Cruzi Infection Rates Research Articles

Human Blood Meals in Sylvatic Triatomines Challenges Domestic-Centered Strategies for Prevention of Trypanosoma cruzi Transmission in Ecuador.

Transmission risk of Chagas disease has been associated with human-vector contacts and triatomines colonizing dwellings, but alternative scenarios, independent of domestic colonization, are poorly documented. In the present work, we estimated the frequency of human blood meals in triatomines from domicile, peridomicile, and sylvatic environments in two endemic regions in Ecuador. Blood meal origins were identified by sequencing a cytb gene fragment. Human blood meals were detected in 42% of the triatomines among 416 analyzed, including 48% of sylvatic triatomines (both adults and nymphs). In triatomines from domicile and peridomicile, Trypanosoma cruzi infection rate was > 20%, and reached 48% in sylvatic triatomines. Human is a common source of blood for triatomines whether they live in or near dwellings in both regions, and the high rate of T. cruzi infection represents an important risk of transmission of Chagas disease. Consequently, control strategies should also take into account possible nondomestic transmission.

The potential risk of enzootic Trypanosoma cruzi transmission inside four training and re-training military battalions (BITER) in Colombia

BackgroundColombia’s National Army is one of the largest military institutions in the country based on the number of serving members and its presence throughout the country. There have been reports of cases of acute or chronic cases of Chagas disease among active military personnel. These may be the result of military-associated activities performed in jungles and other endemic areas or the consequence of exposure to Trypanosoma cruzi inside military establishments/facilities located in endemic areas. The aim of the present study was to describe the circulation of T. cruzi inside facilities housing four training and re-training battalions [Battalions of Instruction, Training en Re-training (BITERs)] located in municipalities with historical reports of triatomine bugs and Chagas disease cases. An entomological and faunal survey of domestic and sylvatic environments was conducted inside each of these military facilities.MethodsInfection in working and stray dogs present in each BITER location was determined using serological and molecular tools, and T. cruzi in mammal and triatomine bug samples was determined by PCR assay. The PCR products of the vertebrate 12S rRNA gene were also obtained and subjected to Sanger sequencing to identify blood-feeding sources. Finally, we performed a geospatial analysis to evaluate the coexistence of infected triatomines and mammals with the military personal inside of each BITER installation.ResultsIn total, 86 specimens were collected: 82 Rhodnius pallescens, two Rhodnius prolixus, one Triatoma dimidiata and one Triatoma maculata. The overall T. cruzi infection rate for R. pallescens and R. prolixus was 56.1 and 100% respectively, while T. dimidiata and T. maculata were not infected. Eight feeding sources were found for the infected triatomines, with opossum and humans being the most frequent sources of feeding (85.7%). Infection was most common in the common opossum Didelphis marsupialis, with infection levels of 77.7%. Sylvatic TcI was the most frequent genotype, found in 80% of triatomines and 75% of D. marsupialis. Of the samples collected from dogs (n = 52), five (9.6%; 95% confidence interval: 3.20–21.03) were seropositive based on two independent tests. Four of these dogs were creole and one was a working dog. The spatial analysis revealed a sympatry between infected vectors and mammals with the military population.ConclusionsWe have shown a potential risk of spillover of sylvatic T. cruzi transmission to humans by oral and vectorial transmission in two BITER installations in Colombia. The results indicate that installations where 100,000 active military personnel carry out training activities should be prioritized for epidemiological surveillance of Chagas disease.Graphical abstract

Trypanosoma cruzi infection follow-up in a sylvatic vector of Chagas disease: Comparing early and late stage nymphs.

