Triatomine Vectors Research Articles

Evaluation of the toxic effects of doramectin, ivermectin and eprinomectin against Triatoma infestans using a rat model.

Pyrethroids have been frequently and intensively used for controlling the triatomine vectors of Trypanosoma cruzi. The emergence of resistance to these insecticides has resulted in an urgent need to identify novel, alternative and complementary control strategies. To evaluate the toxic effects of ivermectin, doramectin and eprinomectin on the bloodfeeding behaviour of Triatoma infestans using a rodent model. Fifth instar nymphs of T. infestans were fed at different times on Wistar rats pretreated with doramectin, ivermectin, eprinomectin or dimethylsulfoxide (excipient control) topically or orally administered. We determined the effects of each insecticide and of dimethyl sulfoxide on the amount of ingested blood, the volume of faecal discharge, and the mortality rates in triatomines. Only the rate of triatomine mortality was associated with the antiparasitic compounds administered and the route of administration utilized. Doramectin administration was associated with a higher mortality rate (21.5%) than ivermectin, eprinomectin and dimethylsulfoxide (16, 11 and 2.5%, respectively), and topical administration was found to be most effective for inducing mortality (23 vs. 9.3 %). These results demonstrate the toxic effects of the three assessed insecticides on T. infestans. The administration of ecto/endoparasiticides to domiciliary or peridomiciliary animals may serve as an interesting complementary strategy to the use of pyrethroids for the control of T. infestans.

Development of conventional and real-time multiplex PCR-based assays for estimation of natural infection rates and Trypanosoma cruzi load in triatomine vectors

BackgroundChagas disease is a complex anthropozoonosis with distinct domestic and sylvatic mammal species acting as potential reservoirs. The diversity of vector species and their habitats are among the factors that hinder the control of the disease. Control programs periodically monitor the prevalence of T. cruzi infection in insect bugs through microscopical observation of diluted feces. However, microscopy presents limited sensitivity in samples with low parasite numbers, difficulties in examining all evolutionary stages of the insect and may in turn be limited to differentiate T. cruzi from other morphologically similar trypanosomatids. Here, we report two highly sensitive and accurate methodologies to infer T. cruzi infection rates and to quantify parasite load in the gut of field-collected triatomines.MethodsTriatomines were manually collected in the period 2011–2012 and 2014–2015, in domestic, peridomestic or sylvatic habitats in rural areas of 26 municipalities, encompassing three distinct Brazilian biomes: Caatinga, Cerrado and Atlantic Rainforest. Following morphological and taxonomical identification, the search for flagellated protozoa was performed by optical microscopy. A conventional PCR targeting T. cruzi kDNA and a TaqMan qPCR directed to the parasite nuclear satellite DNA (SAT) were developed, both in multiplex, with the triatomine 12S subunit ribosomal RNA gene, used as internal amplification control. Both methods were used for detection (kDNA-PCR) and parasite load quantification (SAT-DNA-qPCR), to investigate T. cruzi infection in captured triatomines.ResultsThe combined methods were assayed on a panel of 205 field-collected triatomine samples. Diagnostic analysis revealed 21% positivity for the kDNA-PCR, whereas microscopic examination enabled identification of T. cruzi in only 7.0% of the PCR-positive samples. Negative PCR results were confirmed by the absence of T. cruzi flagellates using microscopy. Caatinga biome yielded the highest T. cruzi infection rate (60%), followed by the Atlantic Rainforest and Cerrado with 7.1 and 6.1%, respectively. In addition, a wide range distribution of parasite load, varying from 8.05 × 10-2 to 6.31 × 1010 was observed with a median of 2.29 × 103 T. cruzi/intestine units. When parasite load was analyzed by triatomine species, a significantly higher median was found for Panstrongylus lutzi in comparison with Triatoma brasiliensis.ConclusionsOur results demonstrate highly sensitive PCR-based methodologies to monitor T. cruzi infection in triatomines. In addition, the qPCR assay offers the possibility of further evaluation parasite load, as a promising biomarker of the vectorial capacity of triatomines in Chagas disease endemic areas.

