The Effects of City Streets on an Urban Disease Vector.

With increasing urbanization vector-borne diseases are quickly developing in cities, and urban control strategies are needed. If streets are shown to be barriers to disease vectors, city blocks could be used as a convenient and relevant spatial unit of study and control. Unfortunately, existing spatial analysis tools do not allow for assessment of the impact of an urban grid on the presence of disease agents. Here, we first propose a method to test for the significance of the impact of streets on vector infestation based on a decomposition of Moran’s spatial autocorrelation index; and second, develop a Gaussian Field Latent Class model to finely describe the effect of streets while controlling for cofactors and imperfect detection of vectors. We apply these methods to cross-sectional data of infestation by the Chagas disease vector Triatoma infestans in the city of Arequipa, Peru. Our Moran’s decomposition test reveals that the distribution of T. infestans in this urban environment is significantly constrained by streets (p,0.05). With the Gaussian Field Latent Class model we confirm that streets provide a barrier against infestation and further show that greater than 90% of the spatial component of the probability of vector presence is explained by the correlation among houses within city blocks. The city block is thus likely to be an appropriate spatial unit to describe and control T. infestans in an urban context. Characteristics of the urban grid can influence the spatial dynamics of vector borne disease and should be considered when designing public health policies

Is Participation Contagious? Evidence From a Household Vector Control Campaign in Urban Peru

Objective: High rates of household participation are critical to the success of door-to-door vector control campaigns. We used the Health Belief Model to assess determinants of participation, including neighbour participation as a cue to action, in a Chagas disease vector control campaign in Peru. Methods: We evaluated clustering of participation among neighbours; estimated participation as a function of household infestation status, neighbourhood type and number of participating neighbours; and described the reported reasons for refusal to participate in a district of 2911 households. Results: We observed significant clustering of participation along city blocks (p\u3c0.0001). Participation was significantly higher for households in new versus established neighbourhoods, for infested households, and for households with more participating neighbours. The effect of neighbour participation was greater in new neighbourhoods. Conclusions: Results support a ‘contagion’ model of participation, highlighting the possibility that one or two participating households can tip a block towards full participation. Future campaigns can leverage these findings by making participation more visible, by addressing stigma associated with spraying, and by employing group incentives to spray

A country bug in the city: urban infestation by the Chagas disease vector Triatoma infestans in Arequipa, Peru

BACKGROUND:Interruption of vector-borne transmission of Trypanosoma cruzi remains an unrealized objective in many Latin American countries. The task of vector control is complicated by the emergence of vector insects in urban areas.METHODS:Utilizing data from a large-scale vector control program in Arequipa, Peru, we explored the spatial patterns of infestation by Triatoma infestans in an urban and peri-urban landscape. Multilevel logistic regression was utilized to assess the associations between household infestation and household- and locality-level socio-environmental measures.RESULTS:Of 37,229 households inspected for infestation, 6,982 (18.8%95% CI: 18.4 - 19.2%) were infested by T. infestans. Eighty clusters of infestation were identified, ranging in area from 0.1 to 68.7 hectares and containing as few as one and as many as 1,139 infested households. Spatial dependence between infested households was significant at distances up to 2,000 meters. Household T. infestans infestation was associated with household- and locality-level factors, including housing density, elevation, land surface temperature, and locality type.CONCLUSIONS:High levels of T. infestans infestation, characterized by spatial heterogeneity, were found across extensive urban and peri-urban areas prior to vector control. Several environmental and social factors, which may directly or indirectly influence the biology and behavior of T. infestans, were associated with infestation. Spatial clustering of infestation in the urban context may both challenge and inform surveillance and control of vector reemergence after insecticide intervention.This item is part of the UA Faculty Publications collection. For more information this item or other items in the UA Campus Repository, contact the University of Arizona Libraries at [email protected]

