Publications by authors named "Fernando Abad-Franch"

48 Publications

TriatoDex, an electronic identification key to the Triatominae (Hemiptera: Reduviidae), vectors of Chagas disease: Development, description, and performance.

PLoS One 2021 22;16(4):e0248628. Epub 2021 Apr 22.

Laboratório de Parasitologia Médica e Biologia de Vetores, Área de Patologia, Faculdade de Medicina, Universidade de Brasília, Brasília, Brazil.

Correct identification of triatomine bugs is crucial for Chagas disease surveillance, yet available taxonomic keys are outdated, incomplete, or both. Here we present TriatoDex, an Android app-based pictorial, annotated, polytomous key to the Triatominae. TriatoDex was developed using Android Studio and tested by 27 Brazilian users. Each user received a box with pinned, number-labeled, adult triatomines (33 species in total) and was asked to identify each bug to the species level. We used generalized linear mixed models (with user- and species-ID random effects) and information-theoretic model evaluation/averaging to investigate TriatoDex performance. TriatoDex encompasses 79 questions and 554 images of the 150 triatomine-bug species described worldwide up to 2017. TriatoDex-based identification was correct in 78.9% of 824 tasks. TriatoDex performed better in the hands of trained taxonomists (93.3% vs. 72.7% correct identifications; model-averaged, adjusted odds ratio 5.96, 95% confidence interval [CI] 3.09-11.48). In contrast, user age, gender, primary job (including academic research/teaching or disease surveillance), workplace (including universities, a reference laboratory for triatomine-bug taxonomy, or disease-surveillance units), and basic training (from high school to biology) all had negligible effects on TriatoDex performance. Our analyses also suggest that, as TriatoDex results accrue to cover more taxa, they may help pinpoint triatomine-bug species that are consistently harder (than average) to identify. In a pilot comparison with a standard, printed key (370 tasks by seven users), TriatoDex performed similarly (84.5% correct assignments, CI 68.9-94.0%), but identification was 32.8% (CI 24.7-40.1%) faster on average-for a mean absolute saving of ~2.3 minutes per bug-identification task. TriatoDex holds much promise as a handy, flexible, and reliable tool for triatomine-bug identification; an updated iOS/Android version is under development. We expect that, with continuous refinement derived from evolving knowledge and user feedback, TriatoDex will substantially help strengthen both entomological surveillance and research on Chagas disease vectors.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0248628PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8061935PMC
April 2021

Under pressure: phenotypic divergence and convergence associated with microhabitat adaptations in Triatominae.

Parasit Vectors 2021 Apr 8;14(1):195. Epub 2021 Apr 8.

Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK.

Background: Triatomine bugs, the vectors of Chagas disease, associate with vertebrate hosts in highly diverse ecotopes. It has been proposed that occupation of new microhabitats may trigger selection for distinct phenotypic variants in these blood-sucking bugs. Although understanding phenotypic variation is key to the study of adaptive evolution and central to phenotype-based taxonomy, the drivers of phenotypic change and diversity in triatomines remain poorly understood.

Methods/results: We combined a detailed phenotypic appraisal (including morphology and morphometrics) with mitochondrial cytb and nuclear ITS2 DNA sequence analyses to study Rhodnius ecuadoriensis populations from across the species' range. We found three major, naked-eye phenotypic variants. Southern-Andean bugs primarily from vertebrate-nest microhabitats (Ecuador/Peru) are typical, light-colored, small bugs with short heads/wings. Northern-Andean bugs from wet-forest palms (Ecuador) are dark, large bugs with long heads/wings. Finally, northern-lowland bugs primarily from dry-forest palms (Ecuador) are light-colored and medium-sized. Wing and (size-free) head shapes are similar across Ecuadorian populations, regardless of habitat or phenotype, but distinct in Peruvian bugs. Bayesian phylogenetic and multispecies-coalescent DNA sequence analyses strongly suggest that Ecuadorian and Peruvian populations are two independently evolving lineages, with little within-lineage phylogeographic structuring or differentiation.

Conclusions: We report sharp naked-eye phenotypic divergence of genetically similar Ecuadorian R. ecuadoriensis (nest-dwelling southern-Andean vs palm-dwelling northern bugs; and palm-dwelling Andean vs lowland), and sharp naked-eye phenotypic similarity of typical, yet genetically distinct, southern-Andean bugs primarily from vertebrate-nest (but not palm) microhabitats. This remarkable phenotypic diversity within a single nominal species likely stems from microhabitat adaptations possibly involving predator-driven selection (yielding substrate-matching camouflage coloration) and a shift from palm-crown to vertebrate-nest microhabitats (yielding smaller bodies and shorter and stouter heads). These findings shed new light on the origins of phenotypic diversity in triatomines, warn against excess reliance on phenotype-based triatomine-bug taxonomy, and confirm the Triatominae as an informative model system for the study of phenotypic change under ecological pressure .
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http://dx.doi.org/10.1186/s13071-021-04647-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8034103PMC
April 2021

Chagas disease diagnosis and cure assessment: Getting formally hierarchical about a naturally hierarchical problem.

PLoS Negl Trop Dis 2020 10 29;14(10):e0008751. Epub 2020 Oct 29.

Núcleo de Medicina Tropical, Faculdade de Medicina, Universidade de Brasília, Brasília, Brazil.

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http://dx.doi.org/10.1371/journal.pntd.0008751DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7595277PMC
October 2020

Measuring mosquito control: adult-mosquito catches vs egg-trap data as endpoints of a cluster-randomized controlled trial of mosquito-disseminated pyriproxyfen.

Parasit Vectors 2020 Jul 14;13(1):352. Epub 2020 Jul 14.

Núcleo de Medicina Tropical, Faculdade de Medicina, Universidade de Brasília, Brasilia, Brazil.