Quantitative proteome and phosphoproteome analyses highlight the adherent population during Trypanosoma cruzi metacyclogenesis

Trypanosoma cruzi metacyclogenesis is a natural process that occurs inside the triatomine vector and corresponds to the differentiation of non-infective epimastigotes into infective metacyclic trypomastigotes. The biochemical alterations necessary for the differentiation process have been widely studied with a focus on adhesion and nutritional stress. Here, using a mass spectrometry approach, a large-scale phospho(proteome) study was performed with the aim of understanding the metacyclogenesis processes in a quantitative manner. The results indicate that major modulations in the phospho(proteome) occur under nutritional stress and after 12 and 24 h of adhesion. Significant changes involve key cellular processes, such as translation, oxidative stress, and the metabolism of macromolecules, including proteins, lipids, and carbohydrates. Analysis of the signalling triggered by kinases and phosphatases from 7,336 identified phosphorylation sites demonstrates that 260 of these sites are modulated throughout the differentiation process, and some of these modulated proteins have previously been identified as drug targets in trypanosomiasis treatment. To the best of our knowledge, this study provides the first quantitative results highlighting the modulation of phosphorylation sites during metacyclogenesis and the greater coverage of the proteome to the parasite during this process. The data are available via ProteomeXchange with identifier number PXD006171.

Widespread Trypanosoma cruzi infection in government working dogs along the Texas-Mexico border: Discordant serology, parasite genotyping and associated vectors.

BackgroundChagas disease, caused by the vector-borne protozoan Trypanosoma cruzi, is increasingly recognized in the southern U.S. Government-owned working dogs along the Texas-Mexico border could be at heightened risk due to prolonged exposure outdoors in habitats with high densities of vectors. We quantified working dog exposure to T. cruzi, characterized parasite strains, and analyzed associated triatomine vectors along the Texas-Mexico border.Methodology/Principle findingsIn 2015–2016, we sampled government working dogs in five management areas plus a training center in Texas and collected triatomine vectors from canine environments. Canine serum was tested for anti-T. cruzi antibodies with up to three serological tests including two immunochromatographic assays (Stat-Pak and Trypanosoma Detect) and indirect fluorescent antibody (IFA) test. The buffy coat fraction of blood and vector hindguts were tested for T. cruzi DNA and parasite discrete typing unit was determined. Overall seroprevalence was 7.4 and 18.9% (n = 528) in a conservative versus inclusive analysis, respectively, based on classifying weakly reactive samples as negative versus positive. Canines in two western management areas had 2.6–2.8 (95% CI: 1.0–6.8 p = 0.02–0.04) times greater odds of seropositivity compared to the training center. Parasite DNA was detected in three dogs (0.6%), including TcI and TcI/TcIV mix. Nine of 20 (45%) T. gerstaeckeri and T. rubida were infected with TcI and TcIV; insects analyzed for bloodmeals (n = 11) fed primarily on canine (54.5%).Conclusions/SignificanceGovernment working dogs have widespread exposure to T. cruzi across the Texas-Mexico border. Interpretation of sample serostatus was challenged by discordant results across testing platforms and very faint serological bands. In the absence of gold standard methodologies, epidemiological studies will benefit from presenting a range of results based on different tests/interpretation criteria to encompass uncertainty. Working dogs are highly trained in security functions and potential loss of duty from the clinical outcomes of infection could affect the work force and have broad consequences.

MALDI-TOF MS protein profiling for the rapid identification of Chagas disease triatomine vectors and application to the triatomine fauna of French Guiana.

Triatomines are haematophagous insects involved in the transmission of Trypanosoma cruzi, the aetiological agent of Chagas disease. The vector competence of these arthropods can be highly variable, depending on the species. A precise identification is therefore crucial for the epidemiological surveillance of T. cruzi and the determination of at-risk human populations. To circumvent the difficulties of morphological identification and the lack of comprehensiveness of the GenBank database, we hereby propose an alternative method for triatomine identification. The femurs of the median legs of triatomines from eight different species from French Guiana were subjected to matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) analysis. Method evaluation was performed on fresh specimens and was applied to dry specimens collected between 1991 and 2003. Femur-derived protein extracts provided reproducible spectra within the same species along with significant interspecies heterogeneity. Validation of the study by blind test analysis provided 100% correct identification of the specimens in terms of the species, sex and developmental stage. MALDI-TOF mass spectrometry appears to be a powerful tool for triatomine identification, which is a major step forward in the fight against Chagas disease.

Toward an Ecological Framework for Assessing Reservoirs of Vector-Borne Pathogens: Wildlife Reservoirs of Trypanosoma cruzi across the Southern United States.

