A simplified molecular tool for detecting the Chagas etiological agent using a vector feces sample in field conditions.

Triatomine bugs are vectors of Trypanosoma cruzi, the etiologic agent of Chagas disease in the American continent. Here, we have tested a loop-mediated isothermal amplification (LAMP) test for a direct detection of T. cruzi in feces of Triatoma infestans, the main vector of this parasite in the Southern Cone of America. The analytical evaluation showed positive results with samples of triatomine feces artificially inoculated with DNA from strains of T. cruzi corresponding to each Discrete Typing Units (I-VI), with a sensitivity of up to one parasite per reaction. Conversely, the reaction yielded negative results when tested with DNA from Trypanosoma rangeli and other phylogenetically related and unrelated organisms. In triatomines captured under real field conditions (from urban households), and defined as positive or negative for T. cruzi using the reference microscopy technique, the LAMP test achieved a concordance of 100 %. Our results demonstrate that this LAMP reaction exhibits excellent analytical specificity and sensitivity without interference from the fecal matrix, since all the reactions were conducted without purification steps. This simple molecular diagnostic technique can be easily used by vector control agencies under field conditions.

Correction: Urban vectors of Chagas disease in the American continent: A systematic review of epidemiological surveys.

[This corrects the article DOI: 10.1371/journal.pntd.0011003.].

Urban vectors of Chagas disease in the American continent: A systematic review of epidemiological surveys.

BACKGROUND: Chagas is a complex and multidimensional socio-environmental health phenomenon, in which different components converge and interact. Historically, this disease was associated with insect vectors found in the rural environment. However, in the Americas, we are currently facing a new paradigm, in which different scenarios allow maintaining the vectorial transmission of the parasite through triatomine populations that either occasionally enter the dwellings or colonize urban environments. METHODOLOGY/PRINCIPAL FINDINGS: Records of scientific reports available in the PubMed and LILACS search engines were retrieved, using three criteria according to the main triatomine genera of epidemiological importance and to the general scientific production on Chagas disease in urban contexts. Results showed that records on the occurrence of vectors in urban dwellings began to increase in the last three decades. Results also showed that the main species of triatomines collected inside dwellings (18 in total) belong mainly to the genera Triatoma and Panstrongylus, with most species (16/18, 88.8%) infected with the parasite, and that infestation of triatomine species occurs in all types of cities (small, medium and large, including megalopolises), from Argentina to the USA. CONCLUSIONS/SIGNIFICANCE: Urban Chagas represents a new challenge that adds a different dimension to the problem of Chagas disease due to the particular characteristics of the lifestyle in urban agglomerates. The new scenario will require adaptations of the programs of control of vector to this shift from rural to urban settlements.

Urban infestation by Triatoma infestans (Hemiptera: Reduviidae), an overlooked phenomena for Chagas disease in Argentina.

Vector-borne transmission of Chagas disease in urban areas of Argentina has been an overlooked phenomena. We conducted the first comprehensive cross-sectional study of domestic infestation with Triatoma infestans and vector infection with Trypanosoma cruzi in a metropolitan area of San Juan, Argentina. Our results document the occurrence of T. infestans infected with T. cruzi in human sleeping quarters. In this urban setting, we also show that infestation was associated with construction materials, the presence of chickens, cats and a large number of dogs that can provide blood meals for the vector. Our findings reveal new challenges for vectorial control agencies.

Urban infestation by Triatoma infestans (Hemiptera: Reduviidae), an overlooked phenomena for Chagas disease in Argentina

Vector-borne transmission of Chagas disease in urban areas of Argentina has been an overlooked phenomena. We conducted the first comprehensive cross-sectional study of domestic infestation with Triatoma infestans and vector infection with Trypanosoma cruzi in a metropolitan area of San Juan, Argentina. Our results document the occurrence of T. infestans infected with T. cruzi in human sleeping quarters. In this urban setting, we also show that infestation was associated with construction materials, the presence of chickens, cats and a large number of dogs that can provide blood meals for the vector. Our findings reveal new challenges for vectorial control agencies.

Factores de riesgo en Chagas urbano / Risk factors in urban Chagas

San Juan presenta una alta infestación por Triatoma infestans en áreas urbanas, por ello nos propusimos estudiar los factores de riesgo asociados con la transmisión vectorial del T. cruzi en ámbito urbano del Departamento Rawson. Se empleo un diseño observacional y transversal de enfoque mixto; cuali-cuantitativo. Se encuestó sobre las características de la vivienda, de movilidad, de vulnerabilidad socio-sanitarias y de conocimientos de la enfermedad. Se realizaron encuestas entomológicas en las viviendas y serológicas en la población y en los perros. Mediante modelos multinivel se evaluó la importancia relativa de los factores para explicar la seropositividad a T. cruzi y la infestación por Triatoma infestans. Se realizó análisis espacial para estudiar la distribución de la infección e infestación. Se llevaron a cabo encuestas dialogadas a referentes de la comunidad y de los equipos de salud y vectores. Se evaluaron 347/758 viviendas visitadas, el 13,8% presentó infestación que se asoció al número de sitios en el peridomicilio y techos de machimbre y/o caña. Se realizó diagnóstico en 614/1057 habitantes detectándose una prevalencia del 3,09%. Se estudiaron 130 caninos de los cuales 10,0% fueron reactivos. Ninguna variable pudo explicar la infección, se registró una tendencia que asocia positivamente la vulnerabilidad con la presencia de personas infectadas. La infestación no se identificó estadísticamente agregada a nivel de manzana mientras que la infección en perro y humanos si, fenómeno observado también en el análisis espacial. De las encuestas dialogadas surge la necesidad de realizar más difusión, de promover acciones de control integrales y de generar adaptaciones a los protocolos de control vectorial. Nuestro estudio pone en evidencia la extensión y complejidad del problema de la transmisión vectorial de la enfermedad de Chagas en ámbitos urbanos e identifica grandes desafíos para la ejecución de acciones de control