Do the new triatomine species pose new challenges or strategies for monitoring Chagas disease? An overview from 1979-2021

The mitogenome of Triatoma brasiliensis brasiliensis (Hemiptera: Reduviidae), the main Chagas disease vector in the semi-arid region of northeastern Brazil

BACKGROUND

Triatoma brasiliensis brasiliensis is the primary vector of Chagas disease in Brazil's semi-arid regions, exhibiting adaptability to various environments, including domestic and peridomestic. Despite its significance, comprehensive genomic data for this subspecies remain limited.

METHODS

We assembled the complete mitochondrial genome of T. b. brasiliensis using a combination of Illumina and Sanger sequencing technologies, the latter being necessary to obtain the control region with eight primers designed in this study. The mitogenome was annotated to identify gene content and organization. Phylogenetic relationships were inferred using conserved blocks of 13 protein-coding genes and 22 transfer RNA genes. For this analysis, 18 representative triatomines with near-complete mitogenomes were selected, and phylogenetic reconstruction was performed using the maximum ikelihood method.

RESULTS

The complete mitogenome spans 16,575 base pairs and includes 13 protein-coding genes, 22 transfer RNA genes, and two ribosomal RNA genes, consistent with the typical structure of insect mitochondrial genomes. The control region exhibited tandem and inverted repeats arranged in blocks, as observed for other Reduviidae. Given the limited availability of mitogenomes, our phylogenetic analysis provided statistical support for T. b. brasiliensis as a sister taxon to Triatoma infestans, forming a well-supported clade that is sister to Triatoma vitticeps.

CONCLUSIONS

The availability of this mitogenome provides insights into the systematics, biology, and genomics of triatomine species while also enhancing our understanding of their evolutionary relationships. However, the limited number of available mitogenomes, particularly for South American Triatoma species, underscores the need for further sequencing efforts to improve phylogenetic resolution and support comparative genomic studies.

Hybrids versus parental species: insights from wing phenotype similarities and differences in triatomine insects

Introduction

The genus Panstrongylus is one of the most important within the subfamily Triatominae, which includes vectors of Trypanosoma cruzi, the etiological agent of Chagas disease (CD). In particular, Panstrongylus chinai and P. howardi have drawn attention for their role in disease transmission. These species exhibit notable ecological and morphological differences. Previous studies have investigated aspects such as morphometry, cytogenetics, and ecological niches, including experimental crosses between these species that resulted in viable F1 hybrids. However, no F2 generation was produced, as the eggs laid were empty and failed to hatch, limiting the study to F1 hybrids.

Methods

We analyzed wing morphometric traits (size and shape) from 262 individuals, including P. chinai, P. howardi, and their hybrids, using geometric morphometry techniques. This study aimed to build upon previous findings by analyzing the wing morphometric and environmental adaptations of P. chinai, P. howardi, and their hybrids (♀P. howardi × ♂P. chinai) to determine whether the hybrids exhibited similarities in wing size and shape, regardless of maternal or paternal phenotype.

Results

Differences in centroid size were observed between the parental species, with P. howardi having a larger size, but no significant differences were found among the hybrids. Females showed greater shape similarity between P. howardi and the ♀P. chinai × ♂P. howardi hybrids, while males showed similarity among hybrids. Discriminant analysis was more effective for distinguishing parental groups than with hybrids. The K-means algorithm successfully classified the parental species and hybrid groups, although with low assignment percentages and a different number of groups than expected.

Discussion

The smaller wing size in hybrid offspring may indicate lower fitness, potentially due to genetic effects or reduced viability. Geometric morphometry effectively distinguishes parental species from hybrids, supporting previous research in Triatominae. The study suggests that environmental and reproductive pressures may influence these species and explores the dispersive capabilities of triatomines, contributing to the understanding of hybridization processes.

One health research to mitigate health burden of American trypanosomiasis in Mexico

American trypanosomiasis (AT), or Chagas disease, is an ancient disease with an interesting history. Despite efforts to control AT, the global burden of this neglected vector-borne disease persists. More than six million people around the world are infected with Trypanosoma cruzi (T. cruzi), and about 75 million are at risk of infection in the Americas. Mexico is one of the countries most affected by AT with 4 million people at risk of infection with T. cruzi. Approximately 60 % of the accumulated confirmed cases occurred in the southeast region; however, an increase in the number of cases was observed in the northern states of the country in recent years. AT control efforts in Mexico focus on interrupting vector-borne disease transmission through integrated triatomine management and eliminating T. cruzi transmission through the congenital and blood transfusion routes. There is no specific prophylaxis beyond vector control. Research revealed the complexity of AT as a vector-borne disease system and its impact on the health of humans, domestic animals, and wildlife, which calls for comprehensive responses focused on transdisciplinary and multisectoral collaboration. One Health (OH) is an unifying approach aiming to achieve optimal health outcomes among people, animals, and their shared environment, which we suggest can be applied in collaborative research to enhance our understanding of AT as a vector-borne disease system with diverse components across epidemiological landscapes. Suggested action to implement OH research is presented herein for sustainable surveillance and control efforts to mitigate the health burden of AT that affects disproportionately poorer rural and semi-rural sectors of the population in Mexico and other Latin American countries.

