Spatial distribution of Triatoma dimidiata peridomestic colonies modulated by distance between susceptible microhabitat patches.

Triatoma dimidiata is a vector of the hemoparasite Trypanosoma cruzi, the causal agent of Chagas disease. It settles reproductive colonies in the peridomicile of the premises. The peridomicile is comprised of a random set of artificial and natural features that overlap and assemble a network of microenvironmental suitable sites (patches) that interact with each other and favor the structure and proliferation of T. dimidiata colonies. The heterogeneity of patch characteristics hinders the understanding and identification of sites susceptible to colonization. In this study, a classification system using a random forest algorithm was used to identify peridomiciles susceptible to colonization to describe the spatial distribution of these sites and their relationship with the colonies of T. dimidiata in ten localities of Yucatan. From 1,000 peridomiciles reviewed, the classification showed that 13.9 % (139) of the patches were highly susceptible (HSP), and 86.1 % (861) were less susceptible (LSP). All localities had at least one HSP. The occupancy by patch type showed that the percentage of total occupancy and by colonies was higher in the HSP, while the occupancy by adult T. dimidiata without evidence of nymphs or exuviae (propagules) was higher in the LSP. A generalized additive model (GAM) revealed that the percentage of occupied patches increases as the abundance of individuals in the localities increases however, the percentage of occupied patches in LSP is lower than occupied in HSP. Distance analyses revealed that colonies and propagules were located significantly closer (approximately 200 m) to a colony in a HSP than any colony in a LSP. The distribution of T. dimidiata in the localities was defined by the distribution of patch type; as the occupancy in these patches increased, a network of peridomestic populations was configured, which may be promoted by a greater abundance of insects inside the localities. These results reveal that the spatial distribution of T. dimidiata individuals and colonies in the peridomicile at the locality scale corresponds to a metapopulation pattern within the localities through a system of patches mediated by distance and level of the vectors' occupancy.

Exposure to Trypanosoma cruzi and Leishmania parasites in dogs from a rural locality of Yucatan, Mexico. A serological survey.

Trypanosoma cruzi, the causal agent of American trypanosomiasis, and Leishmania spp., the causal agents of Leishmaniasis, are prevalent in more than 20 American countries, including Mexico. Dogs have been reported as incidental hosts for both parasites and may be helpful as transmission sentinels. We surveyed the dog population in a rural locality of the Merida municipality in Yucatan, Mexico, to evaluate the seroreactivity against T. cruzi and Leishmania spp. using two antigens, parasite homogenate (H) and iron superoxide dismutase extract (FeSODe), with two serological techniques (ELISA and Western Blot). Our study found that 3.33% of the tested dogs were seroreactive to T. cruzi using ELISA-H, and 29.5% were seroreactive to FeSODe antigen, with a 94.4% consistency between the two tests. Similarly, for L. mexicana, 1.6% were seroreactive using ELISA-H, and 9.8% were seroreactive using ELISA-FeSODe, with an 83.3% consistency between tests. For L. braziliensis, no dogs were seroreactive using ELISA-H, but 16.4% were seroreactive using ELISA-FeSODe, with a 90% consistency between tests. Finally, for L. infantum, 4.9% were seropositive using ELISA-H, and 6.6% were seropositive using ELISA-FeSODe, with a 75% consistency between tests. These results show noticeable evidence of exposure of dogs to trypanosomatid parasites and highlight the potential disease risk for the people and their companion animals in the region.

Triatomine and Trypanosoma cruzi discrete typing units distribution in a semi-arid area of northeastern Brazil.

