Heterorhabditis indica (Nematoda: Rhabditida) a possible new biological control agent against the vector of Chagas disease.

Chagas disease is a zoonosis caused by the protozoan Trypanosoma cruzi and transmitted through the feces of triatomines, mainly in Latin America. Since the 1950s, chemical insecticides have been the primary method for controlling these triatomines, yet resistance has emerged, prompting the exploration of alternative approaches. The objective of this research was to test the capacity of the entomopathogenic nematodes Heterorhabditis indica and its symbiotic bacteria Photorhabdus luminescens, to produce mortality of Triatoma dimidiata a key vector of T. cruzi in Mexico under laboratory conditions. Two bioassays were conducted. In the first bioassay, the experimental unit was a 250 ml plastic jar with 100 g of sterile soil and three adult T. dimidiata. Three nematode quantities were tested: 2250, 4500, and 9000 nematodes per 100 g of sterile soil (n/100 g) per jar, with 3 replicates for each concentration and 1 control per concentration (1 jar with 100 g of sterile soil and 3 T. dimidiata without nematodes). The experimental unit of the second bioassay was a 500 ml plastic jar with 100 g of sterile soil and 4 adult T. dimidiata. This bioassay included 5, 50, 500, and 5000 n/100 g of sterile soil per jar, with 3 replicates of each quantity and 1 control per quantity. Data were analyzed using Kaplan-Meyer survival analysis. Electron microscopy was used to assess the presence of nematodes and tissue damage in T. dimidiata. The results of the first bioassay demonstrated that the nematode induced an accumulated average mortality ranging from 55.5 % (2250 n/100 g) to 100 % (4500 and 9000 n/100 g) within 144 h. In the second bioassay, the 5000 n/100 g concentration yielded 87.5 % mortality at 86 h, but a concentration as small as 500 n/100 g caused 75 % mortality from 84 h onwards. Survival analysis indicated higher T. dimidiata mortality with increased nematode quantities, with significant differences between the 4500, 5000, and 9000 n/100 g and controls. Electron microscopy revealed the presence of nematodes and its presumably symbiotic bacteria in the digestive system of T. dimidiata. Based on these analyses, we assert that the H. indica and P. luminescens complex causes mortality in adult T. dimidiata under laboratory conditions.

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.

Temporal variation of Triatoma dimidiata abundance and infection with Trypanosoma cruzi in domestic and sylvatic habitats of rural Yucatan, Mexico.

In the Yucatan Peninsula, Mexico, Triatoma dimidiata is the main vector of Chagas disease. This is a native species in the region that principally inhabits sylvatic habitats. Nevertheless, it shows a tolerant behavior to anthropogenic disturbance, with adult bugs frequently infesting human dwellings, principally during the warm and dry season. Yet, whether the temporal variation of abundance is independent of the habitat and how this is related to the infection rate with Trypanosoma cruzi in Yucatan is still poorly understood. The objective of this study was to simultaneously analyze the temporal variations of T. dimidiata abundance and infection with T. cruzi in domestic and sylvatic habitats from two localities of rural Yucatan (Sudzal, 20°52'19″N, 88°59'20″W and Teya, 21°02'55″N, 89°04'25″W) to help for the further improvement of locally adapted strategies aimed at controlling T. cruzi vector transmission. Using community participation and a combination of different trapping techniques, we collected T. dimidiata bugs during 29 consecutive months within domestic and sylvatic habitats. We then assessed by PCR the infection of the bugs with T. cruzi. Generalized linear models were used to evaluate the effect of climatic variables on the abundance of T. dimidiata and the effect of bug sex, season and habitat on the prevalence of infection with T. cruzi. Overall, 3640 specimens of T. dimidiata were collected. We clearly observed peaks of maximum abundance in both habitats during the warm and dry season and found a negative association of bug abundance with relative humidity. The overall prevalence of infection of the bugs with T. cruzi was 15.2 %. Additionally, bugs collected in domestic habitats displayed a significantly higher prevalence of infection than sylvatic bugs (19.6% vs. 6.1 %, respectively), suggesting an increased risk of T. cruzi transmission related with anthropogenic disturbance. Our study is the first to describe the annual pattern of abundance of T. dimidiata in sylvatic habitats of rural Yucatan and constitutes a contribution to the knowledge of T. dimidiata ecology and of T. cruzi transmission cycle dynamics in the region. In Yucatan, where the use of mosquito nets has shown to be effective to limit human dwelling infestation by T. dimidiata, reinforcing the awareness of local residents about the increased risk of T. cruzi transmission during the warm and dry season when realizing activities in the sylvatic ambient should be, among others, also considered to improve control strategies and limit the risk of vector transmission.