Triatoma venosa and Panstrongylus geniculatus challenge the certification of interruption of vectorial Trypanosoma cruzi transmission by Rhodnius prolixus in eastern Colombia

Reactivation of Trypanosoma cruzi transmission by native vectors with different domiciliation capabilities is a major concern for Chagas disease control programs. T. cruzi transmission via intra-domestic Rhodnius prolixus was certified as interrupted by the Pan American Health Organization in Miraflores municipality (Boyacá, Colombia) in 2019. However, Triatoma venosa, a native vector infected with T. cruzi has been increasingly found inside human dwellings across rural areas. In this study, the aim was to describe the eco-epidemiological aspects of T. cruzi transmission in the rural area of Miraflores. For this, we designed a comprehensive, multi-faceted study in 6 rural villages and performed: (i) A cross-sectional serological and molecular study enrolling 155 people and 58 domestic dogs living within 80 households, (ii) a domestic entomological survey, (iii) a determination of the natural infection and blood meal source in collected triatomine bugs, and (iv) an evaluation of synanthropic mammal infection by parasitological and molecular tools. The T. cruzi seroprevalence rates in humans and dogs were 9.03% (14/155) and 22.4% (13/58), respectively. Most infected humans were adults between the ages of 55 and 85 years old. No evidence of T. cruzi DNA was found using qPCR in human blood samples, but we found high parasitemia levels in the infected dogs. In total, 38 triatomine bugs were collected inside dwellings and peridomestic areas: 68.4% (26/38) Triatoma venosa, 29% (11/38) Panstrongylus geniculatus, and 2.6% (1/38) P. rufotuberculatus. Natural infection prevalence was 88% (22/25) for T. venosa, 100% (12/12) for P. geniculatus, and 100% (1/1) P. rufotuberculatus: only TcI was found. No evidence of R. prolixus was found in the area. Two feeding sources were identified in T. venosa (humans and cats), while P. geniculatus fed on cows and bats. Lastly, seven D. marsupialis were captured in peridomestic areas, three were infected with T. cruzi (TcI). The results suggest the existence of T. cruzi transmission cycle between triatomines, dogs, and opossums representing a risk of infection for the human population in rural areas of Miraflores. Despite PAHO declaring Miraflores municipality, Colombia an area of T. cruzi transmission interruption in 2019, this study documents evidence of a secondary vector establishing in domestic settings. T. venosa entomological surveillance is warranted to evaluate prospective human transmission risk in an otherwise 'no-risk' perceived Chagas disease region.

Triatomines in the city: A study of Rhodnius neglectus in Jaboticabal, São Paulo, Brazil, and its epidemiological implications

BACKGROUND

Chagas disease, a significant global health concern rooted in social inequalities and political oversights, remains a challenging public health issue impacting millions worldwide. The increasing detection of triatomines, the vectors of Chagas disease, in urban areas complicates the situation.

METHODS

This study investigated the incidence of Rhodnius neglectus in the urban areas of Jaboticabal, São Paulo, Brazil, following several reports and previous collections of triatomines in the city. An educational approach was adopted, distributing informational materials and engaging the community through social networks to generate notifications that would enable the identification of triatomines. Specimens were collected using various methods, including passive surveillance actions, light traps, and active searches in palm trees.

RESULTS

Rhodnius neglectus was found in urban areas, invading homes in Jaboticabal, and was identified in palm trees. The educational approach led to the collection of 93 triatomines. Colonization was observed in a residence, with eggs, nymphs, and a concerning record of blood-feeding on a resident child. The houses where specimens were captured often had nearby palm trees with birds and nests, facilitating the passive transport of these insects and increasing the risk of invasion due to light attraction. No triatomines infected with Trypanosoma cruzi were identified.

CONCLUSIONS

These findings emphasize the need for preventive measures to reduce the prevalence of R. neglectus in urban environments. The data elucidate the occurrence of R. neglectus in the city of Jaboticabal, associated with its potential behavioral adaptation in urban environments, underscoring the need for innovative control strategies.

Entomological indicators and food sources of triatomines in the Brazilian semi-arid region

BACKGROUND

Triatomines are biological vectors of Trypanosoma cruzi, the etiological agent of Chagas Disease (CD) and have various mammalian hosts. This study evaluated the entomological indicators and food sources of triatomines in Petrolina in the semi-arid region of Brazil, where CD is endemic.

METHODS

Triatomines were captured indoors and outdoors through an active search and entomological indices (household and natural infections) were calculated. Parasitological analyses were performed through microscopic visualization using Giemsa-stained insect feces, and DNA sequencing was employed to identify food sources from the gut contents of 82 insects (9.05%) that were better preserved.

RESULTS

We captured triatomines (906) in peridomicile (807) and intradomicile (99): Triatoma brasiliensis (84.7%, 767 specimens), Triatoma spp. (8.2%, 74 specimens), T. pseudomaculata (6.5%, 59 specimens), Rhodnius spp. (0.4%, four specimens), R. nasutus (0.1%, one specimen), and T. sordida (0.1%, one specimen). The household infestation index is 11.8%. Thirty-five triatomines were infected (33 T. brasiliensis and two T. pseudomaculata), corresponding to a natural infection index of 3.8%. The identified food sources were human T. pseudomaculata and T. brasiliensis, dogs for T. brasiliensis and rodents (Mus musculus) for T. brasiliensis.