Chagas disease is caused by Trypanosoma cruzi and transmitted by the triatomine Mepraia spinolai in the southwest of South America. Here, we examined the T. cruzi-infection dynamics of field-caught M. spinolai after laboratory feeding, with a follow-up procedure on bug populations collected in winter and spring of 2017 and 2018. Bugs were analyzed twice to evaluate T. cruzi-infection by PCR assays of urine/fecal samples, the first evaluation right after collection and the second 40 days after the first feeding. We detected bugs with: the first sample positive and second negative (+/-), the first sample negative and second positive (-/+), and with both samples positive or negative (+/+; -/-). Bugs that resulted positive on both occasions were the most frequent, with the exception of those collected in winter 2018. Infection rate in spring was higher than winter only in 2018. Early and late stage nymphs presented similar T. cruzi-infection rates except for winter 2017; therefore, all nymphs may contribute to T. cruzi-transmission to humans. Assessment of infection using two samples represents a realistic way to determine the infection a triatomine can harbor. The underlying mechanism may be that some bugs do not excrete parasites unless they are fed and maintained for some time under environmentally controlled conditions before releasing T. cruzi, which persists in the vector hindgut. We suggest that T. cruzi-infection dynamics regarding the three types of positive-PCR results detected by follow-up represent: residual T. cruzi in the rectal lumen (+/-), colonization of parasites attached to the rectal wall (-/+), and presence of both kinds of flagellates in the hindgut of triatomines (+/+). We suggest residual T. cruzi-infections are released after feeding, and result 60–90 days after infection persisting in the rectal lumen after a fasting event, a phenomenon that might vary between contrasting seasons and years.

Investigación de la fauna triatomina (Hemiptera: Triatominae) y su infección por Trypanosoma cruzi Chagas (Kinetoplastida: Trypanosomatidae), en un área con un brote de enfermedad de Chagas en la Amazonía sudoccidental brasileña

The present study aims to describe the occurrence of triatomines and their infection rate by Trypanosoma cruzi, in an area of Chagas disease outbreak in Rodrigues Alves municipality, Acre state, Brazil. Collections were performed by passive search (capture of specimens by local people) and dissection of palm trees (Attalea butyracea and Mauritia flexuosa). Thirty two triatomines belonging to four species grouped into two genera (Rhodnius and Eratyrus) had T. cruzi infection rate of 15.6%. Only in A. butyracea triatomines were captured. The passive search was the most effective method for collection. The Nova Cintra triatomine fauna comprises four species and it is important to carry out future studies to understand the biology of these triatomines.

Assessing the entomo-epidemiological situation of Chagas disease in rural communities in the state of Piauí, Brazilian semi-arid region.

In northeastern Brazil, the wild nature of Trypanosoma cruzi vectors has challenged control actions. This study aims to describe the entomological and epidemiological scenario of Chagas disease in rural communities in the state of Piauí. A cross-sectional study (n=683 individuals/244 dwellings) was carried out to obtain serum samples, sociodemographic data and intra- and peridomestic triatomines. The overall seroprevalence rate was 8.1%, with no positive tests among subjects <30y of age. Prevalence rates reached 34.3% and 39.1% among subjects 61-75 and >75y of age, respectively; 1474 triatomines were collected, of which 90.3% were found in peridomiciliary structures and 9.7% inside houses; 87.2% were classified as Triatoma brasiliensis. T. cruzi infection rates in insects were 0.5% by light microscopy and 0.9% by culture in NNN/LIT medium. Five cultivated isolates were submitted to molecular genotyping, three of which were identified as T. cruzi I and two as T. cruzi II. Although no vector transmission currently occurs, prevalence rates are high in adults and the elderly. This disease should be targeted by primary healthcare providers. Insect surveillance and control activities should not be discontinued in an environment favourable to the perpetuation of house colonization by triatomines.

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.