Adoption of community-based strategies for sustainable vector control and prevention.

Community engagement strategies provide tools for sustainable vector-borne disease control. A previous cluster randomized control trial engaged nine intervention communities in seven participatory activities to promote management of the domestic and peri-domestic environment to reduce risk factors for vector-borne Chagas disease. This study aims to assess the adoption of this innovative community-based strategy, which included chickens' management, indoor cleaning practices, and domestic rodent infestation control, using concepts from the Diffusion of Innovations Theory. We used questionnaires and semi-structured interviews to understand perceptions of knowledge gained, intervention adoption level, innovation attributes, and limiting or facilitating factors for adoption. The analysis process focused on five innovation attributes proposed by the Diffusion of Innovations Theory: relative advantage, compatibility, complexity, trialability, and observability. Rodent management was highly adopted by participants, as it had a relative advantage regarding the use of poison and was compatible with local practices. The higher complexity was reduced by offering several types of trapping systems and having practical workshops allowed trialability. Observability was limited because the traps were indoors, but information and traps were shared with neighbors. Chicken management was not as widely adopted due to the higher complexity of the method, and lower compatibility with local practices. Using the concepts proposed by the Diffusion of Innovations Theory helped us to identify the enablers and constraints in the implementation of the Chagas vector control strategy. Based on this experience, community engagement and intersectoral collaboration improve the acceptance and adoption of novel and integrated strategies to improve the prevention and control of neglected diseases.

Acute toxicity of two insecticides on two species of Chagas disease vectors.

The control of triatomine vectors of Chagas disease is mainly based on the use of pyrethroid insecticides. Because chemical control is the primary method for managing these insects, it is crucial to diversify the range of products utilized to mitigate the risk of resistance development. This study evaluated the toxicity of two insecticides with different modes of action on Triatoma dimidiata Latreille and T. pallidipennis Stal first and third instar nymphs. Our study focused on the effects of two insecticides, buprofezin (a growth regulator) and flunocamid (an anti-feeder), on the mortality rate of triatomine bugs in a laboratory setting. Moreover, we investigated how direct and indirect (film method) exposure to these insecticides impacted the survival of the insects. Flonicamid emerged as a promising insecticide for triatomine control since it caused 100% mortality in first-instar nymphs 48 h after direct exposure. While, in third instar nymphs, the maximum mortality was 88% at 72 h after exposure. Our result can be used as a basis for future triatomine control plans.

Identification of a triatomine infected with Trypanosoma cruzi in an urban area of the state of Veracruz, Mexico: A comprehensive study.

Chagas disease, considered a neglected disease, was initially confined to rural localities in endemic areas; however, in recent years through the process of urbanization and migration of infected people, the disease is gaining importance in urban environments. The presence of the vector in urban areas in most cases is due to the passive transport of vectors, but recently, its presence seems to be linked to vector adaptation processes associated with climate change. This paper reports the occurrence of an infected triatomine in the peridomicile of a house in an urban area of Córdoba, Veracruz, Mexico, where the species found is described, the molecular characteristics and resistance to BZN and NFX of the Trypanosoma cruzi isolate obtained, as well as serological data of the dwelling inhabitants. These urban disease scenarios make it possible to generate new scientific knowledge and enable the creation of new control strategies for Chagas disease vectors.

Laboratory Evaluation and Field Feasibility of Micro-Encapsulated Insecticide Effect on Rhodnius prolixus and Triatoma dimidiata Mortality in Rural Households in Boyacá, Colombia.

