RESUMO
Chagas disease is caused by the protozoan parasite Trypanosoma cruzi (Chagas, 1909). One of the primary vectors of T. cruzi in South America is Triatoma infestans (Klug, 1834). This triatomine species is distributed across a huge latitudinal gradient, inhabiting domiciliary , peridomiciliary , and wild environments. Its wide geographic distribution provides an excellent opportunity to study the relationships between environmental gradients and intraspecific morphological variation. In this study, we investigated variations in wing size and shape in T. infestans across six ecoregions. We aimed to address the following questions: How do wing size and shape vary on a regional scale, does morphological variation follow specific patterns along an environmental or latitudinal gradient, and what environmental factors might contribute to wing variation? Geometric morphometric methods were applied to the wings of 162 females belonging to 21 T. infestans populations, 13 from Argentina (n = 105), 5 from Bolivia (n = 42), and 3 from Paraguay (n = 15). A comparison of wing centroid size across the 21 populations showed significant differences. Canonical Variate Analysis (CVA) revealed significant differences in wing shape between the populations from Argentina, Bolivia, and Paraguay, although there was a considerable overlap, especially among the Argentinian populations. Well-structured populations were observed for the Bolivian and Paraguayan groups. Two analyses were performed to assess the association between wing size and shape, geographic and climatic variables: multiple linear regression analysis (MRA) for size and Partial Least Squares (PLS) regression for shape. The MRA showed a significant general model fit. Six temperature-related variables, one precipitation-related variable, and the latitude showed significant associations with wing size. The PLS analysis revealed a significant correlation between wing shape with latitude, longitude, temperature-related, and rainfall-related variables. Wing size and shape in T. infestans populations varied across geographic distribution. Our findings demonstrate that geographic and climatic variables significantly influence T. infestans wing morphology.
Assuntos
Triatoma , Asas de Animais , Animais , Triatoma/anatomia & histologia , Triatoma/fisiologia , Triatoma/crescimento & desenvolvimento , Triatoma/classificação , Asas de Animais/anatomia & histologia , Feminino , Argentina , Bolívia , Paraguai , Doença de Chagas/transmissãoRESUMO
BACKGROUND: The Gran Chaco region is a major hotspot of Chagas disease. We implemented a 9-year program aimed at suppressing house infestation with Triatoma infestans and stopping vector-borne transmission to creole and indigenous (Qom) residents across Pampa del Indio municipality (Argentine Chaco). The aim of the present study was to assess the intervention effects on parasite-based transmission indices and the spatial distribution of the parasite, and test whether house-level variations in triatomine infection with Trypanosoma cruzi declined postintervention and were influenced by household ethnicity, persistent infestation linked to pyrethroid resistance and other determinants of bug infection. METHODS: This longitudinal study assessed house infestation and bug infection with T. cruzi before and after spraying houses with pyrethroids and implemented systematic surveillance-and-response measures across four operational areas over the period 2007-2016. Live triatomines were individually examined for infection by optical microscopy or kinetoplast DNA (kDNA)-PCR and declared to be infected with T. cruzi when assessed positive by either method. RESULTS: The prevalence of infection with T. cruzi was 19.4% among 6397 T. infestans examined. Infection ranged widely among the study areas (12.5-26.0%), household ethnicity (15.3-26.9%), bug ecotopes (1.8-27.2%) and developmental stages (5.9-27.6%), and decreased from 24.1% (baseline) to 0.9% (endpoint). Using random-intercept multiple logistic regression, the relative odds of bug infection strongly decreased as the intervention period progressed, and increased with baseline domestic infestation and bug stage and in Qom households. The abundance of infected bugs and the proportion of houses with ≥ 1 infected bug remained depressed postintervention and were more informative of area-wide risk status than the prevalence of bug infection. Global spatial analysis revealed sharp changes in the aggregation of bug infection after the attack phase. Baseline domestic infestation and baseline bug infection strongly predicted the future occurrence of bug infection, as did persistent domestic infestation in the area with multiple pyrethroid-resistant foci. Only 19% of houses had a baseline domestic infestation and 56% had ever had ≥ 1 infected bug. CONCLUSIONS: Persistent bug infection postintervention was closely associated with persistent foci generated by pyrethroid resistance. Postintervention parasite-based indices closely agreed with human serosurveys at the study endpoint, suggesting transmission blockage. The program identified households and population subgroups for targeted interventions and opened new opportunities for risk prioritization and sustainable vector control and disease prevention.