Urban landscape and infection risk in free-roaming cats

Altres ajuts: Fundação para a Ciência e a Tecnologia (FCT) CEECIND/01428/2018. FEDER UID/AMB/50017/2019Despite public concern on the role of free-roaming cats as reservoirs of zoonotic agents, little is known about the influence of urban and peri-urban landscapes on the exposure risk. We evaluated the seroprevalence of three zoonotic agents (Chlamydia felis, Coxiella burnetii and Toxoplasma gondii) in domestic cats (Felis catus). Two hundred and ninety-one free-roaming cats were trapped in Murcia municipality (Southeast Spain), and their sera were tested for specific antibodies against T. gondii using a modified agglutination test (MAT), and for C. felis, C. burnetii and feline immunodeficiency virus (FIV) antibodies with ELISA technique. Pathogen seroprevalence at 95% CI was calculated for each sex and age category (up to and over 12 months) and compared with a chi-squared test. The role of human population density and urban landscape characteristics on the risk of pathogen exposure in the cat population was explored using generalized linear models. Seropositivity against a single pathogen was found in 60% of the cats, while 19% was seropositive for two or three pathogens. Seroprevalence of C. felis was 8% (CI: 5-11), 37% (CI: 31-42) for C. burnetii and 42% (CI: 36-47) for T. gondii. In addition to these three pathogens, FIV seropositivity was low (1%, CI: −0.1 to 2) and adult cats were more likely to be seropositive to C. burnetii than young individuals (OR: 2.3, CI: 1.2-4.2). No sex or age class differences in seroprevalence were observed for the rest of the pathogens. Seropositivity was correlated with water surface areas for C. felis, and not with crop areas. Coxiella burnetii seropositivity was correlated with the percentage of urban areas (continuous with only buildings and discontinuous, that include buildings, parks, and pedestrian and urban green areas), human population size and peri-urban areas with shrubs, and not correlated with other agricultural landscapes (orchards and crop areas). However, the seroprevalence of T. gondii was only associated with agricultural landscapes such as orchards. The detection of hotspot areas of high pathogen exposure risk is the basis for municipal services to implement surveillance and risk factor control campaigns in specific-risk areas, including (a) efficient health management of urban cat colonies by geographical location, population census and health status monitoring of the components of each cat colony, (b) improvement of hygiene and sanitary conditions at the feeding points of the cat colony and (c) free-roaming cat trapping for health monitoring and, in the long term, to know the evolution of the health status of their populations

Dispersal Patterns And Reproductive Strategies Of Trypanosoma Cruzi In An Urban Environment

Interactions with novel environments result in both population extinctions and explosions, depending on life history strategies, ecological circumstances and historical contingencies. Understanding how populations interact with novel environments is more important now than ever because of the rapid increase in anthropogenic environmental alterations. While many native populations perish during urbanization, other populations successfully invade and thrive in these novel environments including many pests and pathogens that are detrimental to human health and economy. Pathogens contain a diversity of life history strategies and are thus good models for understanding how life history strategies interact with novel environments to promote or hinder the dynamic processes of invasion. In order to determine how life history strategies affect the evolution of a population during invasion, we studied a population of Trypanosoma cruzi – a protozoan parasite and causative agent of Chagas disease in humans – in the city of Arequipa in southern Peru. To estimate population structure and evolutionary history, we sequenced and assembled 133 T. cruzi genomes collected throughout Arequipa (N=123) and South America, and performed phylogenetic and population genetic analyses. We found that (1) the extant T. cruzi population in Arequipa was founded by a single introduction; (2) T. cruzi readily disperses between houses in a city block, but rarely disperses between blocks; (3) We resolve an apparent contradiction between the perceived clonal population structure of T. cruzi and its capacity for sexual reproduction by showing that this population regularly underwent meiosis and fertilization as the it expanded throughout the city, but that exclusive inbreeding resulted in a clonal population structure. As urbanization increases worldwide, it is important to understand how life history strategies affect the invasion of urban environments

La estructura metapoblacional de Triatoma infestans en Los Llanos Riojanos y su implicancia para el control vectorial