CONCLUSIONS

The results reinforce the need to intensify CD diagnosis, surveillance, and control actions, as an increase in entomological indices was recorded. Blood from humans and domestic and synanthropic animals was detected in the infected triatomines, suggesting a risk of CD vector transmission in Petrolina. As CD is a zoonosis, multidisciplinary and intersectoral CD surveillance must be conducted in the context of the One Health.

Comparative morphology of eggs of Rhodnius domesticus Neiva & Pinto, Rhodnius neglectus Lent and Rhodnius prolixus Stål (Hemiptera: Reduviidae: Triatominae)

Rhodnius species are potential vectors of the etiological agent of Chagas disease (CD), the protozoan Trypanosoma cruzi. CD impacts around seven million people in Latin America, resulting in approximately fourteen thousand deaths per year. Several species of Rhodnius are notable not only for their epidemiological relevance, but also for the challenging distinction between their species. Rhodnius has twenty species, each with its specific epidemiological importance. Rhodnius neglectus and Rhodnius prolixus are found with colonies in domiciliary environments. The observation of eggs in human dwellings signals the colonization process of these insects, increasing the risk of contamination of the population, since correct identification of eggs is necessary to help more effective vector control programs. Here we highlight diagnostic characters of eggs for these three species.

Presence of Triatoma breyeri (Reduviidae, Triatominae) in Bolivia

The study focuses on identifying and understanding the ecological dynamics of Triatoma breyeri in Bolivia. Morphological identification and molecular analysis using gene fragments (COI, CytB and 16S) confirms T. breyeri's presence and its relation to other species. The species has been consistently found in the Estancia-Mataral-La Palma region since 2010 but has not spread to other regions in Bolivia. The region of occurrence is a small characteristic dry inter-Andean valley. A MaxEnt model suggests part of the Bolivian Montane Dry Forest ecoregion serves as a unique habitat within its range. The infrequent presence in Bolivia and the distance from its main range in Argentina suggest recent accidental introduction, possibly through human transport. Further research is needed to comprehend its persistence in this small area of Bolivia.

The risk of vector transmission of Trypanosoma cruzi remains high in the State of Paraná

BACKGROUND

Monitoring and analysing the infection rates of the vector of Trypanosoma cruzi, that causes Chagas disease, helps assess the risk of transmission.

OBJECTIVES

A study was carried out on triatomine in the State of Paraná, Brazil, between 2012 and 2021 and a comparison was made with a previous study. This was done to assess the risk of disease transmission.

METHODS

Ecological niche models based on climate and landscape variables were developed to predict habitat suitability for the vectors as a proxy for risk of occurrence.

FINDINGS

A total of 1,750 specimens of triatomines were recorded, of which six species were identified. The overall infection rate was 22.7%. The areas with the highest risk transmission of T. cruzi are consistent with previous predictions in municipalities. New data shows that climate models are more accurate than landscape models. This is likely because climate suitability was higher in the previous period.

MAIN CONCLUSION

Regardless of uneven sampling and potential biases, risk remains high due to the wide presence of infected vectors and high environmental suitability for vector species throughout the state and, therefore, improvements in public policies aimed at wide dissemination of knowledge about the disease are recommended to ensure the State remains free of Chagas disease.

Vector species richness predicts local mortality rates from Chagas disease

Vector species richness may drive the prevalence of vector-borne diseases by influencing pathogen transmission rates. The dilution effect hypothesis predicts that higher biodiversity reduces disease prevalence, but with inconclusive evidence. In contrast, the amplification effect hypothesis suggests that higher vector diversity may result in greater disease transmission by increasing and diversifying the transmission pathways. The relationship between vector diversity and pathogen transmission remains unclear and requires further study. Chagas disease is a vector-borne disease most prevalent in Brazil and transmitted by multiple species of insect vectors of the subfamily Triatominae, yet the drivers of spatial variation in its impact on human populations remain unresolved. We tested whether triatomine species richness, latitude, bioclimatic variables, human host population density, and socioeconomic variables predict Chagas disease mortality rates across over 5000 spatial grid cells covering all of Brazil. Results show that species richness of triatomine vectors is a good predictor of mortality rates caused by Chagas disease, which supports the amplification effect hypothesis. Vector richness and the impact of Chagas disease may also be driven by latitudinal components of climate and human socioeconomic factors. We provide evidence that vector diversity is a strong predictor of disease prevalence and give support to the amplification effect hypothesis.

Transmission ecology of Trypanosoma cruzi by Rhodnius prolixus (Reduviidae: Triatominae) infesting palm-tree species in the Colombian Orinoco, indicates risks to human populations

BACKGROUND

Chagas disease, affecting approximately eight million individuals in tropical regions, is primarily transmitted by vectors. Rhodnius prolixus, a triatomine vector, commonly inhabits in ecotopes with diverse palm tree species, creating optimal conditions for vector proliferation. This study aims to explore the transmission ecology of Trypanosoma cruzi, the causative parasite of Chagas disease, by investigating the feeding patterns and natural infection rates of R. prolixus specimens collected from various wild palm species in the Colombian Orinoco region.

MATERIALS AND METHODS

To achieve this objective, we sampled 35 individuals from three palm species (Attalea butyracea, Acrocomia aculeata, and Mauritia flexuosa) in a riparian forest in the Casanare department of eastern Colombia, totaling 105 sampled palm trees. DNA was extracted and analyzed from 115 R. prolixus specimens at different developmental stages using quantitative PCR (qPCR) for T. cruzi detection and identification of discrete typing units. Feeding preferences were determined by sequencing the 12S rRNA gene amplicon through next-generation sequencing.