Chagas disease is a neglected vector-borne zoonosis caused by the parasite Trypanosoma cruzi that is primarily transmitted by insects of the subfamily Triatominae. Although control efforts targeting domestic infestations of Rhodnius prolixus have been largely successful, with several regions in Boyacá department certified free of T. cruzi transmission by intradomicile R. prolixus, novel native species are emerging, increasing the risk of disease. Triatoma dimidiata is the second most important species in Colombia, and conventional control methods seem to be less effective. In this study we evaluated the efficacy and usefulness of micro-encapsulated insecticide paints in laboratory conditions and its applicability in rural communities to avoid triatomine domiciliation. Laboratory conditions measured mortality at 6 months and 12 months, with an average mortality between 93-100% for T. dimidiata and 100% for R. prolixus. Evaluation of triatomine infestation in rural households was measured after one year, with an overall perception of effectiveness in reducing household domiciliation. Although triatomines were still spotted inside and around the homes, our findings demonstrate the ability of micro-encapsulated insecticide to prevent colonization inside the households when comparing infestation rates from previous years. Current control measures suggest insecticide spraying every six months, which implies great economic cost and logistical effort. Complementary triatomine control measures with insecticide spraying and micro-encapsulated insecticide paint would make public health efforts more efficient and reduce the frequency of treatment.

Re-emerging threat of Trypanosoma cruzi vector transmission in El Salvador, update from 2018 to 2020.

BACKGROUND: Since the late twentieth century, Chagas disease gained global attention to suppress the vector burden as a main control strategy in endemic countries. In Central America, multi-national initiative successfully achieved significant reduction in the estimated disease prevalence as well as elimination of the region's principal vector species at the time in 2012. While the last decade has witnessed significant changes in ecosystem-such as urbanization and replacement of the main vector species-that can possibly affect the vector's habitation and residual transmission, the up-to-date vector burden in the region has not been evaluated thoroughly due to the cessation of active vector surveillance. The aim of this study was to update the risk of vector-borne Trypanosoma cruzi infection in El Salvador, the top Chagas disease-endemic country in Central America. METHODS: A nationwide vector survey was conducted in the domestic environment of El Salvador from September 2018 to November 2020. The selection of the houses for inspection was based on expert purposeful sampling. Infection for T. cruzi was examined by microscopic observation of the insects' feces, followed by a species confirmation using PCR. The data were analyzed using R software version 4.1.3. Proportion estimates with 95% confidence intervals were inferred using the Jeffrey's method provided under the epiR package. RESULTS: A total of 1529 Triatoma dimidiata was captured from 107 houses (infestation rate, 34.4%; 107/311) in all the fourteen departments of the country visited within the period; prevalence of T. cruzi infection was as high as 10% (153/1529). In the country, domestic T. dimidiata infestation was distributed ubiquitously, while T. cruzi infection rates varied across the departments. Five out of fourteen departments showed higher infection rates than the average, suggesting sporadic high-risk areas in the country. CONCLUSIONS: Our comprehensive study revealed substantial T. cruzi infection of T. dimidiata across the country, indicating potential active transmission of the disease. Therefore, strengthened surveillance for both vector and human infection is required to truly eliminate the risk of T. cruzi transmission in Central America.

Presence of Anti-T. cruzi Antibodies in Inhabitants and Dogs of Two Rural Settlements in the Sierra de Los Tuxtlas, Veracruz, Mexico.

PURPOSE: The aim of this study was to identify the risk factors associated with house infestation by Triatoma dimidiata as well as with Trypanosoma cruzi infection in humans and owned dogs in two rural communities from the municipality of Catemaco, Veracruz, Mexico. METHODS: One hundred and 16 human blood samples and 34 dog blood samples were collected. The presence of anti-T. cruzi antibodies was determined using four different ELISA assays. Moreover, reactive ELISA sera from humans and dogs were processed by indirect immunofluorescence (IFI) to confirm the presence of anti-T. cruzi antibodies. RESULTS: Serologic tests for T. cruzi infection showed a prevalence of 5.1% (6/116) in humans and of 50% (17/34) in owned dogs. CONCLUSION: The presence of animals (dogs, chickens and wild animals), as well as some characteristics of house construction were identified as risk factors for infestation and infection. Complementary studies must be carried out to allow a better understanding of the transmission dynamics in the state of Veracruz, Mexico, and the implementation of adequate control programs.

Distribution of Triatoma dimidiata sensu lato (Reduviidae: Triatominae) and Risk Factors Associated with Household Invasion in Northern Belize, Central America.