Wildlife species are critical for both feeding vectors and serving as reservoirs of zoonotic vector-borne pathogens. Transmission pathways leading to disease in humans or other target taxa might be better understood and managed given a complete understanding of the relative importance of different reservoir species in nature. Using the conceptual framework of “reservoir potential,” which considers elements of both reservoir competence and vector-host contact, we review the wildlife reservoirs of Trypanosoma cruzi in the southern United States, where many species of triatomine vectors occur and wildlife maintain enzootic cycles that create a risk of spillover to humans, domestic dogs, and captive nonhuman primates that may develop Chagas disease. We reviewed 77 published reports of T. cruzi infection in at least 26 wildlife species across 15 southern states. Among the most well-studied and highly infected reservoirs are raccoon (Procyon lotor), woodrat (Neotoma spp.), and opossum (Didelphis virginiana), with aggregate overall infection prevalences of 36.4, 34.7, and 22.9%, respectively. Just over 60% of studies utilized methods from which an infectiousness index could be generated and show that raccoons and striped skunk (Mephitis mephitis) are among the most infectious wildlife hosts. Triatomine-host contact has sparsely been quantified in the southern United States, but 18 of the 24 host species previously identified to have been fed upon by triatomines are wildlife. Future studies to parameterize the reservoir potential model, especially to quantify wildlife infectiousness, vector-host contact, and the epidemiological importance of parasite strains maintained by wildlife, could open new doors for managing enzootic cycles and reducing T. cruzi spillover risk.

Chagas Disease Knowledge and Risk Behaviors of the Homeless Population in Houston, TX.

Chagas disease is a parasitic infection, caused by Trypanosoma cruzi, endemic in Latin America. Sylvatic T. cruzi-infected triatomine vectors are present in rural and urban areas in the southern USA and may transmit T. cruzi infection to at-risk populations, such as homeless individuals. Our study aimed to evaluate Chagas disease knowledge and behaviors potentially associated with transmission risk of Chagas disease among Houston, Texas' homeless population by performing interviews with 212 homeless individuals. The majority of the 212 surveyed homeless individuals were male (79%), African-American (43%), American-born individuals (96%). About 30% of the individuals reported having seen triatomines in Houston, and 25% had evidence of blood-borne transmission risk (IV drug use and/or unregulated tattoos). The median total time homeless was significantly associated with recognition of the triatomine vector. Our survey responses indicate that the homeless populations may exhibit potential risks for Chagas disease, due to increased vector exposure, and participation in blood-borne pathogen risk behaviors. Our findings warrant additional research to quantify the prevalence of Chagas disease among homeless populations.

Temporal Variation in the Abundance and Timing of Daily Activity of Chagas Disease Vector Triatoma gerstaeckeri (Stål, 1859) in a Natural Habitat in the Lower Rio Grande Valley, South Texas.

Chagas disease caused by Trypanosoma cruzi is a burden to millions of people in South and Central America. A sylvatic life cycle of the parasite exists in the Southern United States, but recent studies indicate an active peri-domestic life cycle of T. cruzi in Texas. The United States-Mexico border region in Texas displays areas of high poverty and sub-standard housing conditions which are important risk factors for a potential spill-over transmission to a domestic life cycle including humans. The objectives of the study were to examine short- and long-term temporal variation in vector activity and to evaluate the effect of different combinations of attractants on the capture of potential triatomine vectors. We collected local triatomine vectors (all of them identified as Triatoma gerstaeckeri) from a natural habitat in South Texas during the course of a year. The exact time of collection was recorded to examine the timing of flight activity of the triatomine vector. We also conducted a comparative study of the efficiency of 2 commonly used attractants (light and CO2) and the combination of those on the capture rate of Tr. gerstaeckeri. Our study indicates a short season of dispersal of Tr. gerstaeckeri (April/May) and it suggests a unimodal distribution of activity peaking between 2 and 3 hr after sunset. Ultra-violet light served as the main attractant of Tr. gerstaeckeri while CO2 from dry ice did not significantly contribute to the collection of vectors. The pronounced timing of activity in Tr. gerstaeckeri reported in this study contributes to our understanding of the epidemiology of T. cruzi in wildlife and its potential as a Chagas disease vector to humans in the Rio Grande Valley, South Texas.

Trypanosoma cruzi reservoir-triatomine vector co-occurrence networks reveal meta-community effects by synanthropic mammals on geographic dispersal.

