Time filter

Source Type

Abad-Franch F.,Instituto Leonidas e Maria Deane Fiocruz Amazonia | Valenca-Barbosa C.,Instituto Oswaldo Cruz Fiocruz | Sarquis O.,Instituto Oswaldo Cruz Fiocruz | Lima M.M.,Instituto Oswaldo Cruz Fiocruz
PLoS Neglected Tropical Diseases | Year: 2014

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.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.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. © 2014 Abad-Franch et al.

Rojas de Arias A.,Chilean Center of Nanosciences and Nanotechnology | Abad-Franch F.,Instituto Leonidas e Maria Deane Fiocruz Amazonia | Acosta N.,National University of Asunción | Lopez E.,National University of Asunción | Gonzalez N.,National University of Asunción
PLoS Neglected Tropical Diseases | Year: 2012

Background: Chagas disease prevention critically depends on keeping houses free of triatomine vectors. Insecticide spraying is very effective, but re-infestation of treated dwellings is commonplace. Early detection-elimination of re-infestation foci is key to long-term control; however, all available vector-detection methods have low sensitivity. Chemically-baited traps are widely used in vector and pest control-surveillance systems; here, we test this approach for Triatoma spp. detection under field conditions in the Gran Chaco. Methodology/Principal Findings: Using a repeated-sampling approach and logistic models that explicitly take detection failures into account, we simultaneously estimate vector occurrence and detection probabilities. We then model detection probabilities (conditioned on vector occurrence) as a function of trapping system to measure the effect of chemical baits. We find a positive effect of baits after three (odds ratio [OR] 5.10; 95% confidence interval [CI95] 2.59-10.04) and six months (OR 2.20, CI95 1.04-4.65). Detection probabilities are estimated at p ≈ 0.40-0.50 for baited and at just p ≈ 0.15 for control traps. Bait effect is very strong on T. infestans (three-month assessment: OR 12.30, CI95 4.44-34.10; p ≈ 0.64), whereas T. sordida is captured with similar frequency in baited and unbaited traps. Conclusions/Significance: Chemically-baited traps hold promise for T. infestans surveillance; the sensitivity of the system at detecting small re-infestation foci rises from 12.5% to 63.6% when traps are baited with semiochemicals. Accounting for imperfect detection, infestation is estimated at 26% (CI95 16-40) after three and 20% (CI95 11-34) after six months. In the same assessments, traps detected infestation in 14% and 8.5% of dwellings, whereas timed manual searches (the standard approach) did so in just 1.4% of dwellings only in the first survey. Since infestation rates are the main indicator used for decision-making in control programs, the approach we present may help improve T. infestans surveillance and control program management. © 2012 Rojas de Arias et al.

Abad-Franch F.,Instituto Leonidas e Maria Deane Fiocruz Amazonia | Grimmer G.H.,Instituto Leonidas e Maria Deane Fiocruz Amazonia | de Paula V.S.,Instituto Oswaldo Cruz Fiocruz | Figueiredo L.T.M.,University of Sao Paulo | And 2 more authors.
PLoS Neglected Tropical Diseases | Year: 2012