Triatoma infestans (Hemiptera: Reduviidae) es un insecto hematófago, vector del parásito Trypanosoma cruzi, agente etiológico de la Enfermedad de Chagas, considerada endémica de Argentina. En el sur de La Rioja, la persistente infestación por triatominos, fomentó que a partir del año 2008, se implementara un Programa de Erradicación de Ranchos y construcción de Viviendas Nuevas en la zona rural, con el objetivo de disminuir la infestación. Al analizar esta situación desde el contexto de la teoría de metapoblaciones, se considera que cada vivienda se comporta como un parche con distintos grados de calidad, en relación a la disponibilidad de refugios para T. infestans. De esta forma, las Viviendas Nuevas son consideradas de menor calidad comparadas con las Viviendas Rancho-Tradicionales. Los principales objetivos del presente trabajo fueron actualizar el estado de infestación en los Llanos riojanos, identificar los factores de riesgo asociados a la misma y evaluar la infestación en parches de diferente calidad y tamaño. El estudio se realizó analizando 397 viviendas con distintas Tipologías pertenecientes a los Departamentos Ángel Vicente Peñaloza, Rosario Vera Peñaloza y San Martín (Los Llanos, La Rioja) durante el período 2014-2017. Se realizaron muestreos pasivos y activos para estimar la infestación por T. infestans en los diferentes parches.Los principales resultados mostraron heterogeneidad espacial respecto a la infestación por T. infestans en el área de estudio, siendo Rosario Vera Peñaloza y San Martín los Departamentos con mayor infestación. El análisis de factores de riesgo a través de un enfoque de inferencia multimodelo, permitió ponderar las variables con mayor impacto en la probabilidad de infestación. Se observó que la Cantidad de Viviendas y su condición entomológica influyen de manera directa en la infestación de la Unidad Domiciliaria. Otras variables, como Cantidad de Estructuras Peridomésticas y Tipología de la Vivienda, no mostraron efecto cuantificable sobre la probabilidad de infestación. Durante el período estudiado, se registraron cambios en el estado de colonización y extinción de los parches entre tiempos consecutivos, permitiendo evaluar la dinámica de infestación en el área. Se constató que parches de diferentes características, incluso los considerados de baja calidad y menor tamaño, se encontraban ocupados por T. infestans. Adicionalmente, se obtuvo un registro detallado de las especies, que junto a T. infestans, invaden los parches en estudio, siendo las más frecuentes T. guasayana y T. garciabesi. La integración de estos resultados, permitió evaluar el impacto de la construcción de Nuevas Viviendas y el control químico aplicado en el área, sobre la prevalencia de infestación por T. infestans, en un contexto metapoblacional.Triatoma infestans (Hemiptera: Reduviidae) is a hematophagous insect, vector of the parasite Trypanosoma cruzi, etiological agent of Chagas disease, considered endemic in Argentina. In the south of La Rioja, as from 2008, the persistent infestation by triatomines, encouraged, a “Progama de Erradicación de Ranchos” and the construction of new housing in the rural area with the aim of reducing infestation. When analyzing this situation from the metapopulation theory context, it is considered that each dwelling behaves as a patch with different degrees of quality, in relation to the availability of shelters for T. infestans. In this way, the New Houses are considered of lower quality compared to the Traditional Houses. The main objectives of this study were to update the state of infestation in Los Llanos of La Rioja, to identify the risk factors associated with it and to evaluate the infestation in patches of different quality and size. The study was carried out analyzing 397 houses with different Typologies belonging to the Departments Ángel Vicente Peñaloza, Rosario Vera Peñaloza and San Martín (Los Llanos, La Rioja) during the period 2014-2017. Passive and active samplings were taken to estimate the infestation by T. infestans in the different patches. The main results showed spatial heterogeneity with respect to infestation by T. infestans in the study area. Rosario Vera Peñaloza and San Martín were the Departments with the highest infestation. The analysis of risk factors through a multimodal inference approach allowed us to weigh the variables with the greatest impact on the probability of infestation. It was observed that the Number of Houses and their entomological condition directly influence the infestation of the House. Other variables, such as Number of peridomestic Structures and Housing Typology, showed no measurable effect on the probability of infestation. During the period studied, changes were recorded in the colonization and the extinction status of the patches between consecutive times, allowing the evaluation of the infestation dynamics in the area. It was found that patches of different characteristics, even those considered of low quality and smaller size, were occupied by T. infestans. Additionally, a detailed record of the species was obtained, which together with T. infestans, invade the patches under study, being T. guasayana and T. garciabesi the most frequent ones. The integration of these results, allowed us to evaluate the impact of the construction of New Houses and the chemical control applied in the area, on the prevalence of infestation by T. infestans, in a metapopulation context.Fil: Cavallo, María José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; Argentin

