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Search Results: 1 - 10 of 307930 matches for " Mario J. Grijalva "
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Dynamics of Sylvatic Chagas Disease Vectors in Coastal Ecuador Is Driven by Changes in Land Cover
Mario J. Grijalva ,David Terán,Olivier Dangles
PLOS Neglected Tropical Diseases , 2014, DOI: 10.1371/journal.pntd.0002960
Abstract: Background Chagas disease is a serious public health problem in Latin America where about ten million individuals show Trypanosoma cruzi infection. Despite significant success in controlling domiciliated triatomines, sylvatic populations frequently infest houses after insecticide treatment which hampers long term control prospects in vast geographical areas where vectorial transmission is endemic. As a key issue, the spatio-temporal dynamics of sylvatic populations is likely influenced by landscape yet evidence showing this effect is rare. The aim of this work is to examine the role of land cover changes in sylvatic triatomine ecology, based on an exhaustive field survey of pathogens, vectors, hosts, and microhabitat characteristics' dynamics. Methodology and Principal Findings The study was performed in agricultural landscapes of coastal Ecuador as a study model. Over one year, a spatially-randomized sampling design (490 collection points) allowed quantifying triatomine densities in natural, cultivated and domestic habitats. We also assessed infection of the bugs with trypanosomes, documented their microhabitats and potential hosts, and recorded changes in landscape characteristics. In total we collected 886 individuals, mainly represented by nymphal stages of one triatomine species Rhodnius ecuadoriensis. As main results, we found that 1) sylvatic triatomines had very high T. cruzi infection rates (71%) and 2) densities of T. cruzi-infected sylvatic triatomines varied predictably over time due to changes in land cover and occurrence of associated rodent hosts. Conclusion We propose a framework for identifying the factors affecting the yearly distribution of sylvatic T. cruzi vectors. Beyond providing key basic information for the control of human habitat colonization by sylvatic vector populations, our framework highlights the importance of both environmental and sociological factors in shaping the spatio-temporal population dynamics of triatomines. A better understanding of the dynamics of such socio-ecological systems is a crucial, yet poorly considered, issue for the long-term control of Chagas disease.
Life cycle, feeding and defecation patterns of Rhodnius ecuadoriensis (Lent & León 1958) (Hemiptera: Reduviidae: Triatominae) under laboratory conditions
Villacís, Anita G;Arcos-Terán, Laura;Grijalva, Mario J;
Memórias do Instituto Oswaldo Cruz , 2008, DOI: 10.1590/S0074-02762008000700011
Abstract: rhodnius ecuadoriensis is the second most important vector of chagas disease (cd) in ecuador. the objective of this study was to describe (and compare) the life cycle, the feeding and defecation patterns under laboratory conditions of two populations of this specie [from the provinces of manabí (coastal region) and loja (andean region)]. egg-to-adult (n = 57) development took an average of 189.9 ± 20 (manabí) and 181.3 ± 6.4 days (loja). mortality rates were high among lojan nymphs. pre-feeding time (from contact with host to feeding initiation) ranged from 4 min 42 s [nymph i (ni)] to 8 min 30 s (male); feeding time ranged from 14 min 45 s (ni)-28 min 25 s (male) (manabí) and from 15 min 25 s (ni)-28 min 57 s (nymph v) (loja). the amount of blood ingested increased significantly with instar and was larger for manabí specimens (p < 0.001). defecation while feeding was observed in manabí specimens from stage nymph iii and in lojan bugs from stage nymph iv. there was a gradual, age-related increase in the frequency of this behaviour in both populations. our results suggest that r. ecuadoriensis has the bionomic traits of an efficient vector of trypanosoma cruzi. together with previous data on the capacity of this species to infest rural households, these results indicate that control of synanthropic r. ecuadoriensis populations in the coastal and andean regions may have a significant impact for cd control in ecuador and northern peru.
