomines in terrestrial and arboreal silvatic habitats and represents a promising tool for ecological studies. Various lines of research are contemplated to improve the performance of this trapping system

Un modelo de prevención primaria de las enfermedades de transmisión sexual y del VIH/sida en adolescentes / A model for the primary prevention of sexually transmited disease and HIV/AIDS among adolescents

Objetivos. Desarrollar, aplicar y evaluar un modelo educativo de prevención primaria de enfermedades de transmisión sexual (ETS) y síndrome de inmunodeficiencia adquirida (sida) basdo en los conocimientos, actitudes y prácticas (CAP) sexuales de los adolescentes y en sus percepciones y conductas al respecto, con el objetivo final de contribuir al desarrollo de herramientas educativas y conductas al respecto, con el objetivo final de contribuir al desarrollo de herramientas educativas de prevención de las ETS y de la infección por virus de la inmunodeficiencia humana (VIH). Métodos. Se aplico un modelo de prevención primaria de ETS y VIH/sida a escolares adolescentes (12 a 15 años) de Santo Domingo de los Colorados, Ecuador. Se formaron dos grupos con características similares:el grupo de intervención(grupoI,n=358)y el grupo de control(grupo C,n=288). Las escuelas se seleccionaron por criterios de inclusión, y los adolescentes de cada escuela, al azar. Se aplicó una guía de discusión a 16 grupos focales;con esta información se elaboró una encuesta sobre conocimientos, actitudes y prácticas (CAP) que después de su validación,fue aplicada a ambos grupos. En el grupo I se implementó un programa educativo de prevención diriguido a estudiantes y docentes. Ocho meses más tarde se aplicó una segunda encuesta CAP a los dos grupos. las diferencias en los CAP antes y después de la intervención fueron evaluadas utilizando la prueba de la X2. Resultados. no existieron diferencias significativas entre los dos grupos antes de la intervención, pero después de ella las diferencias fueron estadisticamentesignificativas (P=0,0012)se verificó un aumento de conocimiento sobre sexualidad y ETS/sida en el grupo I, aunque todavía no se ha evaluado la modificación de conductas a largo plazo. Conclusiones. Este estudio permitió validar un modelo multifactorial de prevención de ETS/sida adecuado a la realidad de los adolescentes, y sugiere la posibilidad de extrapolar la experiencia a escalas mayores en contextos similares a los de la población investigada

Biogeography of Triatominae (Hemiptera: Reduviidae) in Ecuador: implications for the design of control strategies

Chagas disease control strategies strongly depend on the triatomine vector species involved in Trypanosoma cruzi transmission within each area. Here we report the results of the identification of specimens belonging to various species of Triatominae captured in Ecuador (15 species from 17 provinces) and deposited in the entomological collections of the Catholic University of Ecuador (Quito), Instituto Oswaldo Cruz (Brazil), the Natural History Museum London (UK), the London School of Hygiene and Tropical Medicine (UK), the National Institute of Hygiene (Quito), and the Vozandes Hospital (Quito). A critical review of published information and new field records are presented. We analysed these data in relation to the life zones where triatomines occur (11 life zones, excluding those over 2,200 m altitude), and provide biogeographical maps for each species. These records are discussed in terms of epidemiological significance and design of control strategies. Findings relevant to the control of the main vector species are emphasised. Different lines of evidence suggest that Triatoma dimidiata is not native to Ecuador-Peru, and that synanthropic populations of Rhodnius ecuadoriensis in southern Ecuador-northern Peru might be isolated from their sylvatic conspecifics. Local eradication of T. dimidiata and these R. ecuadoriensis populations might therefore be attainable. However, the presence of a wide variety of native species indicates the necessity for a strong longitudinal surveillance system

Control de la enfermedad de chagas en el Ecuador: datos y reflexiones para una política de estado

La enfermedad de Chagas es uno de los graves problemas de salud de América Latina: más de 11 millones de personas están infectadas por Trypanosoma cruzi, el parásito que la produce. Felizmente, varios programas de control coordinados (Cono Sur, Area Andina, América Central, etc.) han resultado en la interrupción de la transmisión en grandes áreas del continente. Sólo Ecuador, entre los países andinos, carece de un programa estructurado de control. Se estima que 120000 personas están infectadas en el país, lo que supone unas 300 muertes y unos 3000 nuevos casos por año. La carga financiera relacionada con la ausencia de medidas preventivas pueden calcularse en unos 30 millones de dólares anuales. Sin embargo, el costo de un programa de control no superaría los 1.67 millones de dólares/año...

Epidemiology of Chagas disease in Ecuador: a brief review

Chagas disease is a complex public health problem that has been underestimated in Ecuador. Here we review the relevant published information, and present unpublished and new data that help to understand the current Chagas disease epidemiological situation and its evolution in the country. Three main characteristics have been identified: (i) persistence of Trypanosoma cruzi transmission in already known foci; (ii) a marked endemicity in some urban areas of Guayaquil; and (iii) the transformation of new Amazon foci into truly endemic areas. The situation in other suspect areas remains uncertain. Five Triatominae species have been implicated in the transmission of T. cruzi to people in Ecuador (Triatoma dimidiata, Rhodnius ecuadoriensis, R. pictipes, R. robustus and Panstrongylus geniculatus), but some others may also play a role in some areas (P. rufotuberculatus, P. howardi, T. carrioni and P. chinai). Other Triatominae reported seem to have little or no epidemiological relevance (T. venosa, T. dispar, Eratyrus mucronatus, E. cuspidatus, P. lignarius and Cavernicola pilosa). High frequency of acute cases and severe chronic disease has been observed. Although cardiomyopathy is more frequent, serious digestive disease is also present. It is estimated that around 120,000-200,000 people may be infected. 2.2 to 3.8 million people are estimated to live under transmission risk conditions.