RESULTS

A total of 676 R. prolixus specimens were collected from the sampled palms. The study revealed variation in population densities and developmental stages of R. prolixus among palm tree species, with higher densities observed in A. butyracea and lower densities in M. flexuosa. TcI was the exclusive T. cruzi discrete typing unit (DTU) found, with infection frequency positively correlated with R. prolixus abundance. Insects captured in A. butyracea exhibited higher abundance and infection rates than those from other palm species. The feeding sources comprised 13 mammal species, showing no significant differences between palm species in terms of blood sources. However, Didelphis marsupialis and Homo sapiens were present in all examined R. prolixus, and Dasypus novemcinctus was found in 89.47% of the insects.

CONCLUSION

This study highlights the significance of wild palms, particularly A. butyracea, as a substantial risk factor for T. cruzi transmission to humans in these environments. High population densities and infection rates of R. prolixus were observed in each examined palm tree species.

Experimental Hybrids of the Triatoma brasiliensis Species Complex Show Higher Susceptibility to the Trypanosoma cruzi Infection Than Their Parentals

The Triatoma brasiliensis species complex is a monophyletic group encompassing two subspecies and six species. Recently, a hybrid zone of members of this complex was recorded in the state of Pernambuco. Questions concerning the capability of the hybrids to become infected with Trypanosoma cruzi have been raised. This study aimed to compare the susceptibility of Triatoma b. brasiliensis, Triatoma juazeirensis, and their experimental hybrids to infection with T. cruzi. We infected the parentals and their experimental hybrids (obtained through reciprocal crosses) through artificial feeding with citrated rabbit blood, to which the TcI 0354 strain of T. cruzi had been added. The insects were weighed before and after feeding on the rabbit blood, and then they were dissected on the 10th, 20th, and 30th day after infection. Both the hybrids and the parentals remained infected throughout the experiment. The parasite was mostly found in the epimastigote form. The number of epimastigotes was significantly lower in the stomach and small intestine of T. juazeirensis than in the hybrids or in T. b. brasiliensis. A significantly higher percentage of metacyclic trypomastigotes was detected in the small intestine and rectum of the hybrids. Hybrids demonstrated higher susceptibility to the TcI 0354 strain than their parentals, opening up new avenues to be investigated.

Wild mammals involved in the transmission of Trypanosoma cruzi and food sources of Triatoma sherlocki in an endemic region of northeastern Brazil

The present study, carried out in the municipality of Gentio do Ouro, Bahia, Brazil aimed to evaluate which wild mammals may be involved in the transmission of T. cruzi and which are the blood sources for triatomines collected in the study area. PCR analysis of 31 wild mammals captured revealed T. cruzi infection in 6.4% (2/31): one specimen of the opossum Didelphis albiventris (1/3) and one of the rodent Kerodon rupestris (1/5); despite being more frequent in the area, no specimen of the rodent Thrichomys sp. (0/23) was infected. A total of 169 triatomines were captured. The conclusive detection of food sources was possible only for Triatoma sherlocki Papa et al., 2002 (n = 56), with evidence for: K. rupestris (35.7%), Gallus (17.9%), D. albiventris (14.3%), Homo sapiens (14.3%), Tropidurus hispidus (7.1%), Leopardus geoffroyi (5.3%), Conepatus semistriatus (1.8%), Thrichomys inermis (1.8%) and Rattus norvegicus (1.8%). Triatomines of the species T. sherlocki showed food eclecticism, including feeding on humans, with some of them being captured at dwellings. These facts make this triatomine a potential link for the transmission of T. cruzi between wild and anthropic environments, highlighting a latent risk of the reemergence of Chagas disease outbreaks.

Characterization of External Female Genitalia in Five Triatoma Laporte Species of South America (Hemiptera: Reduviidae: Triatominae)

Currently, there are 158 valid species of triatomines, all of which are potential vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. The correct taxonomic identification of triatomines is essential since each species hos a different epidemiological importance. The aim of the study is to compare five species of South American Triatoma. Here we present a comparative study of terminal abdominal segments in females by scanning electron microscopy (SEM) of the species Triatoma delpontei, T. jurbergi, T. infestans var. melanosoma, T. platensis, and T. vandae. The results showed diagnostic characters for the studied species. The dorsal view featured more valuable characters, with seven informative characters. Similarities were observed among T. delpontei, T. infestans var. melanosoma, and T. platensis, and between T. jurbergi and T. vandae, correlating with previous studies. Thus, female genital characters proved to be reliable and useful in the diagnosis of the Triatoma species studied here; additional studies, along with other sets of behavioral, morphological, and molecular data, helped to reinforce the hypotheses found here.