The occurrence of triatomine species, their bloodmeal sources and the discrete typing units (DTUs) of Trypanosoma cruzi isolated from them were determined in different municipalities of the state of Rio Grande do Norte, Brazil. Triatomine captures were carried out in the rural areas of 23 municipalities. The genotyping of T. cruzi isolates was performed using the mitochondrial cytochrome c oxidase subunit 2 (coii) gene, the D7 region of the 24Sα rDNA, and the spliced leader intergenic region (SL-IR). Five triatomine species were captured, and the most frequent was Triatoma brasiliensis (84.3%; 916/1086), which was found in 16 of the 23 municipalities surveyed, and infested all types of environment investigated. The TcI DTU was found in all mesoregions surveyed in 51.5% (17/33) of the culture-positive samples. In contrast, TcII (9.1%; 3/33) was detected in the Central mesoregion, while TcIII (27.3%; 9/33) was found in all mesoregions. The geographic distribution and spatial overlap of different DTUs was inferred using the superposition of the radius of occurrence of isolates and using ecological niche distribution modelling. Triatoma brasiliensis was found infected in all mesoregions and with all three T. cruzi DTUs, including mixed infections. With regard to bloodmeal sources, the DNA of rodents was found in triatomines infected with either TcI or TcIII, while that of domestic animals and humans was associated with both single and mixed infections. Our findings demonstrate that different DTUs of T. cruzi are widely dispersed among triatomines in our study area. The association of T. brasiliensis with several different mammalian hosts, as well as overlapping areas with different DTUs, suggests that this triatomine species may have an important role as a vector in both anthropic and sylvatic environments.

Factors associated with the occurrence of Triatoma sordida (Hemiptera: Reduviidae) in rural localities of Central-West Brazil

This study estimates the factors of artificial environments (houses and peridomestic areas) associated with Triatoma sordida occurrence. Manual searches for triatomines were performed in 136 domiciliary units (DUs) in two rural localities of Central-West Brazil. For each DU, 32 structural, 23 biotic and 28 management variables were obtained. Multiple logistic regression analysis was performed in order to identify statistically significant variables associated with occurrence of T. sordida in the study areas. A total of 1,057 specimens (99% in peridomiciles, mainly chicken coops) of T. sordida were collected from 63 DUs (infestation: 47%; density: ~8 specimens/DU; crowding: ~17 specimens/infested DU; colonisation: 81%). Only six (0.6%) out of 945 specimens examined were infected with Trypanosoma cruzi. The final adjusted logistic regression model indicated that the probability of T. sordida occurrence was higher in DU with wooden chicken coops, presence of > 30 animals in wooden corrals, presence of wood piles and presence of food storeroom. The results show the persistence of T. sordida in peridomestic habitats in rural localities of Central-West Brazil. However, the observed low intradomestic colonisation and minimal triatomine infection rates indicate that T. sordida has low potential to sustain high rates of T. cruzi transmission to residents of these localities.

Anthropic effects on sand fly (Diptera: Psychodidae) abundance and diversity in an Amazonian rural settlement, Brazil.

Sand flies (Diptera: Psychodidae) are responsible for the transmission of protozoan parasites that cause leishmaniases. They are found predominantly in forests, but some species exploit environments that have been subject to deforestation and subsequent human colonization. Studies conducted in Brazil over the past 30 years show that some species are adapting to peri-urban and urban settings. We evaluated sand fly diversity and abundance in the rural settlement of Rio Pardo, Presidente Figueiredo Municipality, Amazonas State, Brazil. Settlement households were divided into four categories. These categories were determined by the human population density and the degree of deforestation in the immediate area. We used CDC light traps to sample the area surrounding 24 households (6 households in each category). Samples were taken on six occasions during September-November 2009 and June-August 2010. A total of 3074 sand fly specimens were collected, including 1163 females and 1911 males. These were classified into 13 genera and 52 species. The greatest abundance of sand flies and the greatest richness of species were observed in areas where human population density was highest. Our results show that changes in the human occupancy and vegetation management in rural settlements may affect the population dynamics and distribution of sand fly species, thereby affecting the local transmission of cutaneous leishmaniases.

Potential sources of Triatoma infestans reinfesting peridomiciles identified by morphological characterization in Los Llanos, La Rioja, Argentina

The presence of Triatoma infestans in habitats treated with insecticides constitutes a frequent problem in endemic areas. Basing our study on the hypothesis that descendants of a residual population should be more similar to the pre-treatment population than to any other, we compared the indications of two quantitative morphological approaches. This study seeks to find the origin of 247 T. infestans from three populations found in two chicken coops and a goat corral after treatment with insecticides. The results obtained by quantitative morphology suggest that the T. infestans found between three-34 months after the application of insecticides formed mixed populations with insects derived from residual foci and neighbouring habitats. Our analyses also showed the presence of a phenotype which does not resemble neither the pre-treatment phenotype nor the one from neighbouring populations, suggesting the presence of a particular post-treatment phenotype. The heads size showed some variations in males from different populations and remained unchanged in females, which reinforces the hypothesis of an intraspecific competition for food with priority for females. This article presents, for the first time, the combined analysis of geometric morphometry of heads and antennal phenotypes to identify the composition of reinfesting populations.

