Rhodnius Research Articles

Chagas Disease Vectors of Alagoas, Brazil: First Report of Panstrongylus geniculatus (Latreille, 1811) (Hemiptera, Triatominae) in the Brazilian State and Update of the Dichotomous Key Based on Cytogenetic Data.

Panstrongylus geniculatus is the most widely distributed species of Panstrongylus in Brazil and merits attention from vector control programs due to its potential for domiciliation. Specimens infected with Trypanosoma cruzi have already been reported in both peridomiciliary and domiciliary environments. Building on these findings, we report, for the first time, the presence of P. geniculatus in the state of Alagoas and provide an updated dichotomous key (based on cytogenetic data) for species in Alagoas. Panstrongylus geniculatus has been identified in Boca da Mata, Joaquim Gomes, and Novo Lino. In light of the recent notification of Rhodnius domesticus and this record of P. geniculatus, we present an updated identification key enabling the differentiation of all species in Alagoas. Emphasis is placed on the importance of correctly identifying triatomine species because it is crucial for the development of effective control measures, thereby aiding in the mitigation of Chagas disease.

Taxonomic reassessment of Rhodnius zeledoni Jurberg, Rocha & Galvão: a morphological and morphometric analysis comparing its taxonomic relationship with Rhodnius domesticus Neiva & Pinto

BackgroundRhodnius zeledoni was described from a single specimen. Since its description, doubts have arisen regarding the taxonomic status of this species in relation to Rhodnius domesticus.MethodsThe present study reviewed and compared R. zeledoni with R. domesticus based on morphological analysis and head geometric morphometrics.ResultsOur analysis revealed the absence of distinctive diagnostic characters between the two species at specific levels. Rhodnius zeledoni and R. domesticus show morphological and morphometric similarity, with only minor differences in coloration observed between them. Contrary to previous statements, our analysis showed that R. zeledoni and R. paraensis are not closely related species, not corroborating previous studies with such an assumption.ConclusionsTherefore, we formally propose R. zeledoni as a junior synonym of R. domesticus.

Climate and Environmental Changes and Their Potential Effects on the Dynamics of Chagas Disease: Hybridization in Rhodniini (Hemiptera, Triatominae).

Chagas disease affects about eight million people. In view of the issues related to the influence of anthropogenic changes in the dynamics of the distribution and reproductive interaction of triatomines, we performed experimental crosses between species of the Rhodniini tribe in order to evaluate interspecific reproductive interactions and hybrid production capacity. Reciprocal crossing experiments were conducted among Rhodnius brethesi × R. pictipes, R. colombiensis × R. ecuadoriensis, R. neivai × R. prolixus, R. robustus × R. prolixus, R. montenegrensis × R. marabaensis; R. montenegrensis × R. robustus, R. prolixus × R. nasutus and R. neglectus × R. milesi. With the exception of crosses between R. pictipes ♀ × R. brethesi ♂, R. ecuadoriensis ♀ × R. colombiensis ♂ and R. prolixus ♀ × R. neivai ♂, all experimental crosses resulted in hybrids. Our results demonstrate that both allopatric and sympatric species produce hybrids, which can generate concern for public health agencies in the face of current anthropogenic events. Thus, we demonstrate that species of the Rhodniini tribe are capable of producing hybrids under laboratory conditions. These results are of great epidemiological importance and raise an important discussion about the influence of climatic and environmental interactions on Chagas disease dynamics.

Distribuição espacial de triatomíneos no município de Santana do Ipanema, Alagoas, Brasil: um estudo descritivo transversal

