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Search Results: 1 - 10 of 24357 matches for " Fernando Abad-Franch "
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Molecular research and the control of Chagas disease vectors
Abad-Franch, Fernando;Monteiro, Fernando A.;
Anais da Academia Brasileira de Ciências , 2005, DOI: 10.1590/S0001-37652005000300007
Abstract: chagas disease control initiatives are yielding promising results. molecular research has helped successful programs by identifying and characterizing introduced vector populations and by defining intervention targets accurately. however, researchers and health officials are facing new challenges throughout latin america. native vectors persistently reinfest insecticide-treated households, and sylvatic triatomines maintain disease transmission in humid forest regions (including amazonia) without colonizing human dwellings. in these scenarios, fine-scale vector studies are essential to define epidemiological risk patterns and clarify the involvement of little-known triatomine taxa in disease transmission. these eco-epidemiological investigations, as well as the planning and monitoring of control interventions, rely by necessity on accurate taxonomic judgments. the problems of cryptic speciation and phenotypic plasticity illustrate this need - and how molecular systematics can provide the fitting answers. molecular data analyses also illuminate basic aspects of vector evolution and adaptive trends. here we review the applications of molecular markers (concentrating on allozymes and dna sequencing) to the study of triatomines. we analyze the suitability, strengths and weaknesses of the various techniques for taxonomic, systematic and evolutionary investigations at different levels (populations, species, and higher taxonomic categories).
Biogeography and evolution of Amazonian triatomines (Heteroptera: Reduviidae): implications for Chagas disease surveillance in humid forest ecoregions
Abad-Franch, Fernando;Monteiro, Fernando A;
Memórias do Instituto Oswaldo Cruz , 2007, DOI: 10.1590/S0074-02762007005000108
Abstract: 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.
Molecular research and the control of Chagas disease vectors
Abad-Franch Fernando,Monteiro Fernando A.
Anais da Academia Brasileira de Ciências , 2005,
Abstract: Chagas disease control initiatives are yielding promising results. Molecular research has helped successful programs by identifying and characterizing introduced vector populations and by defining intervention targets accurately. However, researchers and health officials are facing new challenges throughout Latin America. Native vectors persistently reinfest insecticide-treated households, and sylvatic triatomines maintain disease transmission in humid forest regions (including Amazonia) without colonizing human dwellings. In these scenarios, fine-scale vector studies are essential to define epidemiological risk patterns and clarify the involvement of little-known triatomine taxa in disease transmission. These eco-epidemiological investigations, as well as the planning and monitoring of control interventions, rely by necessity on accurate taxonomic judgments. The problems of cryptic speciation and phenotypic plasticity illustrate this need - and how molecular systematics can provide the fitting answers. Molecular data analyses also illuminate basic aspects of vector evolution and adaptive trends. Here we review the applications of molecular markers (concentrating on allozymes and DNA sequencing) to the study of triatomines. We analyze the suitability, strengths and weaknesses of the various techniques for taxonomic, systematic and evolutionary investigations at different levels (populations, species, and higher taxonomic categories).
Sex Bias in Infectious Disease Epidemiology: Patterns and Processes
Felipe Guerra-Silveira, Fernando Abad-Franch
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0062390
Abstract: 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.
Chagas Disease Vector Control in a Hyperendemic Setting: The First 11 Years of Intervention in Cochabamba, Bolivia
Natalisisy Espinoza,Rafael Borrás,Fernando Abad-Franch
PLOS Neglected Tropical Diseases , 2014, DOI: 10.1371/journal.pntd.0002782
Abstract: 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.
Attraction of Chagas disease vectors (Triatominae) to artificial light sources in the canopy of primary Amazon rainforest
Castro, Marcelo CM;Barrett, Toby V;Santos, Walter S;Abad-Franch, Fernando;Rafael, José A;
Memórias do Instituto Oswaldo Cruz , 2010, DOI: 10.1590/S0074-02762010000800019
Abstract: 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.
Trapping Triatominae in Silvatic Habitats
Noireau Fran?ois,Abad-Franch Fernando,Valente Sebasti?o AS,Dias-Lima Artur
Memórias do Instituto Oswaldo Cruz , 2002,
Abstract: 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% and reaching 48.4% 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.
Biogeography of Triatominae (Hemiptera: Reduviidae) in Ecuador: implications for the design of control strategies
Abad-Franch Fernando,Paucar C Aura,Carpio C Carlos,Cuba Cuba César A
Memórias do Instituto Oswaldo Cruz , 2001,
Abstract: 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.
Epidemiology of Chagas disease in Ecuador. A brief review
Aguilar V H Marcelo,Abad-Franch Fernando,Racines V José,Paucar C Aura
Memórias do Instituto Oswaldo Cruz , 1999,
Abstract: 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.
All That Glisters Is Not Gold: Sampling-Process Uncertainty in Disease-Vector Surveys with False-Negative and False-Positive Detections
Fernando Abad-Franch ,Carolina Valen?a-Barbosa,Otília Sarquis,Marli M. Lima
PLOS Neglected Tropical Diseases , 2014, DOI: 10.1371/journal.pntd.0003187
Abstract: 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 na?ve 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 na?ve indices, the approach we illustrate has potential to critically strengthen vector-borne disease control-surveillance systems.
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