Contemporary patterns of land use and global climate change are modifying regional pools of parasite host species. The impact of host community changes on human disease risk, however, is difficult to assess due to a lack of information about zoonotic parasite host assemblages. We have used a recently developed method to infer parasite-host interactions for Chagas Disease (CD) from vector-host co-occurrence networks. Vector-host networks were constructed to analyze topological characteristics of the network and ecological traits of species’ nodes, which could provide information regarding parasite regional dispersal in Mexico. Twenty-eight triatomine species (vectors) and 396 mammal species (potential hosts) were included using a data-mining approach to develop models to infer most-likely interactions. The final network contained 1,576 links which were analyzed to calculate centrality, connectivity, and modularity. The model predicted links of independently registered Trypanosoma cruzi hosts, which correlated with the degree of parasite-vector co-occurrence. Wiring patterns differed according to node location, while edge density was greater in Neotropical as compared to Nearctic regions. Vectors with greatest public health importance (i.e., Triatoma dimidiata, T. barberi, T. pallidipennis, T. longipennis, etc), did not have stronger links with particular host species, although they had a greater frequency of significant links. In contrast, hosts classified as important based on network properties were synanthropic mammals. The latter were the most common parasite hosts and are likely bridge species between these communities, thereby integrating meta-community scenarios beneficial for long-range parasite dispersal. This was particularly true for rodents, >50% of species are synanthropic and more than 20% have been identified as T. cruzi hosts. In addition to predicting potential host species using the co-occurrence networks, they reveal regions with greater expected parasite mobility. The Neotropical region, which includes the Mexican south and southeast, and the Transvolcanic belt, had greatest potential active T. cruzi dispersal, as well as greatest edge density. This information could be directly applied for stratification of transmission risk and to design and analyze human-infected vector contact intervention efficacy.

The contemporary distribution of Trypanosoma cruzi infection in humans, alternative hosts and vectors

Chagas is a potentially fatal chronic disease affecting large numbers of people across the Americas and exported throughout the world through human population movement. It is caused by the Trypanosoma cruzi parasite, which is transmitted by triatomine vectors to humans and a wide range of alternative host species. The database described here was compiled to allow the risk of vectorial transmission to humans to be mapped using geospatial models. The database collates all available records, published since 2003, for prevalence and occurrence of infection in humans, vectors and alternative hosts, and links each record to a defined time and location. A total of 16,802 records of infection have been extracted from the published literature and unpublished sources. The resulting database can be used to improve our understanding of the geographic variation in vector infection prevalence and to estimate the risk of vectorial transmission of T. cruzi to humans.

Hosts and vectors of Trypanosoma cruzi discrete typing units in the Chagas disease endemic region of the Paraguayan Chaco.

Active Trypanosoma cruzi transmission persists in the Gran Chaco region, which is considered hyperendemic for Chagas disease. Understanding domestic and sylvatic transmission cycles and therefore the relationship between vectors and mammalian hosts is crucial to designing and implementing improved effective control strategies. Here we describe the species of triatomine vectors and the sylvatic mammal reservoirs of T. cruzi, in different localities of the Paraguayan and Bolivian Chaco. We identify the T. cruzi genotypes discrete typing units (DTUs) and provide a map of their geographical distribution. A total of 1044 triatomines and 138 sylvatic mammals were captured. Five per cent of the triatomines were microscopically positive for T. cruzi (55 Triatoma infestans from Paraguay and one sylvatic Triatoma guasayana from Bolivia) and 17 animals (12·3%) comprising eight of 28 (28·5%) Dasypus novemcinctus, four of 27 (14·8%) Euphractus sexcinctus, three of 64 (4·7%) Chaetophractus spp. and two of 14 (14·3%) Didelphis albiventris. The most common DTU infecting domestic triatomine bugs was TcV (64%), followed by TcVI (28%), TcII (6·5%) and TcIII (1·5%). TcIII was overwhelmingly associated with armadillo species. We confirm the primary role of T. infestans in domestic transmission, armadillo species as the principal sylvatic hosts of TcIII, and consider the potential risk of TcIII as an agent of Chagas disease in the Chaco.

Epidemiology and Molecular Typing of Trypanosoma cruzi in Naturally-Infected Hound Dogs and Associated Triatomine Vectors in Texas, USA.