To date, Triatoma dimidiata sensu lato [Reduviidae: Triatominae (Latreille 1811)] remains the sole vector species associated with Chagas disease transmission reported from Belize. Human infection data are limited for Belize and the disease transmission dynamics have not been thoroughly investigated, yet the likelihood of autochthonous transmission is supported by the widespread collection of infected vectors from within local households. Here, we report updated infection rates of the vector population and infestation rates for villages in north and central Belize. Overall, 275 households were enrolled in an ongoing vector surveillance program. Of the 41 insects collected, 25 were PCR positive for T. cruzi, indicating an infection rate as high as 60%. To further characterize the epidemiological risk of human-vector contact, determinants of household invasion were modeled. Local households were surveyed and characterized with respect to over 25 key factors that may be associated with household infestation by T. dimidiata s.l. While final models were not strongly predictive with respect to the risk factors that were surveyed, likely due to the low number of collection observations, the presence of domestic/peri-domestic dogs, nearby light sources, and household structure materials could be the focus of continued risk assessments. In northern Belize, this vector survey lends support to T. dimidiata s.l. inhabiting sylvatic settings as opposed to the classical paradigm of domiciliated vector populations. This designation has strong implications for the local level of human exposure risk which can help guide vector surveillance and control resources.

Determination of insecticides' lethal concentrations and metabolic enzyme levels in Triatoma dimidiata / Determinación de concentraciones letales y niveles de enzimas metabólicas de insecticidas en Triatoma dimidiata

Abstract: Objective: The feasibility of the use of WHO impregnated paper and biochemical assays to determine lethal concentrations (LC50 and LC99) and insecticide metabolic enzyme levels of Triatoma dimidiata. Materials and methods: LC50 and LC99 were calculated with WHO papers impregnated at different concentrations of malathion, propoxur and deltamethrin; the percentage of insensitive acetylcholinesterase (iAChE); and the levels of esterases, glutathione S-transferases, and monooxygenases in laboratory nymphs of the first stage (5 to 7 days), were undertaken using the WHO biochemical assays. Results: Respectively the LC50 and LC99 µg/cm2 obtained for malathion were 43.83 and 114.38, propoxur 4.71 and 19.29, and deltamethrin 5.80 and 40.46. A 30% of the population had an iAChE, and only a few individuals had high P450 and β-eterase levels. Conclusion: Impregnated papers and biochemical tests developed by WHO for other insects, proved to be feasible methods in monitoring insecticide resistance and metabolic enzymes involved in T. dimidiata.

Resumen: Objetivo: La factibilidad de usar los papeles impregnados y ensayos bioquímicos según la OMS para determinar concentraciones letales (CL50 y CL99) y niveles enzimáticos en la resistencia a insecticidas en Triatoma dimidiata. Material y métodos: Se calcularon la CL50 y CL99 con papeles impregnados según la OMS a diferentes concentraciones de malatión, propoxur y deltametrina; el porcentaje de acetilcolinesterasa insensible (iAChE); y los niveles de esterasas, glutatión S-transferasas, y monooxigenasas en ninfas de laboratorio del estadio I (5-7 días) se determinaron usando los ensayos bioquímicos según la OMS. Resultados: Se obtuvieron las CL50 y CL99 µg / cm2 respectivamente para malatión 43.83 y 114.38, propoxur 4.71 y 19.29, y deltametrina 5.80 y 40.46. Un 30% de las chinches tuvo iAChE, y sólo pocos individuos tuvieron niveles superiores de P450 y β-eterasas. Conclusión: Los papeles impregnados y ensayos bioquímicos que describe la OMS para otros insectos demostraron ser métodos factibles para monitorear la resistencia a insecticidas y las enzimas metabólicas involucradas en T. dimidiata.

Determination of insecticides' lethal concentrations and metabolic enzyme levels in Triatoma dimidiata.

OBJECTIVE: The feasibility of the use of WHO impregnated paper and biochemical assays to determine lethal concentrations (LC50 and LC99) and insecticide metabolic enzyme levels of Triatoma dimidiata. MATERIALS AND METHODS: LC50 and LC99 were calculated with WHO papers impregnated at different concentrations of malathion, propoxur and deltamethrin; the percentage of insensitive acetylcholinesterase (iAChE); and the levels of esterases, glutathione S-transferases, and monooxygenases in laboratory nymphs of the first stage (5 to 7 days), were undertaken using the WHO biochemical assays. RESULTS: Respectively the LC50 and LC99 µg/cm2 obtained for malathion were 43.83 and 114.38, propoxur 4.71 and 19.29, and deltamethrin 5.80 and 40.46. A 30% of the population had an iAChE, and only a few individuals had high P450 and ß-eterase levels. CONCLUSIONS: Impregnated papers and biochemical tests developed by WHO for other insects, proved to be feasible methods in monitoring insecticide resistance and metabolic enzymes involved in T. dimidiata.

