Chagas' disease, a neglected tropical illness for which current therapy is unsatisfactory, is caused by the intracellular parasite Trypanosoma cruzi. The goal of this work is to investigate the in vitro and in vivo effects of the arylimidamide (AIA) DB766 against T. cruzi. This arylimidamide exhibits strong trypanocidal activity and excellent selectivity for bloodstream trypomastigotes and intracellular amastigotes (Y strain), giving IC 50 s (drug concentrations that reduce 50% of the number of the treated parasites) of 60 and 25 nM, respectively. DB766 also exerts striking effects upon different parasite stocks, including those naturally resistant to benznidazole, and displays higher activity in vitro than the reference drugs. By fluorescent and transmission electron microscopy analyses, we found that this AIA localizes in DNA-enriched compartments and induces considerable damage to the mitochondria. DB766 effectively reduces the parasite load in the blood and cardiac tissue and presents efficacy similar to that of benznidazole in mouse models of T. cruzi infection employing the Y and Colombian strains, using oral and intraperitoneal doses of up to 100 mg/kg/day that were given after the establishment of parasite infection. This AIA ameliorates electrocardiographic alterations, reduces hepatic and heart lesions induced by the infection, and provides 90 to 100% protection against mortality, which is similar to that provided by benznidazole. Our data clearly show the trypanocidal efficacy of DB766, suggesting that this AIA may represent a new lead compound candidate to Chagas' disease treatment.

BackgroundChagas disease is caused by Trypanosoma cruzi, which is transmitted by triatomine vectors. The northeastern region of Brazil is endemic for Chagas disease and has the largest diversity of triatomine species. T. cruzi development in its triatomine vector depends on diverse factors, including the composition of bacterial gut microbiota.MethodsWe characterized the triatomines captured in the municipality of Russas (Ceará) by sequencing the cytochrome c oxidase subunit I (COI) gene. The composition of the bacterial community in the gut of peridomestic Triatoma brasiliensis and Triatoma pseudomaculata was investigated using culture independent methods based on the amplification of the 16S rRNA gene by polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE), DNA fragment cloning, Sanger sequencing and 454 pyrosequencing. Additionally, we identified TcI and TcII types of T. cruzi by sequencing amplicons from the gut metagenomic DNA with primers for the mini-exon gene.ResultsTriatomines collected in the peridomestic ecotopes were diagnosed as T. pseudomaculata and T. brasiliensis by comparing their COI sequence with GenBank. The rate of infection by T. cruzi in adult triatomines reached 80% for T. pseudomaculata and 90% for T. brasiliensis. According to the DNA sequences from the DGGE bands, the triatomine gut microbiota was primarily composed of Proteobacteria and Actinobacteria. However, Firmicutes and Bacteroidetes were also detected, although in much lower proportions. Serratia was the main genus, as it was encountered in all samples analyzed by DGGE and 454 pyrosequencing. Members of Corynebacterinae, a suborder of the Actinomycetales, formed the next most important group. The cloning and sequencing of full-length 16S rRNA genes confirmed the presence of Serratia marcescens, Dietzia sp., Gordonia terrae, Corynebacterium stationis and Corynebacterium glutamicum.ConclusionsThe study of the bacterial microbiota in the triatomine gut has gained increased attention because of the possible role it may play in the epidemiology of Chagas disease by competing with T. cruzi. Culture independent methods have shown that the bacterial composition of the microbiota in the guts of peridomestic triatomines is made up by only few bacterial species.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-015-0836-z) contains supplementary material, which is available to authorized users.

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BackgroundChagas disease is a trypanosomiasis whose agent is the protozoan parasite Trypanosoma cruzi, which is transmitted to humans by hematophagous bugs known as triatomines. Even though insecticide treatments allow effective control of these bugs in most Latin American countries where Chagas disease is endemic, the disease still affects a large proportion of the population of South America. The features of the disease in humans have been extensively studied, and the genome of the parasite has been sequenced, but no effective drug is yet available to treat Chagas disease. The digestive tract of the insect vectors in which T. cruzi develops has been much less well investigated than blood from its human hosts and constitutes a dynamic environment with very different conditions. Thus, we investigated the composition of the predominant bacterial species of the microbiota in insect vectors from Rhodnius, Triatoma, Panstrongylus and Dipetalogaster genera.Methodology/Principal FindingsMicrobiota of triatomine guts were investigated using cultivation-independent methods, i.e., phylogenetic analysis of 16s rDNA using denaturing gradient gel electrophoresis (DGGE) and cloned-based sequencing. The Chao index showed that the diversity of bacterial species in triatomine guts is low, comprising fewer than 20 predominant species, and that these species vary between insect species. The analyses showed that Serratia predominates in Rhodnius, Arsenophonus predominates in Triatoma and Panstrongylus, while Candidatus Rohrkolberia predominates in Dipetalogaster.Conclusions/SignificanceThe microbiota of triatomine guts represents one of the factors that may interfere with T. cruzi transmission and virulence in humans. The knowledge of its composition according to insect species is important for designing measures of biological control for T. cruzi. We found that the predominant species of the bacterial microbiota in triatomines form a group of low complexity whose structure differs according to the vector genus.

