Localization of rDNA sites in holocentric chromosomes of three species of triatomines (Heteroptera, Triatominae).

Chromatin organization in the holocentric chromosomes of three triatomines species was cytologically studied by fluorescent in situ hybridization with a 45S rDNA probe of Drosophila melanogaster to localize ribosomal genes. In Triatoma tibiamaculata, metaphases I showed telomeric highlights in a single, larger bivalent. In T. protacta, hybridization was detected in one of the telomeres of an autosomal chromosome. In T. platensis, there were highlights in a single, smaller chromosome (X chromosome). The results obtained did not agree with the expected localization of rDNA genes in the sex chromosomes of triatomines, as demonstrated by silver impregnation, and suggest that the chromosome reorganization that occurred in this group during evolution may be a more important mechanism involved in rDNA distribution.

Differential characterization of holocentric chromosomes in triatomines (Heteroptera, Triatominae) using different staining techniques and fluorescent in situ hybridization

A comparative study of holocentric chromosomes in the triatomine species Panstrongylus megistus, Rhodnius pallescens and Triatoma infestans was carried out in order to characterize heterochromatin, rDNA active sites and nucleolar proteins. Cytological preparations of seminiferous tubules were stained by silver impregnation, C banding, fluorochromes CMA 3/DA and DAPI/DA, and fluorescent in situ hybridization (FISH) with Drosophila melanogaster 28S rDNA probe. Our results showed interesting aspects of the organization of chromatin and chromosomes in the meiotic cells of these insects. In R. pallescens, sex chromosomes (X, Y) were distinct from autosomes, when submitted to silver impregnation, C banding, CMA 3 staining, and FISH, confirming that these chromosomes bear nucleolar organizer regions (NORs). In P. megistus, two of the three sex chromosomes were CMA 3/DAPI-; at early meiotic prophase and at diakinesis, silver impregnation corresponded with FISH signals, indicating that in this species, two chromosomes (probably a sex chromosome and an autosome) bear NORs. In T. infestans, silver nitrate and FISH also stained corresponding areas on meiotic chromosomes. Our data suggest that in triatomines, in general, the number and location of NORs are species-specific. These regions may be considered important chromosome markers for comparative studies to improve the understanding of evolutionary mechanisms in these hematophagous insects. ©FUNPEC-RP.

Analysis of spermiogenesis like a tool in the study of the triatomines of the Brasiliensis subcomplex

The specific identification and systematic of triatomines have been based fundamentally on morphological observations. These organisms are classified into complexes and specific subcomplexes, principally for morphological parameters and geographical disposition. The use of cytogenetic analyzes has been represented as a tool in systematic and taxonomy of triatomines. Thus, the present work, through the analysis of spermiogenesis, aims to characterize this stage of spermatogenesis in triatomines little studied, and especially to compare it among the species Triatoma lenti and T. sherlocki, to assist in the diagnosis of differentiation of these insects. The presence of the heteropyknotic corpuscle is shown as a diagnostic tool to differentiate T. sherlocki and T. lenti, since it is absent in T. lenti. The analysis of the spermiogenesis in T. sherlocki also allowed us to address morphological differences between elongating cells, which were relatively smaller and more filamentous when compared to T lenti. Furthermore, the flagellum was observed in all stages of cell differentiation and elongation. This structure, which helps in the locomotion of the sperm, is hardly observed in cytogenetic analysis, especially throughout spermiogenesis. Thus, although other comparative approaches should be taken, this paper allowed emphasizing the analysis of spermiogenesis as an important cytotaxonomic tool that assists in the differentiation of morphologically related species, such as T. lenti and T. sherlocki. © 2013 Académie des sciences.

