Search Results (34)

The protozoan Trypanosoma cruzi is the etiological agent of Chagas disease, a neglected tropical disease that mostly affects the population of Latin American countries, with an estimated 7 million infected people and more than 10,000 deaths per year worldwide. T. cruzi is typically transmitted by hematophagous triatomine insects, with Rhodnius prolixus being a major insect vector in South America. While the microbiome of triatomine insects has been investigated to a certain extent, the ternary interaction between triatomes insects, T. cruzi, and viruses remains virtually unexplored. In this study, we show by transmission electron microscopy and by RT-PCR that Rhodnius prolixus viruses (RpVs) can infect the intestine of R. prolixus, which places them in close contact with the gut microbiota. These observations suggest that T. cruzi can be infected by the insect viruses while transiting through the gut. Here, we show that the RpVs are capable of infecting the epimastigote forms of T. cruzi in vitro and maintain the viral load stabilized for 3 to 7 days after infection. We also show that, at least in the case of the iFlavirus RpV1, viral genomes are detectable in the T. cruzi cytoplasm. Interestingly, R. prolixus ovarian extracts enriched with RpVs decrease epimastigote proliferation and their capacity for differentiation into the ineffective metacyclic trypomastigotes in vitro. Our results start to shed light on the interaction between RpVs and T. cruzi, suggesting possible routes of infection and unveiling a role for viral infections in the development of this important pathogen. Full article

The saliva of hematophagous arthropods, such as ticks and triatomines, contains bioactive ligands capable of modulating immune molecules, including cytokines. Cytokines play a critical role in immune regulation and have therapeutic relevance in inflammatory and immune-mediated diseases. Despite recent advances, identifying cytokine-binding molecules remains a significant challenge. Interferon-gamma (IFN-γ), interleukin-4 (IL-4), and interleukin-17 (IL-17) are key cytokines involved in inflammation, adaptive immunity, and host defense. This study evaluated the ability of salivary components from Amblyomma sculptum and compared the results to the triatomine Rhodnius neglectus (used as control) to bind to IL-2, IL-4, IL-6, IL-10, IL-17, IFN-γ, and TNF-α using ELISA assays with human cytokines. Saliva samples were tested at dilutions of 1:25, 1:50, and 1:100. Saliva from A. sculptum, which demonstrated significant anti-cytokine activity, was fractionated via HPLC to identify the active components. The results confirmed the inhibitory capacity of A. sculptum saliva on IFN-γ, IL-4, and IL-17, with inhibition rates ranging from 30% to 70%, depending on the cytokine and dilution. No inhibitory activity was observed against IL-2, IL-6, IL-10, or TNF-α. These findings underscore the immunomodulatory role of A. sculptum saliva during tick feeding and suggest its potential for the development of novel immunobiologics to treat inflammatory and immune-mediated diseases. Full article

The kissing bug Rhodnius prolixus is a nocturnal species; however, its temporal mating patterns remain unexplored. Copulation lasts about fifty minutes, during which time the couple remains almost motionless. We hypothesized that R. prolixus copulates within shelters to reduce its vulnerability. To test this, we examined the spatial and temporal patterns of its copulation, as well as the potential endogenous regulation of its circadian rhythm, under three conditions: a light:dark cycle (L/D), constant light (L/L), and constant darkness (D/D). Over ten days, the number and the timing of copulation of pairs in arenas containing a shelter were video-recorded. Under the L/D cycle, the pairs mated mainly during daylight hours. This rhythm persisted under the D/D cycle, with a peak extending from the first half of the subjective day to the first half of the subjective night. No rhythm was observed under the L/L cycle. A greater proportion of mating occurred within the shelters during the L/D and L/L cycles, whereas its spatial distribution was random under the D/D cycle. Our results reveal an endogenously controlled circadian rhythm of mating behavior, with mating activity mainly occurring during daylight hours. Additionally, we showed that the pairs copulated inside the shelters. These results provide new insights into the reproductive behavior of R. prolixus. Full article