OBJETIVO: La factibilidad de usar los papeles impregnados y ensayos bioquímicos según la OMS para determinar concentraciones letales (CL50 y CL99) y niveles enzimáticos en la resistencia a insecticidas en Triatoma dimidiata. MATERIAL Y MÉTODOS: Se calcularon la CL50 y CL99 con papeles impregnados según la OMS a diferentes concentraciones de malatión, propoxur y deltametrina; el porcentaje de acetilcolinesterasa insensible (iAChE); y los niveles de esterasas, glutatión S-transferasas, y monooxigenasas en ninfas de laboratorio del estadio I (5-7 días) se determinaron usando los ensayos bioquímicos según la OMS. RESULTADOS: Se obtuvieron las CL50 y CL99 µg / cm2 respectivamente para malatión 43.83 y 114.38, propoxur 4.71 y 19.29, y deltametrina 5.80 y 40.46. Un 30% de las chinches tuvo iAChE, y sólo pocos individuos tuvieron niveles superiores de P450 y ß-eterasas. CONCLUSIONES: Los papeles impregnados y ensayos bioquímicos que describe la OMS para otros insectos demostraron ser métodos factibles para monitorear la resistencia a insecticidas y las enzimas metabólicas involucradas en T. dimidiata.

Eco-epidemiological study reveals the importance of Triatoma dimidiata in the Trypanosoma cruzi transmission, in a municipality certified without transmission by Rhodnius prolixus in Colombia.

Boyaca department is an endemic area for Chagas disease in Colombia, where 24 of its municipalities have been certified by the PAHO with interruption of Trypanosoma cruzi transmission by R. prolixus. However, the presence of secondary vectors, represent a risk of parasite transmission for citizens and a challenge for the health care institutions. The aim of this work was to investigate eco-epidemiological features of Chagas disease in the municipality of Socota (Boyaca), in order to improve control and surveillance strategies. To understand the transmission dynamics of T. cruzi in this area, we designed a comprehensive, multi-faceted study including: (i) entomological survey in five villages (La Vega, Comaita, Chusvita, Guaquira and Pueblo Nuevo), (ii) blood meal source determination, (iii) T. cruzi infection rate in collected triatomines, (iv) identification of circulating T. cruzi genotypes, (v) serological determination of T. cruzi infection in domestic dogs; and (vi) evaluation of infection in synanthropic mammals. A total of 90 T. dimidiata were collected, of which 73.3% (66/90) and 24.4% (22/90) were collected inside dwellings and peridomestic areas, respectively, while the rest (2/90) in Chusvita Elementary School. T. cruzi infection was evidenced in 40% (36/90) of triatomine bugs using PCR analyses, in which only DTU I was found, and TcI Dom was the most distributed. Blood-meal analysis showed that T. dimidiata only fed of humans. Seroprevalence in domestic dogs was 4.6% (3/66), while that two Didelphis marsupialis captured showed no infection. In conclusion, the high dispersion and colonization of T. dimidiata shown in this municipality, along the high rate of T. cruzi (TcI) infection and its anthropophilic behavior constitute a risk situation for Chagas disease transmission in this municipality certified without R. prolixus. The epidemiological implications of these findings are herein discussed.

Disentangling Trypanosoma cruzi transmission cycle dynamics through the identification of blood meal sources of natural populations of Triatoma dimidiata in Yucatán, Mexico.