Background: Aedes aegypti and Culex quinquefasciatus are the main urban vectors of arthropod-borne viruses causing human disease, including dengue, Zika, or West Nile. Although key to disease prevention, urban-mosquito control has met only limited success. Alternative vector-control tactics are therefore being developed and tested, often using entomological endpoints to measure impact. Here, we test one promising alternative and assess how three such endpoints perform at measuring its effects.

Methods: We conducted a 16-month, two-arm, cluster-randomized controlled trial (CRCT) of mosquito-disseminated pyriproxyfen (MD-PPF) in central-western Brazil. We used three entomological endpoints: adult-mosquito density as directly measured by active aspiration of adult mosquitoes, and egg-trap-based indices of female Aedes presence (proportion of positive egg-traps) and possibly abundance (number of eggs per egg-trap). Using generalized linear mixed models, we estimated MD-PPF effects on these endpoints while accounting for the non-independence of repeated observations and for intervention-unrelated sources of spatial-temporal variation.

Results: On average, MD-PPF reduced adult-mosquito density by 66.3% (95% confidence interval, 95% CI: 47.3-78.4%); Cx. quinquefasciatus density fell by 55.5% (95% CI: 21.1-74.8%), and Ae. aegypti density by 60.0% (95% CI: 28.7-77.5%). In contrast, MD-PPF had no measurable effect on either Aedes egg counts or egg-trap positivity, both of which decreased somewhat in the intervention cluster but also in the control cluster. Egg-trap data, therefore, failed to reflect the 60.0% mean reduction of adult Aedes density associated with MD-PPF deployment.

Conclusions: Our results suggest that the widely used egg-trap-based monitoring may poorly measure the impact of Aedes control; even if more costly, direct monitoring of the adult mosquito population is likely to provide a much more realistic and informative picture of intervention effects. In our CRCT, MD-PPF reduced adult-mosquito density by 66.3% in a medium-sized, spatially non-isolated, tropical urban neighborhood. Broader-scale trials will be necessary to measure MD-PPF impact on arboviral-disease transmission.
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http://dx.doi.org/10.1186/s13071-020-04221-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7362459PMC
July 2020

Enduring extreme climate: Effects of severe drought on Triatoma brasiliensis populations in wild and man-made habitats of the Caatinga.

PLoS Negl Trop Dis 2019 10 10;13(10):e0007766. Epub 2019 Oct 10.

Grupo Triatomíneos, Instituto René Rachou-Fiocruz, Belo Horizonte, Minas Gerais, Brazil.

Background: Triatoma brasiliensis, a triatomine-bug vector of Chagas disease, evolved in the semiarid Caatinga, where it occupies rocky outcrops, shrubby cacti, and human dwellings. Dwellings and rocks are considered high-quality microhabitats for this saxicolous species, whereas cacti probably represent secondary, lower-quality microhabitats. This 'microhabitat-quality hierarchy' hypothesis predicts that T. brasiliensis populations occupying dwellings or rocks should endure harsh environmental conditions better than their cactus-living relatives.

Methods/findings: We tested this prediction by comparing T. brasiliensis infestation (proportion of microhabitats with bugs), density (bugs per microhabitat), and crowding (bugs per infested microhabitat) in dwellings, rocks, and cacti sampled before and during the extreme drought that ravaged the Caatinga in 2012-2016. We used random-intercepts generalized linear mixed models to account for microhabitat spatial clustering and for variations in bug-catch effort; we assessed model performance and computed model-averaged effect estimates using Akaike's information criterion. Pre-drought infestation was similar across microhabitat types; during the drought, infestation remained stable in dwellings and rocks but dropped in cacti. Pre-drought bug density declined from dwellings to rocks to cacti; an additional decline associated with the drought was largely comparable across microhabitats, albeit perhaps somewhat larger in cacti. Finally, pre-drought bug crowding was higher in dwellings than in rocks or cacti and changed little during the drought-possibly with a downward trend in dwellings and an upward trend in cacti.

Conclusions: Triatoma brasiliensis populations fared better in dwellings and rocks than in cacti during extreme drought. Estimates of microhabitat and drought effects on infestation, density, and crowding suggest that only a few cacti (versus many rocks and dwellings) represent good-quality habitat under such extremely harsh conditions. Our findings provide empirical support to the microhabitat-quality hierarchy hypothesis, and imply that T. brasiliensis can endure extreme climate by exploiting high-quality microhabitats, whether wild or man-made, in the semiarid Caatinga.
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http://dx.doi.org/10.1371/journal.pntd.0007766DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6805010PMC
October 2019

Dehydration-Stress Resistance in Two Sister, Cryptic Rhodnius Species-Rhodnius prolixus and Rhodnius robustus Genotype I (Hemiptera: Reduviidae).

J Med Entomol 2019 06;56(4):1019-1026

Grupo Triatomíneos, Instituto René Rachou, Fundação Oswaldo Cruz - Fiocruz, Belo Horizonte, Minas Gerais, Brazil.

Rhodnius prolixus Stål, a major Chagas disease vector, often colonizes in houses, whereas its sister species, Rhodnius robustus Larrousse genotype I, does not colonize in houses and has little medical relevance. Factors potentially underlying this crucial difference remain largely uncharted. The 'microclimate-adaptation hypothesis' notes that R. prolixus is adapted to the dry microclimate of small-crowned Copernicia palms, whereas R. robustus I exploits the high-moisture microclimate of large-crowned Attalea and Acrocomia. Hence, R. prolixus, but not R. robustus I, would be (pre)adapted to the relatively dry microclimate typical of man-made habitats. This hypothesis predicts that, while severe dehydration should harm both species similarly, R. prolixus should withstand moderate-to-mild dehydration stress better than R. robustus I. To test this prediction, we compared fitness metrics of genotyped R. prolixus and R. robustus I kept at 28°C and under severe (20% relative humidity, RH), moderate (40% RH), or mild dehydration stress (75% RH). Egg-hatching success increased with decreasing dehydration stress in R. robustus I (0% → 19% → 100%), but was high across treatments in R. prolixus (78% → 100% → 100%). Both species underwent high, early mortality under severe dehydration; under moderate and mild stress, R. prolixus experienced less mortality and survived longer than R. robustus I. Our results suggest that adaptation to distinct palm-crown microclimates may partly underlie the so far unexplained differences in house-colonization ability among Rhodnius Stål species. Experimental replication across additional species/populations will be required to further probe this adaptive hypothesis-which, if supported, may also provide insight into the likely responses of Chagas disease vectors to climate change.
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http://dx.doi.org/10.1093/jme/tjz041DOI Listing
June 2019

Transcriptome-based molecular systematics: Rhodnius montenegrensis (Triatominae) and its position within the Rhodnius prolixus-Rhodnius robustus cryptic-species complex.

