1,721,003 research outputs found
Reservoir host competence and the role of domestic and commensal hosts in the transmission of Trypanosoma cruzi
No full textWe review the epidemiological role of domestic and commensal hosts of Trypanosoma cruzi using aquantitative approach, and compiled >400 reports on their natural infection. We link the theory under-lying simple mathematical models of vector-borne parasite transmission to the types of evidence usedfor reservoir host identification: mean duration of infectious life; host infection and infectiousness; andhost-vector contact. The infectiousness of dogs or cats most frequently exceeded that of humans. Thehost-feeding patterns of major vectors showed wide variability among and within triatomine speciesrelated to their opportunistic behavior and variable ecological, biological and social contexts. The evi-dence shows that dogs, cats, commensal rodents and domesticated guinea pigs are able to maintain T. cruzi in the absence of any other host species. They play key roles as amplifying hosts and sources of T. cruzi in many (peri)domestic transmission cycles covering a broad diversity of ecoregions, ecotopes andtriatomine species: no other domestic animal plays that role. Dogs comply with the desirable attributes ofnatural sentinels and sometimes were a point of entry of sylvatic parasite strains. The controversies on therole of cats and other hosts illustrate the issues that hamper assessing the relative importance of reservoirhosts on the basis of fragmentary evidence. We provide various study cases of how eco-epidemiologicaland genetic-marker evidence helped to unravel transmission cycles and identify the implicated hosts. Keeping dogs, cats and rodents out of human sleeping quarters and reducing their exposure to triatominebugs are predicted to strongly reduce transmission risks.Fil: Gurtler, Ricardo Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Cardinal, Marta Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin
Eco-epidemiology of Trypanosoma cruzi transmission cycles in Northwestern Argentina
No full textCon el fin de comprender cuál es la estructura de los ciclos de transmisión de Trypanosoma cruzi en comunidades rurales de Santiago del Estero, se realizaron los siguientes estudios: a) Estudio prospectivo de los efectos de la vigilancia vectorial sostenida luego de un rociado comunitario con insecticidas sobre la infección por Trypanosoma cruzi en perros y gatos. Utilizando los perros domésticos como centinelas de la transmisión, se determinó el impacto a largo plazo de rociados selectivos realizados por la comunidad luego de un rociado masivo con insecticidas piretroides sobre la transmisión de T. cruzi en comunidades bajo vigilancia entomológica entre 1992 y 2002. En los años 2000 y 2002 se registraron leves infestaciones por Triatoma infestans y se examinaron serológicamente o por xenodiagnóstico 523 perros y gatos. La prevalencia de infección por T. cruzi en perros disminuyó desde 65% en el estudio de base a 8,9% y 4,7% a los 7,5 y 10 años del comienzo de la vigilancia vectorial sostenida, respectivamente. La fuerza anual promedio de infección cayó 260 veces, de 72,7 por cada 100 perros-años en el estudio de base a <0,3% en 2002. La sostenida declinación de la infección por T. cruzi en perros y gatos fue el resultado de los rociados selectivos con insecticidas realizados por la comunidad que mantuvieron la abundancia de T. infestans infectados a niveles marginales, una alta tasa de reemplazo poblacional de los hospedadores y una baja tasa de inmigración de áreas con transmisión activa. b) Impacto del control vectorial comunitario sobre la infestación doméstica y la infección por Trypanosoma cruzi en Triatoma infestans, perros y gatos en el Chaco Argentino. Se determinó el impacto relativo de dos estrategias de control vectorial basadas en la participación comunitaria en dos áreas rurales vecinas abarcando 40 pequeños poblados y 323 viviendas. La prevalencia y abundancia de infestación doméstica fue 1,5 y 6,5 veces mayor, respectivamente, en el área bajo acciones de control por pulsos, no supervisadas, operando bajo los lineamientos del Programa Nacional de Control de Vectores (PNCV) que en el área bajo vigilancia vectorial sostenida y supervisada llevada a cabo conjuntamente por nuestro grupo de investigación y el PNCV. En ambas áreas se detectó una elevada agregación de los hospedadores infectados al nivel de la vivienda. En el área bajo control por pulsos, la prevalencia de infección en vinchucas, perros y gatos fue de 2 a 3 veces mayor que en el área bajo vigilancia sostenida, la mayoría de los animales infectados calificaban como casos autóctonos y se observó evidencia de transmisión vectorial activa reciente. c) Uso de un dispositivo inmunocromatográfico para la detección rápida de anticuerpos contra Trypanosoma cruzi en sueros de perros. Se evaluó un dispositivo inmunocromatográfico para la detección de infección por T. cruzi en muestras de sueros caninos provenientes de áreas endémicas y no endémicas para la enfermedad de