American trypanosomiasis, known as Chagas disease, is a potentially fatal disease caused by the unicellular flagellated protozoan Trypanosoma cruzi, and its intermediate host is the hematophagous insect named the triatomine. In Brazil, 10 genera of triatomines are of epidemiological importance for the disease. Because of the preventive measures and epidemiological monitoring, this study aimed to verify the triatomine species in the municipality of Santana do Ipanema, belonging to the state of Alagoas, since there is no data in the literature with such information. For this, a cross-sectional descriptive study was conducted with data from the secretariat of the municipality of Santana do Ipanema to verify the species of captured and positive triatomines, between the years 2016 and 2020. During the study period, a total of 405 triatomines collected in the municipality were recorded, and three species were identified. It was observed that most of the collections occurred in the rural area of the municipality with almost 15 times more collections than in the urban area; however, the highest rate of positivity occurred in the urban area. The most common triatomine found in the municipality studied was Rhodnius domesticus, while Triatoma brasiliensis obtained more positive specimens. Although there are no confirmed cases of Chagas disease in the population of Santana do Ipanema, it was found that there is the presence of vectors that transmit Chagas disease and positive vectors for Trypanosoma cruzi. Therefore, our study suggests that entomological surveillance should be more present and continuous in both areas of the municipality for the effective control of Chagas disease

Historical Biogeography and the Evolution of Hematophagy in Rhodniini (Heteroptera: Reduviidae: Triatominae)

The Rhodniini tribe is one of the five tribes in the subfamily Triatominae and is notorious for its domestic blood-sucking pests and vectors ofTrypanosoma cruziacross Latin America. The human and economic costs of the Chagas disease in the American tropics are considerable, and these insects are of unquestionable importance to humans. We used mitochondrial rDNA (16S), nuclear ribosomal RNA (28S) and wingless (Wg) sequences to perform phylogenetic analysis to derive trees based on parsimony and maximum likelihood. Nucleotide sequences were used in molecular-clock analyses to estimate time divergence between species of Rhodniini. The potential distribution of each species was modeled and compared with Kappa statistic. Multivariate niches with bioclimatic variables were used to describe differences between the species using discriminant analysis. The results of this study indicate that the Rhodniini originated 17.91 Mya ago.Rhodnius domesticusis the oldest species having its origin at 9.13 Mya. Rhodniini are closely related to Salyavatinae that are specialist termite predators and diverged from this subfamily 30.43 Mya. Most species are clearly allopatric and have distinct bioclimatic niches. The colonization of bromeliads, palms trees and bird nests represent important events for the speciation of these taxa. The hematophagous habit can be described as a scenario where Rhodniini’s ancestor could be pre-adapted for the invasion of bromeliads, palm trees, and bird nests where they would find significant water availability and thermal damping. These environments are widely used by vertebrate inquilines that would be the source of food for the species of Rhodniini. Lastly, our results show an alternative position ofPsammolestesin the phylogenetic tree.

Comparative dissection of the peripheral olfactory system of the Chagas disease vectors Rhodnius prolixus and Rhodnius brethesi.

American trypanosomiasis, or Chagas disease, is transmitted by both domestic and sylvatic species of Triatominae which use sensory cues to locate their vertebrate hosts. Among them, odorants have been shown to play a key role. Previous work revealed morphological differences in the sensory apparatus of different species of Triatomines, but to date a comparative functional study of the olfactory system is lacking. After examining the antennal sensilla with scanning electronic microscopy (SEM), we compared olfactory responses of Rhodnius prolixus and the sylvatic Rhodnius brethesi using an electrophysiological approach. In electroantennogram (EAG) recordings, we first showed that the antenna of R. prolixus is highly responsive to carboxylic acids, compounds found in their habitat and the headspace of their vertebrate hosts. We then compared responses from olfactory sensory neurons (OSNs) housed in the grooved peg sensilla of both species, as these are tuned to these compounds using single-sensillum recordings (SSRs). In R. prolixus, the SSR responses revealed a narrower tuning breath than its sylvatic sibling, with the latter showing responses to a broader range of chemical classes. Additionally, we observed significant differences between these two species in their response to particular volatiles, such as amyl acetate and butyryl chloride. In summary, the closely related, but ecologically differentiated R. prolixus and R. brethesi display distinct differences in their olfactory functions. Considering the ongoing rapid destruction of the natural habitat of sylvatic species and the likely shift towards environments shaped by humans, we expect that our results will contribute to the design of efficient vector control strategies in the future.

Revisiting the Chromosomal Diversification of the Genus Rhodnius (Stål, 1859) (Hemiptera, Triatominae).