Dichotomous Keys Based on Cytogenetic Data for Triatomines Reported in Brazilian Regions with Outbreaks of Orally Transmitted Chagas Disease (Pernambuco and Rio Grande Do Norte)

Chagas disease (CD) affects about eight million people worldwide. Brazil has the highest number of estimated cases and the largest number of deaths due to CD. Considering the recent outbreaks of oral CD involving at least 27 cases of acute CD in Pernambuco (PE) as well as 18 cases and 2 deaths in the Rio Grande do Norte (RN), we developed dichotomous keys for the identification of triatomine species in these Brazilian states based on cytogenetic data. All triatomine species could be distinguished by cytogenetic characteristics, emphasizing the importance of the newly developed taxonomic keys for the correct identification of triatomes from PE and RN, particularly for species that exhibit morphological similarities, such as Triatoma brasilensis and T. petrocchiae (present in both states) and T. maculata and T. pseudomaculata (as T. pseudomaculata has been misidentified as T. maculata in PE and RN). These alternative keys are expected to provide a useful tool for the scientific community and, above all, health agents, aimed at preventing mistakes from occurring in the identification of the vectors present in PE and RN related to CD outbreaks caused by oral infection.

Vector mapping and bloodmeal metabarcoding demonstrate risk of urban Chagas disease transmission in Caracas, Venezuela

Chagas disease is a significant public health risk in rural and semi-rural areas of Venezuela. Triatomine infection by the aetiological agent Trypanosoma cruzi is also observed in the Metropolitan District of Caracas (MDC), where foodborne T. cruzi outbreaks occasionally occur but active vector-to-human transmission (infection during triatomine bloodmeal) is considered absent. Citizen science-based domiciliary triatomine collection carried out between 2007 and 2013 in the MDC has advanced understanding of urban T. cruzi prevalence patterns and represents an important public awareness-building tool. The present study reports on the extension of this triatomine collection program from 2014 to 2019 and uses mitochondrial metabarcoding to assess feeding behavior in a subset of specimens. The combined, thirteen-year dataset (n = 4872) shows a high rate of T. cruzi infection (75.2%) and a predominance of Panstrongylus geniculatus (99.01%) among triatomines collected in domiciliary areas by MDC inhabitants. Collection also involved nymphal stages of P. geniculatus in 18 of 32 MDC parishes. Other collected species included Triatoma nigromaculata, Triatoma maculata, Rhodnius prolixus, and Panstrongylus rufotuberculatus. Liquid intestinal content indicative of bloodmeal was observed in 53.4% of analyzed specimens. Dissection pools representing 108 such visually blooded P. geniculatus specimens predominantly tested positive for human cytochrome b DNA (22 of 24 pools). Additional bloodmeal sources detected via metabarcoding analysis included key sylvatic T. cruzi reservoirs (opossum and armadillo), rodents, and various other synanthropic and domesticated animals. Results suggest a porous sylvatic-domiciliary transmission interface and ongoing adaptation of P. geniculatus to the urban ecotope. Although P. geniculatus defecation traits greatly limit the possibility of active T. cruzi transmission for any individual biting event, the cumulation of this low risk across a vast metropolitan population warrants further investigation. Efforts to prevent triatomine contact with human food sources also clearly require greater attention to protect Venezuela's capital from Chagas disease.

Resisting an invasion: A review of the triatomine vector (Kissing bug) defense strategies against a Trypanosoma sp infection

Triatomines are an important group of insects in the Americas. They serve as transmission vectors for Trypanosoma cruzi, the etiologic agent responsible for the deadly Chagas disease in humans. The digenetic parasite has a complex life cycle, alternating between mammalian and insect hosts, facing different environments. In the insect vector, the metacyclic trypomastigote (non-replicative) and epimastigote (replicative) stages face a set of insect-mediated environmental changes, such as intestinal pH, body temperature, nutrient availability, and vector immune response. These insects have the ability to differentiate between self and non-self-particles using their innate immune system. This immune system comprises physical barriers, cellular responses (phagocytosis, nodules and encapsulation), humoral factors, including effector mechanisms (antimicrobial peptides and prophenoloxidase cascade) and the intestinal microbiota. Here, we consolidate and synthesize the available literature to describe the defense mechanisms deployed by the triatomine vector against the parasite, as documented in recent years, the possible mechanisms developed by the parasite to protect against the insect's specific microenvironment and innate immune responses, and future perspectives on the Triatomine-Trypanosome interaction.

Morphological, Cytological and Molecular Studies and Feeding and Defecation Pattern of Hybrids from Experimental Crosses between Triatoma sordida and T. rosai (Hemiptera, Triatominae)

Under laboratory conditions, Triatoma rosai and T. sordida are able to cross and produce hybrids. In the face of climate and environmental changes, the study of hybrids of triatomines has evolutionary and epidemiological implications. Therefore, we performed morphological, cytological and molecular studies and characterized the feeding and defecation pattern of hybrids from crosses between T. sordida and T. rosai. The morphological characterization of the female genitalia of the hybrids showed that characteristics of both parental species segregated in the hybrids. Cytogenetic analyzes of hybrids showed regular metaphases. According to molecular studies, the mitochondrial marker Cytochrome B (CytB) related the hybrids with T. sordida and the nuclear marker Internal Transcribed Spacer 1 (ITS-1) related the hybrids with T. rosai. Both parents and hybrids defecated during the blood meal. Thus, the hybrids resulting from the cross between T. sordida and T. rosai presented segregation of phenotypic characters of both parental species, 100% homeology between homeologous chromosomes, phylogenetic relationship with T sordida and with T. rosai (with CytB and ITS-1, respectively), and, finally, feeding and defecation patterns similar to the parents.