Parasit Vectors 2019 Jun 17;12(1):305. Epub 2019 Jun 17.

Grupo Triatomíneos, Instituto René Rachou, Fiocruz Minas Gerais, Fundação Oswaldo Cruz (Fiocruz), Belo Horizonte, Brazil.

Background: Rhodnius montenegrensis (Triatominae), a potential vector of Chagas disease, was described after R. robustus-like bugs from southwestern Amazonia. Mitochondrial cytb sequence near-identity with sympatric R. robustus (genotype II) raised doubts about the taxonomic status of R. montenegrensis, but comparative studies have reported fairly clear morphological and genetic differences between R. montenegrensis and laboratory stocks identified as R. robustus. Here, we use a transcriptome-based approach to investigate this apparent paradox.

Results: We retrieved publicly-available transcriptome sequence-reads from R. montenegrensis and from the R. robustus stocks used as the taxonomic benchmark in comparative studies. We (i) aligned transcriptome sequence-reads to mitochondrial (cytb) and nuclear (ITS2, D2-28S and AmpG) query sequences (47 overall) from members of the R. prolixus-R. robustus cryptic-species complex and related taxa; (ii) computed breadth- and depth-coverage for the 259 consensus sequences generated by these alignments; and, for each locus, (iii) appraised query sequences and full-breadth-coverage consensus sequences in terms of nucleotide-sequence polymorphism and phylogenetic relations. We found evidence confirming that R. montenegrensis and R. robustus genotype II are genetically indistinguishable and, hence, implying that they are, in all likelihood, the same species. Furthermore, we found compelling genetic evidence that the benchmark 'R. robustus' stocks used in R. montenegrensis description and in later transcriptome-based comparisons are in fact R. prolixus, although likely mixed to some degree with R. robustus (probably genotype II, a.k.a. R. montenegrensis).

Conclusions: We illustrate how public-domain genetic/transcriptomic data can help address challenging issues in disease-vector systematics. In our case-study, taxonomic confusion apparently stemmed from the misinterpretation of sequence-data analyses and misidentification of taxonomic-benchmark stocks. More generally, and together with previous reports of mixed and/or misidentified Rhodnius spp. laboratory colonies, our results call into question the conclusions of many studies (on morphology, genetics, physiology, behavior, bionomics or interactions with microorganisms including trypanosomes) based on non-genotyped 'R. prolixus' or 'R. robustus' stocks. Correct species identification is a prerequisite for investigating the factors that underlie the physiological, behavioral or ecological differences between primary domestic vectors of Chagas disease, such as R. prolixus, and their sylvatic, medically less-relevant relatives such as R. robustus (s.l.) including R. montenegrensis.
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http://dx.doi.org/10.1186/s13071-019-3558-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6580618PMC
June 2019

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

Sci Rep 2018 May 4;8(1):7439. Epub 2018 May 4.

Laboratório de Parasitologia Médica e Biologia de Vetores, Faculdade de Medicina, Universidade de Brasília, Brasília, 72910-900, Brazil.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
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http://dx.doi.org/10.1038/s41598-018-24849-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5934402PMC
May 2018

Evolution, Systematics, and Biogeography of the Triatominae, Vectors of Chagas Disease.

Adv Parasitol 2018 ;99:265-344

Grupo Triatomíneos, Instituto René Rachou, FIOCRUZ, Belo Horizonte, Brazil.

In this chapter, we review and update current knowledge about the evolution, systematics, and biogeography of the Triatominae (Hemiptera: Reduviidae)-true bugs that feed primarily on vertebrate blood. In the Americas, triatomines are the vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. Despite declining incidence and prevalence, Chagas disease is still a major public health concern in Latin America. Triatomines occur also in the Old World, where vector-borne T. cruzi transmission has not been recorded. Triatomines evolved from predatory reduviid bugs, most likely in the New World, and diversified extensively across the Americas (including the Caribbean) and in parts of Asia and Oceania. Here, we first discuss our current understanding of how, how many times, and when the blood-feeding habit might have evolved among the Reduviidae. Then we present a summary of recent advances in the systematics of this diverse group of insects, with an emphasis on the contribution of molecular tools to the clarification of taxonomic controversies. Finally, and in the light of both up-to-date phylogenetic hypotheses and a thorough review of distribution records, we propose a global synthesis of the biogeography of the Triatominae. Over 130 triatomine species contribute to maintaining T. cruzi transmission among mammals (sometimes including humans) in almost every terrestrial ecoregion of the Americas. This means that Chagas disease will never be eradicated and underscores the fact that effective disease prevention will perforce require stronger, long-term vector control-surveillance systems.
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http://dx.doi.org/10.1016/bs.apar.2017.12.002DOI Listing
July 2019

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

Sci Rep 2018 01 9;8(1):151. Epub 2018 Jan 9.

Laboratório de Parasitologia Médica e Biologia de Vetores, Faculdade de Medicina, Universidade de Brasília, Brasília, 72910-900, Brazil.

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.
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http://dx.doi.org/10.1038/s41598-017-18532-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5760667PMC
January 2018

Drivers of house invasion by sylvatic Chagas disease vectors in the Amazon-Cerrado transition: A multi-year, state-wide assessment of municipality-aggregated surveillance data.