BACKGROUND: In the Yucatán Peninsula, Mexico, Triatoma dimidiata is the main vector of Trypanosoma cruzi, the causative agent of Chagas disease. Little effort has been made to identify blood meal sources of T. dimidiata in natural conditions in this region, although this provides key information to disentangle T. cruzi transmission cycles and dynamics and guide the development of more effective control strategies. We identified the blood meals of a large sample of T. dimidiata bugs collected in different ecotopes simultaneously with the assessment of bug infection with T. cruzi, to disentangle the dynamics of T. cruzi transmission in the region. METHODS: A sample of 248 T. dimidiata bugs collected in three rural villages and in the sylvatic habitat surrounding these villages was used. DNA from each bug midgut was extracted and bug infection with T. cruzi was assessed by PCR. For blood meal identification, we used a molecular assay based on cloning and sequencing following PCR amplification with vertebrate universal primers, and allowing the detection of multiple blood meals in a single bug. RESULTS: Overall, 28.7% of the bugs were infected with T. cruzi, with no statistical difference between bugs from the villages or from sylvatic ecotopes. Sixteen vertebrate species including domestic, synanthropic and sylvatic animals, were identified as blood meal sources for T. dimidiata. Human, dog and cow were the three main species identified, in bugs collected in the villages as well as in sylvatic ecotopes. Importantly, dog was highlighted as the main blood meal source after human. Dog was also the most frequently identified animal together with human within single bugs, and tended to be associated with the infection of the bugs. CONCLUSIONS: Dog, human and cow were identified as the main mammals involved in the connection of sylvatic and domestic transmission cycles in the Yucatán Peninsula, Mexico. Dog appeared as the most important animal in the transmission pathway of T. cruzi to humans, but other domestic and synanthropic animals, which most were previously reported as important hosts of T. cruzi in the region, were evidenced and should be taken into account as part of integrated control strategies aimed at disrupting parasite transmission.

Efecto de la educación comunitaria para control integrado del Triatoma Dimidiata (Hemiptera: Reduviidae) / EEffect of community education in an integrate control for Triatoma dimidiata (Hemiptera: Reduviidae) / EEffect of community education in an integrate control for Triatoma dimidiata (Hemiptera: Reduviidae)

Introduction: The Mesoamerican endemic specieTriatoma dimidiata is the main vector of Chagas disease in Central America, after the elimination of an introduced vector Rhodnius prolixus. The traditional method of vector control using insecticides results in reinfestation. An integrated Ecohealth approach, including education, house improvements and domestic animal management was shown effective for long-term control ofT. dimidiata, and it was applied in several villages in Guatemala. Objective: To evaluate the changes in community practices after an Ecohealth intervention in La Prensa, Olopa Chiquimula. Methods: Through three surveys, we measured risk factors associated withT. dimidiatainfestation, the infestation index, blood sources of T. dimidiata, the presence of Trypanosoma cruzi were analyzed using PCR. Statistics analysis included Wilcoxon signed-rank tests, Mc-Nemar test, Chi-square test and Fisher exact test to compare the surveys. Results: Over the years, risk factors associated with the presence of T. dimidiata and population density of the vector were observed. We found a decrease in consumption of human blood and the parasite in the vector population. However, we found the consumption of bird blood meal increased Conclusions: Our results provide evidence that an ecohealth approach for an endemic Chagas vector has impact on reducing vector-human contact, possibly by influencing people's behavior. Increasing the community knowledge about these risk factors can be an effective strategy to further reduce the risk of house reinfestation and Chagas transmission(AU)

Introducción: La especie endémica mesoamericana Triatoma dimidiata es el vector principal de la enfermedad de Chagas en América Central, después de la eliminación de un vector introducido Rhodnius prolixus. El método tradicional de control de vectores que utiliza insecticidas resulta en reinfestación. Se demostró que un enfoque integrado de ecosalud, que incluye la educación, mejorías en el hogar y manejo de animales domésticos, es efectivo para el control a largo plazo del T. dimidiata, y se aplicó en varias aldeas de Guatemala. Objetivo: evaluar los cambios en las prácticas comunitarias después de una intervención de ecosalud en La Prensa, Olopa Chiquimula. Métodos: a través de tres encuestas, se midieron los factores de riesgo asociados con la infestación de T. dimidiata, el índice de infestación, las fuentes sanguíneas de T. dimidiata y la presencia de Trypanosoma cruzi. Estas encuestas se analizaron mediante PCR. El análisis estadístico incluyó pruebas de Wilcoxon de rango con signo, la prueba de Mc-Nemar, la prueba de Chi-cuadrado y la prueba exacta de Fisher para comparar las encuestas. Resultados: A lo largo de los años, se observaron factores de riesgo asociados con la presencia de T. dimidiata y la densidad de población del vector. Encontramos una disminución del parásito en la población de vectores y en el consumo de sangre humana. Sin embargo, encontramos que aumentó el consumo de harina de sangre de aves. Conclusiones: Nuestros resultados proporcionan evidencia de que un enfoque de ecosalud para un vector de Chagas endémico impacta en la reducción del contacto vector-humano, posiblemente al influir en el comportamiento de las personas. Aumentar el conocimiento de la comunidad sobre estos factores de riesgo puede ser una estrategia efectiva para reducir aun más el riesgo de reinfestación en la casa y la transmisión de Chagas(AU)

Protein mass spectrometry detects multiple bloodmeals for enhanced Chagas disease vector ecology.