Interrogating the transmission dynamics of Trypanosoma cruzi (Trypanosomatida, Trypanosomatidae) by Triatoma venosa (Hemiptera: Reduviidae) after the elimination of vector transmission by Rhodnius prolixus in Boyacá eastern Colombia

Chagas disease (CD) is a parasitic zoonosis (Trypanosoma cruzi) that is endemic in Colombia. Vector control of Rhodnius prolixus, the main domestic T. cruzi vector, has been achieved in a large part of the area with historically vector transmission of CD. It is necessary to understand the ecological behavior characteristics of local native vectors to ensure sustainability of the vector control programs. To evaluate the long-term success of a recent vector control campaign in the Boyacá department (Colombia), we used a combined strategy of entomological surveillance with co-existing canine surveillance from ten rural villages within six municipalities of the Tenza valley region (Boyacá, Colombia): Chinavita, Garagoa, Guateque, Somondoco, Sutatenza and Tenza, with historical reports of R. prolixus and secondary vectors. Collected triatomines and canine whole blood were analyzed for T. cruzi infection and genotyping. Triatomine bugs specimens were evaluated for blood meal source. Canine serology was performed using two distinct antibody assays. In total, 101 Triatoma venosa were collected by active search in domestic and peridomestic habitats. A natural infection prevalence of 13.9% (14/101) and four feeding sources were identified: human, dog, rat, and hen. A frequency infection of 46.5% (40/87) was observed from two independent serological tests and T. cruzi DNA was detected in 14 dogs (16.4%). Only TcIsylvatic DTU was detected. The results suggest that T. venosa present eco-epidemiological characteristics to maintain the transmission of T. cruzi in Tenza valley. This species has reinfested the intervened households and it has an active role in domestic and peridomestic transmission of T. cruzi due to their infection rates and feeding behavior. Therefore, this species should be considered as epidemiologically relevant for vector control strategies. Moreover, there is a need for human serological studies to have a close up of risk they are exposed to.

Panstrongylusnoireaui, a remarkable new species of Triatominae (Hemiptera, Reduviidae) from Bolivia

Panstrongylusnoireaui sp. nov. from Bolivia is described based on male and female specimens. Although morphologically almost indistinguishable from Panstrongylusrufotuberculatus (Champion, 1899), the new species shows remarkable chromosome and molecular features, which are very distinctive among all others Panstrongylus species. The new species is also separated by some characteristics of the processes of the endosoma of the male genitalia. An updated key for species of Panstrongylus is provided.

Morphological Stasis in Time? A Triatoma brasiliensis brasiliensis Study Using Geometric Morphometrics in the Long Run

Simple Summary

Triatomines are vector insects capable of transmitting the protozoan that causes Chagas disease, thus representing a health risk in several countries, especially in Central and South America. Triatoma brasiliensis brasiliensis, the main triatomine vector in northeastern Brazil, needs frequent monitoring as it is able to colonize various natural and artificial ecotopes as well as to infest domiciles. This research uses geometric morphometrics as a tool to evaluate changes in the morphology and analyze a large temporal dataset of 102 years of collections of T. b. brasiliensis. Finding novelty results which indicate a morphological stasis in the morphology.

Abstract

Triatoma brasiliensis brasiliensis Neiva, 1911 is one of the most important vectors of Chagas disease in the Brazilian semiarid regions in the north-east. The risk imposed by T. b. brasiliensis to the human populations, due to frequent invasions and/or colonization of the domiciles, demands constant monitoring and control actions as well as an understanding of its evolutionary process. In this context, the following research studies the pattern of shape adaptation over time using a large dataset from 102 years of specimen collections in order to identify the morphological plasticity of this vector in Brazil. This dataset was analyzed using geometric morphometrics tools and the timescale was divided into eight different groups, containing specimens from 1912 to 2014. Geometric morphometrics analysis showed an interesting morphological stasis in the wing shape of T. b. brasiliensis, which allowed us to understand the high capacity of adaptation to changes in climate condition through time, and the invasive status which Triatoma species have around the world. Moreover, these results showed novel findings as an interesting phenotypic pattern, with no modifications in more than 100 years, leading us to understand the shape evolution in Triatominae as a vector species of diseases.

The Effects of a Male Audience on Male and Female Mating Behaviour in the Blood-Sucking Bug Rhodnius prolixus

Social context is a key factor affecting sexual behaviour and cannot be neglected in gregarious species, such as triatomine blood-sucking bugs. Here we study the influence of the social context on the sexual reproductive behaviour of males and females of Rhodnius prolixus Stål. Specifically, we identify and compare the frequencies and sequence of sexual behaviours exhibited by a focal pair in presence or absence of a male audience. We expect that in presence of a male audience females increase their selectiveness level since the risk of losing infertile eggs decreases in presence of more candidates and females can benefit from copulating with a better quality male. Besides, in presence of potential rivals, we expect changes in the sexual behaviour of focal males, associated to a reduction in the risk of sperm competition. As expected, in presence of a male audience, females significantly increased the exhibition of rejection behaviour. Moreover, focal males exhibited shorter latencies to mount the female, longer duration of copula, and differences in their stereotyped behaviour exhibited during copula. We discuss the influence of the social context on the reproductive behaviour of females and males of R. prolixus.