Deltamethrin resistance in Chagas disease vectors colonizing oil palm plantations: implications for vector control strategies in a public health-agriculture interface

BackgroundTriatomine bugs are responsible for the vectorial transmission of the parasite Trypanosoma cruzi, etiological agent of Chagas disease, a zoonosis affecting 10 million people and with 25 million at risk of infection. Several triatomine species of the genus Rhodnius have been found inhabiting palm crowns where insects can find shelter in leaves axils and blood from palm-associated vertebrates. Rhodnius prolixus insects have been collected in oil palms in Colombia, and high T. cruzi infection rates were found. Since pest control is carried out in oil palm plantations, continuous exposure to insecticides could be occurring in these triatomines. Some insecticides suggested for pest control in oil palm plantations are also recommended for triatomine control in human dwellings. In this study, our objective was to assess if triatomines inhabiting oil palms exhibit resistance to deltamethrin, an insecticide used for vector control.MethodsRhodnius prolixus nymphs were sampled in oil palms located in Tauramena, Colombia. To determine deltamethrin resistance, biological and biochemical assays were carried out on fifth-instar nymphs from the F1 generation. For biological assays, pure and commercial deltamethrin were used, and in biochemical assays, activities of detoxifying enzymes related to pyrethroid resistance, such as oxidases, esterases and transferases, were quantified.ResultsDeltamethrin lethal dosage 50 and 90 in R. prolixus from oil palms was significantly higher than in those from a susceptible colony suggesting possible deltamethrin resistance. Moreover, mortality with commercial deltamethrin was very low in insects from oil palms. In biochemical assays, the activity of evaluated detoxifying enzymes was significantly higher in R. prolixus from oil palms than in those from the susceptible colony.ConclusionsPossible deltamethrin resistance found in R. prolixus insects from oil palms could threaten traditional vector control strategies in urban settings if insecticide-resistant triatomines can migrate from oil palms plantations. In palm oil producer countries such as Colombia, the oil palm plantations are growing constantly during the last years. We suggest that pest control strategies in oil palm crops should include triatomine surveillance and toxicological monitoring, especially in zones with several Chagas disease cases.

Wide distribution of Trypanosoma cruzi-infected triatomines in the State of Bahia, Brazil

BackgroundThe identification of Trypanosoma cruzi and blood-meal sources in synanthropic triatomines is important to assess the potential risk of Chagas disease transmission. We identified T. cruzi infection and blood-meal sources of triatomines caught in and around houses in the state of Bahia, northeastern Brazil, and mapped the occurrence of infected triatomines that fed on humans and domestic animals.MethodsTriatominae bugs were manually captured by trained agents from the Epidemiologic Surveillance team of Bahia State Health Service between 2013 and 2014. We applied conventional PCR to detect T. cruzi and blood-meal sources (dog, cat, human and bird) in a randomized sample of triatomines. We mapped triatomine distribution and analyzed vector hotspots with kernel density spatial analysis.ResultsIn total, 5906 triatomines comprising 15 species were collected from 127 out of 417 municipalities in Bahia. The molecular analyses of 695 triatomines revealed a ~10% T. cruzi infection rate, which was highest in the T. brasiliensis species complex. Most bugs were found to have fed on birds (74.2%), and other blood-meal sources included dogs (6%), cats (0.6%) and humans (1%). Trypanosoma cruzi-infected triatomines that fed on humans were detected inside houses. Spatial analysis showed a wide distribution of T. cruzi-infected triatomines throughout Bahia; triatomines that fed on dogs, humans, and cats were observed mainly in the northeast region.ConclusionsSynanthropic triatomines have a wide distribution and maintain the potential risk of T. cruzi transmission to humans and domestic animals in Bahia. Ten species were recorded inside houses, mainly Triatoma sordida, T. pseudomaculata, and the T. brasiliensis species complex. Molecular and spatial analysis are useful to reveal T. cruzi infection and blood-meal sources in synanthropic triatomines, identifying areas with ongoing threat for parasite transmission and improving entomological surveillance strategies.

Detection of Trypanosoma cruzi strains circulating in Córdoba department (Colombia) isolated from triatomines (Hemiptera: Reduviidae) collected by the community.