Triatomines are vectors of Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae), the agent of Chagas disease. Stercorarian transmission occurs when infectious parasites are passed in insect feces to vertebrates through the biting wound or mucosa. Defecating on hosts during or shortly after blood feeding is, therefore, critical for transmission, and delayed triatomine defecation behavior has been posited to contribute to a low incidence of human Chagas disease in the U.S. We allowed nymphal T. cruzi-infected and uninfected Triatoma gerstaeckeri (Stål, 1859) and Triatoma sanguisuga (LeConte, 1855) to interact with restrained guinea pigs and measured insect feeding and defecation events; South American Rhodnius prolixus (Stål, 1859; Latin America) served as a comparison group. In 148 trials, 40.0% of insects fed, of which 71.2% defecated. Compared to R. prolixus, T. gerstaeckeri had >9 times higher odds of feeding, and T. sanguisuga fed longer. Observations of defecation while feeding occurred across all three species. The post-feeding defecation interval (PFDI) of R. prolixus was significantly shorter (4.54 ± 2.46 min) than that of T. gerstaeckeri (9.75 ± 2.52 min) and T. sanguisuga (20.69 ± 8.98 min). Furthermore, the PFDI was shorter for TcI-infected insects compared to uninfected insects. Triatoma gerstaeckeri and T. sanguisuga are capable of stercorarian transmission, although the calculated metrics suggest they are less efficient vectors than R. prolixus. Full article

Chagas disease (ChD) is a neglected tropical disease caused by Trypanosoma cruzi, endemic in 21 countries across the Americas, with increasing cases globally. In São Paulo, Brazil, vector control has focused on Triatoma infestans, but secondary triatomine species continue to pose transmission risks. This study aimed to investigate the prevalence of T. cruzi in triatomine feces and characterize its genetic diversity using molecular techniques. Fecal samples were collected from 570 triatomines across 25 municipalities in São Paulo, followed by DNA extraction and PCR amplification targeting the mitochondrial cytochrome b gene and the V7V8 region of the 18S rRNA gene. The results revealed a low overall infection rate (3.2%). However, excluding the triatomines collected in palm trees, all of which were negative, we found mainly Panstrongylus megistus in residences and peridomiciles, showing the highest infection rate (65%) for T. cruzi, followed by Triatoma sordida and Rhodnius neglectus. Phylogenetic analysis confirmed that DTU TcI was the most prevalent genotype, consistent with previous findings in the region. This study highlights the importance of continued vector surveillance, as these secondary species are capable of maintaining T. cruzi transmission in both urban and rural environments, underscoring the ongoing risk of ChD resurgence in São Paulo. Full article

Species of the Rhodnius genus have a complex taxonomy because the events of phenotypic plasticity and cryptic speciation make it difficult to correctly classify these vectors. During the taxonomic history of the genus, five synonymization events occurred. Additionally, some authors suggest that R. milesi possibly represent only phenotypic polymorphisms of R. neglectus. Thus, we analyzed the specific status of R. milesi in relation to R. neglectus using phylogenetic studies with the mitochondrial gene cytochrome B and the study of reproductive barriers. The phylogenetic reconstruction grouped R. milesi together with R. neglectus from different localities, demonstrating that these taxa represent the same species based on the phylogenetic species concept. Experimental crosses demonstrate the absence of pre- and postzygotic barriers under laboratory conditions. Additionally, when the hatch rates of crosses are compared to intraspecific crosses, it can be noted that they are high and very similar. Finally, the mortality rate of the hybrids does not indicate hybrid inviability, the absence of chromosome pairing errors does not indicate hybrid sterility, and the proportion between male and female hybrids demonstrates that Haldane’s rule was not acting. Therefore, we perform the formal synonymization of R. milesi with R. neglectus. Full article