Distribution of constitutive heterochromatin in two species of triatomines: Triatoma lenti Sherlock and Serafim (1967) and Triatoma sherlocki Papa, Jurberg, Carcavallo, Cerqueira & Barata (2002)

Triatoma lenti and Triatoma sherlocki are hemipterans that belong to the brasiliensis subcomplex. In triatomines, the constitutive heterochromatin pattern is species-specific and allows, in many cases, for the grouping of species. Thus, we cytogenetically analyzed T. sherlocki and T. lenti using C-banding, and we compared the results with previous ones obtained in other species of the brasiliensis subcomplex. Both species were found to have a male diploid chromosome number of 22 chromosomes (2n = 20A. +. XY) with heterochromatic blocks at one or both chromosomal ends of all autosomal pairs. During early meiotic prophase, they showed a large heteropycnotic chromocenter constituted by the association of both sex chromosomes plus two autosomal pairs and many heterochromatic blocks dispersed inside the nucleus. All of these cytogenetic characteristics are similar to those observed in other species of brasiliensis subcomplex, results which confirm the grouping of T. sherlocki and T. lenti within this subcomplex. However, we emphasize the importance of other approaches, such as molecular analysis, to confirm the placement of T. lenti within the brasiliensis subcomplex. © 2012 Elsevier B.V.

Coloration of the testicular peritoneal sheath as a synapomorphy of triatomines (Hemiptera, Reduviidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Distribution of constitutive heterochromatin in species of triatomines with fragmentation of sex chromosomes X

Cytogenetic analyses of triatomines are considered to be important taxonomic tools. Thus, we analyzed the pattern of constitutive heterochromatin in 7 species of triatomine with fragmentation of the sex chromosome X, focusing on the cytotaxonomy of these triatomines. The species analyzed included Triatoma vitticeps, Triatoma melanocephala, Triatoma tibiamaculata, Triatoma protracta, Meccus pallidipennis, Panstrongylus megistus, and Panstrongylus lignarius. The seminiferous tubules of the adult males were subjected to C-banding. P. megistus and P. lignarius showed differences in chromosome number and disposition of constitutive heterochromatin, as only P. lignarius showed C-blocks in autosomes. C-banding can differentiate these species, since one of the sex chromosome (X) is heterochromatic in T. vitticeps. T. protracta showed C-blocks in both ends of all autosomes, T. tibiamaculata showed terminal C-dots in some autosomal pairs and M. pallidipennis did not show constitutive heterochromatin in autosomes. Thus, we confirmed the heterochromatic pattern of 7 species of insects and emphasized the importance of cytogenetic techniques for C-banding for taxonomy studies of the triatomines, which are important vectors of Chagas disease.

Molecular identification of food sources in triatomines in the Brazilian northeast: roles of goats and rodents in Chagas disease epidemiology

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Using captive sentinels to collect wild triatomines in the region of Marília-SP, Brasil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Natural infection of triatomines (Hemiptera: Reduviidae) by trypanosomatids in two different environments in the municipality of Ouro Preto do Oeste, State of Rondonia, Brazil

Introduction: This study analyzed the occurrence and the contamination of triatomines by trypanosomatids in Orbignya speciosa (babassu) specimens in the State of Rondonia, Brazil, in two different environments (pasture and woods). Methods: Capture of triatomines on babassus and microscopic search for trypanosomatids in their digestive tube were carried out. Results: Four hundred ninety-four (494) specimens were captured (Rhodnius prolixus and R.robustus), of which 35.6% of the triatomines were positive for trypanosomatids. Conclusions: The high index of natural infection along with the abundance of triatomines points out to the necessity to create an epidemiological surveillance system to monitor vector-borne transmission and deepen the studies on the ecology of such vectors in the Amazon.

Natural infection of triatomines (Hemiptera: Reduviidae) by trypanosomatids in two different environments in the municipality of Ouro Preto do Oeste, State of Rondônia, Brazil

INTRODUCTION: This study analyzed the occurrence and the contamination of triatomines by trypanosomatids in Orbignya speciosa (babassu) specimens in the State of Rondônia, Brazil, in two different environments (pasture and woods). METHODS: Capture of triatomines on babassus and microscopic search for trypanosomatids in their digestive tube were carried out. RESULTS: Four hundred ninety-four (494) specimens were captured (Rhodnius prolixus and R.robustus), of which 35.6% of the triatomines were positive for trypanosomatids. CONCLUSIONS: The high index of natural infection along with the abundance of triatomines points out to the necessity to create an epidemiological surveillance system to monitor vector-borne transmission and deepen the studies on the ecology of such vectors in the Amazon.