Sex, Subdivision, and Domestic Dispersal of Trypanosoma cruzi Lineage I in Southern Ecuador
Sofía Oca?a-Mayorga,Martin S. Llewellyn,Jaime A. Costales,Michael A. Miles,Mario J. Grijalva
PLOS Neglected Tropical Diseases , 2010, DOI: 10.1371/journal.pntd.0000915
Abstract: Background Molecular epidemiology at the community level has an important guiding role in zoonotic disease control programmes where genetic markers are suitably variable to unravel the dynamics of local transmission. We evaluated the molecular diversity of Trypanosoma cruzi, the etiological agent of Chagas disease, in southern Ecuador (Loja Province). This kinetoplastid parasite has traditionally been a paradigm for clonal population structure in pathogenic organisms. However, the presence of naturally occurring hybrids, mitochondrial introgression, and evidence of genetic exchange in the laboratory question this dogma. Methodology/Principal Findings Eighty-one parasite isolates from domiciliary, peridomiciliary, and sylvatic triatomines and mammals were genotyped across 10 variable microsatellite loci. Two discrete parasite populations were defined: one predominantly composed of isolates from domestic and peridomestic foci, and another predominantly composed of isolates from sylvatic foci. Spatial genetic variation was absent from the former, suggesting rapid parasite dispersal across our study area. Furthermore, linkage equilibrium between loci, Hardy-Weinberg allele frequencies at individual loci, and a lack of repeated genotypes are indicative of frequent genetic exchange among individuals in the domestic/peridomestic population. Conclusions/Significance These data represent novel population-level evidence of an extant capacity for sex among natural cycles of T. cruzi transmission. As such they have dramatic implications for our understanding of the fundamental genetics of this parasite. Our data also elucidate local disease transmission, whereby passive anthropogenic domestic mammal and triatomine dispersal across our study area is likely to account for the rapid domestic/peridomestic spread of the parasite. Finally we discuss how this, and the observed subdivision between sympatric sylvatic and domestic/peridomestic foci, can inform efforts at Chagas disease control in Ecuador.
Ecological factors related to the widespread distribution of sylvatic Rhodnius ecuadoriensis populations in southern Ecuador
Mario J Grijalva, Victoria Suarez-Davalos, Anita G Villacis, Sofia Oca?a-Mayorga, Olivier Dangles
Parasites & Vectors , 2012, DOI: 10.1186/1756-3305-5-17
Abstract: Manual triatomine searches were conducted by skilled bug collectors in 23 communities. Sylvatic searched sites were selected by a) directed sampling, where microhabitats were selected by the searchers and b) random sampling, where sampling points where randomly generated. Domiciliary triatomine searches were conducted using the one man-hour method. Natural trypanosome infection was determined by microscopic examination and PCR. Generalized linear models were used to test the effect of environmental factors on the presence of sylvatic triatomines.In total, 1,923 sylvatic individuals were collected representing a sampling effort of 751 man-hours. Collected sylvatic triatomines were associated with mammal and bird nests. The 1,219 sampled nests presented an infestation index of 11.9%, a crowding of 13 bugs per infested nest, and a colonization of 80% of the nests. Triatomine abundance was significantly higher in squirrel (Sciurus stramineus) nests located above five meters from ground level and close to the houses. In addition, 8.5% of the 820 examined houses in the same localities were infested with triatomines. There was a significant correlation between R. ecuadoriensis infestation rates found in sylvatic and synanthropic environments within communities (p = 0.012). Parasitological analysis revealed that 64.7% and 15.7% of the sylvatic bugs examined (n = 300) were infected with Trypanosoma cruzi and T. rangeli respectively, and 8% of the bugs presented mixed infections.The wide distribution of sylvatic R. ecuadoriensis populations may jeopardize the effectiveness of control campaigns conducted to eliminate domestic populations of this species. Also, the high T. cruzi infection rates found in sylvatic R. ecuadoriensis populations in southern Ecuador could constitute a risk for house re-infestation and persistent long-term Chagas disease transmission in the region.Chagas disease is caused by the hemoflagellate protozoan parasite Trypanosoma cruzi and is transmitted ma