Although all triatomines are considered as potential vectors of the Chagas disease, the Triatoma, Panstrongylus, and Rhodnius genera are the most important from the epidemiological point of view. Based on cytogenetic analyzes carried out so far (C banding and FISH), the species of the genus Rhodnius show little interspecific chromosomal variation. Thus, we analyzed the distribution of AT- and CG-rich DNA in the chromatin and chromosomes of the genus Rhodnius and discuss the chromosome evolution of these vectors. Except for Rhodnius domesticus, Rhodnius nasutus, Rhodnius pictipes, Rhodnius colombiensis, and Rhodnius pallescens, all Rhodnius species have euchromatic autosomes with the absence of AT- and CG-rich blocks. Curiously, the same species that have heterochromatin blocks in the autosomes also have chromomycin A3 (CMA3 +) blocks dispersed in the prophasic nucleus (demonstrating that the heterochromatin of these species is rich in CG). Thus, we characterize the AT- and CG-rich DNA pattern for the genus Rhodnius, and we suggest that the pattern of CG-rich heterochromatin in the autosomes of these vectors evolved independently in pallescens, pictipes, and prolixus groups.

The rediscovery of Rhodnius domesticus Neiva & Pinto, 1923 (Hemiptera: Reduviidae: Triatominae) in the state of Espírito Santo, Brazil.

INTRODUCTION: Rhodnius domesticus Neiva & Pinto, 1923 is a rare sylvatic triatomine endemic to the Atlantic Forest, with one known record for Espírito Santo (ES), Brazil from 1969. We present here its rediscovery in ES, 42 years after its first record. METHODS: In January 2011, a triatomine specimen was collected from a rural area of the municipality of Santa Teresa, ES. RESULTS: We confirmed this as a new record of R. domesticus in the Baixo Caldeirão locality.CONCLUSIONS: This finding supports the possibility of a wild population of R. domesticus in the mountainous region of the Atlantic forest of ES.

Triatomine bugs (Hemiptera, Reduviidae, Triatominae) in the Domiciles of the Guaribas Valley Territory, in Northeastern Brazil.

INTRODUCTION Triatomine bugs are hematophagous insects that are extremely important in public health because they are natural vectors of Trypanosoma cruzi, the causative agent of Chagas disease. In this study, we aimed to assess the occurrence of triatomine species and the natural T. cruzi infection in the Guaribas Valley territory, an endemic region for Chagas disease in northeastern Brazil. METHODS Insects were actively captured from July 2017 to October 2019 in the intra- and peridomiciles of 16 municipalities of the Guaribas Valley territory, in the southeast area of Piauí state. Triatomine species were identified following a taxonomic key, and natural infection was investigated through insects’ fresh feces exams. RESULTS A total of 430 triatomines were collected, including 211 nymphs and 219 adults. Of all collected specimens, 39 (9.1%) were from the intradomiciles and 391 (90.9%) from peridomiciles. Nine species, including two subspecies, could be identified: Triatoma brasiliensis brasiliensis, T. brasiliensis macromelasoma, T. pseudomaculata, T. sordida, T. juazeirensis, T. melanocephala, Panstrongylus lutzi, Rhodnius domesticus, R. nasutus, and R. robustus. T. brasiliensis were the most frequently collected bugs, representing 72% of all the identified insects. None of the examined invertebrates presented flagellate forms of T. cruzi. CONCLUSIONS: This is the first report of T. b. macromelasoma and T. juazeirensis in the Guaribas Valley territory. The persistence of triatomine species in the domiciles in an endemic area for Chagas disease emphasizes the relevance of entomological surveillance and vector control measures in the studied area.

Surveillance of seroepidemiology and morbidity of Chagas disease in the Negro River, Brazilian Amazon.