Análisis poblacional y filogeográfico de vectores de la enfermedad de Chagas en Perú basado en análisis multigénicos del ADN ribosomal y mitocondrial

La enfermedad de Chagas, cuyo agente causal es Trypanosoma cruzi, constituye un grave problema de salud pública en toda Latinoamérica. La principal forma de transmisión es la vectorial, de la que son responsables hemípteros redúvidos de la subfamilia Triatominae adaptados a los hábitats doméstico y peridoméstico. Puesto que el parásito se mantiene en un ciclo zoonótico silvestre y es imposible de eliminar, la principal forma de lucha contra la transmisión vectorial consiste en la eliminación de las poblaciones domiciliadas del vector. Los estudios moleculares constituyen una herramienta de gran utilidad a la hora de planificar las campañas de control vectorial, puesto que permiten conocer y comprender la estructura poblacional y los procesos de dispersión y adaptación de estos insectos. Entre los principales países endémicos para esta parasitosis, se encuentra Perú, donde se han descrito 19 especies de triatominos, muchas de las cuales son reconocidos vectores de la enfermedad de Chagas. La presente Tesis Doctoral tiene como principal objetivo el haplotipaje molecular multigénico de las principales especies de vectores de Chagas en Perú de los géneros Triatoma y Panstrongylus. Se ha realizado además, un estudio de genética poblacional de la especie T. infestans y un estudio filogenético de especies del género Panstrongylus. T. infestans es el vector mejor adaptado al ambiente doméstico y el responsable de la mitad de los casos humanos de la enfermedad de Chagas en todo el mundo. Esta especie presenta una clara estructuración poblacional, de acuerdo a su variabilidad genética, que la separa en dos grupos ampliamente extendidos en Latinoamérica: el grupo Andino y el no-Andino. Los T. infestans analizados de Perú proceden de ambientes rurales e incluso urbanos y se integran dentro del grupo Andino. El haplotipaje molecular multigénico se ha hecho mediante marcadores del ADN ribosomal (ITS-1, 5.8S, ITS-2) y del ADN mitocondrial (16S, ND1, COI y Cyt b). Para ello, se han estudiado 129 ejemplares de T. infestans de los cuales: 113 son de Perú; 12 de Bolivia, 2 de Argentina y 2 de Chile. No se han encontrado diferencias genéticas ni en el estudio por altitudes geográficas desde los 432 a los 2.979 metros sobre el nivel del mar, ni en el estudio por departamentos de Perú. Destaca la uniformidad genética de T. infestans en Perú, no habiéndose detectado variabilidad de haplotipos en los marcadores utilizados con la excepción del marcador COI, el único que mostró variabilidad (3 haplotipos) y que podría estar relacionada con resistencias a los insecticidas. Se aporta por primera vez, la secuencia completa del gen Cyt b para esta especie. Los test de neutralidad muestran que T. infestans ha sufrido una fuerte reducción poblacional, debido a las campañas de control pero que actualmente está en expansión. En cuanto al estudio de especies del género Panstrongylus se han analizado los mismos marcadores que en T. infestans de un total de 168 especímenes: 51 de P. chinai; 14 de P. geniculatus y 103 de P. herreri. En el estudio del ADNr se han detectado grandes diferencias relacionadas con minisatélites que pueden ser consecuencias de retenciones de polimorfismos de un ancestro común. En el estudio del ADNmt se ha obtenido por primera vez, la secuencia completa del gen Cyt b en especies el género Panstrongylus. No se han observado diferencias genéticas entre poblaciones domésticas y peridomésticas, indicando que existe flujo genético entre ambos ecotopos. En el estudio filogenético de Panstrongylus los árboles obtenidos con marcadores ribosomales evidencian su utilidad en la separación de especies con elevado soporte estadístico. Los marcadores mitocondriales no alcanzan resolución a nivel específico pero sí, a nivel poblacional. Las matrices combinadas con secuencias obtenidas del GenBank muestran claras incongruencias que evidencian confusiones de clasificación taxonómica o bien, posibles hibridaciones