Limitations of selective deltamethrin application for triatomine control in central coastal Ecuador
Mario J Grijalva, Anita G Villacís, Sofía Oca?a-Mayorga, César A Yumiseva, Esteban G Baus
Parasites & Vectors , 2011, DOI: 10.1186/1756-3305-4-20
Abstract: Surveys for triatomines revealed peridomestic infestation with Rhodnius ecuadoriensis and Panstrongylus howardi, with infestation indices remaining high during the study (13%, 17%, and 10%, at initial, 6-month, and 12-month visits, respectively), which indicates a limitation of this strategy for triatomine population control. Infestation was found 6 and 12 months after spraying with deltamethrin. In addition, a large number of previously vector-free domestic units also were found infested at the 6- and 12-month surveys, which indicates new infestations by sylvatic triatomines. The predominance of young nymphs and adults suggests new infestation events, likely from sylvatic foci. In addition, infection with Trypanosoma cruzi was found in 65%, 21% and 29% at initial, 6-month and 12-month visits, respectively. All parasites isolated (n = 20) were identified as TcI.New vector control strategies need to be devised and evaluated for reduction of T. cruzi transmission in this region.Chagas disease in Ecuador affects approximately 230,000 people, and 6.2 million people are at risk of infection by Trypanosoma cruzi, its causative agent [1]. In the absence of satisfactory therapy or vaccines against Chagas disease, control of the disease relies primarily on interrupting transmission by eliminating domestic populations of triatomines. Triatomines Rhodnius ecuadoriensis and Panstrongylus howardi are important vectors of Chagas disease in the Manabí province, located on the central coast of Ecuador, and there is evidence of host (vectors and reservoirs) infected with T. cruzi, circulating in the area [2-6].R. ecuadoriensis is widely distributed in Ecuador's central and southern coast [7], its southern Andean region, and in northern Perú [3]. In the coastal region, R. ecuadoriensis is usually found in association with Phytelephas aequatorialis, an endemic palm species, [5,8] and in nests of squirrel (Sciurus stramineus) and bird (Campylorhynchus fasciatus) [6]. In this region, th
Absence of domestic triatomine colonies in an area of the coastal region of Ecuador where Chagas disease is endemic
Grijalva, Mario J;Palomeque, Francisco S;Villacís, Anita G;Black, Carla L;Arcos-Terán, Laura;
Memórias do Instituto Oswaldo Cruz , 2010, DOI: 10.1590/S0074-02762010000500013
Abstract: rhodnius ecuadoriensis is considered the second most important vector of chagas disease in ecuador. it is distributed across six of the 24 provinces and occupies intradomiciliary, peridomiciliary and sylvatic habitats. this study was conducted in six communities within the coastal province of guayas. triatomine searches were conducted in domestic and peridomestic habitats and bird nests using manual searches, live-bait traps and sensor boxes. synantrhopic mammals were captured in the domestic and peridomestic habitats. household searches (n = 429) and randomly placed sensor boxes (n = 360) produced no live triatomine adults or nymphs. in contrast, eight nymphs were found in two out of six searched campylorhynchus fasciatus (troglodytidae) nests. finally, trypanosoma cruzi dna was amplified from the blood of 10% of the 115 examined mammals. environmental changes in land use (intensive rice farming), mosquito control interventions and lack of intradomestic adaptation are suggested among the possible reasons for the lack of domestic triatomine colonies.