Chagas. El dispositivo tuvo una especificidad de al menos 94% y una sensibilidad de al menos 96%. En consecuencia, resulta promisorio para el tamizaje de sueros en la vigilancia de la enfermedad o en los programas de intervención. d) Epidemiología molecular de la infección silvestre y doméstica por Trypanosoma cruzi en el Noroeste de Argentina. Se obtuvieron 99 aislados de T. cruzi de las áreas de estudio. A partir de ellos se determinó y analizó la distribución de linajes de T. cruzi (identificados mediante estrategias de PCR) en T. infestans, perros y gatos domésticos, humanos y mamíferos silvestres. El linaje T. cruzi IIe predominó en los hábitats domésticos, hallándose en el 87% de los 54 aislados de T. infestans, en el 82% de los 33 aislados de perros y en los 4 gatos hallados infectados. El linaje I predominó entre los 6 aislados obtenidos de mamíferos silvestres. Los ciclos domésticos y silvestres se solapaban en el área de estudio a fines de los 1980s, cuando ocurría intensa transmisión doméstica, y aún se solapan marginalmente en el presente. La introducción de T. cruzi desde los hábitats silvestres a los domésticos ocurriría muy raramente en el actual contexto epidemiológico local. La distribución por vivienda de los linajes de T. cruzi muestra que las vinchucas, perros y gatos de una determinada vivienda comparten el mismo linaje parasitario en la mayoría de los casos. Los resultados obtenidos refuerzan el rol de los perros y gatos como principales reservorios domésticos del parásito y demuestran que, para áreas de alto riesgo como las comunidades rurales del noroeste argentino, es necesaria la implementación de una vigilancia vectorial sostenida y supervisada para lograr una efectiva disminución de la transmisión doméstica de T. cruzi.With the aim of understanding the structure of Trypanosoma cruzi transmission cycles in rural communities of Santiago del Estero Province, we performed the following studies: a) A prospective study of the effects of sustained vector surveillance following communitywide insecticide application on Trypanosoma cruzi infection of dogs and cats. Domestic dogs were used as natural sentinels to assess the long-term impact of selective, communitybased spraying with pyrethroid insecticides following community-wide spraying on transmission of Trypanosoma cruzi in rural villages under surveillance between 1992 and 2002. In 2000 and 2002 light infestations by Triatoma infestans were recorded, and 523 dogs and cats were examined serologically or by xenodiagnosis. The prevalence of T. cruzi infection in dogs decreased from 65% at baseline to 8.9% and 4.7% at 7.5 and 10 years after sustained vector surveillance, respectively. The average annual force of infection dropped 260-fold from 72.7 per 100 dog-years at baseline to <0.3% in 2002. The sustained decline in T. cruzi infections in dogs and cats was the result of selective, community-based insecticide spraying that kept the abundance of infected T. infestans at marginal levels, fast host population turnover, and low immigration rates from areas with active transmission. b) Impact of community-based vector control on house infestation and Trypanosoma cruzi infection in Triatoma infestans, dogs and cats in the Argentine Chaco. The relative impact of two community-based vector control strategies was assessed in two neighboring rural areas comprising 40 small villages and 323 houses in one of the regions most endemic for Chagas disease in northern Argentina. The prevalence and abundance of domestic infestation were 1.5- and 6.5-fold higher, respectively, in the area under pulsed, nonsupervised control actions operating under the guidelines of the National Vector Control Program (NCVP) than in the area under sustained, supervised surveillance carried out jointly by the UBA research team and NCVP. T. cruzi infection was highly aggregated at the household level in both areas. In the pulsed control area, the prevalence of infection in bugs, dogs and cats was two- to three-fold higher than in the area under sustained surveillance, most of the infected animals qualified as autochthonous cases, and evidence of recent vector-borne transmission was observed. c) Use of an Immunochromatographic Dipstick Test for Rapid Detection of Trypanosoma cruzi in Sera from Animal Reservoir Hosts We evaluated an immunochromatographic dipstick test to detect Trypanosoma cruzi infection in canine serum samples from areas of endemicity and nonendemicity for Chagas’ disease. The dipstick test had a specificity of at least 94% and a sensitivity of at least 96%. Consequently, the dipstick results are promising for serum screening purposes in disease surveillance or intervention programs. d) Molecular epidemiology of domestic and sylvatic Trypanosoma cruzi infection in rural Northwestern Argentina. T. cruzi isolates were obtained from 99 infected hosts and vectors and were used to assess the distribution of T. cruzi lineages (identified by PCR strategies) in Triatoma infestans, domestic dogs, cats, humans and sylvatic mammals. T. cruzi lineage IIe predominated