BACKGROUNDChagas disease in the Brazilian Amazon Region was previously regarded as an enzootic disease of wild animals. More recently, in situations where humans have penetrated the wild ecotope or where triatomines and/or wild animals (marsupials) have invaded human homes resulting in disease transmission, Chagas disease has come to be regarded as an anthropozoonosis. We found that the highest incidence of infection due to Trypanosoma cruzi and Chagas disease occurred among piassaba fibre gatherers and their families.OBJECTIVESConsidering the results of previous surveys, we conducted a new survey of piassaba gatherers and their families in the creeks of the Aracá, Curuduri, Demini, Ererê and Padauiri rivers, which are tributaries on the left bank of the Negro River, in the municipality of Barcelos; Barcelos-Caurés highway; Negro River in Santa Isabel of the Negro River; and Marié River, on the right bank of the Negro River.METHODSA questionnaire was applied to 482 piassaba gatherers and their families who accompanied them. We collected 5-mL blood samples (with permission from each subject), separated the serum, and performed serological tests using indirect immunofluorescence and conventional and recombinant enzyme-linked immunosorbent assays (ELISA). We performed brief clinical examination and electrocardiograms. Only 273 subjects attended our field base for detailed clinical examination and electrocardiogram.FINDINGS AND MAIN CONCLUSIONSThe questionnaire revealed that 100% of the 482 patients recognised the triatomine Rhodnius brethesi, which they had seen in the piassaba plantation and 81% in their field huts. A total of 79% of subjects had previously been bitten by this vector and 21% did not know. The 25 subjects seropositive for T. cruzi infection (5.2%) stated that they had been bitten more than 10 times by this insect. Of the 273 subjects who underwent electrocardiogram, 22% showed conditions that were possibly attributable to Chagas disease or other cardiovascular disease.

Sobre la biología del Telenomus fariai Lima, 1927 (Hymenoptera: Scelionidae), parásito endófago de huevos de algunos Triatominae

A study is presented of the,outstanding aspects of the biology of Central American Telenomus fariai, an endophagolis parasite on eggs or certain Tria­tominae, found on eggs of Triatoma phyllosoma in the laboratory by Dr. Luis M, Penalver of El Salvador. The little wasp was found capable of parasitizing under experimental conditions eggs of T. dimidiata of Costa Rica, of T. phyllosoma of Mexico, of Panstrongylus chinai of Ecuador, and of P. megistus of Brasil. It proved unable to attack eggs of T. infestans of Chile, of Rhodnius prolixus of El Salvador, and of R. pallescens of Panama. The fact that it does not attack eggs of T. infestans is the only difference observed from Telenomus fariai described in Brazil by Costa Lima, other than an apparently inferior capacity for laying and shorter mean duration of life. Infestation may or may not follow the attack on eggs of hemipterae in advanced stages of development; in the negative case, death results occasionally from mechanical injury. Several counts were made of the little wasps developing within the eggs of T. phyllosoma, T. dimidiata, and P. chinai, noting the total number of insects, the number of each sex and the mean number of wasps per egg. The relation­ ship of the latter figures with the size of the host eggs was investigated, and a close relationship was found between the two values: each Telenomus requires from 0.00019 to 0.00025 gm. and from 0.178 to 0.193 mm3. With a variable temperature incubator the influence of temperature on development of Telenomus was demonstrated. At 30° C. complete development was obtained in 19 days on P. chinai and in 20 days in T. phyllosoma. At room temperature development was completed in from 32 to 42 days. Host eggs were dissected just before the parasites left them and groups of females were separated after periods of various length. It was shown that females separated after up to 1 hr. of initial contact with the male gave parth­ enogenetic progeny; fertilization, therefore, occurs after that periodo Measurements were made on females and on both types of males of Telenomus; parthenogenetic males were found to be larger than normal males, and females to be larger than either. Remarks are made on the possibility of biological control of vectors of Chagas disease.

Miocarditis chagásica aguda mortal

1) A fatal case is reported of acute Chagas miocarditis a 17-year-old male, a resident of a suburb of San Jose CR. 2) The etiological diagnosis was not made i n the clinic, nor at the macroscopic autopsy. 3) The principal clinical facts were: an indefinite infectious state of a month's duration, which in the last week changed to a picture of violent cardiac insufficiency, with global cardiomegaly and gallop rhythm, without any sign of valvular disease. The hemogram showed lymphomonocytosis 40%. 4) The anatomopathologic findings included: signs of chronic pulmonary and abdominal visceral stasis; moderate cardiomegaly (360 gr.), parietal throm­bosis in the left ventricle, miocardial flaccidity with dilatation of all the cavities. Acute intense miocarditis; reticular hyperplasia in Peyer's patches, mesenteric ganglia and spleen. 5) Epidemiologic investigation showed 32 out of 116 dwellings of the neigh­borhood where the patient lived, to be infested by triatomids, 30% of which were infested with Trypanosoma cruzi. 6) Domestic carriers of T. cruzi so far reported from Costa Rica are and Rhodnius prolixus. Triatoma dimidiata 7) Up to April 1954, 20 cases have been reported from Costa Rica of Chagas disease, 3 of which have be en fatal.