Assuntos
Doença de Chagas , Piretrinas , Triatoma , Trypanosoma cruzi , Animais , Humanos , Triatoma/parasitologia , Prevalência , Estudos Longitudinais , Insetos Vetores/parasitologia , Doença de Chagas/epidemiologia , Doença de Chagas/prevenção & controle , Piretrinas/farmacologia , DNA de Cinetoplasto , Argentina/epidemiologiaRESUMO
BACKGROUND: The elimination of Triatoma infestans, the main domestic vector of Trypanosoma cruzi, is lagging behind expectations in the Gran Chaco region. We implemented an insecticide-based intervention program and assessed its long-term effects on house infestation and bug abundance in a resource-constrained municipality (Pampa del Indio, northeastern Argentina) inhabited by creole and the Qom indigenous people (2007-2016). Key questions were whether district-wide data integration revealed patterns concealed at lower spatial levels; to what extent preintervention infestation and pyrethroid resistance challenged the effectiveness of insecticide-based control efforts, and how much control effort was needed to meet defined targets. METHODS: Supervised vector control teams i) georeferenced every housing unit at baseline (1,546); ii) evaluated house infestation using timed-manual searches with a dislodging aerosol across four rural areas designated for district-wide scaling up; iii) sprayed with pyrethroid insecticide 92.7% of all houses; iv) periodically monitored infestation and promoted householder-based surveillance, and v) selectively sprayed the infested houses, totaling 1,823 insecticide treatments throughout the program. RESULTS: Baseline house infestation (mean, 26.8%; range, 14.4-41.4%) and bug abundance plummeted over the first year postintervention (YPI). Timed searches at baseline detected 61.4-88.0% of apparent infestations revealed by any of the methods used. Housing dynamics varied widely among areas and between Qom and creole households. Preintervention triatomine abundance and the cumulative frequency of insecticide treatments were spatially aggregated in three large clusters overlapping with pyrethroid resistance, which ranged from susceptible to high. Persistent foci were suppressed with malathion. Aggregation occurred mainly at house compound or village levels. Preintervention domestic infestation and abundance were much greater in Qom than in creole households, whereas the reverse was recorded in peridomestic habitats. House infestation, rare (1.9-3.7%) over 2-6 YPI, averaged 0.66% (95% confidence interval, 0.28-1.29%) at endpoint. CONCLUSIONS: Upscale integration revealed multiple coupled heterogeneities (spatial, sociodemographic and biological) that reflect large inequalities, hamper control efforts, and provide opportunities for targeted, sustainable disease control. High-coverage, professional insecticide spraying combined with systematic surveillance-and-response were essential ingredients to achieve the quasi-elimination of T. infestans within 5 YPI and concomitant transmission blockage despite various structural threats and constraints.
Assuntos
Doença de Chagas , Inseticidas , Piretrinas , Triatoma , Animais , Humanos , Triatoma/fisiologia , Inseticidas/farmacologia , Controle de Insetos/métodos , Doença de Chagas/epidemiologia , Piretrinas/farmacologia , Argentina/epidemiologiaRESUMO
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.
Assuntos
Doença de Chagas , Panstrongylus , Triatoma , Trypanosoma cruzi , Animais , Humanos , Doença de Chagas/parasitologia , Triatoma/parasitologia , Panstrongylus/parasitologia , Cidades/epidemiologiaRESUMO
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.