in domestic habitats; it was found in 87% of 54 isolates from T. infestans, in 82% of 33 isolates from dogs, and in the four cats found infected. Domestic and sylvatic cycles overlapped in the study area in the late 1980s, when intense domestic transmission occurred, and still overlap at present though marginally. The introduction of T. cruzi from sylvatic into domestic habitats would occur very rarely in the current epidemiological context. The household distribution of T. cruzi lineages showed that bugs, dogs and cats from a given house compound shared the same parasite lineage in most cases. Based on molecular evidence, this result lends further support to the importance of dogs and cats as domestic reservoir hosts of T. cruzi. In Argentina, this is the first time that lineage IIc has been isolated from naturally infected domestic dogs and T. infestans. Our results reinforce the role of domestic dogs and cats as major domestic reservoirs of T.cruzi and show that sustained, supervised vector surveillance is crucial for effectively controlling T.cruzi domestic transmission in rural Northwestern Argentina.Fil: Cardinal, Marta Victoria. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
The Role Of Humans In The Transmission Of Trypanosoma Cruzi In A Rural Area Of The Argentine Chaco From A Molecular Epidemiology Approach
No full textEl parásito Trypanosoma cruzi, agente etiológico de la enfermedad de Chagas, puede infectar un gran número de mamíferos, pero pocos de ellos califican como reservorios. Para que una especie se considere como reservorio debe tener un R0 mayor a 1, lo cual significa que a partir de un caso primario se debe producir más de un caso secundario. En el caso de la enfermedad de Chagas, se ha propuesto la identificación de hospedadores reservorios en base a la duración media de la infectividad, la prevalencia de infección e infectividad al vector y el contacto vector- hospedador. Esta Tesis buscó evaluar el rol de los humanos como posible reservorio de T. cruzi en un área rural bien definida del municipio de Pampa del Indio en el Chaco Argentino. El área de estudio abarca unas 650 viviendas rurales donde viven cerca de 2800 personas, de las cuales el 65% pertenece a la etnia Qom. Se realizó el diagnóstico serológico para la infección por T. cruzi a 1338 personas, alcanzando una cobertura del 48% de la población. La prevalencia de infección global fue del 24,4%. Como factores de riesgo asociados positivamente a la infección por T. cruzi se identificaron la edad, la cantidad de cohabitantes infectados en la vivienda y si la madre se encontraba infectada en un modelo lineal generalizado. Haber nacido luego del inicio de un programa de control vectorial que incluyó el rociado masivo de todas las viviendas con insecticidas piretroides fue un importante factor de protección. Se practicaron 117 xenodiagnósticos artificiales (XD) a un subgrupo de las personas seropositivas abarcando un rango de edad desde los 5 hasta los 71 años. El 33% (IC=25-42) de las personas presentaron XD positivos y la infectividad media fue del 5% (IC=4-6). La infectividad se vio afectada por la interacción entre etnia y edad, la carga parasitaria y el IMC. También se colectaron 121 muestras de Sangre-Guanidina que fueron analizadas por PCR convencional (kDNA-PCR) y 55 por qPCR (SAT-DNA-qPCR). La carga parasitaria media fue de 2,9 ep/ml. Se realizaron aislados parasitarios de los 39 pacientes que presentaron triatominos infectados en los xenodiagnósticos y se identificaron las Unidades Discretas de Tipificación (UDTs) parasitarias utilizando dos protocolos. El 92% de los aislados resultaron TcV, y debido a que no fue posible descartar infecciones mixtas, entre el 8-36% fueron TcVI. Debido a que los protocolos empleados no suelen identificar UDTs directamente a partir de muestras sanguíneas de pacientes crónicos, utilizando una nueva herramienta diagnóstica, se realizó un ensayo serológico rápido para identificar un epítope específico para TcII/V/VI. Se analizaron 320 sueros que fueron reactivos para la infección para T. cruzi por serología convencional y 69,7% también fueron reactivos para esta técnica, confirmando que las UDTs ampliamente mayoritarias son TcV o TcVI, más allá del método de identificación. Debido a las frecuentes y predominantes ingestas en humanos detectadas en los triatominos domésticos del área de estudio, la elevada prevalencia de infección en la población humana, a que un tercio de las personas infectadas presentaron XD positivos, pero con una relativamente baja infectividad al vector, concluimos que, en el área de estudio, en el contexto de casi 8 años de control vectorial sostenido, los humanos serían importantes fuentes de parásitos si existiera reinfestación domiciliaria y su contribución a la infección de los triatominos domésticos sería aproximadamente 4 veces mayor que los perros, el tradicionalmente reconocido reservorio doméstico.Trypanosoma cruzi, the etiological agent of Chagas disease, can infect a large number of mammals, but few qualify as reservoir hosts. For a species