This overview initially describes insect immune reactions and then brings together present knowledge of the interactions of vector insects with their invading parasites and pathogens. It is a way of introducing this Special Issue with subsequent papers presenting the latest details of these interactions in each particular group of vectors. Hopefully, this paper will fill a void in the literature since brief descriptions of vector immunity have now been brought together in one publication and could form a starting point for those interested and new to this important area. Descriptions are given on the immune reactions of mosquitoes, blackflies, sandflies, tsetse flies, lice, fleas and triatomine bugs. Cellular and humoral defences are described separately but emphasis is made on the co-operation of these processes in the completed immune response. The paper also emphasises the need for great care in extracting haemocytes for subsequent study as appreciation of their fragile nature is often overlooked with the non-sterile media, smearing techniques and excessive centrifugation sometimes used. The potential vital role of eicosanoids in the instigation of many of the immune reactions described is also discussed. Finally, the priming of the immune system, mainly in mosquitoes, is considered and one possible mechanism is presented. Full article

Chagas disease (CD) is a typical tropical illness caused by Trypanosoma cruzi. The objective of this study was to assess the prevalence of Chagas disease in communities in two states of the Brazilian Amazon. Data collection occurred in July in the Alto Juruá region of Acre and in December in the communities of Humaitá, Amazonas, in 2019. A total of 477 participants were included in the study. In the communities of Alto Juruá, triatomine collections and analyses of T. cruzi infection were also carried out. All confirmed cases were found in the state of Acre, resulting in a total prevalence of 1.67. Of these eight cases, seven underwent ECG, all of which were concluded as normal by the physician team’s cardiologists. Seventeen triatomine bugs, all belonging to the Rhodnius genus, were captured. The natural infection rate by T. cruzi was 25% in the Nova Cintra community and 66.67% in the Boca do Moa community (Alto Juruá). This research found that more than 1% of the studied population exhibited positive serological results for Chagas disease in the riverine communities during the study period, representing a small portion of cases among those who have not yet been diagnosed. Full article

Female insects belonging to the genera Anopheles, Aedes, Glossina, and Rhodnius account for the majority of global vector-borne disease mortality. In response to mating, these female insects undergo several molecular, physiological, and behavioral changes. Studying the dynamic post-mating molecular responses in these insects that transmit human diseases can lead to the identification of potential targets for the development of novel vector control methods. With the continued advancements in bioinformatics tools, we now have the capability to delve into various physiological processes in these insects. Here, we discuss the availability of multiple datasets describing the reproductive physiology of the common blood-feeding insects at the molecular level. Additionally, we compare the male-derived triggers transferred during mating to females, examining both shared and species-specific factors. These triggers initiate post-mating genetic responses in female vectors, affecting not only their reproductive success but also disease transmission. Full article

Chagas disease (CD) is a neglected illness affecting approximately seven million individuals, with vector transmission occurring via triatomine bugs. The Rhodniini tribe comprises 24 species, grouped into the Rhodnius and Psammolestes genera. Given the importance of accurately identifying CD vectors, the taxonomy of Psammolestes spp. was revisited using morphological and morphometric data. Specimens of P. tertius, P. coreodes, and P. arthuri were collected, and the morphological characteristics of the head, thorax, abdomen, and eggs were analyzed. Morphometric studies of eggs were also conducted. Dichotomous keys allowing for the differentiation of Psammolestes spp. were elaborated based on adult insect and egg morphological characteristics. Through these studies, it was possible to differentiate the three Psammolestes species and confirm that this genus should not be classified under the Rhodnius genus, contributing to Rhodniini taxonomy. Full article

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. Full article

The gross anatomy of the male reproductive structures and their associated musculature are described in the blood-gorging vector of Chagas disease, Rhodnius prolixus. The male reproductive system is composed of muscular tissues each performing contractions that aid in the movement of sperm out of the testis into the vas deferens, seminal vesicle and then into the ejaculatory duct, along with proteins and lipids from the transparent and opaque accessory glands. Phalloidin staining shows the various patterns of muscle fiber layers, from thin circular to more complex crisscross patterns, implying subtle differences in the form of the contractions and movement of each of the structures, allowing for waves of contractions or twisting patterns. The transcripts for the receptors for proctolin, myosuppressin (RhoprMS) and for the extended FMRFamides are expressed in the various regions of the reproductive system, and the nerve processes extending over the reproductive structures are positive for FMRFamide-like immunoreactivity, as are neurosecretory cells lying on the nerves. Proctolin and AKDNFIRFamide are strong stimulators for the frequency of the contractions, and RhoprMS can inhibit the proctolin-induced contractions. Taken together, this work implicates these two families of peptides in coordinating the male reproductive structures for the successful transfer of sperm and the associated accessory gland fluid to the female during copulation. Full article