PLoS Negl Trop Dis 2017 Nov 16;11(11):e0006035. Epub 2017 Nov 16.

Grupo Triatomíneos, Instituto René Rachou-Fiocruz Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.

Background: Insecticide spraying efficiently controls house infestation by triatomine bugs, the vectors of Trypanosoma cruzi. The strategy, however, is ineffective against sylvatic triatomines, which can transmit Chagas disease by invading (without colonizing) man-made structures. Despite growing awareness of the relevance of these transmission dynamics, the drivers of house invasion by sylvatic triatomines remain poorly understood.

Methods/findings: About 12,000 sylvatic triatomines were caught during routine surveillance in houses of Tocantins state, Brazil, in 2005-2013. Using negative binomial regression, information-theoretic model evaluation/averaging, and external model validation, we investigated the effects of regional (Amazon/Cerrado), landscape (preservation/disturbance), and climate covariates (temperature, rainfall) on the municipality-aggregated numbers of house-invading Rhodnius pictipes, R. robustus, R. neglectus, and Panstrongylus geniculatus. House invasion by R. pictipes and R. robustus was overall more frequent in the Amazon biome, tended to increase in municipalities with more well-preserved land, and decreased in rainier municipalities. Across species, invasion decreased with higher landscape-disturbance levels and in hotter-day municipalities. Invasion by R. neglectus and P. geniculatus increased somewhat with more land at intermediate disturbance and peaked in average-rainfall municipalities. Temperature effects were more pronounced on P. geniculatus than on Rhodnius spp.

Conclusions: We report widespread, frequent house invasion by sylvatic triatomines in the Amazon-Cerrado transition. Our analyses indicate that readily available environmental metrics may help predict the risk of contact between sylvatic triatomines and humans at coarse geographic scales, and hint at specific hypotheses about climate and deforestation effects on those vectors-with some taxon-specific responses and some seemingly general trends. Thus, our focal species appear to be quite sensitive to higher temperatures, and might be less common in more heavily-disturbed than in better-preserved environments. This study illustrates, in sum, how entomological routine-surveillance data can be efficiently used for Chagas disease risk prediction and stratification when house-colonizing vectors are absent.
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http://dx.doi.org/10.1371/journal.pntd.0006035DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5689836PMC
November 2017

Triatoma costalimai (Hemiptera: Reduviidae) in and Around Houses of Tocantins State, Brazil, 2005-2014.

J Med Entomol 2017 11;54(6):1771-1774

Grupo Triatomíneos, Instituto René Rachou, Fundação Oswaldo Cruz - Fiocruz, Belo Horizonte, Minas Gerais, Brazil.

Triatoma costalimai Verano & Galvão, a little-known vector of Trypanosoma cruzi Chagas, occupies rocky environments in the Brazilian Cerrado and occasionally infests man-made habitats. Entomological surveillance records show that T. costalimai occurs fairly often inside and around houses in south-eastern Tocantins, Brazil, with 859 specimens reported in 2005-2014. Most adults were caught indoors, and breeding colonies were found inside and around houses. Trypanosoma cruzi was detected in 13.7% of 839 bugs. These data suggest that T. costalimai can contribute to T. cruzi transmission in human environments, underscoring the need for long-term entomological-epidemiological surveillance wherever native Chagas disease vectors occur.
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http://dx.doi.org/10.1093/jme/tjx135DOI Listing
November 2017

Mosquito-Disseminated Insecticide for Citywide Vector Control and Its Potential to Block Arbovirus Epidemics: Entomological Observations and Modeling Results from Amazonian Brazil.

PLoS Med 2017 Jan 17;14(1):e1002213. Epub 2017 Jan 17.

Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, Instituto Leônidas e Maria Deane, Fundação Oswaldo Cruz, Manaus, Amazonas, Brazil.

Background: Mosquito-borne viruses threaten public health worldwide. When the ratio of competent vectors to susceptible humans is low enough, the virus's basic reproductive number (R0) falls below 1.0 (each case generating, on average, <1.0 additional case) and the infection fades out from the population. Conventional mosquito control tactics, however, seldom yield R0 < 1.0. A promising alternative uses mosquitoes to disseminate a potent growth-regulator larvicide, pyriproxyfen (PPF), to aquatic larval habitats; this kills most mosquito juveniles and substantially reduces adult mosquito emergence. We tested mosquito-disseminated PPF in Manacapuru, a 60,000-inhabitant city (~650 ha) in Amazonian Brazil.

Methods And Findings: We sampled juvenile mosquitoes monthly in 100 dwellings over four periods in February 2014-January 2016: 12 baseline months, 5 mo of citywide PPF dissemination, 3 mo of focal PPF dissemination around Aedes-infested dwellings, and 3 mo after dissemination ended. We caught 19,434 juvenile mosquitoes (66% Aedes albopictus, 28% Ae. aegypti) in 8,271 trap-months. Using generalized linear mixed models, we estimated intervention effects on juvenile catch and adult emergence while adjusting for dwelling-level clustering, unequal sampling effort, and weather-related confounders. Following PPF dissemination, Aedes juvenile catch decreased by 79%-92% and juvenile mortality increased from 2%-7% to 80%-90%. Mean adult Aedes emergence fell from 1,077 per month (range 653-1,635) at baseline to 50.4 per month during PPF dissemination (range 2-117). Female Aedes emergence dropped by 96%-98%, such that the number of females emerging per person decreased to 0.06 females per person-month (range 0.002-0.129). Deterministic models predict, under plausible biological-epidemiological scenarios, that the R0 of typical Aedes-borne viruses would fall from 3-45 at baseline to 0.004-0.06 during PPF dissemination. The main limitations of our study were that it was a before-after trial lacking truly independent replicates and that we did not measure mosquito-borne virus transmission empirically.