Ecology of phlebotomines (Diptera, Psychodidae) in rural foci of leishmaniasis in tropical Brazil / Ecologia de flebotomíneos (Diptera, Psychodidae) em foco rural de leishmaniose no Brasil tropical

INTRODUCTION: This work aimed to study the community structure of sandflies, with regard to the richness, constancy, abundance, and monthly frequency of the species with a focus on the transmission of leishmaniasis. METHODS: The study was conducted in the rural villages of Bom Jardim and Santa Maria, situated on the edge of a tropical rain forest in the municipality of São Jose de Ribamar, Maranhão, Brazil. The phlebotomines were captured in the intradomiciles and peridomiciles of each village, with Centers for Disease Control (CDC) light traps set in 10 homes in each village, for 1 year, once a month, from 18h to 6h. RESULTS: We collected 1,378 individuals of 16 sandfly species. The capture success rate was higher in Bom Jardim (0.61 specimens/hour/trap) than that of Santa Maria (0.35/specimens/hour/trap). The sandflies were more abundant in the peridomiciles (86.1%) and in the rainy season (77%). Five species were considered constants (occurring in more than 50% of samples), 5 accessory (25%-50%), and 6 accidental (<25%). The most abundant species were Lutzomyia longipalpis (59.7%) and L whitmani (28%). The permutation analysis showed differences between the species composition of the villages and no separation between the intradomicile and peridomicile of each village. The species that most contributed to the dissimilarity between the light traps of the 2 villages were L. longipalpis, L. whitmani, and L. evandroi, contributing to 80.8% of the variation among groups. CONCLUSIONS: The high level of richness and abundance of species and the presence of competent vectors throughout the year and around houses justify the occurrence of leishmaniasis cases reported in the area.

INTRODUÇÃO: Este trabalho teve como objetivo estudar a estrutura da comunidade de flebotomíneos, dando a conhecer a riqueza, constância, abundância e a frequência mensal das espécies em foco de transmissão de leishmaniose. MÉTODOS: O estudo foi realizado nas localidades rurais de Bom Jardim e Santa Maria, situadas às margens de uma mata ombrófila infestada por esses insetos, no município de São José de Ribamar, Maranhão, Brasil. Os flebotomíneos foram capturados no intra e peridomicílio de cada vila, com 10 armadilhas luminosas tipo CDC em cada vila, durante um ano, uma vez por mês, das 18h às 6h. RESULTADOS: Foram capturados 1.378 indivíduos de dezesseis espécies e o esforço de captura foi maior em Bom Jardim (0,61 indivíduos/hora/armadilha) que em Santa Maria (0,35). Os flebotomíneos prevaleceram no peridomicílio (86,1%) e na estação chuvosa (77%). Cinco espécies foram consideradas constantes (ocorreram em mais de 50% das coletas), cinco acessórias (25% e 50%) e seis acidentais (< 25%). As espécies mais abundantes foram Lutzomyia longipalpis (59,7%) e Lutzomyia whitmani (28%). Estatisticamente, detectou-se uma diferença na composição das espécies entre os povoados. As espécies que mais contribuíram para a dissimilaridade entre as armadilhas das duas vilas foram Lutzomyia longipalpis, Lutzomyia whitmani e Lutzomyia evandroi, com 80,8% de variação entre os grupos. CONCLUSÕES: A elevada riqueza e abundância de flebotomíneos e a presença de vetores competentes ao longo do ano, justificam a ocorrência de casos de leishmanioses relatados na área.

Cuidados do domicílio pela população em área infestada por triatoma sordida / Cuidados del domicilio por la población en area infestada por triatoma sordida / Care of the household population in the area infested by triatoma sordida

