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Scientific Reports Aug 2022Juvenile hormone (JH) signalling, via its receptor Methoprene-tolerant (Met), controls metamorphosis and reproduction in insects. Met belongs to a superfamily of...
Juvenile hormone (JH) signalling, via its receptor Methoprene-tolerant (Met), controls metamorphosis and reproduction in insects. Met belongs to a superfamily of transcription factors containing the basic Helix Loop Helix (bHLH) and Per Arnt Sim (PAS) domains. Since its discovery in 1986, Met has been characterized in several insect species. However, in spite of the importance as vectors of Chagas disease, our knowledge on the role of Met in JH signalling in Triatominae is limited. In this study, we cloned and sequenced the Dipetalogaster maxima Met transcript (DmaxMet). Molecular modelling was used to build the structure of Met and identify the JH binding site. To further understand the role of the JH receptor during oogenesis, transcript levels were evaluated in two main target organs of JH, fat body and ovary. Functional studies using Met RNAi revealed significant decreases of transcripts for vitellogenin (Vg) and lipophorin (Lp), as well as their receptors. Lp and Vg protein amounts in fat body, as well as Vg in hemolymph were also decreased, and ovarian development was impaired. Overall, these studies provide additional molecular insights on the roles of JH signalling in oogenesis in Triatominae; and therefore are relevant for the epidemiology of Chagas´ disease.
Topics: Animals; Female; Juvenile Hormones; Methoprene; Oogenesis; Triatominae; Vitellogenins
PubMed: 35988007
DOI: 10.1038/s41598-022-18384-5 -
Parasites & Vectors Jun 2022Rhodnius robustus and Rhodnius pictipes are vectors of Trypanosoma cruzi, the etiologic agent of Chagas disease (CD), that are found in the Brazilian Amazon region....
Infection susceptibility and vector competence of Rhodnius robustus Larrousse, 1927 and R. pictipes Stal, 1872 (Hemiptera, Reduviidae, Triatominae) for strains of Trypanosoma cruzi (Chagas, 1909) (Kinetoplastida, Trypanosomatidae) I, II and IV.
BACKGROUND
Rhodnius robustus and Rhodnius pictipes are vectors of Trypanosoma cruzi, the etiologic agent of Chagas disease (CD), that are found in the Brazilian Amazon region. Susceptibility to infection and vector competence depend on the parasite-vector relationship. Our objective was to evaluate the interaction between T. cruzi and these two triatomine vectors in pure and mixed experimental infections of T. cruzi strains from the same or different geographic regions.
METHODS
Fifth-instar nymphs of R. robustus and R. pictipes were fed on mice infected with four T. cruzi strains, namely genotypes TcIAM, TcIMG, TcIIPR, and TcIVAM, respectively, from the Brazilian states of Amazonas, Minas Gerais and Paraná. Over a period of 120 days, excreta were examined every 20 days to assess vector competence, and intestinal contents (IC) were examined every 30 days to determine susceptibility to infection.
RESULTS
The highest positive rate in the fresh examination (%+FE, 30.0%), the highest number of parasitic forms (PF, n = 1969) and the highest metacyclogenesis rate (%MC, 53.8%) in the excreta were recorded for R. robustus/TcIVAM. Examination of the IC of R. pictipes revealed a higher number of PF in infections with TcIAM (22,680 PF) and TcIIPR (19,845 PF) alone or in association (17,145 PF), as well as a %+FE of 75.0% with TcII, in comparison with the other genotypes. The highest %MC (100%) was recorded for the mixed infections of TcIAM with TcIIPR or TcIVAM in the IC of R. pictipes.
CONCLUSIONS
Overall, both species were found to be susceptible to the T. cruzi strains studied. Rhodnius robustus showed vector competence for genotypes TcIVAM and TcIAM+TcIVAM and R. pictipes for TcIAM+TcIVAM and TcIAM+TcIIPR; there was elimination of infective forms as early as at 20 days. Our results suggest that both the genetics of the parasite and its geographic origin influence the susceptibility to infection and vector competence, alone or in association.
Topics: Animals; Chagas Disease; Kinetoplastida; Mice; Rhodnius; Triatominae; Trypanosoma cruzi; Trypanosomatina
PubMed: 35773725
DOI: 10.1186/s13071-022-05350-3 -
Parasites & Vectors Feb 2020Melanic (dark) morphs have been barely reported in peridomestic and sylvatic conditions for Triatoma infestans, the most important vector of Chagas disease in the...