to be considered a reservoir, it must have a R0 greater than 1, which means that more than one secondary case must be produced from a primary case. In the case of Chagas disease, the identification of reservoir hosts has been based on the average duration of infectivity, the prevalence of infection, infectivity to the vector and the vector-host contact rate. This Thesis sought to evaluate the role of humans as potential reservoirs of T. cruzi based on an in-depth study of the eco-epidemiology of T. cruzi infection in a well-defined rural area of the municipality of Pampa del Indio in the argentine Chaco. The study area covers 650 rural households, inhabited by about 2,800 people with a majority (65%) belonging to the Qom ethnic group. By means of serodiagnosis of nearly half (48%) of the inhabitants, we found high levels (24.4%, n=1338) of T. cruzi infection. Age, the number of infected cohabitants and maternal infection status were positively associated with T. cruzi infection in a generalized linear model. Being born after the onset of the vector control program was a significant and important protective factor. A total of 117 seropositive people was examined by artificial xenodiagnoses (XD), ranging from 5 to 71 years of age. Nearly a third (33%, CI = 25-42) of them were infective (i.e. exhibited a positive XD) and the mean infectivity was 5% (CI = 4-6). Infectivity was associated with the interaction between ethnicity and age, parasitic load and BMI. We also collected 121 Blood-Guanidine samples that were analyzed by conventional PCR (kDNA-PCR) and 55 by qPCR (SAT-DNA-qPCR). The mean parasitic load was 2.9 ep/ml. Parasites were successfully isolated from the 39 patients with infected triatomines in the XD and parasite Discrete Typing Units (DTUs) were identified using two PCR-based protocols. We found that 92% of the isolates were TcV, and because it was not possible to rule out mixed infections, between 8-36% could also be TcVI. In an attempt to further expand DTUs identification, we assayed a new rapid serological test to identify a specific epitope for TcII / V / VI. A total of 320 seropositive sera samples were analyzed and 69.7% were also reactive for this technique, confirming that the predominant DTUs in the study population are TcV or TcVI, beyond the identification method. Considering the frequent and predominant blood meal intakes from humans detected in domestic triatomines of the study area, the high prevalence of infection in the human population, that nearly a third of the infected persons were infective but with a relatively low infectivity to the vector, we conclude that, in the study area in the context of almost 8 years of sustained vector control, humans would be important sources of parasites if domestic reinfestation occurred and their contribution to domestic bugs infection would be nearly 4 times higher than the contribution of dogs, the classical domestic reservoir host.Fil: Macchiaverna, Natalia Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Laboratorio de Eco-Epidemiología; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Microcavia australis (Caviidae, Rodentia), a new highly competent host of Trypanosoma cruzi I in rural communities of northwestern Argentina
No full textRodents are well-known hosts of Trypanosoma cruzi but little is known on the role of some caviomorph rodents. We assessed the occurrence and prevalence of T. cruzi infection in Microcavia australis (“southern mountain, desert or small cavy”) and its infectiousness to the vector Triatoma infestans in four rural communities of Tafí del Valle department, northwestern Argentina. Parasite detection was performed by xenodiagnosis and polymerase chain reaction amplification of the hyper-variable region of kinetoplast DNA minicircles of T. cruzi (kDNA-PCR) from blood samples. A total of 51 cavies was captured in traps set up along cavy paths in peridomestic dry-shrub fences located between 25 and 85 m from the nearest domicile. We document the first record of M. australis naturally infected by T. cruzi. Cavies presented a very high prevalence of infection (46.3%; 95% confidence interval, CI = 33.0–59.6%). Only one (4%) of 23 cavies negative by xenodiagnosis was found infected by kDNA-PCR. TcI was the only discrete typing unit identified in 12 cavies with a positive xenodiagnosis. The infectiousness to T. infestans of cavies positive by xenodiagnosis or kDNA-PCR was very high (mean, 55.8%; CI = 48.4–63.1%) and exceeded 80% in 44% of the hosts. Cavies are highly-competent hosts of T. cruzi in peridomestic habitats near human dwellings in rural communities of Tucumán province in northwestern Argentina.Fil: Cecere, Maria Carla. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Cardinal, Marta Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Arrabal, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Moreno, Claudio. Coordinación Nacional de Control de Vectores; ArgentinaFil: Gurtler, Ricardo Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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