Relaciones huésped-parásito en Tripanosomiasis Rangeli I. Infección intestinal y hemolinfática comparativa de Rhodnius prolixus y Triatoma infestans

In this initial contribution on host-parasite relationships in Rangeli Trypanosomiasis, the results on the infection of 837 nymphs of Rhodnius prolixus and 827 of Triatoma infestans , by artificial xenodiagnosis, with two different strains of T. rangeli , are discussed. The insects were divided in groups in different experiments and in sorne cases the feces were examined and in others only the hemolymph. R. prolixus gave higher rates of infection, by feces exam· ination, than T. infestans at 15 and 30 days. The Venezuelan strain produced higher rates than the Costa Rican strain in both species. The rates in the two species were even higher when the insects were examined by dissecting the intostine, due to the lack of colonization of the flagellates in the rectum: With the Venezuelan strain T. infestans tended to lose the infection, and the same was true for both species with the Costa Rican strain. In the groups where hemolymph was examined for up to two months, it was shown that the haemocoele is more commonly invaded in Rhodnius, and at a higher rate with Venezuelan strain. With this strain a few T. infestans gave light infections with only a few flagellates present, and the Costa Rican strain gave not a single infection in this species. There was no correlation between the feces and hemolymph since it was possible to find insects positive in the latter and negative in the former or viceversa. The implications of the results as far as the experimental conditions used, the life cycle in the invertebrate, and the influence of the insect and different strains of the flagellate are discussed.

Phenotypic Variability of the Amazonian Species Rhodnius brethesi (Hemiptera: Reduviidae).

The wild species Rhodnius brethesi (Matta, 1919) (Hemiptera: Reduviidae) is found in areas of piassabais in microregion of Rio Negro, Amazonas, Brazil. Its geographical distribution overlaps the areas of Leopoldinia piassaba palm. In areas where palm trees are found, transmission cycle of Trypanosoma cruzi is related to the extractive activity of the palm fiber, exposing workers to wild vector transmission of this parasite. The close association with the palm tree L. piassaba suggests that this wild triatomine has special features in its sensory system allowing specificity of ecotope. The objective of the study is to identify the antennal sensilla phenotype and morphologically characterize the size and shape of the wings of wild R. brethesi, and to compare with the phenotype present in individuals reared in the laboratory. From the samples taken in the field, the presence of the species R. brethesi was found on both banks of the Rio Negro. The techniques used to verify the morphological patterns are important resources for observations of the triatomine populations, be they in an artificial or natural habitat.

Fecundación de una hembra de Rhodnius prolixus Stal, 1852, por dos machos

Homozygous red-eyed (recessive) females of Rhodnius prolixus (R.O.R. strain) were mated with homozygous red-eyed males, and later with homozygous black-eyed males. The offspring showed that sperm fmm both males is mixed in the female, that the eggs were fertilized by sperm from either male, and that sperm from both males was still capable of fertilizing eight weeks after copulation. These experiments point to serious obstacles to attempts to eradicate Rhodnius prolixus by the release in the natural habitat of males sterilized by radiation.

Triatoma dimidiata capitata, a natural vector of Trypanosoma rangeli in Colombia.

Triatoma dimidiata capilata were abundant in houses of the village San Joaquin (Dept. Santander), Colombia. Five of these triatomids presented salivary gland infestation with Trypanosoma rangeli . Two showed hemofymph infection and 8 showed intestinal infection with crithidiae of T. rangeli . Mice bitten by naturally infected triatomids became infected with T. rangeli . The flagellates were easy to cultivate in diphasic blood agar media, and able to produce salivary gland infection in Rhodnius prolixtus . An U.S. citizen frequently bitten by the triatomids in San Joaquin presented infection with T. rangeli .