Conclusions: Mosquito-disseminated PPF has potential to block mosquito-borne virus transmission citywide, even under adverse scenarios. Our results signal new avenues for mosquito-borne disease prevention, likely including the effective control of Aedes-borne dengue, Zika, and chikungunya epidemics. Cluster-randomized controlled trials will help determine whether mosquito-disseminated PPF can, as our findings suggest, develop into a major tool for improving global public health.
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http://dx.doi.org/10.1371/journal.pmed.1002213DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5240929PMC
January 2017

2 nd Brazilian Consensus on Chagas Disease, 2015.

Rev Soc Bras Med Trop 2016 Dec;49Suppl 1(Suppl 1):3-60

Universidade Estadual de Londrina, Faculdade de Medicina, Londrina-PR, Brasil.

Chagas disease is a neglected chronic condition with a high burden of morbidity and mortality. It has considerable psychological, social, and economic impacts. 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 the articulation and strategic contribution of renowned Brazilian experts with knowledge and experience on various aspects of the disease. It is the result of a close collaboration between the Brazilian Society of Tropical Medicine and the Ministry of Health. It is hoped that this document will strengthen the development of integrated actions against Chagas disease in the country, focusing on epidemiology, management, comprehensive care (including families and communities), communication, information, education, and research .
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http://dx.doi.org/10.1590/0037-8682-0505-2016DOI Listing
December 2016

[Brazilian Consensus on Chagas Disease, 2015].

Epidemiol Serv Saude 2016 06;25(spe):7-86

Universidade Estadual de Londrina, Faculdade de Medicina, Londrina-PR, Brasil.

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.
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http://dx.doi.org/10.5123/S1679-49742016000500002DOI Listing
June 2016

A simple, biologically sound, and potentially useful working classification of Chagas disease vectors.

Mem Inst Oswaldo Cruz 2016 Oct;111(10):649-651

Fundação Oswaldo Cruz, Centro de Pesquisas René Rachou, Belo Horizonte, MG, Brasil.

Current working classifications of Chagas disease vectors rely on a loose mix-up of biological and operational matters. They are therefore confusing and ineffective. I propose a very simple classification that makes biological sense and can be operationally useful. It considers a four-level hierarchy of species (which can be native or non-native); populations (either wild or non-wild); infestation foci (natural, domestic or peridomestic); and individual bugs (which can be solitary house-invaders or part of a hidden infestation focus). This classification translates into a clear, algorithmic scheme for triatomine control-surveillance that may be useful at every operationally relevant scale, from multi-country initiatives to on-site control-surveillance action.
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http://dx.doi.org/10.1590/0074-02760160203DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5066332PMC
October 2016

Genome of Rhodnius prolixus, an insect vector of Chagas disease, reveals unique adaptations to hematophagy and parasite infection.

Proc Natl Acad Sci U S A 2015 Dec 16;112(48):14936-41. Epub 2015 Nov 16.

Programa de Biologia Molecular e Biotecnologia, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-591, Brazil;

Rhodnius prolixus not only has served as a model organism for the study of insect physiology, but also is a major vector of Chagas disease, an illness that affects approximately seven million people worldwide. We sequenced the genome of R. prolixus, generated assembled sequences covering 95% of the genome (∼ 702 Mb), including 15,456 putative protein-coding genes, and completed comprehensive genomic analyses of this obligate blood-feeding insect. Although immune-deficiency (IMD)-mediated immune responses were observed, R. prolixus putatively lacks key components of the IMD pathway, suggesting a reorganization of the canonical immune signaling network. Although both Toll and IMD effectors controlled intestinal microbiota, neither affected Trypanosoma cruzi, the causal agent of Chagas disease, implying the existence of evasion or tolerance mechanisms. R. prolixus has experienced an extensive loss of selenoprotein genes, with its repertoire reduced to only two proteins, one of which is a selenocysteine-based glutathione peroxidase, the first found in insects. The genome contained actively transcribed, horizontally transferred genes from Wolbachia sp., which showed evidence of codon use evolution toward the insect use pattern. Comparative protein analyses revealed many lineage-specific expansions and putative gene absences in R. prolixus, including tandem expansions of genes related to chemoreception, feeding, and digestion that possibly contributed to the evolution of a blood-feeding lifestyle. The genome assembly and these associated analyses provide critical information on the physiology and evolution of this important vector species and should be instrumental for the development of innovative disease control methods.
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http://dx.doi.org/10.1073/pnas.1506226112DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4672799PMC
December 2015

On palms, bugs, and Chagas disease in the Americas.

Acta Trop 2015 Nov 18;151:126-41. Epub 2015 Jul 18.

Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA.

Palms are ubiquitous across Neotropical landscapes, from pristine forests or savannahs to large cities. Although palms provide useful ecosystem services, they also offer suitable habitat for triatomines and for Trypanosoma cruzi mammalian hosts. Wild triatomines often invade houses by flying from nearby palms, potentially leading to new cases of human Chagas disease. Understanding and predicting triatomine-palm associations and palm infestation probabilities is important for enhancing Chagas disease prevention in areas where palm-associated vectors transmit T. cruzi. We present a comprehensive overview of palm infestation by triatomines in the Americas, combining a thorough reanalysis of our published and unpublished records with an in-depth review of the literature. We use site-occupancy modeling (SOM) to examine infestation in 3590 palms sampled with non-destructive methods, and standard statistics to describe and compare infestation in 2940 palms sampled by felling-and-dissection. Thirty-eight palm species (18 genera) have been reported to be infested by ∼39 triatomine species (10 genera) from the USA to Argentina. Overall infestation varied from 49.1-55.3% (SOM) to 62.6-66.1% (dissection), with important heterogeneities among sub-regions and particularly among palm species. Large palms with complex crowns (e.g., Attalea butyracea, Acrocomia aculeata) and some medium-crowned palms (e.g., Copernicia, Butia) are often infested; in slender, small-crowned palms (e.g., Euterpe) triatomines associate with vertebrate nests. Palm infestation tends to be higher in rural settings, but urban palms can also be infested. Most Rhodnius species are probably true palm specialists, whereas Psammolestes, Eratyrus, Cavernicola, Panstrongylus, Triatoma, Alberprosenia, and some Bolboderini seem to use palms opportunistically. Palms provide extensive habitat for enzootic T. cruzi cycles and a critical link between wild cycles and transmission to humans. Unless effective means to reduce contact between people and palm-living triatomines are devised, palms will contribute to maintaining long-term and widespread, albeit possibly low-intensity, transmission of human Chagas disease.
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http://dx.doi.org/10.1016/j.actatropica.2015.07.005DOI Listing
November 2015

Mosquito-disseminated pyriproxyfen yields high breeding-site coverage and boosts juvenile mosquito mortality at the neighborhood scale.