Multidisciplinary approach detects speciation within the kissing bug Panstrongylus rufotuberculatus populations (Hemiptera, Heteroptera, Reduviidae)

BACKGROUND

Panstrongylus rufotuberculatus (Hemiptera-Reduviidae) is a triatomine species with a wide geographic distribution and a broad phenotypic variability. In some countries, this species is found infesting and colonising domiciliary ecotopes representing an epidemiological risk factor as a vector of Trypanosoma cruzi, etiological agent of Chagas disease. In spite of this, little is known about P. rufotuberculatus genetic diversity.

METHODS

Cytogenetic studies and DNA sequence analyses of one nuclear (ITS-2) and two mitochondrial DNA sequences (cyt b and coI) were carried out in P. rufotuberculatus individuals collected in Bolivia, Colombia, Ecuador and Mexico. Moreover, a geometric morphometrics study was applied to Bolivian, Colombian, Ecuadorian and French Guiana samples.

OBJECTIVES

To explore the genetic and phenetic diversity of P. rufotuberculatus from different countries, combining chromosomal studies, DNA sequence analyses and geometric morphometric comparisons.

FINDINGS

We found two chromosomal groups differentiated by the number of X chromosomes and the chromosomal position of the ribosomal DNA clusters. In concordance, two main morphometric profiles were detected, clearly separating the Bolivian sample from the other ones. Phylogenetic DNA analyses showed that both chromosomal groups were closely related to each other and clearly separated from the remaining Panstrongylus species. High nucleotide divergence of cyt b and coI fragments were observed among P. rufotuberculatus samples from Bolivia, Colombia, Ecuador and Mexico (Kimura 2-parameter distances higher than 9%).

MAIN CONCLUSIONS

Chromosomal and molecular analyses supported that the two chromosomal groups could represent different closely related species. We propose that Bolivian individuals constitute a new Panstrongylus species, being necessary a detailed morphological study for its formal description. The clear morphometric discrimination based on the wing venation pattern suggests such morphological description might be conclusive.

Coleção de Vetores de Tripanosomatídeos (Fiocruz/COLVET) held at the institution Fiocruz Minas in Brazil: diversity of Triatominae (Hemiptera, Reduviidae) and relevance for research, education, and entomological surveillance

The Coleção de Vetores de Tripanosomatídeos (Fiocruz/COLVET), Minas Gerais, Brazil, stands out as one of the most important collections of blood-sucking triatomines, the vectors of Trypanosomacruzi that causes Chagas disease. The aim is to describe the collection and the services it provides to support scientific research, educational activities, and entomological surveillance between 2013-2019.The data associated with the specimens held in Fiocruz/COLVET is available from the Sistema de Informação sobre a Biodiversidade Brasileira (SiBBr). These specimen metadata were analyzed and either tabulated or plotted on graph and maps. The records of services provided by the collection between 2013-2019 were also categorized and analyzed. There are 12,568 triatomine specimens deposited in the collection that belong to 77 species and 11 genera, from 15 American countries. Of the ~ 65 species of triatomines found in Brazil, 38 (57.6%) are present in the collection, including specimens from all biomes and all but three Brazilian states. The occurrence of Triatomacostalimai, Triatomalenti, Rhodniusnasutus, and Panstrongyluslenti apparently collected beyond their known distribution ranges are reported and discussed. The collection provided 168 services, supporting educational activities (41.7%), scientific research (35.7%), and regional/national entomological surveillance of triatomines (22.6%). Between the years 2014 and 2020, the number of biological specimens deposited in the Fiocruz/COLVET repository increased from 4,778 to 12,568 triatomine specimens. In addition to its great value to biodiversity conservation, the collection is of great importance because of its support of research and educational activities, and contributions to entomological surveillance, and, therefore, to public health.

Revisiting the Hybridization Processes in the Triatoma brasiliensis Complex (Hemiptera, Triatominae): Reproductive Isolation between Triatoma petrocchiae and T. b. brasiliensis and T. lenti

Simple Summary

Although all triatomines are potential vectors of Chagas disease, there are species with greater or lesser vectorial importance. Therefore, the correct identification of triatomine species is essential for vector control programs. In general, triatomines are identified by external morphological characters. However, some species are very similar or even morphologically identical, making the use of complementary analyses for the correct identification of species important. For this reason, this study focused on the use of experimental crosses to assess the specific status of species of the Triatoma brasiliensis species complex. The crosses did not result in hybrids, demonstrating that there are pre-zygotic reproductive barriers installed between T. petrocchiae and the other species of the T. brasiliensis complex (which confirms the specific status of the species according to the biological species concept). On the basis of the results above, we demonstrated that T. petrocchiae is reproductively isolated from T. b. brasiliensis and T. lenti. Furthermore, we suggest that T. petrocchiae is the species most derived from the T. brasiliensis complex.