O objetivo deste estudo foi realizar vistoria em imóveis para identificar condições facilitadoras para a instalação de colônias de triatomíneos. Selecionaram-se localidades caracterizadas pela persistência de infestação durante toda a década de 1990. Realizaram-se pesquisas de triatomíneos em todos os domicílios, confeccionando-se ?croquis? do peridomicílio com descrição dos anexos e distância entre cada anexo e o domicílio. Foram vistoriados os imóveis em quatro momentos diferentes. Ensinou-se aos moradores o modo correto de manutenção e limpeza do intradomicílio e peridomicílio. Identificaram-se 72 moradores, com mediana de idade de 41,5 anos. Composto por 65 domicílios, foram identificados 27,6 porcento positivos para triatomíneos, com coleta de 355 exemplares, representados principalmente por T. sordida 97,3 porcento. Os tipos de anexos mais expressivos foram árvores com ninhos 21,8 porcento e galinheiros 13,8 porcento. A distância média observada dos anexos em relação à moradia foi de 15,7 metros. Houve acréscimo de 8,6 porcento de anexos no período. Não se encontrou relação entre o fato de o morador ser proprietário do imóvel e a infestação por triatomíneos. A instrumentalização da população para práticas educativas adequadas de saúde pode atuar como moderadora do impacto da infestação por vetores da doença de Chagas, o que não foi observado neste estudo, refletindo na qualidade de vida e proteção de novas gerações.

The objective of this study was to perform inspections in properties to identify facilitating conditions for the installation of triatomine colonies. Places characterized by infestation persistence during the whole 1990 were selected. Triatomines researches were conducted in all households, producing sketches of the peridomicile area with description of the annexes and the distance between each annex and the household. The properties were inspected in four different moments. The correct way of maintaining and cleaning of the intradomicile and peridomicile area was taught to the inhabitants. They identified 72 inhabitants with a mean age of 41.5. Of the 65 studied residences 27.6 porcento tested positive for triatomine with collection of 355 samples, the majority being T. sordida 97.3 porcent. The more expressive types of annex were trees with nests 21.8 porcent and hen houses 13.8 porcento. The average distance observed of the annex in relation to the dwellings was 15.7 meters. There was an increase of 8.6 porcento of annexes in the period. There was no relationship found between the fact that the inhabitant is the owner of the property and the infestation by triatomines. Providing the population with the tools for the suitable educational practices of health may serve as a mitigator of the impact of the infestation by vectors of Chagas disease, a fact that was not observed in this study and that reflects in the life quality and protection of new generations.

El objetivo de este estudio fue realizar una vistoria en imuebles para identificar condiciones facilitadoras para la instalación de colonias de triatomíneos. Se seleccionaron localidades caracterizadas por la persistencia de infestación durante toda la década del 1990. Se realizaron investigaciones de triatomíneos en todos los domicilios, confeccionándose ?croquis? del peridomicilio con descripción de los anexos y distancia entre cada anexo y el domicílio. Fueron vistoriados los imuebles en cuatro momentos diferentes. Se enseñó a los habitantes el modo correcto de mantención y limpieza del intradomicilio y peridomicilio. Se identificaron 72 habitantes, con edad media de 41,5 años. Compuesto por 65 domicilios, fueron identificados27,6 por ciento positivos para triatomíneos, con colecta de 355 ejemplares, representados, principalmente por T. sordida 97,3 por ciento. Los tipos de anexos más expresivos fueron árboles con nidos 21,8 por ciento y gallineros 13,8 por ciento. La distancia media observada de los anexos en relación a la moradia fue de 15,7 metros. Hubo incremento de 8,6 por ciento de anexos en el período. No se encontró relación entre el hecho del habitante ser propietario del imueble y la infestación por triatomíneos. La instrumentalización de la población para prácticas educativas adecuadas de salud puede actuar como moderadora del impacto de la infestación por vetores de la enfermedad de Chagas, lo que no fue observado en este estudio, reflejando en la calidad de vida y protección de lãs nuevas geraciones.

Epidemiología de la tripanosomiasis americana en el Norte de Corrientes / Epidemiology of American trypanosomiasis in the North of Corrientes province, Argentina