BackgroundTrypanosoma cruzi is the etiologic agent of Chagas disease throughout the Americas. Few population-level studies have examined the epidemiology of canine infection and strain types of T. cruzi that infect canines in the USA. We conducted a cross-sectional study of T. cruzi infection in working hound dogs in south central Texas, including analysis of triatomine vectors collected within kennel environments.Methodology/Principle FindingsPaired IFA and Chagas Stat-Pak serological testing showed an overall seroprevalence of 57.6% (n = 85), with significant variation across kennels. Dog age had a marginally significant effect on seropositivity, with one year of age increase associated with a 19.6% increase in odds of being seropositive (odds ratio 95% CI 0.996–1.435; p = 0.055). PCR analyses of blood revealed 17.4% of dogs harbored parasite DNA in their blood, including both seronegative and seropositive dogs. Molecular screening of organs from opportunistically sampled seropositive dogs revealed parasite DNA in heart, uterus, and mammary tissues. Strain-typing showed parasite discrete typing units (DTU) TcI and TcIV present in dog samples, including a co-occurrence of both DTUs in two individual dogs. Bloodmeal analysis of Triatoma gerstaeckeri and Triatoma sanguisuga insects collected from the kennels revealed exclusively dog DNA. Vector infection with T. cruzi was 80.6% (n = 36), in which T. gerstaeckeri disproportionately harbored TcI (p = 0.045) and T. sanguisuga disproportionately harbored TcIV (p = 0.029). Tracing infection status across dog litters showed some seropositive offspring of seronegative dams, suggesting infection of pups from local triatomine vectors rather than congenital transmission.Conclusions/SignificanceCanine kennels are high-risk environments for T. cruzi transmission, in which dogs likely serve as the predominant parasite reservoir. Disease and death of working dogs from Chagas disease is associated with unmeasured yet undoubtedly significant financial consequences because working dogs are highly trained and highly valued.

Molecular identification and genotyping of Trypanosoma cruzi DNA in autochthonous Chagas disease patients from Texas, USA

The parasitic protozoan Trypanosoma cruzi, the causative agent of Chagas disease, is widely distributed throughout the Americas, from the southern United States (US) to northern Argentina, and infects at least 6 million people in endemic areas. Much remains unknown about the dynamics of T. cruzi transmission among mammals and triatomine vectors in sylvatic and peridomestic eco-epidemiological cycles, as well as of the risk of transmission to humans in the US. Identification of T. cruzi DTUs among locally-acquired cases is necessary for enhancing our diagnostic and clinical prognostic capacities, as well as to understand parasite transmission cycles. Blood samples from a cohort of 15 confirmed locally-acquired Chagas disease patients from Texas were used for genotyping T. cruzi. Conventional PCR using primers specific for the minicircle variable region of the kinetoplastid DNA (kDNA) and the highly repetitive genomic satellite DNA (satDNA) confirmed the presence of T. cruzi in 12/15 patients. Genotyping was based on the amplification of the intergenic region of the miniexon gene of T. cruzi and sequencing. Sequences were analyzed by BLAST and phylogenetic analysis by Maximum Likelihood method allowed the identification of non-TcI DTUs infection in six patients, which corresponded to DTUs TcII, TcV or TcVI, but not to TcIII or TcIV. Two of these six patients were also infected with a TcI DTU, indicating mixed infections in those individuals. Electrocardiographic abnormalities were seen among patients with single non-TcI and mixed infections of non-TcI and TcI DTUs. Our results indicate a greater diversity of T. cruzi DTUs circulating among autochthonous human Chagas disease cases in the southern US, including for the first time DTUs from the TcII-TcV-TcVI group. Furthermore, the DTUs infecting human patients in the US are capable of causing Chagasic cardiac disease, highlighting the importance of parasite detection in the population.

Entomological survey in the state of Piauí, Northeastern Brazil, reveals intradomiciliary colonization of Triatoma brasiliensis macromelasoma.

ABSTRACTThis survey aimed to assess the presence of triatomine vectors of Chagas disease within the rural communities of São João do Piauí, Northeast Brazil. Intradomiciliary and peridomiciliary collection strategies were implemented wherein 279 specimens of Triatoma brasiliensis macromelasoma, both nymph and adult were found in 15 (50%) of the studied homes. Of the intradomiciliary insects, 73 (67.6%) were identified as nymph instars (1st instar [N1]= 6, N2= 14, N3= 28, N4= 7 and N5= 18). In the studied communities, a continuous interaction between triatomine bugs and humans could be shown. It is therefore urgent that suitable strategies for the control of the triatomine vector are implemented in this area.