From 2011 to 2016, 24 cases of Chagas disease were reported in Córdoba according to the national public health surveillance system (Sistema Nacional de Vigilancia en Salud Pública, Sivigila), but the information regarding Trypanosoma cruzi circulating strains and infection rates are unknown. To establish the triatomine species with which people come in contact and recognize as Chagas disease vectors, as well as to assess the infection with trypanosomes and make an exploratory approach to host feeding preferences with the participation of the local community. Triatomines sampling was conducted in 12 municipalities between 2011 and 2016; T. cruzi infection was established by k-PCR, SAT-PCR, while strain genotyping was done by mini-exon and SL-IR (spliced-leader intergenic region) sequence characterization. We also screened for blood sources. Local community members collected the majority of triatomines and we identified three species: Rhodnius pallescens, Panstrongylus geniculatus, and Eratyrus cuspidatus. The overall T. cruzi infection rate in collected triatomines was 66.6% and we detected the TcIDOM and TcI sylvatic strains. Community-based insect collection allowed reporting the presence of P. geniculatus in two new disperse rural settlements, T. cruzi infection of P. geniculatus in Córdoba, and the first report of triatomines infected with T. cruzi in Montería municipality. These results revealed the presence of triatomines infected with T. cruzi inside dwellings in five municipalities of Córdoba. The dominant circulating T. cruzi strain was TcIDOM, a genotype associated with human Chagas disease and cardiomyopathies in Colombia. Our results highlight the importance of local community participation in entomological surveillance tasks.

Insect vectors of Chagas disease (Trypanosoma cruzi) in Northeastern Brazil.

Chagas disease remains a public health problem in the rural and urban areas of 19 countries in the Americas. The aim of the present study was to investigate the Trypanosoma cruzi infection rate of triatomines collected from both intra- and peridomiciliary areas in eleven municipalities of Southeastern Ceará, Brazil, from 2009 to 2015. A total of 32,364 triatomine specimens, including nymphs and adults, were collected, and 31,736 (98.06%) of these were examined. More nymphs were collected than adults, and the greatest number of triatomines (n = 8,548) was collected in 2010, for which the infection rate was 1.3%, with the highest rate of infections observed for specimens from Quixere. The species collected during the study were identified as Triatoma pseudomaculata, Triatoma brasiliensis, Panstrongylus megistus, Panstrongylus lutzi, and Rhodnius nasutus, with T. pseudomaculata being the most abundant (n = 19,962). These results verify the presence of triatomines in both intra- and peridomiciliary areas, thereby ensuring persistence of the pathogen and consequently, the disease, as the presence of infected vectors in households is an important risk factor. According to these findings, the Chagas Disease Control Program should intensify its efforts in order to prevent the spread of the disease.

Molecular characterization of Trypanosoma cruzi samples derived from Triatoma vitticeps and Panstrongylus geniculatus of the Atlantic rainforest, southeast Brazil

Background: In rural areas of Espírito Santo state, southeast Brazil, triatomine species attracted by light frequently invade residences. The aim of this study was to investigate the Trypanosoma cruzi discrete typing units (DTUs) harbored by these triatomines. Methods: Triatomine’s intestinal contents were examined, inoculated in mice, and the positive samples were cultivated. Flagellates obtained from infected mice hemoculture were submitted to DNA extraction using a salting-out method and to TcSC5D gene amplification. The amplified samples were sequenced, and polymorphism was analyzed for DTU identification. Results: Three hundred and ninety-four triatomines were identified: Triatoma vitticeps (90.03%), Panstrongylus geniculatus (8.89%), Panstrongylus megistus (0.54%), Panstrongylus diasi (0.27%), and Triatoma tibiamaculata (0.27%). Among the specimens, 251/394 (67.65%) presented flagellated forms similar to T. cruzi. After triatomine intestinal content inoculation into mice, 134 mice presented T. cruzi-like trypomastigotes from Tr. vitticeps and P. geniculatus and 89 samples were positive in hemoculture. Sixty-two samples were analyzed for the TcSC5D gene and TcI, TcII, TcIII, and TcIV DTUs were identified. Conclusions: We observed T. cruzi DTU diversity in Tr. vitticeps and P. geniculatus, which showed the predominance of TcII and occurrence of TcI, TcIII and TcIV. Triatomines presented high T. cruzi infection rates. Since little is known regarding the possible mammalian hosts that maintain the T. cruzi cycle, further studies are necessary to obtain a better understanding of the parasite transmission cycle in this region.