PLoS Negl Trop Dis 2015 Apr 7;9(4):e0003702. Epub 2015 Apr 7.

Laboratório de Ecologia de Doenças Transmissíveis na Amazônia, Instituto Leônidas e Maria Deane-Fiocruz Amazônia, Manaus, Brazil.

Background: Mosquito-borne pathogens pose major public health challenges worldwide. With vaccines or effective drugs still unavailable for most such pathogens, disease prevention heavily relies on vector control. To date, however, mosquito control has proven difficult, with low breeding-site coverage during control campaigns identified as a major drawback. A novel tactic exploits the egg-laying behavior of mosquitoes to have them disseminate tiny particles of a potent larvicide, pyriproxyfen (PPF), from resting to breeding sites, thus improving coverage. This approach has yielded promising results at small spatial scales, but its wider applicability remains unclear.

Methodology/principal Findings: We conducted a four-month trial within a 20-month study to investigate mosquito-driven dissemination of PPF dust-particles from 100 'dissemination stations' (DSs) deployed in a 7-ha sub-area to surveillance dwellings and sentinel breeding sites (SBSs) distributed over an urban neighborhood of about 50 ha. We assessed the impact of the trial by measuring juvenile mosquito mortality and adult mosquito emergence in each SBS-month. Using data from 1,075 dwelling-months, 2,988 SBS-months, and 29,922 individual mosquitoes, we show that mosquito-disseminated PPF yielded high coverage of dwellings (up to 100%) and SBSs (up to 94.3%). Juvenile mosquito mortality in SBSs (about 4% at baseline) increased by over one order of magnitude during PPF dissemination (about 75%). This led to a >10-fold decrease of adult mosquito emergence from SBSs, from approximately 1,000-3,000 adults/month before to about 100 adults/month during PPF dissemination.

Conclusions/significance: By expanding breeding-site coverage and boosting juvenile mosquito mortality, a strategy based on mosquito-disseminated PPF has potential to substantially enhance mosquito control. Sharp declines in adult mosquito emergence can lower vector/host ratios, reducing the risk of disease outbreaks. This approach is a very promising complement to current and novel mosquito control strategies; it will probably be especially relevant for the control of urban disease vectors, such as Aedes and Culex species, that often cause large epidemics.
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http://dx.doi.org/10.1371/journal.pntd.0003702DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4388722PMC
April 2015

All that glisters is not gold: sampling-process uncertainty in disease-vector surveys with false-negative and false-positive detections.

PLoS Negl Trop Dis 2014 Sep 18;8(9):e3187. Epub 2014 Sep 18.

Chagas Disease Eco-epidemiology Laboratory, Instituto Oswaldo Cruz - Fiocruz, Rio de Janeiro, Brazil.

Background: Vector-borne diseases are major public health concerns worldwide. For many of them, vector control is still key to primary prevention, with control actions planned and evaluated using vector occurrence records. Yet vectors can be difficult to detect, and vector occurrence indices will be biased whenever spurious detection/non-detection records arise during surveys. Here, we investigate the process of Chagas disease vector detection, assessing the performance of the surveillance method used in most control programs--active triatomine-bug searches by trained health agents.

Methodology/principal Findings: Control agents conducted triplicate vector searches in 414 man-made ecotopes of two rural localities. Ecotope-specific 'detection histories' (vectors or their traces detected or not in each individual search) were analyzed using ordinary methods that disregard detection failures and multiple detection-state site-occupancy models that accommodate false-negative and false-positive detections. Mean (± SE) vector-search sensitivity was ∼ 0.283 ± 0.057. Vector-detection odds increased as bug colonies grew denser, and were lower in houses than in most peridomestic structures, particularly woodpiles. False-positive detections (non-vector fecal streaks misidentified as signs of vector presence) occurred with probability ∼ 0.011 ± 0.008. The model-averaged estimate of infestation (44.5 ± 6.4%) was ∼ 2.4-3.9 times higher than naïve indices computed assuming perfect detection after single vector searches (11.4-18.8%); about 106-137 infestation foci went undetected during such standard searches.

Conclusions/significance: We illustrate a relatively straightforward approach to addressing vector detection uncertainty under realistic field survey conditions. Standard vector searches had low sensitivity except in certain singular circumstances. Our findings suggest that many infestation foci may go undetected during routine surveys, especially when vector density is low. Undetected foci can cause control failures and induce bias in entomological indices; this may confound disease risk assessment and mislead program managers into flawed decision making. By helping correct bias in naïve indices, the approach we illustrate has potential to critically strengthen vector-borne disease control-surveillance systems.
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http://dx.doi.org/10.1371/journal.pntd.0003187DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4169387PMC
September 2014

Epidemiology of cutaneous leishmaniasis in central Amazonia: a comparison of sex-biased incidence among rural settlers and field biologists.

Trop Med Int Health 2014 Aug 26;19(8):988-95. Epub 2014 May 26.

Biological Dynamics of Forest Fragments Project, Smithsonian Tropical Research Institute & Instituto Nacional de Pesquisas da Amazônia, Manaus AM, Brazil; Graduate Program in Ecology, Instituto Nacional de Pesquisas da Amazônia, Manaus AM, Brazil; Department of Biology, University of Missouri St Louis, St Louis, MO, USA.