Chagas disease, a neglected tropical disease endemic in Latin America, is caused by the protozoan parasite Trypanosoma cruzi and is responsible for significant health impacts, especially in rural communities. The parasite is transmitted by insect vectors in the Triatominae subfamily and due to lack of vaccines and limited treatment options, vector control is the main way of controlling the disease. Knowing what vectors are feeding on directly enhances our understanding of the ecology and biology of the different vector species and can potentially aid in engaging communities in active disease control, a concept known as Ecohealth management. We evaluated bloodmeals in rural community, house-caught insect vectors previously evaluated for bloodmeals via DNA analysis as part of a larger collaborative project from three countries in Central America, including Guatemala. In addition to identifying bloodmeals in 100% of all samples using liquid chromatography tandem mass spectrometry (LC-MS/MS) (n = 50), strikingly for 53% of these samples there was no evidence of a recent bloodmeal by DNA-PCR. As individual vectors often feed on multiple sources, we developed an enhanced detection pipeline, and showed the ability to quantify a bloodmeal using stable-isotope-containing synthetic references peptides, a first step in further exploration of species-specific bloodmeal composition. Furthermore, we show that a lower resolution mass spectrometer is sufficient to correctly identify taxa from bloodmeals, an important and strong attribute of our LC-MS/MS-based method, opening the door to using proteomics in countries where Chagas disease is endemic.

Description of Triatoma mopan sp. n. from a cave in Belize (Hemiptera, Reduviidae, Triatominae).

In this paper, Triatoma mopansp. n. is described based on five males and six females collected in the Rio Frio cave, Cayo District, Belize. This species is similar to Triatoma dimidiata (Latreille), but can be distinguished by characters found on the pronotum, legs, and abdomen. Geometric morphometry and phylogenetic comparisons are also provided. Presently, the species is known only from the type locality and is a potential Chagas vector.

Toxicidad y afectación en la locomoción de Triatoma dimidiata (Latreille 1811) (Hemiptera: Reduviidae: Triatominae) tratados con análogos de girgensohnina / Toxicity and affectation in locomotion of Triatoma dimidiata (Latreille 1811) (Hemiptera: Reduviidae: Triatominae) treated with analogues of girgensohnine

Resumen Introducción: Análogos del alcaloide girgensohnina, diseñados y sintetizados para inhibir a la enzima acetilcolinesterasa, han presentado efecto insecticida sobre insectos vectores de enfermedades. Objetivo: Determinar la actividad insecticida de 12 análogos sintéticos de gingersohnina sobre ninfas del primer estadio de Triatoma dimidiata. Materiales y Métodos: Se tomó como referencia el protocolo de la OMS 2005. Ninfas del primer estadio de T. dimidiata fueron expuestas a los análogos por aplicación tópica y exposición a superficies para determinar las dosis letales (DL50 y DL95) y verificar alteración en la locomoción mediante el software Videomex V. Resultados: El análogo 6 presentó la mayor actividad insecticida a las 72h con una mortalidad del 20,8% ± 3,57 para el tratamiento de topicación 25% ± 0,00 para las superficies no porosas. Las dosis letales de la molécula 6 fueron: DL50 1036,8 ± 0,38 ng/insecto y DL95 3991,4 ± 0,50 ng/insecto respectivamente. Con respecto a la locomoción, el análogo indujo un comportamiento similar al insecticida comercial deltametrina.