Background: Arboviral diseases are major global public health threats. Yet, our understanding of infection risk factors is, with a few exceptions, considerably limited. A crucial shortcoming is the widespread use of analytical methods generally not suited for observational data - particularly null hypothesis-testing (NHT) and step-wise regression (SWR). Using Mayaro virus (MAYV) as a case study, here we compare information theory-based multimodel inference (MMI) with conventional analyses for arboviral infection risk factor assessment. Methodology/Principal Findings: A cross-sectional survey of anti-MAYV antibodies revealed 44% prevalence (n = 270 subjects) in a central Amazon rural settlement. NHT suggested that residents of village-like household clusters and those using closed toilet/latrines were at higher risk, while living in non-village-like areas, using bednets, and owning fowl, pigs or dogs were protective. The "minimum adequate" SWR model retained only residence area and bednet use. Using MMI, we identified relevant covariates, quantified their relative importance, and estimated effect-sizes (β±SE) on which to base inference. Residence area (βVillage = 2.93±0.41; βUpland = -0.56±0.33, βRiverbanks = -2.37±0.55) and bednet use (β = -0.95±0.28) were the most important factors, followed by crop-plot ownership (β = 0.39±0.22) and regular use of a closed toilet/latrine (β = 0.19±0.13); domestic animals had insignificant protective effects and were relatively unimportant. The SWR model ranked fifth among the 128 models in the final MMI set. Conclusions/Significance: Our analyses illustrate how MMI can enhance inference on infection risk factors when compared with NHT or SWR. MMI indicates that forest crop-plot workers are likely exposed to typical MAYV cycles maintained by diurnal, forest dwelling vectors; however, MAYV might also be circulating in nocturnal, domestic-peridomestic cycles in village-like areas. This suggests either a vector shift (synanthropic mosquitoes vectoring MAYV) or a habitat/habits shift (classical MAYV vectors adapting to densely populated landscapes and nocturnal biting); any such ecological/adaptive novelty could increase the likelihood of MAYV emergence in Amazonia. © 2012 Abad-Franch et al.

Santarem M.C.A.,Instituto Oswaldo Cruz Fiocruz | Santarem M.C.A.,Federal University of Rio de Janeiro | Farias E.S.,Instituto Leonidas e Maria Deane Fiocruz Amazonia | Felippe-Bauer M.L.,Instituto Oswaldo Cruz Fiocruz
Anais da Academia Brasileira de Ciencias | Year: 2015

A new species of the reticulatus species group, C. castelloni Santarém and Felippe-Bauer, is described and illustrated based on female specimens from the state of Amazonas, Brazil. A systematic key, wing photographs and table with numerical characters of females and a synopsis of 24 species of the Culicoides reticulatus group are presented. This paper presents further new records for seven species of the reticulatus group. © 2015, Academia Brasileira de Ciencias. All rights reserved.

Newton P.,University of East Anglia | Peres C.A.,University of East Anglia | Desmouliere S.J.M.,Instituto Leonidas e Maria Deane Fiocruz Amazonia | Watkinson A.R.,University of East Anglia
Forest Ecology and Management | Year: 2012

Successful management of tropical forest resources depends upon an understanding of their patterns of density and spatial distribution, since these affect the potential for harvesting. The variation in these patterns across different spatial scales has rarely been explored. We assessed the extent to which different spatial scales are useful in understanding resource distribution, using the example of an economically-significant tropical tree genus, Copaifera, which is valued across Brazilian Amazonia for its medicinal oleoresin. We mapped the spatial distribution of Copaifera trees at three nested spatial scales: basin-wide (across Brazilian Amazonia), landscape (across two contiguous extractive reserves) and local (within a 100-ha plot). Using data from our own study and an Amazon-wide forest inventory (Projeto RADAMBRASIL), we quantified the population distribution, density and size structure at the genus and species level at all three scales, relating these to two environmental variables - forest type and elevation. Spatial statistics were used to further characterize the resource at the landscape and local levels. The distribution, density and adult population structure differed between species and forest types at all three spatial scales. Overall tree densities ranged from 0.37ha -1 (basin-wide scale) to 1.13ha -1 (local scale) but varied between forest types, with várzea containing a Copaifera tree density just 43% of that in terra firme forest at the landscape scale. Spatial distribution analyses showed significant clumping of some species, especially C. multijuga which averaged 61m between neighbouring trees. We compare our cross-scale density estimates and discuss the relative merits of studying the distribution of non-timber forest products (NTFP) at more than one spatial scale. Our results have implications for the management and extraction of this important Amazonian forest resource. © 2012 Elsevier B.V.

Guerra-Silveira F.,Instituto Leonidas e Maria Deane Fiocruz Amazonia | Guerra-Silveira F.,University of the State of Amazonas | Abad-Franch F.,Instituto Leonidas e Maria Deane Fiocruz Amazonia
PLoS ONE | Year: 2013

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. © 2013 Guerra-Silveira, Abad-Franch.