Assuntos
Doença de Chagas , Triatoma , Trypanosoma cruzi , Animais , Argentina , Gatos , Galinhas , Estudos Transversais , Cães , Insetos VetoresRESUMO
BACKGROUND: Rapid reinfestation of insecticide-treated dwellings hamper the sustained elimination of Triatoma infestans, the main vector of Chagas disease in the Gran Chaco region. We conducted a seven-year longitudinal study including community-wide spraying with pyrethroid insecticides combined with periodic vector surveillance to investigate the house reinfestation process in connection with baseline pyrethroid resistance, housing quality and household mobility in a rural section of Pampa del Indio mainly inhabited by deprived indigenous people (Qom). METHODOLOGY/PRINCIPAL FINDINGS: Despite evidence of moderate pyrethroid resistance in local T. infestans populations, house infestation dropped from 31.9% at baseline to 0.7% at 10 months post-spraying (MPS), with no triatomine found at 59 and 78 MPS. Household-based surveillance corroborated the rare occurrence of T. infestans and the house invasion of other four triatomine species. The annual rates of loss of initially occupied houses and of household mobility were high (4.6-8.0%). Housing improvements did not translate into a significant reduction of mud-walled houses and refuges for triatomines because most households kept the former dwelling or built new ones with mud walls. CONCLUSIONS/SIGNIFICANCE: Our results refute the assumption that vector control actions performed in marginalized communities of the Gran Chaco are doomed to fail. The larger-than-expected impacts of the intervention program were likely associated with the combined effects of high-coverage, professional insecticide spraying followed by systematic vector surveillance-and-response, broad geographic coverage creating a buffer zone, frequent housing replacement and residential mobility. The dynamical interactions among housing quality, mobility and insecticide-based control largely affect the chances of vector elimination.
Assuntos
Doença de Chagas/prevenção & controle , Transmissão de Doença Infecciosa/prevenção & controle , Controle de Insetos/métodos , Grupos Populacionais , Adolescente , Adulto , Aerossóis/administração & dosagem , Idoso , Idoso de 80 Anos ou mais , Animais , Argentina , Características da Família , Feminino , Humanos , Inseticidas/administração & dosagem , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Piretrinas/administração & dosagem , Inquéritos e Questionários , Triatoma/efeitos dos fármacos , Triatoma/crescimento & desenvolvimento , Adulto JovemRESUMO
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
Assuntos
Doença de ChagasRESUMO
BACKGROUND The eco-epidemiological status of Chagas disease in the Monte Desert ecoregion of western Argentina is largely unknown. We investigated the environmental and socio-demographic determinants of house infestation with Triatoma infestans, bug abundance, vector infection with Trypanosoma cruzi and host-feeding sources in a well-defined rural area of Lavalle Department in the Mendoza province. METHODS Technical personnel inspected 198 houses for evidence of infestation with T. infestans, and the 76 houses included in the current study were re-inspected. In parallel with the vector survey, an environmental and socio-demographic survey was also conducted. Univariate risk factor analysis for domiciliary infestation was carried out using Firth penalised logistic regression. We fitted generalised linear models for house infestation and bug abundance. Blood meals were tested with a direct ELISA assay, and T. cruzi infection was determined using a hot-start polymerase chain reaction (PCR) targeting the kinetoplast minicircle (kDNA-PCR). FINDINGS The households studied included an aged population living in precarious houses whose main economic activities included goat husbandry. T. infestans was found in 21.2% of 198 houses and in 55.3% of the 76 re-inspected houses. Peridomestic habitats exhibited higher infestation rates and bug abundances than did domiciles, and goat corrals showed high levels of infestation. The main host-feeding sources were goats. Vector infection was present in 10.2% of domiciles and 3.2% of peridomiciles. Generalised linear models showed that peridomestic infestation was positively and significantly associated with the presence of mud walls and the abundance of chickens and goats, and bug abundance increased with the number of all hosts except rabbits. MAIN CONCLUSIONS We highlight the relative importance of specific peridomestic structures (i.e., goat corrals and chicken coops) associated with construction materials and host abundance as sources of persistent bug infestation driving domestic colonisation. Environmental management strategies framed in a community-based programme combined with improved insecticide spraying and sustained vector surveillance are needed to effectively suppress local T. infestans populations.