Objective: Cutaneous leishmaniasis (CL) is more frequently reported in men than in women; this may be due to male-biased exposure to CL vectors, female-biased resistance against the disease or both. We sought to determine whether gender-specific exposure to vector habitats explains male-biased CL incidence in two human populations of central Amazonia.

Methods: We compared the CL incidence in one population of field researchers (N = 166), with similar exposure for males and females, and one population of rural settlers (N = 646), where exposure is overall male-biased. We used a combination of questionnaires and clinical data to quantify CL cases, and modelled disease incidence in a Bayesian framework.

Results: There was a moderately higher incidence of CL among men than among women in both populations, but male bias decreased as exposure time increased. Disease incidence was overall higher among field researchers, suggesting that they are an important but understudied CL risk group.

Conclusion: Our comparison of two contrasting populations provided epidemiological evidence that CL incidence can be male-biased even when exposure is comparable in both sexes.
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http://dx.doi.org/10.1111/tmi.12337DOI Listing
August 2014

Modeling disease vector occurrence when detection is imperfect II: Drivers of site-occupancy by synanthropic Triatoma brasiliensis in the Brazilian northeast.

PLoS Negl Trop Dis 2014 May 8;8(5):e2861. Epub 2014 May 8.

Infectious Disease Ecology Laboratory, Instituto Leônidas e Maria Deane - Fiocruz, Manaus, Brazil.

Background: Understanding the drivers of habitat selection by insect disease vectors is instrumental to the design and operation of rational control-surveillance systems. One pervasive yet often overlooked drawback of vector studies is that detection failures result in some sites being misclassified as uninfested; naïve infestation indices are therefore biased, and this can confound our view of vector habitat preferences. Here, we present an initial attempt at applying methods that explicitly account for imperfect detection to investigate the ecology of Chagas disease vectors in man-made environments.

Methodology: We combined triplicate-sampling of individual ecotopes (n = 203) and site-occupancy models (SOMs) to test a suite of pre-specified hypotheses about habitat selection by Triatoma brasiliensis. SOM results were compared with those of standard generalized linear models (GLMs) that assume perfect detection even with single bug-searches.

Principal Findings: Triatoma brasiliensis was strongly associated with key hosts (native rodents, goats/sheep and, to a lesser extent, fowl) in peridomestic environments; ecotope structure had, in comparison, small to negligible effects, although wooden ecotopes were slightly preferred. We found evidence of dwelling-level aggregation of infestation foci; when there was one such focus, same-dwelling ecotopes, whether houses or peridomestic structures, were more likely to become infested too. GLMs yielded negatively-biased covariate effect estimates and standard errors; both were, on average, about four times smaller than those derived from SOMs.

Conclusions/significance: Our results confirm substantial population-level ecological heterogeneity in T. brasiliensis. They also suggest that, at least in some sites, control of this species may benefit from peridomestic rodent control and changes in goat/sheep husbandry practices. Finally, our comparative analyses highlight the importance of accounting for the various sources of uncertainty inherent to vector studies, including imperfect detection. We anticipate that future research on infectious disease ecology will increasingly rely on approaches akin to those described here.
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http://dx.doi.org/10.1371/journal.pntd.0002861DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4014420PMC
May 2014

A common Caatinga cactus, Pilosocereus gounellei, is an important ecotope of wild Triatoma brasiliensis populations in the Jaguaribe valley of northeastern Brazil.

Am J Trop Med Hyg 2014 Jun 7;90(6):1059-62. Epub 2014 Apr 7.

Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil; Secretaria Estadual de Saúde do Ceará, Fortaleza, Brazil; Instituto Leônidas e Maria Deane, Fiocruz Amazônia, Manaus, Brazil.

Triatoma brasiliensis is the most important vector of Chagas disease in the Caatinga eco-region of northeastern Brazil. Wild T. brasiliensis populations have been reported only from rocky outcrops. However, this species frequently infests/re-infests houses in rock-free sedimentary lowlands. We therefore hypothesized that it should also occupy other natural ecotopes. We show that a common Caatinga cactus, Pilosocereus gounellei, locally known as xiquexique, often harbors T. brasiliensis breeding colonies apparently associated with rodents (n = 44 cacti, infestation rate = 47.7%, 157 bugs captured). Our findings suggest that infested cacti might be involved in house re-infestation by T. brasiliensis in the Caatinga region.
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http://dx.doi.org/10.4269/ajtmh.13-0204DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4047729PMC
June 2014

Chagas disease vector control in a hyperendemic setting: the first 11 years of intervention in Cochabamba, Bolivia.

PLoS Negl Trop Dis 2014 Apr 3;8(4):e2782. Epub 2014 Apr 3.

Instituto Leônidas e Maria Deane - Fiocruz Amazônia, Manaus, Brazil.

Background: Chagas disease has historically been hyperendemic in the Bolivian Department of Cochabamba. In the early 2000s, an extensive vector control program was implemented; 1.34 million dwelling inspections were conducted to ascertain infestation (2000-2001/2003-2011), with blanket insecticide spraying in 2003-2005 and subsequent survey-spraying cycles targeting residual infestation foci. Here, we assess the effects of this program on dwelling infestation rates (DIRs).

Methodology/principal Findings: Program records were used to calculate annual, municipality-level aggregate DIRs (39 municipalities); very high values in 2000-2001 (median: 0.77-0.69) dropped to ∼0.03 from 2004 on. A linear mixed model (with municipality as a random factor) suggested that infestation odds decreased, on average, by ∼28% (95% confidence interval [CI95] 6-44%) with each 10-fold increase in control effort. A second, better-fitting mixed model including year as an ordinal predictor disclosed large DIR reductions in 2001-2003 (odds ratio [OR] 0.11, CI95 0.06-0.19) and 2003-2004 (OR 0.22, CI95 0.14-0.34). Except for a moderate decrease in 2005-2006, no significant changes were detected afterwards. In both models, municipality-level DIRs correlated positively with previous-year DIRs and with the extent of municipal territory originally covered by montane dry forests.