Modeling Disease Vector Occurrence when Detection Is Imperfect: Infestation of Amazonian Palm Trees by Triatomine Bugs at Three Spatial Scales
Fernando Abad-Franch ,Gon?alo Ferraz,Ciro Campos,Francisco S. Palomeque,Mario J. Grijalva,H. Marcelo Aguilar,Michael A. Miles
PLOS Neglected Tropical Diseases , 2010, DOI: 10.1371/journal.pntd.0000620
Abstract: Background Failure to detect a disease agent or vector where it actually occurs constitutes a serious drawback in epidemiology. In the pervasive situation where no sampling technique is perfect, the explicit analytical treatment of detection failure becomes a key step in the estimation of epidemiological parameters. We illustrate this approach with a study of Attalea palm tree infestation by Rhodnius spp. (Triatominae), the most important vectors of Chagas disease (CD) in northern South America. Methodology/Principal Findings The probability of detecting triatomines in infested palms is estimated by repeatedly sampling each palm. This knowledge is used to derive an unbiased estimate of the biologically relevant probability of palm infestation. We combine maximum-likelihood analysis and information-theoretic model selection to test the relationships between environmental covariates and infestation of 298 Amazonian palm trees over three spatial scales: region within Amazonia, landscape, and individual palm. Palm infestation estimates are high (40–60%) across regions, and well above the observed infestation rate (24%). Detection probability is higher (~0.55 on average) in the richest-soil region than elsewhere (~0.08). Infestation estimates are similar in forest and rural areas, but lower in urban landscapes. Finally, individual palm covariates (accumulated organic matter and stem height) explain most of infestation rate variation. Conclusions/Significance Individual palm attributes appear as key drivers of infestation, suggesting that CD surveillance must incorporate local-scale knowledge and that peridomestic palm tree management might help lower transmission risk. Vector populations are probably denser in rich-soil sub-regions, where CD prevalence tends to be higher; this suggests a target for research on broad-scale risk mapping. Landscape-scale effects indicate that palm triatomine populations can endure deforestation in rural areas, but become rarer in heavily disturbed urban settings. Our methodological approach has wide application in infectious disease research; by improving eco-epidemiological parameter estimation, it can also significantly strengthen vector surveillance-control strategies.
Hybridism between Biomphalaria cousini and Biomphalaria amazonica and its susceptibility to Schistosoma mansoni
Teodoro, Tatiana Maria;Jannotti-Passos, Liana Konovaloff;Carvalho, Omar dos Santos;Grijalva, Mario J;Baús, Esteban Guilhermo;Caldeira, Roberta Lima;
Memórias do Instituto Oswaldo Cruz , 2011, DOI: 10.1590/S0074-02762011000700011
Abstract: molecular techniques can aid in the classification of biomphalaria species because morphological differentiation between these species is difficult. previous studies using phylogeny, morphological and molecular taxonomy showed that some populations studied were biomphalaria cousini instead of biomphalaria amazonica. three different molecular profiles were observed that enabled the separation of b. amazonica from b. cousini. the third profile showed an association between the two and suggested the possibility of hybrids between them. therefore, the aim of this work was to investigate the hybridism between b. cousini and b. amazonica and to verify if the hybrids are susceptible to schistosoma mansoni. crosses using the albinism factor as a genetic marker were performed, with pigmented b. cousini and albino b. amazonica snails identified by polymerase chain reaction-restriction fragment length polymorphism. this procedure was conducted using b. cousini and b. amazonica of the type locality accordingly to paraense, 1966. in addition, susceptibility studies were performed using snails obtained from the crosses (hybrids) and three s. mansoni strains (le, sj, al). the crosses between b. amazonica and b. cousini confirmed the occurrence of hybrids. moreover, hybrids can be considered potential hosts of s. mansoni because they are susceptible to le, sj and al strains (4.4%, 5.6% and 2.2%, respectively). these results indicate that there is a risk of introducing schistosomiasis mansoni into new areas.