Assuntos
Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Triatoma/fisiologia , Triatoma/parasitologia , Trypanosoma cruzi/isolamento & purificação , Doença de Chagas/transmissão , Comportamento Alimentar/fisiologia , Insetos Vetores/fisiologia , Insetos Vetores/parasitologia , Argentina , População Rural , Fatores Socioeconômicos , Cabras , Gatos , Galinhas , Fatores de Risco , Densidade Demográfica , CãesRESUMO
BACKGROUND: The eco-epidemiological status of Chagas disease in the Monte Desert ecoregion of western Argentina is largely unknown. We investigated the environmental and socio-demographic determinants of house infestation with Triatoma infestans, bug abundance, vector infection with Trypanosoma cruzi and host-feeding sources in a well-defined rural area of Lavalle Department in the Mendoza province. METHODS: Technical personnel inspected 198 houses for evidence of infestation with T. infestans, and the 76 houses included in the current study were re-inspected. In parallel with the vector survey, an environmental and socio-demographic survey was also conducted. Univariate risk factor analysis for domiciliary infestation was carried out using Firth penalised logistic regression. We fitted generalised linear models for house infestation and bug abundance. Blood meals were tested with a direct ELISA assay, and T. cruzi infection was determined using a hot-start polymerase chain reaction (PCR) targeting the kinetoplast minicircle (kDNA-PCR). FINDINGS: The households studied included an aged population living in precarious houses whose main economic activities included goat husbandry. T. infestans was found in 21.2% of 198 houses and in 55.3% of the 76 re-inspected houses. Peridomestic habitats exhibited higher infestation rates and bug abundances than did domiciles, and goat corrals showed high levels of infestation. The main host-feeding sources were goats. Vector infection was present in 10.2% of domiciles and 3.2% of peridomiciles. Generalised linear models showed that peridomestic infestation was positively and significantly associated with the presence of mud walls and the abundance of chickens and goats, and bug abundance increased with the number of all hosts except rabbits. MAIN CONCLUSIONS: We highlight the relative importance of specific peridomestic structures (i.e., goat corrals and chicken coops) associated with construction materials and host abundance as sources of persistent bug infestation driving domestic colonisation. Environmental management strategies framed in a community-based programme combined with improved insecticide spraying and sustained vector surveillance are needed to effectively suppress local T. infestans populations.
Assuntos
Comportamento Alimentar/fisiologia , Insetos Vetores/fisiologia , Triatoma/fisiologia , Adulto , Idoso , Animais , Argentina , Gatos , Doença de Chagas/transmissão , Galinhas , Cães , Feminino , Cabras , Humanos , Insetos Vetores/parasitologia , Masculino , Pessoa de Meia-Idade , Densidade Demográfica , Fatores de Risco , População Rural , Fatores Socioeconômicos , Triatoma/parasitologia , Trypanosoma cruzi/isolamento & purificaçãoRESUMO
We investigated the dynamics and underlying causes of house (re)infestation with Triatoma infestans (Klug 1834) after a community-wide residual spraying with pyrethroids in a well-defined rural section of Pampa del Indio municipality (northeastern Argentina) over a 4-yr period. House infestation was assessed by timed manual searches, during insecticide applications, and by opportunistic householders' bug collections. All reinfested houses were selectively re-sprayed with insecticides. The resident population comprised Qom (66.6%) and Creole (33.4%) households, whose sociodemographic profiles differed substantially. The prevalence of house infestation dropped, less than expected, from 20.5% at baseline to 5.0% at 14 months postspraying (MPS), and then fluctuated between 0.8 and 4.2% over 21-51 MPS. Postspraying house infestation was positively and highly significantly associated with prespraying infestation. Most of the foci detected over 14-21 MPS were considered persistent (residual), some of which were moderately resistant to pyrethroids and were suppressed with malathion. Infestation patterns over 27-51 MPS suggested bug invasion from internal or external foci, but the sources of most findings were unaccounted for. Local spatial analysis identified two hotspots of postspraying house infestation. Using multimodel inference with model averaging, we corroborated that baseline domestic infestation was closely related to refuge availability, housing quality, and occurrence of peridomestic infestation. The diminished effectiveness of single pyrethroid treatments, partly attributable to moderate resistance compounded with rather insensitive vector detection methods and poor housing conditions, contributed to vector persistence. Improved control strategies combined with broad social participation are needed for the sustainable elimination of vector-borne human Chagas disease from the Gran Chaco.