BACKGROUND
Melanic (dark) morphs have been barely reported in peridomestic and sylvatic conditions for Triatoma infestans, the most important vector of Chagas disease in the Southern Cone of South America. Adults with dark and small yellow markings on the connexivum were collected after manual searches conducted by technical personnel in 62 domiciliary units in Cruz del Eje, Córdoba Province, Argentina. The last community-wide insecticide spraying campaign before the study had been conducted three years earlier. We investigated if there was a measurable color morph variation (melanic and non-melanic) in wings and connexivum; we determined infestation, distribution of melanic and non-melanic forms, and correspondence of colorimetric variation with variations in morphology (wing size and shape and body length), development (wing fluctuating asymmetry), physiology (nutritional status) or behaviour (flight initiation).
RESULTS
Forty-nine females, 54 males and 217 nymphs were collected in 24 domiciliary units. House infestation and colonization were 53% and 47%, respectively. Most of the T. infestans individuals (83.2%) were collected in chicken coops; intradomicile infestation was recorded in only one case. The chromatic cluster analysis showed two well-defined groups: melanic and non-melanic. The melanic group included 17 (35%) females and 25 (46%) males. Peridomestic infestation was lower for melanic than for non-melanic adults. Melanic morphs were collected in houses from several localities. Sexual dimorphisms were confirmed by morphometric measurements. Body length was large in melanic adults (P < 0.01 only for males). Differences between groups were significant for wing size and shape, but not for weight or weight/body length ratio. Melanic females and males showed significantly higher fluctuating asymmetry (FA) indices than their non-melanic counterparts.
CONCLUSIONS
This is the second report of melanic forms of T. infestans in domestic and peridomestic habitats in the Dry Chaco region of Argentina. Although non-melanic adults exhibited a higher infestation rate, melanic adults were widespread in the area and were collected in the infested domicile and in most types of peridomestic annexes. Differences in morphometric variables between groups might be due to different ecological adaptations. The higher FA levels observed in melanic individuals suggest a higher developmental instability and a selective advantage of non-melanic individuals in domestic and peridomestic habitats.
Topics: Animals; Chagas Disease; Color; Ecosystem; Humans; Insect Vectors; Melanins; Selection, Genetic; Triatoma
PubMed: 32014037
DOI: 10.1186/s13071-020-3912-y -
Parasites & Vectors Sep 2021Triatomine bugs transmit Chagas disease across Latin America, where vector control-surveillance is increasingly decentralized. Locally run systems often deal with highly...
BACKGROUND
Triatomine bugs transmit Chagas disease across Latin America, where vector control-surveillance is increasingly decentralized. Locally run systems often deal with highly diverse native-vector faunas-plus, in some areas, domestic populations of non-native species. Flexible entomological-risk indicators that cover native and non-native vectors and can support local decision-making are therefore needed.
METHODS
We present a local-scale entomological-risk score ("TriatoScore") that leverages and builds upon information on the ecology-behavior and distribution-biogeography of individual triatomine bug species. We illustrate our approach by calculating TriatoScores for the 417 municipalities of Bahia state, Brazil. For this, we (i) listed all triatomine bug species recorded statewide; (ii) derived a "species relevance score" reflecting whether each species is native/non-native and, if native, whether/how often it invades/colonizes dwellings; (iii) mapped each species' presence by municipality; (iv) for native vectors, weighted presence by the proportion of municipal territory within ecoregions occupied by each species; (v) multiplied "species relevance score" × "weighted presence" to get species-specific "weighted scores"; and (vi) summed "weighted scores" across species to get municipal TriatoScores. Using standardized TriatoScores, we then grouped municipalities into high/moderate/low entomological-risk strata.
RESULTS
TriatoScores were higher in municipalities dominated by dry-to-semiarid ecoregions than in those dominated by savanna-grassland or, especially, moist-forest ecoregions. Bahia's native triatomines can maintain high to moderate risk of vector-borne Chagas disease in 318 (76.3%) municipalities. Historical elimination of Triatoma infestans from 125 municipalities reduced TriatoScores by ~ 27% (range, 20-44%); eight municipalities reported T. infestans since Bahia was certified free of Trypanosoma cruzi transmission by this non-native species. Entomological-risk strata based on TriatoScores agreed well with Bahia's official disease-risk strata, but TriatoScores suggest that the official classification likely underestimates risk in 42 municipalities. Of 152 municipalities failing to report triatomines in 2006-2019, two and 71 had TriatoScores corresponding to, respectively, high and moderate entomological risk.