Synanthropic triatomines as potential vectors of Trypanosoma cruzi in Central Brazil

Chagas disease surveillance requires current knowledge on synanthropic triatomines. We analyzed the occurrence and Trypanosoma cruzi infection rates of triatomine bugs in central Brazil, during 2012-2014. Triatomines were collected inside or around houses, and T. cruzi infection was determined by optical microscopy and conventional/quantitative polymerase chain reaction. Of the 2706 triatomines collected, Triatoma sordida was the most frequent species in Goiás State, whereas Panstrongylus megistus predominated in the Federal District. Parasites identified were T. cruzi, T. rangeli, and Blastocrithidia sp. P. megistus and T. sordida sustained the risk of T. cruzi transmission to humans in central Brazil.

High Trypanosoma spp. diversity is maintained by bats and triatomines in Espírito Santo state, Brazil.

The aim of this study was to reevaluate the ecology of an area in the Atlantic Forest, southeast Brazil, where Chagas disease (CD) has been found to occur. In a previous study, immediately after the occurrence of a CD case, we did not observe any sylvatic small mammals or dogs with Trypanosoma cruzi cruzi infections, but Triatoma vitticeps presented high T. c. cruzi infection rates. In this study, we investigated bats together with non-volant mammals, dogs, and triatomines to explore other possible T. c. cruzi reservoirs/hosts in the area. Seventy-three non-volant mammals and 186 bats were captured at three sites within the Guarapari municipality, Espírito Santo state. Rio da Prata and Amarelos sites exhibited greater richness in terms of non-volant mammals and bats species, respectively. The marsupial Metachirus nudicaudatus, the rodent Trinomys paratus, and the bats Artibeus lituratus and Carollia perspicillata were the most frequently captured species. As determined by positive hemocultures, only two non-volant mammals were found to be infected by Trypanosoma species: Monodelphis americana, which was infected by T. cascavelli, T. dionisii and Trypanosoma sp., and Callithrix geoffroyi, which was infected by T. minasense. Bats presented T. c. cruzi TcI and TcIII/V, T. c. marinkellei, T. dionisii, T. rangeli B and D, and Trypanosoma sp. infections. Seven dogs were infected with T. cruzi based only on serological exams. The triatomines T. vitticeps and Panstrongylus geniculatus were found to be infected by trypanosomes via microscopy. According to molecular characterization, T. vitticeps specimens were infected with T. c. cruzi TcI, TcII, TcIII/V, and TcIV, T. c. marinkellei and T. dionisii. We observed high trypanosome diversity in a small and fragmented region of the Atlantic Forest. This diversity was primarily maintained by bats and T. vitticeps. Our findings show that the host specificity of the Trypanosoma genus should be thoroughly reviewed. In addition, our data show that CD cases can occur without an enzootic cycle near residential areas.

Chagas disease ecoepidemiology and environmental changes in northern Minas Gerais state, Brazil.