The Double Burden of Obesity and Malnutrition in a Protracted Emergency Setting: A Cross-Sectional Study of Western Sahara Refugees
Carlos S. Grijalva-Eternod ,Jonathan C. K. Wells,Mario Cortina-Borja,Nuria Salse-Ubach,Mélody C. Tondeur,Carmen Dolan,Chafik Meziani,Caroline Wilkinson,Paul Spiegel,Andrew J. Seal
PLOS Medicine , 2012, DOI: 10.1371/journal.pmed.1001320
Abstract: Background Households from vulnerable groups experiencing epidemiological transitions are known to be affected concomitantly by under-nutrition and obesity. Yet, it is unknown to what extent this double burden affects refugee populations dependent on food assistance. We assessed the double burden of malnutrition among Western Sahara refugees living in a protracted emergency. Methods and Findings We implemented a stratified nutrition survey in October–November 2010 in the four Western Sahara refugee camps in Algeria. We sampled 2,005 households, collecting anthropometric measurements (weight, height, and waist circumference) in 1,608 children (6–59 mo) and 1,781 women (15–49 y). We estimated the prevalence of global acute malnutrition (GAM), stunting, underweight, and overweight in children; and stunting, underweight, overweight, and central obesity in women. To assess the burden of malnutrition within households, households were first classified according to the presence of each type of malnutrition. Households were then classified as undernourished, overweight, or affected by the double burden if they presented members with under-nutrition, overweight, or both, respectively. The prevalence of GAM in children was 9.1%, 29.1% were stunted, 18.6% were underweight, and 2.4% were overweight; among the women, 14.8% were stunted, 53.7% were overweight or obese, and 71.4% had central obesity. Central obesity (47.2%) and overweight (38.8%) in women affected a higher proportion of households than did GAM (7.0%), stunting (19.5%), or underweight (13.3%) in children. Overall, households classified as overweight (31.5%) were most common, followed by undernourished (25.8%), and then double burden–affected (24.7%). Conclusions The double burden of obesity and under-nutrition is highly prevalent in households among Western Sahara refugees. The results highlight the need to focus more attention on non-communicable diseases in this population and balance obesity prevention and management with interventions to tackle under-nutrition. Please see later in the article for the Editors' Summary
Development of Peptide-Based Lineage-Specific Serology for Chronic Chagas Disease: Geographical and Clinical Distribution of Epitope Recognition
Tapan Bhattacharyya ,Andrew K. Falconar,Alejandro O. Luquetti,Jaime A. Costales,Mario J. Grijalva,Michael D. Lewis,Louisa A. Messenger,Trang T. Tran,Juan-David Ramirez,Felipe Guhl,Hernan J. Carrasco,Patricio Diosque,Lineth Garcia,Sergey V. Litvinov,Michael A. Miles
PLOS Neglected Tropical Diseases , 2014, DOI: 10.1371/journal.pntd.0002892
Abstract: Background Chagas disease, caused by infection with the protozoan Trypanosoma cruzi, remains a serious public health issue in Latin America. Genetically diverse, the species is sub-divided into six lineages, known as TcI–TcVI, which have disparate geographical and ecological distributions. TcII, TcV, and TcVI are associated with severe human disease in the Southern Cone countries, whereas TcI is associated with cardiomyopathy north of the Amazon. T. cruzi persists as a chronic infection, with cardiac and/or gastrointestinal symptoms developing years or decades after initial infection. Identifying an individual's history of T. cruzi lineage infection directly by genotyping of the parasite is complicated by the low parasitaemia and sequestration in the host tissues. Methodology/Principal Findings We have applied here serology against lineage-specific epitopes of the T. cruzi surface antigen TSSA, as an indirect approach to allow identification of infecting lineage. Chagasic sera from chronic patients from a range of endemic countries were tested by ELISA against synthetic peptides representing lineage-specific TSSA epitopes bound to avidin-coated ELISA plates via a biotin labelled polyethylene glycol-glycine spacer to increase rotation and ensure each amino acid side chain could freely interact with their antibodies. 79/113 (70%) of samples from Brazil, Bolivia, and Argentina recognised the TSSA epitope common to lineages TcII/TcV/TcVI. Comparison with clinical information showed that a higher proportion of Brazilian TSSApep-II/V/VI responders had ECG abnormalities than non-responders (38% vs 17%; p<0.0001). Among northern chagasic sera 4/20 (20%) from Ecuador reacted with this peptide; 1/12 Venezuelan and 1/34 Colombian samples reacted with TSSApep-IV. In addition, a proposed TcI-specific epitope, described elsewhere, was demonstrated here to be highly conserved across lineages and therefore not applicable to lineage-specific serology. Conclusions/Significance These results demonstrate the considerable potential for synthetic peptide serology to investigate the infection history of individuals, geographical and clinical associations of T. cruzi lineages.
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