TriatoKey: a web and mobile tool for biodiversity identification of Brazilian triatomine species.

Triatomines are blood-sucking insects that transmit the causative agent of Chagas disease, Trypanosoma cruzi. Despite being recognized as a difficult task, the correct taxonomic identification of triatomine species is crucial for vector control in Latin America, where the disease is endemic. In this context, we have developed a web and mobile tool based on PostgreSQL database to help healthcare technicians to overcome the difficulties to identify triatomine vectors when the technical expertise is missing. The web and mobile version makes use of real triatomine species pictures and dichotomous key method to support the identification of potential vectors that occur in Brazil. It provides a user example-driven interface with simple language. TriatoKey can also be useful for educational purposes. Database URL: http://triatokey.cpqrr.fiocruz.br

Targets and Patented Drugs for Chemotherapy of Chagas Disease in the Last 15 Years-Period.

The American trypanosomiasis, Chagas disease, is a parasitic infection typically spread by triatomine vectors affecting millions of people all over Latin America. Existing chemotherapy is centered on the nitroaromatic compounds benznidazole and nifurtimox that provide unsatisfactory results and substantial side effects. So, the finding and exploration of novel ways to challenge this neglected disease is a main priority. The biologic and biochemical progress in the scientific knowledge of Trypanosoma cruzi in the period comprising last 15-years has increased the identification of multiple targets for Chagas´ disease chemotherapy. In the middle of the best encouraging targets for trypanocidal drugs, ergosterol biosynthesis pathway and cruzipain, a key cysteine protease (CP) of T. cruzi, have been pointed out. Unfortunately, recent clinical trials investigating the administration of pozoconazole and ravuconazole to chronic indeterminate Chagas disease patients revealed their inferiority compared to the standard drug Benznidazole. In view of the information gained in the preceding years, a reasonable approach for the fast development of novel anti-T. cruzi chemotherapy would be focused on K777, the cysteine proteinase inhibitor (CPI) near to enter to clinical trials, and founded on the clinical evaluation of combination of known drugs with existing trypanocidal agents to obtain more efficiency and less secondary effects. Top series of xanthine have been recently identified as clinical candidate for Chagas disease. In addition, trypanothione biosynthesis, thiol-dependant redox and polyamine metabolism, the glycolytic, glyconeogenic, pentose phosphate, lipidic and polyisoprenoid biosynthetic pathways, and the enzymes from biosynthetic glycoconjugates pathways have been studied. Several specific enzymes from these particular biosynthetic pathways such as hypoxanthine-guaninephosphoribosyl- transferase and farnesyl-pyrophosphate synthase, among others, have also been broadly studied in T. cruzi. Novel synthesized anti-T. cruzi compounds with or without specific single or multi-target assigned are also described in detail. In summary, loans on anti-Chagas disease agents focused to specific parasite targets as their metabolic pathways or specific enzymes will be summarized. Targets will also be specifically discussed. Patent literature collected and published from 2000 to 2015, alleging inhibitors for specific T. cruzi targets or trypanocidal activity was achieved over the search database from Delphion Research intellectual property network including international patents and the European patent office, Espacenet.

Triatomine bugs, their microbiota and Trypanosoma cruzi: asymmetric responses of bacteria to an infected blood meal.

BackgroundTriatomine bugs (Hemiptera: Reduviidae) are vectors of the flagellate Trypanosoma cruzi, the causative agent of Chagas disease. The study of triatomine gut microbiota has gained relevance in the last years due to its possible role in vector competence and prospective use in control strategies. The objective of this study is to examine changes in the gut microbiota composition of triatomines in response to a T. cruzi-infected blood meal and identifying key factors determining those changes.ResultsWe sampled colony-reared individuals from six triatomine vectors (Panstrongylus megistus, Rhodnius prolixus, Triatoma brasiliensis, T. infestans, T. juazeirensis and T. sherlocki) comparing experimentally T. cruzi strain 0354-challenged and non-challenged insects. The microbiota of gut and gonad tissues was characterized using high throughput sequencing of region V3-V4 of bacterial 16S rRNA gene. The triatomine microbiota had a low intra-individual diversity, and a high inter-individual variation within the same host species. Arsenophonous appeared as the dominant triatomine bacterial symbiont in our study (59% of the total 16S coverage), but there were significant differences in the distribution of bacterial genera among vectors. In Rhodnius prolixus the dominant symbiont was Pectobacterium.Conclusions Trypanosoma cruzi-challenge significantly affects microbiota composition, with challenged vectors harbouring a significantly more diverse bacterial community, both in the gut and the gonads. Our results show that blood-feeding with T. cruzi epimastigotes strongly affects microbiota composition in a species-specific manner. We suggest that triatomine-adapted enterobacteria such as Arsenophonus could be used as stable vectors for genetic transformation of triatomine bugs and control of Chagas disease.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1926-2) contains supplementary material, which is available to authorized users.