BACKGROUND Triatoma sordida and Triatoma pseudomaculata are frequently captured triatomine species in the Brazilian savannah and caatinga biomes, respectively, and in Brazilian domiciles.OBJECTIVESThis study identified eco-epidemiological changes in Chagas disease in northern Minas Gerais state, Brazil, and considered the influence of environmental shifts and both natural and anthropogenic effects.METHODSDomicile infestation and Trypanosoma cruzi infection rates were obtained from triatomines and sylvatic reservoirs during the following two time periods: the 1980s and 2007/2008. Entomological and climatic data with land cover classification derived from satellite imagery were integrated into a geographic information system (GIS), which was applied for atmospheric correction, segmentation, image classification, and mapping and to analyse data obtained in the field. Climatic data were analysed and compared to land cover classifications.RESULTSA comparison of current data with data obtained in the 1980's showed that T. sordida colonised domiciliary areas in both periods, and that T. pseudomaculata did not colonise these areas. There was a tendency toward a reduction in T. cruzi infection rates in sylvatic reservoirs, and of triatomines captured in both households and in the sylvatic environment. T. sordida populations have reduced in the sylvatic environment, while T. pseudomaculata showed an expanding trend in the region compared to counts observed in the 1980's in the sylvatic environment. This may be related to high deforestation rates as well as gradual increases in land surface temperature (LST) and temperatures along the years.MAIN CONCLUSIONSOur results suggest a geographical expansion of species into new biomes as a result of anthropogenic and climatic changes that directly interfere with the reproductive and infection processes of vectors.

Interdisciplinary approach at the primary healthcare level for Bolivian immigrants with Chagas disease in the city of São Paulo.

Background/MethodsIn a pioneering cross-sectional study among Bolivian immigrants in the city of São Paulo, Brazil, the epidemiological profile, clinical manifestations and morbidity of Chagas disease were described. The feasibility of the management of Chagas disease at primary healthcare clinics using a biomedical and psychosocial interdisciplinary approach was also tested. Previously, a Trypanosoma cruzi (T. cruzi) infection rate of 4.4% among 633 immigrants was reported. The samples were screened using two commercial enzyme-linked immunoassay (ELISA) tests generated with epimastigote antigens, and those with discrepant or seropositive results were analyzed by confirmatory tests: indirect immunofluorescence (IFI), TESA-blot and a commercial recombinant ELISA. PCR and blood cultures were performed in seropositive patients.ResultsThe majority of the 28 seropositive patients were women, of whom 88.89% were of child-bearing age. The predominant clinical forms of Chagas disease were the indeterminate and atypical cardiac forms. Less than 50% received the recommended antiparasitic treatment of benznidazole. An interdisciplinary team was centered on primary healthcare physicians who applied guidelines for the management of patients. Infectologists, cardiologists, pediatricians and other specialists acted as reference professionals. Confirmatory serology and molecular biology tests, as well as echocardiography, Holter and other tests, were performed for the assessment of affected organs in secondary healthcare centers. The published high performance of two commercial ELISA tests was not confirmed.ConclusionAn interdisciplinary approach including antiparasitic treatment is feasible at the primary healthcare level for the management of Chagas disease in Bolivian immigrants. The itinerant feature of immigration was associated with a lack of adherence to antiparasitic treatment and was considered a main challenge for the clinical management of this population. This approach is recommended for management of the infected population in endemic and nonendemic areas, although different strategies are needed depending on the severity of the disease and the structure of the healthcare system.

Community-Based Entomological Surveillance Reveals Urban Foci of Chagas Disease Vectors in Sobral, State of Ceará, Northeastern Brazil.