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BackgroundUnderstanding the drivers of habitat selection by insect disease vectors is instrumental to the design and operation of rational control-surveillance systems. One pervasive yet often overlooked drawback of vector studies is that detection failures result in some sites being misclassified as uninfested; naïve infestation indices are therefore biased, and this can confound our view of vector habitat preferences. Here, we present an initial attempt at applying methods that explicitly account for imperfect detection to investigate the ecology of Chagas disease vectors in man-made environments.MethodologyWe combined triplicate-sampling of individual ecotopes (n = 203) and site-occupancy models (SOMs) to test a suite of pre-specified hypotheses about habitat selection by Triatoma brasiliensis. SOM results were compared with those of standard generalized linear models (GLMs) that assume perfect detection even with single bug-searches.Principal Findings Triatoma brasiliensis was strongly associated with key hosts (native rodents, goats/sheep and, to a lesser extent, fowl) in peridomestic environments; ecotope structure had, in comparison, small to negligible effects, although wooden ecotopes were slightly preferred. We found evidence of dwelling-level aggregation of infestation foci; when there was one such focus, same-dwelling ecotopes, whether houses or peridomestic structures, were more likely to become infested too. GLMs yielded negatively-biased covariate effect estimates and standard errors; both were, on average, about four times smaller than those derived from SOMs.Conclusions/SignificanceOur results confirm substantial population-level ecological heterogeneity in T. brasiliensis. They also suggest that, at least in some sites, control of this species may benefit from peridomestic rodent control and changes in goat/sheep husbandry practices. Finally, our comparative analyses highlight the importance of accounting for the various sources of uncertainty inherent to vector studies, including imperfect detection. We anticipate that future research on infectious disease ecology will increasingly rely on approaches akin to those described here.

In order to assay the triatomine infestation and domiciliation in the ruralIn the state of Ceará, the presence of triatomines has been known for a long time, as Alencar (1987) has shown in a research that compiled former surveys carried throughout the state. Alencar et al. (1976) have demonstrated that vectors have not been found in only 9 out of the 141 municipal districts that comprise the geographic division of the whole state of Ceará. The authors have cited the semi-domestic Triatoma brasiliensis as being a primary transmitting species and with larger distribution in that state, found in 91.5% houses of municipal districts, many times with high Trypanosoma cruzi infection indexes. Triatoma pseudomaculata, which is believed less domestic, was found in 68.8% of the municipal districts, with an average infection index of 4.2%. In the distribution ranking, the third species in Ceará was Panstrongylus megistus, displaying a variable infection index; this species was found in 61.7% of the municipal districts. Rhodnius nasutus, with an average of 1% infection index, was found in 17.7% of the municipal districts; Panstrongylus lutzi was found in 18.4% of the municipal districts, presenting an average of 17.9% of infection indexes (Alencar et al. 1976).The objective of the present work was to determine infestation indexes, colonization, and density of triatomines in domiciliary units (DUs) that include intradomicile, peridomicile, and ecotopes found in wild habitats of the four localities that belong to the rural area of Jaguaruana municipality, Ceará, Brazil, formerly considered to be highly infested by these vectors. The indexes were determined by relating them with variables such as type of house's wall type and number of peridomiciliary annexes. The authors have also determined the indexes of natural T. cruzi infection in triatomines captured in each studied habitat and ecotopes.

Searches for Chagas disease vectors were performed at the type locality from which Triatoma sherlocki Papa et al. (Hemiptera: Reduviidae: Triatominae) was described in the municipality of Gentio do Ouro, in the state of Bahia, Brazil, and in a small artisan quarry-mining community approximately 13 km distant in a remote area of the same municipality. The latter site represents a new locality record for this species. Adults, nymphs and exuviae of T. sherlocki were found in 21% of human dwellings, indicating that the species is in the process of domiciliation. Prevalence of Trypanosoma cruzi infection in collected bugs was 10.8%. Simple predictive approaches based on environmental similarity were used to identify additional sites likely suitable for this species. The approach successfully predicted an additional five sites for the species in surrounding landscapes. Ecological and entomological indicators were combined to discuss whether this scenario likely represents an isolated case or an emerging public health problem.