El objetivo de esta investigación fue evaluar la presencia de triatominos en ecotopos domésticos y extradomésticos, determinar el índice de infección de los triatominos y estimar la prevalencia humana de anticuerpos contra el Trypanosoma cruzi. Los muestreos se llevaron a cabo en viviendas seleccionadas al azar en áreas rurales (departamentos Mburucuyá en otoño 2007 y Berón de Astrada en verano 2008) de Corrientes, Argentina. El diagnóstico de la infección chagásica se realizó a voluntarios mediante las pruebas de hemaglutinación indirecta, inmunofluorescencia indirecta y ensayo inmunoenzimático. Se exploraron 32 viviendas y 33 peridomicilios en Mburucuyá, y 30 viviendas y 25 peridomicilios en Berón de Astrada. En Mburucuyá la infestación del peridomicilio por Triatoma sordida alcanzó un 3.0%, capturándose 19 ninfas en un gallinero. La infestación del peridomicilio en Berón de Astrada fue 4.0%, detectándose una hembra y 58 huevos en un nidal de ave. Tanto la hembra como las ninfas resultaron negativas al T. cruzi. La prevalencia de seropositivos humanos al T. cruzi fue 5.2% (4/77) en Mburucuyá y 14.3% (11/77) en Berón de Astrada. En el domicilio no se confirmó infestación por triatominos y en el peridomicilio el índice de infestación fue bajo. Es necesario implementar nuevas estrategias de control vectorial, especialmente para las especies que habitan en estructuras peridomésticas y biotopos silvestres. La seroprevalencia fue menor a la observada en investigaciones previas en las áreas rurales de Corrientes. La ausencia de seropositivos de 0-10 años indica que la transmisión vectorial está interrumpida.

The aim of this investigation was to evaluate triatomine colonization in domestic and extradomestic ecotopes, to determine triatomines infection index and to assess human prevalence of anti Trypanosoma cruzi antibodies at Berón de Astrada and Mburucuyá Departments, Corrientes, Argentina. Samplings were performed in 2007 and 2008 in randomly selected households at rural areas. Diagnosis of Chagas infection in volunteer residents was performed using indirect hemagglutination, indirect immunofluorescence and indirect immunoenzimatic assay. Thirty human dwellings and 25 peridomestic ecotopes were searched at Berón de Astrada, and 32 houses and 33 peridomiciles at Mburucuyá. A total of 19 nymphs were captured in a chicken coop at Mburucuyá, the infestation rate was 3.0%. At Berón de Astrada 4.0% of the peridomiciles resulted infested by Triatoma sordida, a female and 58 eggs were collected in a hen nest. Trypanosoma cruzi infection was not detected in Triatoma sordida. The prevalence human rate was 5.2% (11/77) at Mburucuyá and 14.3% (4/77) at Berón de Astrada. Presence of triatomines was not confirmed at the human dwellings, and the infestation of the peridomestic structures was low. It is necessary to implement new strategies of vectorial control, especially for those species that prevail in the peridomicile and sylvatic ecotopes. Seroprevalence was lower that the observed in previous investigations in other rural areas of Corrientes. The absence of seroreactives in the 0-10 age group suggests a halt in T. cruzi transmission in the studied area.

Levantamento da fauna de Triatominae (Hemiptera: Reduviidae) em ambiente domiciliar e infecção natural por Trypanosomatidae no Estado de Mato Grosso do Sul / Survey of Triatominae (Hemiptera: Reduviidae) fauna in domestic environments and natural infection by Trypanosomatidae in the State of Mato Grosso do Sul

Entre 2000 a 2004, foi realizado levantamento da fauna de Triatominae (Hemiptera: Reduviidae) e exame de infecção natural por Trypanosomatidae, no Estado de Mato Grosso do Sul. Um total de 13.671 espécimes foram capturados. Na análise faunística das espécies capturadas, Triatoma sordida foi caracterizada como muito abundante, muito freqüente, constante e dominante. Os índices de infecção natural para Trypanosoma cruzi apresentaram os valores de 3,2 por cento para Panstrongylus geniculatus, 0,6 por cento para Rhodnius neglectus e 0,1 por cento para Triatoma sordida, apesar do Estado de Mato Grosso do Sul apresentar-se livre da transmissão vetorial endêmica.

Between 2000 and 2004, a survey of Triatominae fauna (Hemiptera: Reduviidae) and examination of natural infection caused by Trypanosomatidae in the State of Mato Grosso do Sul, Brazil, was conducted. A total of 13,671 specimens were collected. Through fauna analysis on the insects that were caught, Triatoma sordida was characterized as very abundant, very frequent, constant and dominant. The rates of natural infection with Trypanosoma cruzi were 3.2 percent for Panstrongylus geniculatus, 0.6 percent for Rhodnius neglectus and 0.1 percent for Triatoma sordida. Nevertheless, the State of Mato Grosso do Sul is free from endemic vector transmission.