Spatial distribution of triatomines in domiciles of an urban area of the Brazilian Southeast Region

Reports of triatomine infestation in urban areas have increased. We analysed the spatial distribution of infestation by triatomines in the urban area of Diamantina, in the state of Minas Gerais, Brazil. Triatomines were obtained by community-based entomological surveillance. Spatial patterns of infestation were analysed by Ripley’s K function and Kernel density estimator. Normalised difference vegetation index (NDVI) and land cover derived from satellite imagery were compared between infested and uninfested areas. A total of 140 adults of four species were captured (100 Triatoma vitticeps, 25 Panstrongylus geniculatus, 8 Panstrongylus megistus, and 7 Triatoma arthurneivai specimens). In total, 87.9% were captured within domiciles. Infection by trypanosomes was observed in 19.6% of 107 examined insects. The spatial distributions of T. vitticeps, P. geniculatus, T. arthurneivai, and trypanosome-positive triatomines were clustered, occurring mainly in peripheral areas. NDVI values were statistically higher in areas infested by T. vitticeps and P. geniculatus. Buildings infested by these species were located closer to open fields, whereas infestations of P. megistus and T. arthurneivai were closer to bare soil. Human occupation and modification of natural areas may be involved in triatomine invasion, exposing the population to these vectors.

Inoculation of Triatoma Virus (Dicistroviridae: Cripavirus) elicits a non-infective immune response in mice

Background: Dicistroviridae is a new family of small, non-enveloped, +ssRNA viruses pathogenic to both beneficial arthropods and insect pests. Little is known about the dicistrovirus replication mechanism or gene function, and any knowledge on these subjects comes mainly from comparisons with mammalian viruses from the Picornaviridae family. Due to its peculiar genome organization and characteristics of the per os viral transmission route, dicistroviruses make good candidates for use as biopesticides. Triatoma virus (TrV) is a pathogen of Triatoma infestans (Hemiptera: Reduviidae), one of the main vectors of the human trypanosomiasis disease called Chagas disease. TrV was postulated as a potential control agent against Chagas' vectors. Although there is no evidence that TrV nor other dicistroviruses replicate in species outside the Insecta class, the innocuousness of these viruses in humans and animals needs to be ascertained. Methods: In this study, RT-PCR and ELISA were used to detect the infectivity of this virus in Mus musculus BALB/c mice. Results: In this study we have observed that there is no significant difference in the ratio IgG2a/IgG1 in sera from animals inoculated with TrV when compared with non-inoculated animals or mice inoculated only with non-infective TrV protein capsids. Conclusions: We conclude that, under our experimental conditions, TrV is unable to replicate inmice. This study constitutes the first test to evaluate the infectivity of a dicistrovirus in a vertebrate animal model.

Molecular Techniques for Dicistrovirus Detection without RNA Extraction or Purification

Dicistroviridae is a new family of small, nonenveloped, and +ssRNA viruses pathogenic to both beneficial arthropods and insect pests as well. Triatoma virus (TrV), a dicistrovirus, is a pathogen of Triatoma infestans (Hemiptera: Reduviidae), one of the main vectors of Chagas disease. In this work, we report a single-step method to identify TrV, a dicistrovirus, isolated from fecal samples of triatomines. The identification method proved to be quite sensitive, even without the extraction and purification of RNA virus.

Seroprevalence of Triatoma virus (Dicistroviridae: Cripaviridae) antibodies in Chagas disease patients

Background: Chagas disease is caused by Trypanosoma cruzi, and humans acquire the parasite by exposure to contaminated feces from hematophagous insect vectors known as triatomines. Triatoma virus (TrV) is the sole viral pathogen of triatomines, and is transmitted among insects through the fecal-oral route and, as it happens with T. cruzi, the infected insects release the virus when defecating during or after blood uptake. Methods: In this work, we analysed the occurrence of anti-TrV antibodies in human sera from Chagas disease endemic and non-endemic countries, and developed a mathematical model to estimate the transmission probability of TrV from insects to man, which ranged between 0.00053 and 0.0015. Results: Our results confirm that people with Chagas disease living in Bolivia, Argentina and Mexico have been exposed to TrV, and that TrV is unable to replicate in human hosts. Conclusions: We presented the first experimental evidence of antibodies against TrV structural proteins in human sera.