Conclusions/significance: Insecticide-spraying campaigns had very strong, long-lasting effects on DIRs in Cochabamba. However, post-intervention surveys consistently detected infestation in ∼3% of dwellings, underscoring the need for continuous surveillance; higher DIRs were recorded in the capital city and, more generally, in municipalities dominated by montane dry forest--an eco-region where wild Triatoma infestans are widespread. Traditional strategies combining insecticide spraying and longitudinal surveillance are thus confirmed as very effective means for area-wide Chagas disease vector control; they will be particularly beneficial in highly-endemic settings, but should also be implemented or maintained in other parts of Latin America where domestic infestation by triatomines is still commonplace.
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http://dx.doi.org/10.1371/journal.pntd.0002782DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3974664PMC
April 2014

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

Mem Inst Oswaldo Cruz 2013 ;108 Suppl 1:92-9

Laboratório de Epidemiologia e Sistemática Molecular, Laboratório de Epidemiologia e Sistemática Molecular.

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.
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http://dx.doi.org/10.1590/0074-0276130434DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4109185PMC
December 2014

Phylogeographic pattern and extensive mitochondrial DNA divergence disclose a species complex within the Chagas disease vector Triatoma dimidiata.

PLoS One 2013 5;8(8):e70974. Epub 2013 Aug 5.

Laboratório de Epidemiologia e Sistemática Molecular, Instituto Oswaldo Cruz - Fiocruz, Rio de Janeiro, Brazil.

Background: Triatoma dimidiata is among the main vectors of Chagas disease in Latin America. However, and despite important advances, there is no consensus about the taxonomic status of phenotypically divergent T. dimidiata populations, which in most recent papers are regarded as subspecies.

Methodology And Findings: A total of 126 cyt b sequences (621 bp long) were produced for specimens from across the species range. Forty-seven selected specimens representing the main cyt b clades observed (after a preliminary phylogenetic analysis) were also sequenced for an ND4 fragment (554 bp long) and concatenated with their respective cyt b sequences to produce a combined data set totalling 1175 bp/individual. Bayesian and Maximum-Likelihood phylogenetic analyses of both data sets (cyt b, and cyt b+ND4) disclosed four strongly divergent (all pairwise Kimura 2-parameter distances >0.08), monophyletic groups: Group I occurs from Southern Mexico through Central America into Colombia, with Ecuadorian specimens resembling Nicaraguan material; Group II includes samples from Western-Southwestern Mexico; Group III comprises specimens from the Yucatán peninsula; and Group IV consists of sylvatic samples from Belize. The closely-related, yet formally recognized species T. hegneri from the island of Cozumel falls within the divergence range of the T. dimidiata populations studied.

Conclusions: We propose that Groups I-IV, as well as T. hegneri, should be regarded as separate species. In the Petén of Guatemala, representatives of Groups I, II, and III occur in sympatry; the absence of haplotypes with intermediate genetic distances, as shown by multimodal mismatch distribution plots, clearly indicates that reproductive barriers actively promote within-group cohesion. Some sylvatic specimens from Belize belong to a different species - likely the basal lineage of the T. dimidiata complex, originated ~8.25 Mya. The evidence presented here strongly supports the proposition that T. dimidiata is a complex of five cryptic species (Groups I-IV plus T. hegneri) that play different roles as vectors of Chagas disease in the region.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0070974PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3733668PMC
March 2014

Sex bias in infectious disease epidemiology: patterns and processes.

PLoS One 2013 24;8(4):e62390. Epub 2013 Apr 24.

Instituto Leônidas e Maria Deane - Fiocruz Amazônia, Manaus, Amazonas, Brazil.

Background: Infectious disease incidence is often male-biased. Two main hypotheses have been proposed to explain this observation. The physiological hypothesis (PH) emphasizes differences in sex hormones and genetic architecture, while the behavioral hypothesis (BH) stresses gender-related differences in exposure. Surprisingly, the population-level predictions of these hypotheses are yet to be thoroughly tested in humans.

Methods And Findings: For ten major pathogens, we tested PH and BH predictions about incidence and exposure-prevalence patterns. Compulsory-notification records (Brazil, 2006-2009) were used to estimate age-stratified ♂:♀ incidence rate ratios for the general population and across selected sociological contrasts. Exposure-prevalence odds ratios were derived from 82 published surveys. We estimated summary effect-size measures using random-effects models; our analyses encompass ∼0.5 million cases of disease or exposure. We found that, after puberty, disease incidence is male-biased in cutaneous and visceral leishmaniasis, schistosomiasis, pulmonary tuberculosis, leptospirosis, meningococcal meningitis, and hepatitis A. Severe dengue is female-biased, and no clear pattern is evident for typhoid fever. In leprosy, milder tuberculoid forms are female-biased, whereas more severe lepromatous forms are male-biased. For most diseases, male bias emerges also during infancy, when behavior is unbiased but sex steroid levels transiently rise. Behavioral factors likely modulate male-female differences in some diseases (the leishmaniases, tuberculosis, leptospirosis, or schistosomiasis) and age classes; however, average exposure-prevalence is significantly sex-biased only for Schistosoma and Leptospira.

Conclusions: Our results closely match some key PH predictions and contradict some crucial BH predictions, suggesting that gender-specific behavior plays an overall secondary role in generating sex bias. Physiological differences, including the crosstalk between sex hormones and immune effectors, thus emerge as the main candidate drivers of gender differences in infectious disease susceptibility.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0062390PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3634762PMC
December 2013

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

Mem Inst Oswaldo Cruz 2013 Apr;108(2):251-4

Instituto Leônidas e Maria Deane-Fiocruz, Manaus, AM, Brasil.

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.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3970656PMC
http://dx.doi.org/10.1590/0074-0276108022013022DOI Listing
April 2013