Abstract

Triatoma petrocchiae is a species morphologically similar to T. b. brasiliensis (which resulted in a synonymization event); despite this similarity, genetic, morphological, and experimental crossbreeding studies confirmed the specific status of T. petrocchiae. Considering that both species have been reported living in sympatry and that, for a long time, most species of the T. brasiliensis complex were considered only chromatic variants of T. b. brasiliensis, we carried out experimental crosses between T. b. brasiliensis and T. petrocchiae (to confirm whether these species are reproductively isolated) and between T. lenti and T. petrocchiae (to assess whether T. petrocchiae also presents prezygotic isolation with the other species of the T. brasiliensis complex). Reciprocal experimental crosses were conducted, and weekly, the eggs were collected, counted, and separated in new containers to assess the hatch rate. Neither cross resulted in hybrids, demonstrating that there are pre-zygotic reproductive barriers installed between T. petrocchiae and the other species of the T. brasiliensis complex. On the basis of the results above, we demonstrated that T. petrocchiae is reproductively isolated from T. b. brasiliensis and T. lenti. Furthermore, we suggest that T. petrocchiae is the species most derived from the T. brasiliensis complex.

The connection between Trypanosoma cruzi transmission cycles by Triatoma brasiliensis brasiliensis: A threat to human health in an area susceptible to desertification in the Seridó, Rio Grande do Norte, Brazil

An outbreak of Chagas disease, possibly involving its vector Triatoma brasiliensis brasiliensis, was identified in the state of Rio Grande do Norte (RN). Given the historical significance of this vector in public health, the study aimed to evaluate its role in the transmission dynamics of the protozoan Trypanosoma cruzi in an area undergoing desertification in the Seridó region, RN, Brazil. We captured triatomines in sylvatic and anthropic ecotopes. Natural vector infection was determined using parasitological and molecular methods and we identified discrete typing units (DTUs) of T. cruzi by analyzing the COII gene of mtDNA, 24Sα rDNA, and mini-exon gene. Their blood meals sources were identified by amplification and sequencing of the mtDNA cytochrome b gene. A total of 952 T. b. brasiliensis were captured in peridomestic (69.9%) and sylvatic ecotopes (30.4%). A wide range of natural infection rates were observed in peridomestic (36.0% - 71.1%) and sylvatic populations (28.6% - 100.0%). We observed the circulation of TcI and TcII DTUs with a predominance of Tcl in sylvatic and peridomestic environments. Kerodon rupestris, rocky cavy (13/39), Homo sapiens, human (8/39), and Bos taurus, ox (6/39) were the most frequently detected blood meals sources. Thus, Triatoma b. brasiliensis is invading and colonizing the human dwellings. Furthermore, high levels of natural infection, coupled with the detection of TcI and TcII DTUs, and also the detection of K. rupestris and H. sapiens as blood meals sources of infected T. b. brasiliensis indicate a risk of T. cruzi transmission to human populations in areas undergoing desertification.

Chagas disease currently affects about six to seven million people worldwide, resulting in high morbidity, mortality, and economic burden in endemic countries of Latin America. Its etiological agent, Trypanosoma cruzi, circulates among a wide variety of mammalian and insect vectors. Triatoma brasiliensis brasiliensis is adapted to the dry and warm climate of the Caatinga biome, and is considered the main vector in the semi-arid areas of northeastern Brazil. Information on the infestation, natural infection rates, T. cruzi strains, and blood meals sources of this vector is crucial for understanding the dynamics of T. cruzi transmission in areas susceptible to desertification. Triatoma b. brasiliensis colonizes peridomestic structures, particularly in the stone walls of cattle corrals that emerge as a refuge for sylvatic populations where they access a variety of blood meals sources. The predominance of the TcI strain in the sylvatic and peridomestic environments shows an overlap of transmission cycles by T. cruzi mediated by T. b. brasiliensis. The high rates of natural infection and the evidence of their feeding on humans and the rodent K. rupestris are worrisome and indicate the threat this vector poses to human health in the area studied.

Revisiting the hybridization processes in the Triatoma brasiliensis complex (Hemiptera, Triatominae): Interspecific genomic compatibility point to a possible recent diversification of the species grouped in this monophyletic complex

Triatomines are hematophagous insects of great epidemiological importance, since they are vectors of the protozoan Trypanosoma cruzi, the etiological agent of Chagas disease. Triatoma brasiliensis complex is a monophyletic group formed by two subspecies and six species: T. b. brasiliensis, T. b. macromelasoma, T. bahiensis, T. juazeirensis, T. lenti, T. melanica, T. petrocchiae and T. sherlocki. The specific status of several species grouped in the T. brasiliensis complex was confirmed from experimental crossing and analysis of reproductive barriers. Thus, we perform interspecific experimental crosses between T. lenti and other species and subspecies of the T. brasiliensis complex and perform morphological analysis of the gonads and cytogenetic analysis in the homeologous chromosomes of the hybrids of first generation (F1). Besides that, we rescue all the literature data associated with the study of reproductive barriers in this monophyletic complex of species and subspecies. For all crosses performed between T. b. brasiliensis, T. b. macromelasoma, T. juazeirensis and T. melanica with T. lenti, interspecific copulas occurred (showing absence of mechanical isolation), hybrids were obtained, none of the male hybrids presented the phenomenon of gonadal dysgenesis and 100% pairing between the chromosomes homeologous of the hybrids was observed. Thus, we demonstrate that there are no pre-zygotic reproductive barriers installed between T. lenti and the species and subspecies of the T. brasiliensis complex. In addition, we demonstrate that the hybrids obtained between these crosses have high genomic compatibility and the absence of gonadal dysgenesis. These results point to reproductive compatibility between T. lenti and species and subspecies of the T. brasiliensis complex (confirming its inclusion in the complex) and lead us to suggest a possible recent diversification of the taxa of this monophyletic group.