CONCLUSIONS
TriatoScore can help control-surveillance managers to flexibly assess and stratify the entomological risk of Chagas disease at operationally relevant scales. Integrating eco-epidemiological, demographic, socioeconomic, or operational data (on, e.g., local-scale dwelling-infestation or vector-infection frequencies, land-use change and urbanization, housing conditions, poverty, or the functioning of control-surveillance systems) is also straightforward. TriatoScore may thus become a useful addition to the triatomine bug control-surveillance toolbox.
Topics: Animals; Brazil; Chagas Disease; Entomology; Environment; Housing Quality; Humans; Insect Vectors; Risk Factors; Triatominae; Trypanosoma cruzi
PubMed: 34563255
DOI: 10.1186/s13071-021-04954-5 -
Current Opinion in Insect Science Aug 2019Sensory processes represent an information gathering interface between animals and their surrounding world. Therefore, they serve to scan the environment for resources... (Review)
Review
Sensory processes represent an information gathering interface between animals and their surrounding world. Therefore, they serve to scan the environment for resources and threats. The behavior of kissing bugs has been studied to aid their control because they transmit Chagas disease to humans. Besides, a few triatomines represent important insect models since Wigglesworth times. These hematophagous insects rely on different sensory systems to scan their environment for blood-sources, mating partners, and hiding places. The study of the molecular bases of sensory processes has undergone a dramatic progress due the advent of new technologies allowing mass-sequencing of genes. Here, we focus on reviewing the fundamental knowledge gathered to date about the molecular bases of kissing bug sensory processes.
Topics: Animals; Insect Vectors; Rhodnius; Sensation; Sensory Receptor Cells
PubMed: 31247423
DOI: 10.1016/j.cois.2019.03.010 -
Frontiers in Endocrinology 2023Within insects, corticotropin-releasing factor/diuretic hormones (CRF/DHs) are responsible for the modulation of a range of physiological and behavioural processes such...
Within insects, corticotropin-releasing factor/diuretic hormones (CRF/DHs) are responsible for the modulation of a range of physiological and behavioural processes such as feeding, diuresis, and reproduction. Rhopr-CRF/DH plays a key role in feeding and diuresis in , a blood-gorging insect and a vector for human Chagas disease. Here, we extend our understanding on the role of this neurohormone in reproduction in adult female . Double-label immunohistochemistry displays co-localized staining of CRF-like and the glycoprotein hormone (GPA2/GPB5) subunit GPB5-like immunoreactivity in the same neurosecretory cells (NSCs) in the mesothoracic ganglionic mass (MTGM) and in their neurohemal sites in adult female , suggesting these peptides could work together to regulate physiological processes. qPCR analysis reveals that the transcript for Rhopr-CRF/DH receptor 2 () is expressed in reproductive tissues and fat body (FB) in adult female , and its expression increases post blood meal (PBM), a stimulus that triggers diuresis and reproduction. Using RNA interference, transcript expression of was knocked down, and egg production monitored by examining the major yolk protein, vitellogenin (Vg), the number and quality of eggs laid, and their hatching ratio. Injection of dsCRFR2 into adult females reduces transcript expression, accelerates oogenesis, increases the number of eggs produced, and reduces hatching rate in female . Downregulation of leads to an increase in the transcript expression of in the fat body and ovaries, and increases the transcript level for the Vg receptor, , in the ovaries. A significant increase in Vg content in the fat body and in the hemolymph is also observed. Incubation of isolated tissues with Rhopr-CRF/DH leads to a significant decrease in transcript expression of in the fat body and in the ovaries. In addition, Rhopr-CRF/DH reduces transcript expression of the ecdysteroid biosynthetic enzymes and reduces ecdysteroid titer in the culture medium containing isolated ovaries. These results suggest the involvement of the CRF-signaling pathway in reproduction, and that Rhopr-CRF/DH acts as a gonad-inhibiting hormone in the adult female , as previously shown for the colocalized glycoprotein, GPA2/GPB5.