Abstract Introduction: Analogs of the girgensohnine alkaloid, designed and synthesized to inhibit acetylcholinesterase enzyme, have presented an insecticidal effect on vectors insects of diseases. Objective: To determine the insecticidal activity of 12 synthetic analogs of gingersohnine in first stage nymphs of Triatoma dimidiata. Materials and methods: WHO protocol 2005, using exploratory doses, was used to determine the best molecule according to its mortality. First stage nymphs of T. dimidiata were exposed to different doses of the analogs by topical application and surface exposure. Lethal doses (LD50 and DL95) and alterations in locomotion using Videomex V software were determined. Results: Analog 6 presented the highest insecticidal activity at 72 h with a mortality of 20.8% ± 3.57 for topical treatment and 25%±0,0 for non-porous surfaces evaluation. Analog 6 lethal doses were LD50 1036.8 ± 0.38 ng/insecto and DL95 3991.4 ± 0.508 ng/insecto, respectively. With regard to locomotion, analogue 6 induced a similar behavior to that observed for commercial insecticide deltametrin.

What makes an effective Chagas disease vector? Factors underlying Trypanosoma cruzi-triatomine interactions.

The Chagas disease is caused by the parasite Trypanosoma cruzi, which infect blood-feeding triatomine bugs to finally reach mammal hosts. Chagas disease is endemic in Latin America, and is ranked among the 13 neglected tropical diseases worldwide. Currently, an estimate of 7 million people is infected by T. cruzi, leading to about 22 000 deaths per year throughout the Americas. As occurs with other vectors, a major question towards control programs is what makes a susceptible bug. In this review, we focus on findings linked to insect gut structure and microbiota, immunity, genetics, blood sources, abiotic factors (with special reference to ambient temperature and altitude) to understand the interactions occurring between T. cruzi and triatomine bugs, under a co-evolutionary scenario. These factors lead to varying fitness benefits and costs for bugs, explaining why infection in the insect takes place and how it varies in time and space. Our analysis highlights that major factors are gut components and microbiota, blood sources and temperature. Although their close interaction has never been clarified, knowledge reviewed here may help to boost the success of triatomine control programs, reducing the use of insecticides.

The role of natural selection in shaping genetic variation in a promising Chagas disease drug target: Trypanosoma cruzi trans-sialidase.

Rational drug design creates innovative therapeutics based on knowledge of the biological target to provide more effective and responsible therapeutics. Chagas disease, endemic throughout Latin America, is caused by Trypanosoma cruzi, a protozoan parasite. Current therapeutics are problematic with widespread calls for new approaches. Researchers are using rational drug design for Chagas disease and one target receiving considerable attention is the T. cruzi trans-sialidase protein (TcTS). In T. cruzi, trans-sialidase catalyzes the transfer of sialic acid from a mammalian host to coat the parasite surface membrane and avoid immuno-detection. However, the role of TcTS in pathology variance among and within genetic variants of the parasite is not well understood despite numerous studies. Previous studies reported the crystalline structure of TcTS and the TS protein structure in other trypanosomes where the enzyme is often inactive. However, no study has examined the role of natural selection in genetic variation in TcTS. To understand the role of natural selection in TcTS DNA sequence and protein variation, we examined a 471 bp portion of the TcTS gene from 48 T. cruzi samples isolated from insect vectors. Because there may be multiple parasite genotypes infecting one insect and there are multiple copies of TcTS per parasite genome, all 48 sequences had multiple polymorphic bases. To resolve these polymorphisms, we examined cloned sequences from two insect vectors. The data are analyzed to understand the role of natural selection in shaping genetic variation in TcTS and interpreted in light of the possible role of TcTS as a drug target. The analysis highlights negative or purifying selection on three amino acids previously shown to be important in TcTS transfer activity. One amino acid in particular, Tyr342, is a strong candidate for a drug target because it is under negative selection and amino acid substitutions inactivate TcTS transfer activity. AUTHOR SUMMARY: Chagas disease is caused by the protozoan parasite Trypanosoma cruzi and transmitted to humans and other mammals primarily by Triatomine insects. Being endemic in many South and Central American countries and affecting millions of people the need for new more effective and safe therapies is evident. Here, we examine genetic variation and natural selection on DNA (471 bp) and amino acid (157 aa) sequence data of the T. cruzi trans-sialdiase (TcTS) protein, often suggested as a candidate for rational drug design. In our surveyed region of the protein there were five amino acid residues that have been shown to be integral to the function of TcTS. We found that three were under strong negative selection making them ideal candidates for drug design; however, one was under balancing selection and should be avoided as a drug target. Our study provides new information into identifying potential targets for a new Chagas drug.