Abad-Franch F.,Instituto Leonidas e Maria Deane Fiocruz Amazonia | Santos W.S.,Instituto Leonidas e Maria Deane Fiocruz Amazonia | Schofield C.J.,London School of Hygiene and Tropical Medicine
Acta Tropica | Year: 2010

We present an overview of the two main strategies for the primary (vector control) and secondary (patient care) prevention of Chagas disease (CD). We identify major advances, knowledge gaps, and key research needs in both areas. Improved specific chemotherapy, including more practical formulations (e.g., paediatric) or combinations of existing drugs, and a better understanding of pathogenesis, including the relative weights of parasite and host genetic makeup, are clearly needed. Regarding CD vectors, we find that only about 10-20% of published papers on triatomines deal directly with disease control. We pinpoint the pitfalls of the current consensus on triatomine systematics, particularly within the Triatomini, and suggest how some straightforward sampling and analytical strategies would improve research on vector ecology, naturally leading to sounder control-surveillance schemes. We conclude that sustained research on CD prevention is still crucial. In the past, it provided not only the know-how, but also the critical mass of scientists needed to foster and consolidate CD prevention programmes; in the future, both patient care and long-term vector control would nonetheless benefit from more sharply focused, problem-oriented research. © 2010 Elsevier.

A wave of Haitian immigration into Brazil began in February 2010 through three northern border states: Acre, Rondônia, and Amazonas. Focusing on the state of Amazonas, the article uses an ethnographic approach to explore the social networks involved in this immigrant issue and examines how Brazil’s Sistema Único de Saúde (SUS) responded to the demands placed by this unexpected contingent of new users visà- vis the system’s guiding constitutional principles, particularly equity. A picture is painted of some aspects of the most critical immigration period (March 2010-March 2012) and of the public healthcare system’s reception of these Haitian newcomers. © 2016, Fundacao Oswaldo Cruz. All rights reserved.

Espinoza N.,University of Valencia | Borras R.,University of Valencia | Abad-Franch F.,Instituto Leonidas e Maria Deane Fiocruz Amazonia
PLoS Neglected Tropical Diseases | Year: 2014

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. © 2014 Espinoza et al.

Abad-Franch F.,Instituto Leonidas e Maria Deane Fiocruz Amazonia | Vega M.C.,Chilean Center of Nanosciences and Nanotechnology | Rolon M.S.,Chilean Center of Nanosciences and Nanotechnology | Santos W.S.,Instituto Leonidas e Maria Deane Fiocruz Amazonia | And 2 more authors.
PLoS Neglected Tropical Diseases | Year: 2011

Background: Vector control has substantially reduced Chagas disease (ChD) incidence. However, transmission by household-reinfesting triatomines persists, suggesting that entomological surveillance should play a crucial role in the long-term interruption of transmission. Yet, infestation foci become smaller and harder to detect as vector control proceeds, and highly sensitive surveillance methods are needed. Community participation (CP) and vector-detection devices (VDDs) are both thought to enhance surveillance, but this remains to be thoroughly assessed. Methodology/Principal Findings: We searched Medline, Web of Knowledge, Scopus, LILACS, SciELO, the bibliographies of retrieved studies, and our own records. Data from studies describing vector control and/or surveillance interventions were extracted by two reviewers. Outcomes of primary interest included changes in infestation rates and the detection of infestation/reinfestation foci. Most results likely depended on study- and site-specific conditions, precluding meta-analysis, but we re-analysed data from studies comparing vector control and detection methods whenever possible. Results confirm that professional, insecticide-based vector control is highly effective, but also show that reinfestation by native triatomines is common and widespread across Latin America. Bug notification by householders (the simplest CP-based strategy) significantly boosts vector detection probabilities; in comparison, both active searches and VDDs perform poorly, although they might in some cases complement each other. Conclusions/Significance: CP should become a strategic component of ChD surveillance, but only professional insecticide spraying seems consistently effective at eliminating infestation foci. Involvement of stakeholders at all process stages, from planning to evaluation, would probably enhance such CP-based strategies. © 2011 Abad-Franch et al.

Loading Instituto Leonidas e Maria Deane Fiocruz Amazonia collaborators
Loading Instituto Leonidas e Maria Deane Fiocruz Amazonia collaborators