Presence of Trypanosoma rangeli Tejera, 1920, in Peru. I. The insect vector Rhodnius ecuadoriensis Lent & León, 1958

Results of studies to determine the geographic distribution of Rhodnius ecuadoriensis in the northern part of Peru revealed the presence of the insect in a single locality in each oE the Amazonian and the Pacific watersheds. Xerophitic vegetation is eharacteristic in these areas. All the different stages of the insect were found in human dwellings. In addition, eggs and nymphal instars were al so obtained in tree trunks and a pen where guineapigs were confined. This would indicate a versatile habit of the inseet which provides the opportunity to feed upon a wide variety of hosts under various environmental conditions. A very low infestation was observed during 1963-64. However, particular houses showed indications of possible higher infestations in previous years. Possible reasons for this phenomenon are discussed.

Hematophagous insects as vectors for frog trypanosomes.

Experimental infections of three hematophagous arthropods (Rhodnius prolixus, Aedes aegypti, and Culex pipiens) with a trypanosome of the Trypanosoma rotatorium complex found in the frogs Hyla crepitans and Leptodactylus insularum revealed that A. aegypti is a good host for the flagellate; the course of development in the intestinal tract of the mosquito is described from 15 minutes to 168 hours. C. pipiens showed only low intestinal infections and R. prolixus did not permit development of the parasite. It is postulated that, in addition to the transmission of T. rotatorium by leeches, batrachophilic mosquitoes may transmit the parasite to frogs of more terrestrial habits by being ingested by these anurans.

PRIMEIRO ENCONTRO DE RHODNIUS DOMESTICUS NEIVA & PINTO, 1923 (HEMIPTERA: REDUVIDAE) NO MUNICÍPIO DE AÇUCENA, MINAS GERAIS, BRASIL

Triatomineos are vector insects from Tripanosoma cruzi, the main insect in causing Chagas’s Disease. In August 2013, professional from the Regional Health Superintendence of Coronel Fabriciano, Minas Gerais, registered the arrival of a Triatomine female identified as Rhodnius prolixus. The insect originated from a domestic residence of the people from Caeté, Açucena municipality. In order to confirm its identity, the insect was sent to the Research Center René Rachou (CPqRR/FIOCRUZ). In the identification of the triatominae, they used taxonomic keys and external morphology of the female genitals, allowing the insect to be identified as Rhodnius domesticus. The differentiating features in relation to other species were: the size of 15.5 mm, the brownish-yellow colour with chestnut brown in parts, absence of the spotted or speckled aspect, short head and non-curled feet. As well as this, the female genitals, in dorsal view, presented a moon shaped line dividing the ninth and tenth segment, and in ventral perspective presented the ninth segment finishing slightly below the tenth. The sample was stored in the collection of Chagas’s disease vectors (Fiocruz- COLVEC) do CPqRR/FIOCRUZ. It was the first time that this species was earmarked in the region. It’s important that entomology vigilance service is aware of the presence of the rare triatomines and process their identification correctly. In this way, entomologic collections and reference services have an important role, ensuring a quality service in identification.

Testicular and Color Variation in the Kissing Bug,Rhodnius brethesi, in Amazonas, Brazil

Because of the morphological and morphometric variation of testicular follicles in different genera of the subfamily Triatominae, it was of interest to associate those parameters with the different medial pronotal band patterns (wide and narrow) found in Rhodnius brethesi (Matta) (Hemiptera: Reduviidae). This is a wild species often associated with Leopoldina piassaba Wallace (Arecales: Arecaceae) palm, with a geographical distribution restricted to the Amazon region. The specimens used were from the state of Amazonas, and were kept under conditions of 29 ± 1 °C, 80 ± 5% RH, 12:12 L:D photoperiod, and were fed weekly on blood from Swiss mice. Three—day—old fasting males were separated in accordance with the patterns of the medial pronotal band, dissected, and the testicles removed. After removal of the testicular membrane, the follicles were spread, drawn by camera lucida, and measured. The results showed that the testis of R. brethesi consists of seven follicles, divided into two groups by length; two long and five short. In specimens with a wide medial pronotal band, the long follicles were 5.4 mm in length, but in specimens with a narrow medial band, the long follicles were 5.64 mm in length. The difference was significant. The short follicles were not different in length, suggesting the presence of a possible complex “brethesi” in the Amazon region.