The rigorous balance of endocrine signals that control insect reproductive physiology is crucial for the success of egg production. Rhodnius prolixus, a blood-feeding insect and main vector of Chagas disease, has been used over the last century as a model to unravel aspects of insect metabolism and physiology. Our recent work has shown that nutrition, insulin signaling, and two main types of insect lipophilic hormones, juvenile hormone (JH) and ecdysteroids, are essential for successful reproduction in R. prolixus; however, the interplay behind these endocrine signals has not been established. We used a combination of hormone treatments, gene expression analyses, hormone measurements, and ex vivo experiments using the corpus allatum or the ovary, to investigate how the interaction of these endocrine signals might define the hormone environment for egg production. The results show that after a blood meal, circulating JH levels increase, a process mainly driven through insulin and allatoregulatory neuropeptides. In turn, JH feeds back to provide some control over its own biosynthesis by regulating the expression of critical biosynthetic enzymes in the corpus allatum. Interestingly, insulin also stimulates the synthesis and release of ecdysteroids from the ovary. This study highlights the complex network of endocrine signals that, together, coordinate a successful reproductive cycle. Full article

Trypanosoma cruzi, the causal agent of Chagas disease, is mainly transmitted by insects of the Triatominae subfamily. In Colombia, there are 26 triatomine species, and 16 of them are naturally infected with the parasite. The parasite loads of naturally infected vectors can be significant in targeting specific species that can affect the epidemiology of the disease. Studying their ecology and behavior is vital to understand their role in T. cruzi transmission dynamics. We evaluated the parasite loads of 182 field-collected triatomines corresponding to 10 species in 13 departments across Colombia. We standardized a methodology to quantify T. cruzi DNA in these insects. We obtained a LOD (limit of detection) of 3.05 p-eq/mL. The 82% of triatomines we evaluated were positive for T. cruzi infection, with loads ranging from hundreds to millions of equivalent parasites per milliliter. Panstrongylus geniculatus, Rhodnius prolixus, and Triatoma dimidiata were the species with the highest loads of T. cruzi; however, other species whose role as vectors is still unknown were also found with high loads of parasites. Our results suggest the relevance of secondary species for T. cruzi transmission in Colombia. We hope our data can help improve entomological surveillance and vector control programs in the country and the region. Full article

Acute Chagas disease (ACD) caused by Trypanosoma cruzi has emerged as a major food-borne disease in Brazilian Amazonia. For the first time, we characterized an outbreak of orally acquired ACD in Acre, in the forest community of Seringal Miraflores, affecting 13 individuals who shared the pulp of açai palm berries: 11 adults and two children (one newborn), all diagnosed by thick-drop blood smears. The fluorescent fragment length barcoding method, which simultaneously identifies species/genotypes of trypanosomes in blood samples, uncovered an unprecedented genetic diversity in patients from a single outbreak of ACD: T. cruzi TcI in all patients, mostly concomitantly with the non-pathogenic Trypanosoma rangeli of genotypes TrA or TrB, and TcI, TcIV, and TrB in the child. The patients presented persistent fever, asthenia, myalgia, edema of the face and lower limbs, hepatosplenomegaly and, rarely, cardiac arrhythmia. The clinical symptoms were not correlated to gender, age, or to trypanosome species and genotypes. The inferred SSU rRNA phylogenetic analyses of trypanosomes from humans, triatomines and sylvatic hosts included the first sequences of T. cruzi and T. rangeli from humans in southwestern (Acre and Rondônia) Amazonia, and the first TcI/TcIV sequences from Rhodnius spp. from Acre. The sylvatic transmission cycles of genetically different trypanosomes in landscapes changed by deforestation for human settlements and increasing açai production is a novel scenario favoring trypanosome transmission to humans in Acre. Full article