Screening of Fungi for Biological Control of a Triatomine Vector of Chagas Disease: Temperature and Trypanosome Infection as Factors.

Entomopathogenic fungi have been investigated as an alternative tool for controlling various insects, including triatomine vectors of the protozoan Trypanosoma cruzi, the etiological agent of Chagas disease. Here we tested the pathogenicity and virulence of ten isolates of the fungi Metarhizium spp. and Beauveria bassiana against Rhodnius prolixus and found all of the isolates to be virulent. We used two isolates (URPE-11 Metarhizium anisopliae and ENT-1 Beauveria bassiana) for further screening based on their prolific sporulation in vitro (an important property of fungal biopesticides). We characterized their virulences in a dose-response experiment and then examined virulence across a range of temperatures (21, 23, 27 and 30°C). We found isolate ENT-1 to maintain higher levels of virulence over these temperatures than URPE-11. We therefore used B. bassiana ENT-1 in the final experiment in which we examined the survival of insects parasitized with T. cruzi and then infected with this fungus (once again over a range of temperatures). Contrary to our expectations, the survival of insects challenged with the pathogenic fungus was greater when they had previously been infected with the parasite T. cruzi than when they had not (independent of temperature). We discuss these results in terms of aspects of the biologies of the three organisms. In practical terms, we concluded that, while we have fungal isolates of potential interest for development as biopesticides against R. prolixus, we have identified what could be a critical problem for this biological tool: the parasite T. cruzi appears to confer a measure of resistance to the insect against the potential biopesticide agent so use of this fungus as a biopesticide could lead to selection for vector competence.

Feeding profile of Mepraia spinolai, a sylvatic vector of Chagas disease in Chile

American trypanosomiasis is a chronic disease transmitted mainly by vectors. The hematophagous triatomine vectors transmit Trypanosoma cruzi to a wide variety of mammals, which usually are their food source. This study determined the feeding profile of Mepraia spinolai, a sylvatic triatomine vector, present in endemic areas of Chile. Vectors were captured in the north-central area of Chile. Samples of intestinal contents were analyzed by an Enzyme-linked immunosorbent assay (ELISA) that identifies and discriminates the presence of serum antigens from Homo sapiens and nine animal species (Canis familiaris, Felis catus, Capra hircus, Mus musculus, Gallus gallus, Octodon degus, Thylamys elegans, Phyllotis darwini and Oryctolagus cuniculus). Our data indicate the most frequent feeding source in this area was P. darwini, followed by O. degus, O. cuniculus, M. musculus, G. gallus, T. elegans, C. familiaris, F. catus and C. hircus. Mixed food sources were also identified.

What is the 'true' effect of Trypanosoma rangeli on its triatomine bug vector?

The phrase, "T. rangeli is pathogenic to its insect vector," is commonly found in peer-reviewed publications on the matter, such that it has become the orthodox view of this interaction. In a literature survey, we identified over 20 papers with almost the exact phrase and several others alluding to it. The idea is of particular importance in triatomine population dynamics and the study of vector-borne T. cruzi transmission, as it could mean that triatomines infected with T. rangeli have lower fitness than uninfected insects. Trypanosoma rangeli pathogenicity was first observed in a series of studies carried out over fifty years ago using the triatomine species Rhodnius prolixus. However, there are few studies of the effect of T. rangeli on its other vector species, and several of the studies were carried out with R. prolixus under non-physiological conditions. Here, we re-evaluate the published studies that led to the conclusion that T. rangeli is pathogenic to its vector, to determine whether or not this indeed is the "true" effect of T. rangeli on its triatomine vector.