BackgroundThe aim of this work was to explore the potential risk of vector-borne Chagas disease in urban districts in northeastern Brazil, by analyzing the spatiotemporal distributions and natural infection rates with Trypanosoma cruzi of triatomine species captured in recent years. The main motivation of this work was an acute human case of Chagas disease reported in 2008 in the municipality of Sobral.Methodology/principal findingsWe analyzed data from community-based entomological surveillance carried out from 2010 to 2014. Triatomine natural T. cruzi infection was assessed by examination of insect feces by optical microscopy. Sites of triatomine capture were georeferenced through Google Earth and analyzed with ArcGIS. A total of 191 triatomines were collected, consisting of 82.2% Triatoma pseudomaculata, 7.9% Rhodnius nasutus, 5.8% T. brasiliensis, 3.7% Panstrongylus lutzi, and 0.5% P. megistus, with an overall natural infection index of 17.8%. Most infestations were reported in the districts of Dom José (36.2%), Padre Palhano (24.7%), and Alto do Cristo (10.6%). The overwhelming majority of insects (185/96.9%) were captured inside houses, and most insects tended to be collected in intermittent peaks. Moreover, captured triatomines tended to constitute colonies. The acute case reported in 2008 was found to be situated within a T. pseudomaculata hotspot.ConclusionThe triatomine collection events carried out by dwellers were aggregated in time and space into distinct foci, suggesting that insects are intermittently and artificially introduced into the city, possibly via accidental migration from their natural reservoirs. The relatively high T. cruzi infection rate indicates considerable circulation of the parasite in these areas, increasing the risk of vector-borne Chagas disease infection. These data suggest a need to strengthen epidemiological surveillance and integrate appropriate control actions targeting triatomines, T. cruzi reservoirs, and human populations. Our data also identify Chagas disease transmission as a hazard in urban areas of Sobral.

Interactions Between Trypanosoma cruzi the Chagas Disease Parasite and Naturally Infected Wild Mepraia Vectors of Chile.

Chagas disease, which ranks among the world's most neglected diseases, is a chronic, systemic, parasitic infection caused by the protozoan Trypanosoma cruzi. Mepraia species are the wild vectors of this parasite in Chile. Host-parasite interactions can occur at several levels, such as co-speciation and ecological host fitting, among others. Thus, we are exploring the interactions between T. cruzi circulating in naturally infected Mepraia species in all areas endemic of Chile. We evaluated T. cruzi infection rates of 27 different haplotypes of the wild Mepraia species and identified their parasite genotypes using minicircle PCR amplification and hybridization tests with genotype-specific DNA probes. Infection rates were lower in northern Chile where Mepraia gajardoi circulates (10-35%); in central Chile, Mepraia spinolai is most abundant, and infection rates varied in space and time (0-55%). T. cruzi discrete typing units (DTUs) TcI, TcII, TcV, and Tc VI were detected. Mixed infections with two or more DTUs are frequently found in highly infected insects. T. cruzi DTUs have distinct, but not exclusive, ecological and epidemiological associations with their hosts. T. cruzi infection rates of M. spinolai were higher than in M. gajardoi, but the presence of mixed infection with more than one T. cruzi DTU was the same. The same T. cruzi DTUs (TcI, TcII, TcV, and TcVI) were found circulating in both vector species, even though TcI was not equally distributed. These results suggest that T. cruzi DTUs are not associated with any of the two genetically related vector species nor with the geographic area. The T. cruzi vectors interactions are discussed in terms of old and recent events. By exploring T. cruzi DTUs present in Mepraia haplotypes and species from northern to central Chile, we open the analysis on these invertebrate host-parasite interactions.

Genotype diversity of Trypanosoma cruzi in small rodents and Triatoma sanguisuga from a rural area in New Orleans, Louisiana