Topics: Animals; Female; Adult; Humans; Corticotropin-Releasing Hormone; Diuretics; Rhodnius; Ecdysteroids; Gonadal Hormones; Glycoproteins; Gonads
PubMed: 37842303
DOI: 10.3389/fendo.2023.1279929 -
The American Journal of Tropical... Apr 2021Chagas disease is an illness caused by the protozoan Trypanosoma cruzi that is distributed in 21 countries of Latin America. The main way of transmission of T. cruzi is... (Review)
Review
Chagas disease is an illness caused by the protozoan Trypanosoma cruzi that is distributed in 21 countries of Latin America. The main way of transmission of T. cruzi is through the feces of triatomines infected with the parasite. With technological advances came new technologies called omics. In the pre-genomic era, the omics science was based on cytogenomic studies of triatomines. With the Rhodnius prolixus genome sequencing project, new omics tools were applied to understand the organism at a systemic level and not just from a genomic point of view. Thus, the present review aims to put together the cytogenomic and genomic information available in the literature for Chagas disease vectors. Here, we review all studies related to cytogenomics and genomics of Chagas disease vectors, contributing to the direction of further research with these insect vectors, because it was evident that most studies focus on cytogenomic knowledge of the species. Given the importance of genomic studies, which contributed to the knowledge of taxonomy, systematics, as well as the vector's biology, the need to apply these techniques in other genera and species of Triatominae subfamily is emphasized.
Topics: Animals; Chagas Disease; Chromosomes; Genomics; Humans; Insect Vectors; Phylogeny; Rhodnius; Triatoma; Trypanosoma cruzi
PubMed: 33872207
DOI: 10.4269/ajtmh.20-1047 -
Cutis Jun 2023Members of the Triatoma and Arilus genera (family Reduviidae) often are mistaken as the same arthropod, though their bites have vastly different health implications....
Members of the Triatoma and Arilus genera (family Reduviidae) often are mistaken as the same arthropod, though their bites have vastly different health implications. Bites of the wheel bug (Arilus cristatus) are painful compared to Triatoma bites, which are painless but can cause disease and result in an anaphylactic reaction, posing a risk to human health because these pliable insects commonly infest residential dwellings. A common dermatologic presentation of bites from Triatoma species and A cristatus is an erythematous pruritic papule that can progress to an urticarial wheal, though the presentation can differ from patient to patient. Treatment depends on whether the reaction is localized or systemic, ranging from topicals to systemic agents if anaphylaxis occurs.
Topics: Humans; Animals; Triatoma; Arthropods; Pain; Urticaria
PubMed: 37487132
DOI: 10.12788/cutis.0793 -
Acta Tropica Feb 2023Triatomines are an important group of insects in the Americas. They serve as transmission vectors for Trypanosoma cruzi, the etiologic agent responsible for the deadly... (Review)
Review
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.
Topics: Animals; Humans; Triatoma; Chagas Disease; Trypanosoma cruzi; Life Cycle Stages; Immunity, Innate; Mammals
PubMed: 36375520
DOI: 10.1016/j.actatropica.2022.106745 -
PeerJ 2023In defensive mimicry, resemblance between unequally defended species can be parasitic; this phenomenon has been termed quasi-Batesian mimicry. Few studies have used real...
In defensive mimicry, resemblance between unequally defended species can be parasitic; this phenomenon has been termed quasi-Batesian mimicry. Few studies have used real co-mimics and their predators to test whether the mimetic interactions were parasitic. Here, we investigated the mimetic interaction between two well-defended insect species, the bombardier beetle (Coleoptera: Carabidae) and the assassin bug (Hemiptera: Reduviidae), using their potential predator, the pond frog (Anura: Ranidae), which coexists with these insect species in the same habitat in Japan. We observed behavioural responses of this frog species (adults and juveniles) to adult . and adult . under laboratory conditions. Among the frogs, 100% and 75% rejected . and . , respectively, suggesting that, compared with the assassin bug . , the bombardier beetle . is more well-defended against frogs. An assassin bug or a bombardier beetle was provided to a frog that had encountered the other insect species. Frogs with a history of assassin bug encounter demonstrated a lower rate of attack toward bombardier beetles. Similarly, frogs with a history of bombardier beetle encounter demonstrated a lower rate of attack toward assassin bugs. Therefore, both the bombardier beetle . and the assassin bug . benefit from the mimetic interaction.
Topics: Animals; Insecta; Coleoptera; Triatoma; Biological Mimicry; Anura
PubMed: 37304866
DOI: 10.7717/peerj.15380