BackgroundChagas disease is an anthropozoonosis caused by the protozoan parasite Trypanosoma cruzi that represents a major public health problem in Latin America. Although the United States is defined as non-endemic for Chagas disease due to the rarity of human cases, the presence of T. cruzi has now been amply demonstrated as enzootic in different regions of the south of the country from Georgia to California. In southeastern Louisiana, a high T. cruzi infection rate has been demonstrated in Triatoma sanguisuga, the local vector in this area. However, little is known about the role of small mammals in the wild and peridomestic transmission cycles.MethodsThis study focused on the molecular identification and genotyping of T. cruzi in both small rodents and T. sanguisuga from a rural area of New Orleans, Louisiana. DNA extractions were prepared from rodent heart, liver, spleen and skeletal muscle tissues and from cultures established from vector feces. T. cruzi infection was determined by standard PCR using primers specific for the minicircle variable region of the kinetoplastid DNA (kDNA) and the highly repetitive genomic satellite DNA (satDNA). Genotyping of discrete typing units (DTUs) was performed by amplification of mini-exon and 18S and 24Sα rRNA genes and subsequent sequence analysis.ResultsThe DTUs TcI, TcIV and, for the first time, TcII, were identified in tissues of mice and rats naturally infected with T. cruzi captured in an area of New Orleans, close to the house where the first human case of Chagas disease was reported in Louisiana. The T. cruzi infection rate in 59 captured rodents was 76%. The frequencies of the detected DTUs in such mammals were TcI 82%, TcII 22% and TcIV 9%; 13% of all infections contained more than one DTU.ConclusionsOur results indicate a probable presence of a considerably greater diversity in T. cruzi DTUs circulating in the southeastern United States than previously reported. Understanding T. cruzi transmission dynamics in sylvatic and peridomestic cycles in mammals and insect vectors will be crucial to estimating the risk of local, vector-borne transmission of T. cruzi to humans in the United States.

Abundance, natural infection with trypanosomes, and food source of an endemic species of triatomine, Panstrongylus howardi (Neiva 1911), on the Ecuadorian Central Coast.

The elimination of domestic triatomines is the foundation of Chagas disease control. Regional initiatives are eliminating introduced triatomine species. In this scenario, endemic triatomines can occupy the ecological niches left open and become a threat to long-term Chagas disease control efforts. This study determined the abundance, colonization, and Trypanosoma cruzi infection rate of the endemic Panstrongylus howardi in 10 rural communities located in Ecuador's Manabí Province. In total, 518 individuals of P. howardi were collected. Infestation indices of 1.4% and 6.6% were found in the domestic and peridomestic environments, respectively. We determined a T. cruzi infection rate of 53.2% (N = 47) in this species. P. howardi has a high capacity to adapt to different habitats, especially in the peridomicile. This implies a considerable risk of transmission because of the frequency of intradomicile invasion. Therefore, this species needs to be taken into account in Chagas control and surveillance efforts in the region.

Dynamics of sylvatic Chagas disease vectors in coastal Ecuador is driven by changes in land cover.

BackgroundChagas disease is a serious public health problem in Latin America where about ten million individuals show Trypanosoma cruzi infection. Despite significant success in controlling domiciliated triatomines, sylvatic populations frequently infest houses after insecticide treatment which hampers long term control prospects in vast geographical areas where vectorial transmission is endemic. As a key issue, the spatio-temporal dynamics of sylvatic populations is likely influenced by landscape yet evidence showing this effect is rare. The aim of this work is to examine the role of land cover changes in sylvatic triatomine ecology, based on an exhaustive field survey of pathogens, vectors, hosts, and microhabitat characteristics' dynamics.Methodology and Principal FindingsThe study was performed in agricultural landscapes of coastal Ecuador as a study model. Over one year, a spatially-randomized sampling design (490 collection points) allowed quantifying triatomine densities in natural, cultivated and domestic habitats. We also assessed infection of the bugs with trypanosomes, documented their microhabitats and potential hosts, and recorded changes in landscape characteristics. In total we collected 886 individuals, mainly represented by nymphal stages of one triatomine species Rhodnius ecuadoriensis. As main results, we found that 1) sylvatic triatomines had very high T. cruzi infection rates (71%) and 2) densities of T. cruzi-infected sylvatic triatomines varied predictably over time due to changes in land cover and occurrence of associated rodent hosts.ConclusionWe propose a framework for identifying the factors affecting the yearly distribution of sylvatic T. cruzi vectors. Beyond providing key basic information for the control of human habitat colonization by sylvatic vector populations, our framework highlights the importance of both environmental and sociological factors in shaping the spatio-temporal population dynamics of triatomines. A better understanding of the dynamics of such socio-ecological systems is a crucial, yet poorly considered, issue for the long-term control of Chagas disease.